GCSE
WJEC Eduqas GCSE in
COMBINED SCIENCE
ACCREDITED BY OFQUAL
GUIDANCE FOR TEACHING
Teaching from 2016
This Ofqual regulated qualification is not available for
candidates in maintained schools and colleges in Wales.
Contents
COMPONENT 1 – Concepts in Biology
5
1.1 PROKARYOTIC AND EUKARYOTIC CELLS
5
1.2 GROWTH AND DEVELOPMENT OF CELLS
10
1.3 CELL METABOLISM
11
2 – TRANSPORT SYSTEMS
19
2.1 TRANSPORT IN CELLS
19
2.2 TRANSPORT SYSTEMS IN HUMANS
24
2.3 TRANSPORT SYSTEMS IN PLANTS
28
3 – HEALTH, DISEASE AND THE DEVELOPMENT OF MEDICINE
30
3.1 HEALTH AND DISEASE
30
3.2 COMMUNICABLE DISEASE
31
3.3 TREATING, CURING AND PREVENTING DISEASE
33
3.4 NON-COMMUNICABLE DISEASES IN HUMANS
35
4 – COORDINATION AND CONTROL
36
4.1 NERVOUS COORDINATION AND CONTROL IN HUMANS
36
4.2 HORMONAL COORDINATION AND CONTROL IN HUMANS
40
4.3 HOMEOSTASIS IN HUMANS
42
5 – PHOTOSYNTHESIS
43
6 – ECOSYSTEMS
48
6.1 LEVELS OF ORGANISATION WITHIN AN ECOSYSTEM
48
6.2 THE PRINCIPLE OF MATERIAL CYCLING
49
6.3 BIODIVERSITY
50
7 – INHERITANCE, VARIATION AND EVOLUTION
54
7.1 THE GENOME AND GENE EXPRESSION
54
7.2 INHERITANCE
58
7.3 VARIATION AND EVOLUTION
59
7.4 SELECTIVE BREEDING AND GENE TECHNOLOGY
61
2
COMPONENT 2 – Concepts in Chemistry
62
1 – PURE SUBSTANCES AND MIXTURES
62
2 – PARTICLES AND ATOMIC STRUCTURE
66
3 – CHEMICAL FORMULAE, EQUATIONS AND AMOUNT OF SUBSTANCE
68
4 – THE PERIODIC TABLE AND PROPERTIES OF ELEMENTS
70
5 – BONDING, STRUCTURE AND PROPERTIES
73
6 – REACTIVITY SERIES AND EXTRACTION OF METALS
76
7 – CHEMISTRY OF ACIDS
87
8 – ENERGY CHANGES IN CHEMISTRY
97
9 – RATE OF CHEMICAL CHANGE AND DYNAMIC EQUILIBRIUM
101
10 – CARBON COMPOUNDS
115
11 – LIFE-CYCLE ASSESSMENT AND RECYCLING
116
12 – THE EARTH AND ITS ATMOSPHERE
117
COMPONENT 3 – Concepts in Physics
120
1. ENERGY
120
1.1 ENERGY CHANGES IN A SYSTEM, AND IN THE WAYS ENERGY IS STORED
BEFORE AND AFTER SUCH CHANGES
120
1.2 CONSERVATION, DISSIPATION AND NATIONAL AND GLOBAL ENERGY
SOURCES
126
1.3 ENERGY TRANSFERS
128
2. PARTICLE MODEL OF MATTER
129
3. FORCES
134
4. FORCES AND MOTION
139
4.1 SPEED AND VELOCITY, SPEED AS DISTANCE OVER TIME; ACCELERATION;
DISTANCE-TIME AND VELOCITY-TIME GRAPHS
139
4.2 FORCES, ACCELERATIONS AND NEWTON’S LAWS OF MOTION
141
4.3 SAFETY IN PUBLIC TRANSPORT
145
5. WAVES IN MATTER
146
6 LIGHT AND ELECTROMAGNETIC WAVES
152
6.1 FREQUENCY RANGE OF THE SPECTRUM
152
6.2 INTERACTIONS OF ELECTROMAGNETIC RADIATION WITH MATTER AND
THEIR APPLICATIONS
153
3
7. ELECTRICITY
156
7.1 CURRENT, POTENTIAL DIFFERENCE AND RESISTANCE
156
7.2 SERIES AND PARALLEL CIRCUITS
160
7.3 DOMESTIC USES AND SAFETY
166
8 MAGNETISM AND ELECTROMAGNETISM
167
8.1 PERMANENT AND INDUCED MAGNETISM, MAGNETIC FORCES AND FIELDS
167
8.2 MAGNETIC EFFECTS OF CURRENTS AND THE MOTOR EFFECT
168
9. ATOMIC STRUCTURE
172
9.1 NUCLEAR ATOM AND ISOTOPES
172
9.2 ABSORPTION AND EMISSION OF IONISING RADIATIONS AND OF
ELECTRONS AND NUCLEAR PARTICLES
173
4
COMPONENT 1 – Concepts in Biology
1.1 PROKARYOTIC AND EUKARYOTIC CELLS
Spec Statement
Comment
(a)
draw and label animal and plant cells
Including labels for nucleus, cytoplasm, cell membrane,
cell wall, chloroplast and vacuole.
(b)
describe the differences between
eukaryotic and prokaryotic cells
Prokaryotic cells consist of a cell wall, cell membrane
and cytoplasm. There is no distinct nucleus, no
mitochondria and no chloroplasts.
Prokaryotic cells are much smaller than most eukaryotic
cells
(c)
explain how the following sub-cellular
structures of eukaryotic cells (plants
and animals) and prokaryotic cells
(bacteria) are related to their functions:
nucleus/DNA, plasmids, mitochondria,
chloroplasts, cell membranes,
cytoplasm, vacuole, cell wall
Cell membrane: controls the entry and exit of
substances.
Cytoplasm: site of most cell reactions.
Nucleus: in plants and animal cells, contains
chromosomes which carry genetic information
consisting of DNA.
The genetic information in bacterial cells is carried in a
single loop of DNA.
Plasmids: small circular sections of DNA often found in
the cytoplasm of bacterial cells, separate from the rest
of the cell`s DNA, can transfer genetic information
between one cell and another.
Mitochondria: site of aerobic respiration.
Cell wall containing cellulose : structural support for
plant cells.
Chloroplast: site of photosynthesis in plant cells.
Vacuole: in plant cells, contains a watery sugar solution
(sap), a swollen vacuole pushes the rest of the cell
contents against the cell wall, making the cell firm.
(d)
explain how the development of the
microscope (light, electron, laser
imaging) increased the understanding
of the sub cellular structure of
organisms and the proposal that the
cell is the basic unit of life
A simple understanding of how the light and electron
microscopes and laser imaging work.
Cell theory was devised and refined as microscopes
have developed.
Calculation of total magnification is achieved by the
multiplication of the power of the eyepiece lens by the
power of the objective lenses.
• how a slide is prepared, including that biological
staining allows more detail of the cell to be seen
• the limitations of light microscopy in studying cell
structure: restriction in maximum magnification
• a simple comparison with the electron
microscope: greater magnification but can only
be used to view dead tissue
SPECIFIED PRACTICAL WORK
•
BSP1.1 Examination of plant and animal cells using a light microscope and production of
labelled scientific drawings from observation
5
Examination of animal and plant cells using a light microscope and production of
labelled scientific diagrams from observation
Introduction
Cheek cells are typical animal cells, they have a cell membrane, cytoplasm and a nucleus. Onion
cells are plant cells, they have a cell wall, cell membrane, cytoplasm, nucleus and vacuole. This
practical requires you to prepare cheek cell slides and onion cell slides. These slides can then be
observed using a microscope.
Apparatus
light microscope
2 × glass slides
2 × cover slips
cotton wool bud
mounted needle
forceps
freshly cut onion
0.1 % methylene blue solution
iodine solution
Access to:
beaker of disinfectant
Diagram of Apparatus
6
Method
Cheek Cells:
1.
2.
3.
4.
5.
6.
7.
8.
Put a drop of methylene blue on a glass slide.
Gently rub the inside of your cheek with a cotton bud.
Wipe the end of the cotton bud in the drop of methylene blue on the glass slide.
Place the cotton bud in the beaker of disinfectant.
Use the mounted needle to gently lower a coverslip onto the glass slide.
Using a light microscope, examine the slide using the ×10 objective lens.
Use the ×40 objective lens to identify some of the cell structures.
Draw a cell diagram. Identify and label: cell membrane, cytoplasm and nucleus.
Onion Cells:
1.
2.
3.
4.
5.
6.
7.
Using forceps, peel a thin layer of epidermis from the inside of a freshly cut onion piece.
Lay the epidermis onto a glass slide.
Add a drop of iodine solution to the onion epidermis on the glass slide.
Use the mounted needle to gently lower a coverslip onto the glass slide.
Using a light microscope, examine the slide using the ×10 objective lens.
Use the ×40 objective lens to identify some of the cell structures.
Draw a cell diagram. Identify and label: cell wall, cell membrane, cytoplasm and nucleus.
Analysis
1. Calculate the total magnification of the image seen by multiplying the power of the
objective lens by the power of the eyepiece.
2. Your teacher will tell you the actual size of the cell, calculate the magnification of your
diagram.
7
Risk Assessment
Hazard
Methylene blue
is harmful
and/or irritant
Risk
Control measure
Methylene blue can irritate the eyes
and lungs. Skin contamination
should be avoided.
Use the lowest concentration possible.
Wear eye protection when preparing
the cheek cell slide. Methylene blue is a
stain- avoid contact with skin.
Cheek cells are
a biohazard
There is a very small risk of virus
transmission.
Only handle samples from your own
body. After use, hygienically dispose of
cotton buds and slides in a disinfectant
such as Milton or Virkon.
Coverslips/
mounted
needles are
sharp
Can cut skin
Handle carefully
Teacher/Technician notes
Methylene blue and iodine solution are stains. Avoid contact with the skin. Iodine is a low hazard
chemical as a dilute solution.
Suitable disinfectant would include Milton or Virkon which would need to be diluted to suitable
concentrations.
If the lamp is not an integral part of the microscope, a desk lamp will be needed for each group.
Freshly cut onion is recommended. This should be prepared for student use in pieces
approximately 1 cm2.
Students will need to be briefed regarding safe and effective microscope use prior to this practical
activity. This practical activity is effective at developing microscope skills and biological drawing
skills.
Students can calculate the total magnification of the image as the power of the objective lens
multiplied by the power of the eyepiece. The actual size of the cells can be given to the students
to enable them to calculate the magnification of their diagrams.
8
Practical techniques covered
B3
Use of appropriate apparatus and techniques for the observation and measurement
of biological changes and or processes.
B4
Safe and ethical use of living organisms (plants or animals) to measure physiological
functions and responses to the environment.
B7
Use of appropriate apparatus, techniques and magnification, including microscopes,
to make observations of biological specimens and produce labelled scientific
drawings.
9
1.2 GROWTH AND DEVELOPMENT OF CELLS
Spec Statement
Comment
(a)
describe the process of mitosis
in growth, including the cell
cycle; cell division by mitosis
enables organisms to grow,
replace worn out cells and repair
damaged tissues
The chromosome number remains constant and the
genetic composition of the daughter cells is identical to
the mother cell. The exact spelling of mitosis is
required.
(b)
explain the importance of cell
differentiation to produce
specialised cells for greater
efficiency
Through differentiation in multicellular organisms,
many types of cells are produced which are adapted to
particular functions.
(c)
describe cancer as the result of
changes in cells that lead to
uncontrolled growth and division
A simple understanding that cancer is a result of
uncontrolled mitosis.
(d)
describe the function of stem
cells in embryonic and adult
animals and meristems in plants;
some cells, both plant and
animal, do not lose the ability to
differentiate and are called stem
cells
The bodies of multicellular organisms consist of a
variety of different cells that are adapted for particular
functions. These different cells originate from
undifferentiated stem cells that have the capacity to
develop into specialised cells.
(e)
discuss the potential benefits,
risks and ethical issues
surrounding stem cell
technology in medicine including
the implications for society e.g.
the use of embryonic stem cells
Stem cells are able to treat damaged or diseased
tissue, providing a potent medical tool. The benefits of
using your own stem cells include: no rejection, no
need to find a donor, no need for tissue typing.
However, the use of embryonic stem cells raises
particular ethical issues.
(f)
explain the role of meiotic cell
division in halving the
chromosome number to form
gametes; each meiotic division
produces four cells that are
genetically different because
genes separate and are
reshuffled during the process of
gamete formation
The exact spelling of meiosis is required.
10
1.3 CELL METABOLISM
Spec Statement
Comment
(a)
explain that chemical reactions
in cells are controlled by
enzymes. Enzymes are proteins
made by living cells. Different
proteins are composed of
different amino acids linked
together to form a chain which is
then folded to form a specific
shape held by chemical bonds.
The specific shape of an
enzymes active site enables it to
function. This is called the 'lock
and key' hypothesis. Enzymes
function by the formation of the
enzyme-substrate complex at
the active site
Enzymes are involved in all metabolic reactions
building large molecules from small ones as well
breaking down large molecules into small ones.
Apply knowledge of ‘lock and key’ to the analysis of
simple, stylised diagrams of enzyme/substrate
interactions.
(b)
explain that enzymes speed
up/catalyse the rate of chemical
reactions. Each enzyme has its
own optimum pH and
temperature. Interpret enzyme
activity in terms of molecular
collisions. Boiling denatures
most enzymes by altering their
shape
Understand the term optimum as a particular condition
(such as temperature or pH) at which the rate of
enzyme action is greatest as increased temperature
results in increased collisions between enzymes and
substrates. In a denatured enzyme the specific shape
of the active site is destroyed and can no longer bind
with its substrate, so no reaction occurs. Analyse data
to show how enzyme action is affected by temperature
and pH.
(c)
describe cellular respiration as
an exothermic reaction which is
continuously occurring in all
living cells, enabling cells to
carry out cell processes. Aerobic
respiration occurs in cells when
oxygen is available. It is a series
of chemical reactions within the
cell, controlled by enzymes.
Glucose and oxygen are used
and carbon dioxide, water and
energy are produced. The
energy released is in the form of
ATP. Recall the word equation
for aerobic respiration
Use germinating peas to show that energy is released
as heat during respiration. This should include the role
of Thermos flasks and disinfectant in the experiment.
11
(d)
explain that in the absence of
oxygen, anaerobic respiration
may occur. This is less efficient
than aerobic respiration. In
humans energy is released from
glucose and lactic acid is
produced. An oxygen debt may
occur. In yeast, glucose is
broken down and ethanol and
carbon dioxide are produced.
Recall the word equation for
anaerobic respiration in human
cells and fermentation in yeast.
Explain that there is less ATP
released per molecule of
glucose in anaerobic respiration
than in aerobic respiration
because of the incomplete
breakdown of glucose
Lactic acid is harmful to the body. It has to be removed
from cells and broken down following the resumption
of aerobic respiration (to repay the oxygen debt).
(e)
compare the processes of
aerobic and anaerobic
respiration
Aerobic and anaerobic respiration compared in terms
of oxygen requirement, use of glucose and release of
ATP. Aerobic respiration is more efficient.
(f)
explain that fats, made up of
fatty acids and glycerol, proteins,
made up of amino acids, and
starch (a carbohydrate), made
up of a chain of glucose
molecules, in our food are
insoluble. They are broken down
during digestion into soluble
substances so that they can be
absorbed
The role of the following enzymes in digestion:
carbohydrase – breaks down starch into glucose;
protease – breaks down protein into amino acids;
lipase - breaks down fats into fatty acids and glycerol.
The products of these enzymes are absorbed into the
bloodstream.
SPECIFIED PRACTICAL WORK
•
•
BSP1.3A Investigation into factors affecting enzyme action
BSP1.3B Qualitative identification of starch (iodine), glucose (Benedict's) and protein
(biuret)
12
Investigation into factors affecting enzyme action
Introduction
Iodine is an indicator that turns blue/black when starch is present, but is otherwise brown.
In this investigation a blue/black solution of starch and iodine will change to brown as the enzyme
amylase digests/breaks down the starch into sugar.
The time taken for this reaction to occur is affected by temperature.
Apparatus
test tube rack and six test tubes
marker pen
stopwatch
25 cm3 measuring cylinder
10 cm3 measuring cylinder
beaker of 10 % amylase solution
spotting tile
dropping pipette
Access to:
water bath or alternative method of heating water
Method
Measure 10 cm3 of 1 % starch solution into a test tube.
Measure 2 cm3 of 10 % amylase solution into a second test tube.
Place both tubes into a water bath set at 20 ºC for 3 minutes.
Place a drop of iodine in six wells of a spotting tile.
Remove both test tubes from the water bath. Pour the amylase into the starch/iodine
solution and start the stopwatch.
6. Immediately, use the dropping pipette to place one drop of the mixture onto the first drop of
iodine. Record the colour of the solution.
7. Repeat step 6 every minute for five minutes.
8. Repeat steps 1-7 at 30 ºC, 40 ºC, 50 ºC, 60 ºC.
1.
2.
3.
4.
5.
Analysis
1. Use your observations to reach a conclusion regarding the effect of temperature on enzyme
action.
2. Evaluate your method and suggest possible improvements.
13
Risk Assessment
Hazard
Risk
Control measure
Amylase enzyme could get on to the
skin when pouring into the test tube
Wash hands immediately if amylase
gets on to them/ wear laboratory gloves
10 % amylase
enzyme solution
is irritant
Amylase enzyme could get
transferred to the eyes from the
hands
Wear eye protection.
Teacher/Technician notes
10 % bacterial amylase solution is a suggested concentration. Amylase varies in its effectiveness
with source and age so it will be necessary to try out the experiment before presenting it to
students to establish the optimum concentrations of starch and amylase to use.
Iodine solution is a stain. It is a low hazard chemical as a dilute solution, however contact with the
skin should be avoided
The method as stated does not include repeats, but students should be encouraged to carry out
an appropriate number, if time allows.
Students should be encouraged to look at reproducibility by looking at the results of other groups.
Evaluation should include consideration of the end point of the reaction and possible
improvements.
Students should design their own table, but a suggested table format is shown below.
Temperature of solution (ºC)
at
start
Colour of solution
after 1 after 2
after 3
after 4
after 5
minute minutes minutes minutes minutes
20
30
40
50
60
14
Practical techniques covered
B1
Use of appropriate apparatus to make and record a range of measurements accurately,
including length, area, mass, time, temperature, volume of liquids and gases, and pH.
B2
Safe use of appropriate heating devices and techniques including use of a Bunsen burner
and a water bath or electric heater.
B3
Use of appropriate apparatus and techniques for the observation and measurement
of biological changes and or processes.
B4
Safe and ethical use of living organisms (plants or animals) to measure physiological
functions and responses to the environment.
B5
Measurement of rates of reaction by a variety of methods including production of gas,
uptake of water and colour change of indicator.
15
Qualitative identification of starch (iodine), glucose (Benedict's) and protein (biuret)
Introduction
The identification of the different food types can be carried out using different chemical tests.
A positive result for each food type is determined by a colour change. In this activity you will
carry out the chemical tests for starch, glucose and protein.
Apparatus
3 × test tubes
3 × dropping pipettes
3 × 5 cm3 syringe
iodine solution with dropping pipette
Benedict's reagent with dropping pipette
biuret reagent with dropping pipette
starch solution
glucose solution
albumen (protein) solution
Test for Starch
1. Add 2 cm3 of the starch solution to a test tube.
2. Add 2 drops of iodine solution and record the colour change.
Test for Glucose
1. Mix 2 cm3 of the glucose solution with 2 cm3 of the Benedict's reagent.
2. Heat the mixture in a water bath at a temperature of 60 oC.
3. Observe and record the colour changes.
Testing for Protein
1. Mix 2 cm3 of the protein solution with the 2 cm3 of biuret reagent.
2. Record the colour change.
Use these three tests to identify the contents of three unknown samples and some different types
of food.
16
Risk Assessment
Hazard
Risk
Control measure
Biuret is an
irritant
Could splash onto hands or into
eyes when transferring to a test tube
Wear gloves/eye protection
Hot water can
burn
Splashing water onto skin when
using water bath could burn
Care must be taken when removing
tubes from the water. Avoid splashing
hot water onto the skin
Benedict's and iodine solutions are classed as low hazard by CLEAPSS at these concentrations.
Teacher / Technician notes
Iodine solution
Iodine is only sparingly soluble in water (0.3 g per litre); it is usual to dissolve it in potassium
iodide solution (KI) to make a 0.01 M solution (by tenfold dilution of a 0.1 M solution) to use as a
starch test reagent. Refer to CLEAPSS recipe card 33.
Benedict's reagent
Benedict's reagent can be purchased from a laboratory supplier or it can be made.
1 dm3 of Benedict's reagent contains:
100 g anhydrous sodium carbonate
173 g sodium citrate
17.3 g copper(II) sulfate pentahydrate.
Biuret reagent
Biuret reagent can be purchased from a laboratory supplier or potassium hydroxide and dilute
copper(II) sulfate could be used as an alternative.
Once students are familiar with the tests and positive results they could be asked to investigate
unknown samples or real foods for their chemical make-up by grinding small portions of the food
in water and carrying out the three tests.
The semi-quantitative nature of the Benedict's test could be discussed or further investigated.
Concentration of Glucose (%)
0.5
1
1.5
2
Colour of precipitate
Green
Yellow
Orange
Brick Red
17
Standards of these precipitates could be useful for students investigating real foods to estimate
the amount of glucose in the foods tested rather than just its presence or absence.
Practical techniques covered
B2
Safe use of appropriate heating devices and techniques including use of a Bunsen burner
and a water bath or electric heater.
B3
Use of appropriate apparatus and techniques for the observation and measurement
of biological changes and or processes.
18
2 – TRANSPORT SYSTEMS
2.1 TRANSPORT IN CELLS
Comment
Spec Statement
(a)
explain that diffusion is a passive
process and that only certain
substances pass through the cell
membrane in this way
(b)
explain that diffusion is the
movement of substances down a
concentration gradient including
the use of Visking tubing as a
model of living material. Explain
the role of the cell membrane in
diffusion
(c)
explain the process of osmosis
as the diffusion of water through
a selectively permeable
membrane, from a region of high
water (low solute) concentration
to a region of low water (high
solute) concentration
(d)
explain that active transport
allows substances to enter cells
against a concentration gradient
and requires energy
Respiration provides the energy required in the form
of ATP. (No detail is required of the process of ATP
synthesis or how it is used to release energy)
(e)
explain the need for exchange
surfaces and a transport system
in multicellular organisms in
terms of surface area:volume
ratio
Unlike single -celled organisms, larger multicellular
organisms cannot exchange substances simply by
diffusion through the body surface. This is because
the area is too small, in relation to the volume of the
body.
In a larger organism, such as an animal or plant,
specialised organs with large surface areas are
needed for the exchange of gases and other
substances. A transport system is necessary to bring
substances to and from these organs and to distribute
substances throughout the body.
19
(f)
describe how oxygen, carbon
dioxide, water, dissolved food
molecules, mineral ions and urea
maybe transported into and out
of humans, green plants and
single celled organisms
Single-celled organisms – exchange of substances
occurs by diffusion through the cell surface.
Humans – oxygen and carbon dioxide pass to and
from the air through the lungs and the respiratory
system. The blood carries oxygen and carbon dioxide
to and from all parts of the body.
Dissolved food molecules, water and minerals pass
into the blood, mainly though the intestines and are
distributed to all parts of the body.
Urea diffuses into the blood from cells throughout the
body. It is carried to the kidneys and then excreted.
Plants – oxygen and carbon dioxide pass in and out
through the stomata of leaves. Water and minerals are
taken in through the roots.
SPECIFIED PRACTICAL WORK
•
BSP2.1 Investigation into the effect of solute concentration on osmosis in potato chips
20
Investigation into the effect of solute concentration on osmosis in potato chips
Introduction
In this investigation, you will investigate osmosis in potato cells. You will prepare a range of
dilutions of blackcurrant squash and allow osmosis to occur. The concentration of the
blackcurrant squash will affect osmosis.
Apparatus
100 cm3 beaker containing approximately 95 cm3 of blackcurrant squash
50 cm3 measuring cylinders
6 × boiling tubes
white tile
scalpel
ruler
cork borers
distilled water
marker pen for labelling of boiling tubes
Access to:
blackcurrant squash
electronic balance ± 0.1 g
Method
1. Label boiling tubes with the concentrations of blackcurrant squash (0, 20, 40, 60, 80 and
100 %).
2. Using a measuring cylinder, transfer the relevant quantities of water and blackcurrant
squash into the boiling tubes to produce the solutions shown. Use the table below to help
you.
Concentration of
blackcurrant squash (%)
0
20
40
60
80
100
Volume of blackcurrant
squash needed to make
30 cm3 solution (cm3)
0
6
12
18
24
30
Volume of water needed
to make 30 cm3 solution
(cm3)
30
24
18
12
6
0
3. Place the boiling tubes in a test tube rack.
4. Cut six chips from a potato using a cork borer and cut into 5 cm lengths. Cut off any potato
skin.
21
5. Dry the chips on a paper towel.
6. Record the mass of each chip and place one chip in each of the boiling tubes. The solutions
should completely cover the chips.
7. Leave for 25 minutes.
8. Remove the chip from the 0 % solution boiling tube.
9. Dry the chip on a paper towel.
10. Record the final mass of the chip.
11. Repeat steps 8-10 for the other solutions.
Analysis
1. Calculate the percentage change in mass for each chip.
2. Plot a graph of concentration against percentage change in mass,
3. Determine the concentration when there was no change in mass.
Risk Assessment
Hazard
Sharp scalpel
blade can cut
Risk
Control measure
Cuts to the skin while cutting potato
Always cut downwards and away from
the body
Teacher/ Technician notes
Blackcurrant squash (not sugar free) - 1 litre is enough for 9 working groups.
Large baking potatoes,1 per working group.
A potato chipper will quickly cut chips of uniform size. It saves time if the chips are cut (using a
chipper) just before or at the beginning of the lesson by a technician. Students will still need to
trim the chips to fit into the beaker/ boiling tube. If using a cork borer, each group should use the
same size borer for each of their potato cores.
No repeats are planned, but groups can compare results to discuss reproducibility.
The results should show that the chips gain mass in dilute concentrations of squash, but lose
mass in strong concentrations. The graph should be drawn with the x-axis across the centre of
the page, to show the increase and decrease in mass. Where the plotted line crosses the x-axis
shows the concentration where there is no gain or loss in mass. Students should understand that
this is the isotonic point and the concentration inside the potato cells is equal to that in the
external concentration.
22
Students should design their own table, but a suggested table format is shown below.
Concentration
(%)
Mass at
start (g)
Mass at end
(g)
Change in
mass (g)
Percentage
change in
mass (%)
Practical techniques covered
B1
Use of appropriate apparatus to make and record a range of measurements accurately,
including length, area, mass, time, temperature, volume of liquids and gases, and pH.
B3
Use of appropriate apparatus and techniques for the observation and measurement
of biological changes and or processes.
B4
Safe and ethical use of living organisms (plants or animals) to measure physiological
functions and responses to the environment.
B5
Measurement of rates of reaction by a variety of methods including production of gas,
uptake of water and colour change of indicator.
23
2.2
TRANSPORT SYSTEMS IN HUMANS
Spec Statement
Comment
(a)
describe the human
circulatory system as a double
circulatory system and its
relationship with the gaseous
exchange system. The blood
passes through the heart
twice in every complete
circulation. The right side of
the heart pumps the blood to
the lungs and the left hand
side pumps it around the rest
of the body
The human circulatory system is a double circulatory
system, as it involves one system for the lungs –
pulmonary and one for the other organs of the body –
systemic.
(b)
label on a given diagram of
the heart: the left and right
atria and ventricles, semilunar, bicuspid and tricuspid
valves, pulmonary artery,
pulmonary vein, aorta and
vena cava
Observe a dissected/ model of the heart to include
coronary arteries and internal structure.
(c)
explain how the structure of
the heart is adapted to its
function
The heart is made of cardiac muscle, which contracts to
pump blood around the body. Understand the significance
of the difference in thickness of the muscle in the atria and
ventricles and between the right and left ventricles.
(d)
describe the passage of blood
through the heart including
explaining the functions of the
valves in preventing backflow
of blood
Deoxygenated blood enters the right atrium from the vena
cava. It then goes through the tricuspid valve to the right
ventricle. From the right ventricle, it goes through the
semilunar valve into the pulmonary artery to the lungs.
From the lungs, oxygenated blood is returned to left
atrium in the heart through the pulmonary veins. The
blood then flows through the bicuspid (mitral) valve into
the left ventricle.
From the left ventricle, it goes through the semi-lunar
valve into the aorta. Blood is distributed to the rest of the
body (systemic circulation) from the
aorta.
(e)
describe and be able to
compare the structure of
arteries and veins
In diagrams of arteries and veins, label: tough outer coat,
muscle layer, endothelium and lumen. Compare the
relative thickness of the blood vessel walls and the size of
the lumen in arteries and veins. Veins contain valves.
(f)
explain how arteries and veins
are adapted to their functions
Arteries have thick muscular walls and a smaller lumen to
carry blood under pressure away from the heart to all
organs of the body. Veins carry blood under lower
pressure back to the heart and contain valves which
ensure one directional flow of blood.
24
(g)
describe that in the organs blood
flows through very small blood
vessels called capillaries which
allow exchange of substances.
Explain that the thin walls of the
capillaries are an advantage for
diffusion and that capillaries
form extensive networks so that
every cell is near to a capillary
carrying blood
Capillary walls are one cell thick - very short diffusion
pathway.
There are a large number of capillaries which maintain
the diffusion gradient between the tissue and the
blood.
(h)
describe the functions of the four
main parts of the blood: plasma
(transport of water, nutrients,
hormones, urea, antibodies), red
cells (carry oxygen), white cells
(defence) and platelets (clotting).
Explain how red blood cells,
white blood cells, platelets and
plasma are adapted to their
functions in the blood
Red blood cells have no nucleus and contain
haemoglobin to carry oxygen. White blood cells
include lymphocytes and phagocytes. Lymphocytes
secrete antibodies and antitoxins and phagocytes
ingest and digest micro-organisms. Platelets are
fragments of larger cells which have no nucleus. They
stick to the walls of damaged blood vessels forming a
plug. This triggers a chain of reactions which results in
a mesh forming across the damage (to form a scab).
SPECIFIED PRACTICAL WORK
•
BSP2.2 Examination of artery and vein using a light microscope and production of
labelled scientific drawings of these from observation
25
Examination of artery and vein using a light microscope and production of labelled
scientific drawings of these from observation
Introduction
This practical requires you to observe and draw a prepared slide of an artery, and of a vein.
Apparatus
Light microscope
Slide of a Transverse Section (T.S.) of an artery
Slide of a Transverse Section (T.S.) of a vein
Method
1.
Use a light microscope to examine a T.S artery using the × 10 objective lens.
2.
Use the × 40 objective lens to identify the tough outer layer and the muscular and
elastic fibres.
3.
Draw a diagram to show the distribution of tissues in the correct proportion.
4.
Identify and label: tough outer layer; muscular and elastic fibres; lumen.
5.
Repeat steps 1 - 4 using a T.S. vein.
Analysis
1.
Compare the structure of the artery and vein and relate this to their function.
2.
Calculate the total magnification of the image seen under the microscope by multiplying
the power of the objective lens by the power of the eyepiece.
26
Risk Assessment
Hazard
Risk
Control measure
No significant risks are associated with this investigation.
Teacher/Technician notes
A lamp may be required, if not part of the microscope.
× 10 and × 40 objective lenses are suggested for viewing the slides. It will be necessary to
determine the optimum magnification before presenting the slides to students.
Students will need to be briefed regarding safe and effective microscope use prior to this practical
activity.
Students should produce low power plans of the blood vessels, no individual cells should be
drawn. This practical activity is effective at developing microscope skills and biological drawing
skills. Drawing skills should include using a pencil to draw smooth, continuous lines with no
overlapping or gaps. No shading or colour should be used.
Students can calculate the total magnification of the image as the power of the objective lens
multiplied by the power of the eyepiece. Students could also calculate the magnification of their
drawing if given the mean diameter of the blood vessel used.
A virtual microscope for demonstration purposes is available on the link below.
http://medsci.indiana.edu/a215/virtualscope/docs/chap7_3.htm
Practical techniques covered
B3
Use of appropriate apparatus and techniques for the observation and measurement
of biological changes and or processes.
B7
Use of appropriate apparatus, techniques and magnification, including microscopes,
to make observations of biological specimens and produce labelled scientific
drawings.
27
2.3 TRANSPORT SYSTEMS IN PLANTS
Spec Statement
Comment
(a)
explain that xylem tissue
contains tubes of dead cells
called xylem vessels and explain
how the vessels are adapted to
their role in the transport of
water and minerals from the
roots upwards within plants
The tubes of dead cells in xylem have very strong cell
walls and are hollow. This means they do not collapse
under pressure and water passes through easily.
The tubes pass up from the roots through the stem
and into the veins in every leaf.
(b)
explain how phloem is adapted
to carry sugar from the
photosynthetic areas to other
parts of the plant. Sugar is
moved to other parts of the plant
for use in respiration and
converted into starch for
storage. This is called
translocation
Phloem consists of long, narrow, living cells which
have large spaces inside for transporting sugar
solutions. These phloem cells carry sugars from the
veins in every leaf to all other part of the plant.
( No details of mechanisms are required)
(c)
explain the significance of root
hairs in increasing the area for
absorption, the role of osmosis
in the uptake and movement of
water through a plant and how
mineral salts are taken up by
root hairs by active transport
(d)
describe the structure of a leaf
and be able to label the following
structures on a diagram of a T.S.
leaf: cuticle, epidermis, stomata,
palisade layer, spongy layer,
xylem and phloem
(e)
describe the structure of stomata
to include guard cells and stoma
and how stomata can open and
close to regulate transpiration
When the guard cells surrounding a stoma change
shape the stoma becomes larger or smaller. This
opening and closing of stomata is important in
controlling how much water vapour passes out of the
leaves. Guard cells and stoma should be identified on
a given diagram.
( No details of mechanisms are required)
(f)
describe the process of
transpiration resulting in the
movement of water through a
plant
Transpiration occurs when water vapour, passing out
of the leaves of a plant, creates a negative pressure
on water in the xylem. Water then rises up through the
xylem from the roots.
Transpiration occurs even in conditions of water
shortage.
28
(g)
explain the environmental
factors that can affect
transpiration, including light
intensity, air movement and
temperature and that this can be
investigated with the use of a
simple potometer
Environmental factors affect the rate of loss of water
vapour from leaves and hence the rate of transpiration.
Increased temperatures and increased air movements
tend to increase the rate of transpiration. Light levels
affect the opening and closing of stomata.
29
3 – HEALTH, DISEASE AND THE DEVELOPMENT OF MEDICINE
3.1 HEALTH AND DISEASE
Comment
Spec Statement
(a)
describe the relationship
between health and disease
In the past, health was thought of simply as the
absence of disease. In modern times there is greater
emphasis on the promotion of health and prevention
of disease.
(b)
describe diseases as being
communicable and noncommunicable diseases as
exemplified by influenza and
cardiovascular disease
Communicable diseases – illnesses which result from
infections by micro-organisms (pathogens) and are
contagious among individuals.
e.g. Influenza- caused by a virus, can be caught from
an infected person by contact or droplet infection..
Non-communicable disease – illnesses which are
often the result of unhealthy lifestyles and sometimes
inheritance.
e.g. cardiovascular disease(CVD)- linked to obesity,
lack of exercise, smoking
In former times most disease–related deaths were
caused by communicable diseases. Now, the majority
of serious illnesses are related to non-communicable
diseases.
(c)
describe the interactions
between different types of
disease, as exemplified by the
increased risk of developing skin
cancer when HIV positive and
the increased risk of
cardiovascular disease in
diabetes patients
HIV – The virus weakens the immune system and
reaches high levels in the blood. Skin cells, which
become infected by the virus, divide and grow
uncontrollably, leading to skin cancers such as
Koposi's Sarcoma.
Diabetes- In type II diabetes, blood sugar levels can
become very high (hyperglycaemia). This is can
damage the walls of blood vessels and lead to CVD
(high blood pressure, stroke , heart attack).
30
3.2 COMMUNICABLE DISEASE
Spec Statement
(a)
explain the means by which
communicable diseases caused
by viruses, bacteria, protists and
fungi can be spread in animals
and plants. This should include
by contact, aerosol, body fluids,
water, insects, contaminated
food.
(b)
describe the following diseases,
this should include the causative
agent, the effect on the infected
organism and how they can be
prevented from spreading
• HIV/ AIDS
• Chlamydia
• Ash die back
• Malaria
Comment
AIDS (Acquired Immune Deficency Syndrome) is
caused by HIV (Human Immunodeficiency Virus). The
virus infects lymphocytes which are part of the body's
immune system. Without immunity, the body can
become infected with a variety of micro-organisms,
e.g. tuberculosis or pneumonia. The virus is spread by
blood to blood contact, especially during sexual
intercourse. Methods of prevention include the use of
condoms and disposable gloves should be used where
there is any danger of contact with contaminated
blood. Antiviral agents can be used, but they only
prevent the multiplication of the virus inside cells and
must be taken throughout life.
Chlamydia, this is the most common sexually
transmitted disease in Britain. It is caused by the
bacterium Chlamydia trachmatis and is spread during
sexual intercourse via the vagina and urethra. Its
spread can be prevented by the use of condoms. It
can be treated with antibiotics such as tetracycline or
erythromycin. However, if left untreated, it could cause
infertility in adults. It could also cause conjunctivitis in
babies during the process of birth if the mother is
infected. It can also spread to the babies lungs.
Malaria - This kills over a million people in the world
each year. It is caused by the single celled organism –
Plasmodium. Plasmodium is spread via female
mosquitoes of the genus Anopheles. Anopheles
mosquitoes bite humans and inject Plasmodium into
the blood stream. Plasmodium causes a fever when it
destroys red blood cells in humans. Treatment
consists of killing Plasmodium with anti-malarial drugs,
such as paludrine or daraprim. A vaccine against
Plasmodium has been developed. Prevention methods
include: killing mosquitoes with insecticide, releasing
large numbers of infertile male mosquitoes, biological
control of mosquitoes, use of mosquito nets and
repellents.
31
(c)
describe the non-specific
defence systems of the human
body against pathogens,
including intact skin forming a
barrier against microorganisms
and blood clots sealing wounds
to seal the skin
(d)
explain the role of the immune
system of the human body in
defence against disease. This
should include the roles of
lymphocytes in secreting
antibodies and antitoxins and
phagocytes which ingest and
digest micro-organisms. Explain
the process by which antigens
from micro-organisms trigger
lymphocytes to release antigen
specific antibodies and that
antibodies activate phagocytes
Lymphocytes are activated by the antigens on microorganisms and then multiply to form clones. Each
clone produces large quantities of identical antibodies,
specific to a particular antigen. These antibodies
attack and destroy the infecting micro-organisms. After
the infection is cleared, some of the lymphocytes,
called memory cells, remain in the body.
The first time an infection occurs, the immune system
may respond rather slowly but if the infection returns a
second time the response is much faster. This
because memory cells produce larger quantities of
antibodies and in a much shorter time than on the first
infection.
32
3.3 TREATING, CURING AND PREVENTING DISEASE
Spec Statement
Comment
(a)
explain that a vaccine contains
antigens derived from a diseasecausing organism. A vaccine will
protect against infection by that
organism by stimulating the
white blood cells to produce
antibodies to that antigen.
Vaccines may be produced
which protect against bacteria
and viruses
Vaccines generally use ‘non-active’ microorganisms,
antigens or parts of antigens to stimulate an immune
response (the details of individual vaccines and the
detail of vaccine production are not required).
(b)
discuss the factors influencing
parents in decisions about
whether to have children
vaccinated or not, including the
need for sound scientific
evidence and the effect of the
media and public opinion.
Understand that science can
only provide a statistically based
‘balance of probability’ answer to
such issues
Candidates should consider the consequences for
individuals and society of when individuals decide not
to be vaccinated.
(c)
explain that antibiotics, including
penicillin, were originally
medicines produced by living
organisms, such as fungi.
Explain that antibiotics help to
cure bacterial disease by killing
the infecting bacteria or
preventing their growth
Antibiotics are now often chemically modified and so
are semi-synthetic or synthetic.
(d)
explain that antibiotics may kill
some bacteria but not viruses.
Some resistant bacteria, such as
MRSA, can result from the over
use of antibiotics. Explain
effective control measures for
MRSA
Some bacteria have become resistant to antibiotics.
The use of antibiotics in animal feed, in some
countries, could be discussed as well as overprescription for humans.
(e)
explain and understand the safe
use of basic aseptic techniques
involved in inoculating, plating
and incubating microorganisms
MRSA control measures could include:
• hand washing
• thorough cleaning of hospital wards
• use of alcohol gels
• MRSA screening
•
•
•
33
bacteria and fungi can be grown on
nutrient agar in a Petri dish, to produce
an agar plate.
Petri dishes and nutrient agar should be
sterilised before the agar is poured.
an inoculating loop is used to transfer
•
•
•
•
(f)
describe the process of
discovery and development of
potential new medicines,
including preclinical and clinical
testing. New drug treatments
may have side effects and
extensive, large scale, rigorous
testing is required including risk
management. Preclinical stages
involve testing on human cells
grown in the laboratory, then on
animals and finally a group of
healthy volunteers. The new
medicines are then taken for
clinical testing using small
groups of patients
bacteria and is sterilised before and after
use by heating it to red heat in a Bunsen
flame.
the Petri dish lid prevents micro-organisms
from the air contaminating the culture and
vice versa.
after inoculation the lid of the Petri dish
should be secured in place by strips of
adhesive tape for safety reasons
inoculated agar plates are incubated at
250C in school laboratories, which
encourages growth of the culture
without growing pathogens
for safety reasons plates and equipment
should be sterilised after use.
All drugs may have side effects. New drugs, including
medicinal drugs, may cause side effects that do not
show up until lots of people use them.
The use of the terms blind, double blind and placebo in
the context of drug development should be
understood.
34
3.4 NON-COMMUNICABLE DISEASES IN HUMANS
Comment
Spec Statement
(a)
recall that many noncommunicable human diseases,
including cardiovascular disease,
lung cancer, skin cancer,
emphysema, type 2 diabetes and
cirrhosis can be caused by the
interaction of a number of life
style factors
(b)
explain the effect of the following
lifestyle factors on the incidence
of non-communicable diseases
at local, national and global
levels: exercise, diet, alcohol,
smoking and exposure to UV
radiation
(c)
evaluate the advantages and
disadvantages of the following
treatments for cardiovascular
disease
• statins
• angioplasty
• changes to lifestyle
diet/exercise
Candidates should understand the importance of
exercise and fitness to the individual combined with
the need for a healthy diet to control body mass. This
helps to prevent type 2 diabetes and cardio vascular
disease. Life style choices should also take regard of
the negative effects of smoking, drinking alcohol and
exposure to ultra violet light. The links between these
life style choices and emphysema, cirrhosis and
cancer should be known.
Research the advantages and disadvantages of the
treatments for cardiovascular disease such as:
• Statins, a daily medication to control blood
cholesterol levels, but may cause side effects.
•
Angioplasty, surgery to place a small balloon in
a blood vessel, which is inflated to remove a
blockage. This results in improved blood flow
e.g. in coronary vessels, but sometimes is only
a temporary remedy.
•
Changes to diet/ lifestyle. These include
stopping smoking, taking up regular exercise,
eating more healthy food. These can reduce
risk and lower blood pressure.
However, a high level of self- discipline is
needed to maintain these long-term changes.
35
4 – COORDINATION AND CONTROL
4.1 NERVOUS COORDINATION AND CONTROL IN HUMANS
Comment
Spec Statement
(a)
describe sense organs as groups
of receptor cells, which respond
to specific stimuli: light, sound,
touch, temperature, chemicals,
and then relay this information as
electrical impulses along
neurones to the central nervous
system
(b)
describe the structure of the
nervous system, including the
brain, spinal cord, sensory
neurones, motor neurones and
sensory receptors and the
central nervous system
consisting of the brain and spinal
cord
(c)
explain how the structure of the
nervous system (including CNS,
sensory and motor neurones and
sensory receptors) is adapted to
its functions
(d)
describe the properties of reflex
actions. These reactions are fast
and automatic and some are
protective, as exemplified by the
withdrawal reflex, blinking and
pupil size
(e)
explain how the structure of a
reflex arc is related to its function
and be able to label a diagram to
show: receptor, sensory
neurone, relay neurone in spinal
cord, motor neurone, effector
and synapses
Nerve impulses begin at receptors and pass along
sensory neurones to a coordinator. Motor neurones
pass on impulses to effectors. The function of
synapses should be known but knowledge of the
chemical nature of synaptic neuro transmitters is not
needed.
Candidates need to be able to indicate, on a diagram
of a reflex arc, the direction of travel of the impulse.
SPECIFIED PRACTICAL WORK
•
BSP4.1 Investigation into factors affecting reaction times
36
Investigation into factors affecting reaction time
Introduction
If you notice a ball moving towards your head, the time it takes from when you first notice the ball
to when your arm reaches up to catch it is an example of reaction time. Even though nervous
impulses travel very quickly through your nervous system, your body doesn’t react instantly. In
this activity, you will conduct a simple, measurable experiment to study reaction time and
investigate the hypothesis that reaction time improves with practice.
Apparatus
30 cm ruler
Diagram of Apparatus
37
Method
1. Ask your first volunteer to sit in the chair with good upright posture and eyes looking across
the room.
2. Have the volunteer place their forearm (the part of the arm from elbow to hand) so it
extends over the edge of the table.
3. Ask the volunteer to place their thumb and index (pointer) finger on either side of the bottom
of the vertically placed ruler. The number “1” should be on the bottom, the “30” near the top.
4. Let your volunteer practice holding the ruler with those two fingers.
5. Now, ask your volunteer to remove their fingers from the ruler while you continue to hold it
so that the bottom of the ruler is at a height of 2 cm above the fingers.
6. Tell your volunteer that you will release the ruler without warning. Their job will be to catch it
with their thumb and forefinger as soon as they sense it dropping.
7. Drop the ruler. When your volunteer catches it, record the number on the ruler displayed
just over the thumb. The lower the number, the faster the reaction time.
8. Conduct five trials with the same volunteer, dropping the ruler from 2 cm above their fingers
each time.
9. Repeat the experiment with at least five other volunteers and record your results in a
suitable table
Analysis
1. Use the conversion table below to convert the distance measured to a reaction time for
each volunteer
Catch distance
(cm)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Reaction time
(milliseconds)
50
60
701
80
90
100
120
130
140
140
150
160
160
170
170
Catch distance
(cm)
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
2. Discuss the extent to which your results support the hypothesis.
38
Reaction time
(milliseconds)
180
190
190
200
200
210
210
220
220
230
230
230
240
240
250
Risk Assessment
Hazard
Risk
Control measure
There are no significant risks associated with this procedure
Teacher / Technician notes
A possible alternative activity could be to compare the volunteer's dominant hand with their nondominant hand.
Students should design their own table, but a suggested table format is shown below.
Trial 1
Volunteer
Distance
(cm)
Reaction
time (ms)
Trial 2 etc
Distance
Reaction
(cm)
time (ms)
Practical techniques covered
B1
Use of appropriate apparatus to make and record a range of measurements accurately,
including length, area, mass, time, temperature, volume of liquids and gases, and pH.
B3
Use of appropriate apparatus and techniques for the observation and measurement
of biological changes and or processes.
B4
Safe and ethical use of living organisms (plants or animals) to measure physiological
functions and responses to the environment.
B5
Measurement of rates of reaction by a variety of methods including production of gas,
uptake of water and colour change of indicator.
39
4.2 HORMONAL COORDINATION AND CONTROL IN HUMANS
Spec Statement
Comment
(a)
describe and be able to label the
positions of the following glands
on a diagram of the human body:
pituitary, adrenal, thyroid,
pancreas, ovaries and testes
(b)
describe hormones as chemical
messengers, produced by glands
and carried by the blood, which
control many body functions
(c)
describe the principles of
negative feedback mechanisms
in maintaining optimum
conditions inside the body
Any change from the balance in optimal internal
conditions results in the body's hormonal and nervous
systems compensating for the change and restoring
the balance.
(d)
explain the role of thyroxine in
the body as an example of
negative feedback.
Description should be limited
to effects of TRH and TSH in
the release of thyroxine.
Thyrotropin-releasing hormone (TRH) is made in
the hypothalamus, an area at the base of the brain.
The nerve fibres that come out of it carry TRH and
release it into the blood surrounding the pituitary
gland. The TRH regulates the formation and
secretion of thyroid stimulating hormone in the
pituitary gland.
The pituitary gland secretes thyroid stimulating
hormone (TSH) which causes the thyroid to
secrete thyroxine. A decrease in thyroxine levels
stimulates TRH and therefore TSH secretion,
whereas an increase in thyroxine slows down TRH
secretion.
(e)
explain the action of
adrenaline in the body as an
example of positive feedback.
Description should be limited
to the effects of adrenaline on
the heart, breathing and
muscles. Adrenaline is
converted into a less active
compound by the liver.
The positive feedback mechanism of adrenalin
production causes an increase in pulse rate and
volume of blood pumped by the heart with each
beat. It increases the depth of breathing and
dilates the blood vessels supplying muscles.
(f)
describe the roles of hormones
in human reproduction, including
the menstrual cycle
Testosterone regulates the development of male
secondary sexual characteristics.
Oestrogen stimulates the thickening of the uterine wall
during ovulation.
Progesterone prepares the uterus for pregnancy.
40
(g)
(h)
(i)
explain the interactions of
FSH, LH, oestrogen and
progesterone in the control
of the menstrual cycle
At the beginning of the menstrual cycle, two
hormones from the pituitary gland, follicle
stimulation hormone (FSH) and luteinizing
hormone (LH), stimulate the development of
egg-bearing follicles in the ovaries. As the
follicles mature, they secrete oestrogen.
explain the use of hormones in
contraception and evaluate
hormonal and non-hormonal
methods of contraception
Contraceptive pills or implants contain
combinations of synthetic oestrogen-like and
progesterone-like chemicals. These stop the
secretion of FSH and LH so neither follicle
development (an oestrogen effect) nor ovulation (a
progesterone effect) occurs. Non hormonal forms
of contraception such as condoms reduce the
chance of sexual transmission of diseases. Also
some hormonal forms of contraception may have a
variety of negative side effects such as nausea
and thrombosis.
explain the use of hormones
in modern reproductive
technologies to treat
infertility
Hormones are used to increase fertility.
Synthetic chemicals are used to stimulate
ovulation. They either act as FSH, which
stimulates the development of follicles or they
inhibit the production of oestrogen. Lack of
oestrogen (the normal FSH inhibitor) results in
more FSH being produced which stimulates
multiple follicle development.
41
4.3 HOMEOSTASIS IN HUMANS
Spec Statement
(a)
explain the importance to
animals of maintaining a
constant internal environment in
response to internal and external
change
(b)
explain why and how glucose
levels need to be kept within a
constant range. When the blood
glucose level rises, the pancreas
releases the hormone insulin, a
protein, into the blood. This
causes the liver to reduce the
glucose level by converting
glucose to insoluble glycogen
and then storing it
(c)
explain how glucagon
interacts with insulin to
control blood sugar levels in
the body
(d)
compare type 1 and type 2
diabetes and explain how they
can be treated. Diabetes is a
common disease in which a
person has a high blood sugar
(glucose) level. In Type 1
diabetes this is because the
body does not produce enough
insulin. In Type 2 diabetes the
body cells do not properly
respond to the insulin that is
produced
Comment
Metabolism operates only within a narrow range of
temperature and pH and requires appropriate nutrients
and water.
The detection of glucose in urine is a symptom of
diabetes. Candidates should test artificially prepared
urine samples for the presence of glucose using
Benedict's solution.
The methods of treating diabetes include regularly
injecting insulin, a low sugar and low carbohydrate diet
and possible transplant of pancreatic tissue.
SPECIFIED PRACTICAL WORK
•
SP4.3 Dissection of mammalian kidney
42
5 – PHOTOSYNTHESIS
Comment
Spec Statement
(a)
describe the process of
photosynthesis and describe
photosynthesis as an
endothermic reaction, whereby
green plants and other
photosynthetic organisms use
chlorophyll and light to convert
carbon dioxide and water into
glucose, producing oxygen as a
by-product. Recall the word
equation for photosynthesis
(b)
explain the effect of temperature,
light intensity and carbon dioxide
concentration on the rate of
photosynthesis
(c)
explain the interaction of these
factors in limiting the rate of
photosynthesis
The chemical reactions of photosynthesis within the
cell are controlled by enzymes.
(Details of the enzymes involved in photosynthesis are
not required.).
The practical techniques used to investigate
photosynthesis: the use of sodium hydroxide to
absorb carbon dioxide; how to test a leaf for the
presence of starch; how oxygen and carbon dioxide
sensors and data loggers could be used.
The steps within the method for testing a leaf for
starch include: killing the leaf by placing in boiling
water, decolouration using ethanol, washing to soften,
testing with iodine. Understand the need for destarching the leaf prior to the procedure.
SPECIFIED PRACTICAL WORK
•
BSP5 Investigation into factors affecting the rate of photosynthesis
43
Investigation of the factors affecting photosynthesis
Introduction
Light is one of the factors which affects the rate of photosynthesis.
In this investigation a green plant named Canadian pondweed (Elodea) will produce bubbles of
oxygen as a result of photosynthesis.
The number of bubbles of oxygen produced is affected by light intensity.
Apparatus
250 cm3 beaker
lamp
glass funnel
plasticine
test tube
8 cm length of pondweed (Elodea)
metre ruler ± 1 mm
sodium hydrogen carbonate powder
clamp stand, clamp and boss
spatula
Diagram of Apparatus
44
Method
1. Place the Elodea in a beaker containing 200 cm3 of water.
2. Add one spatula of sodium hydrogen carbonate to the water.
3. Stick 3 small pieces of plasticine to the rim of the funnel and place it upside down over the
plant.
4. Completely fill a test tube with water and carefully place over the end of the funnel with the
end under the water, clamp into place.
5. Place the lamp 5 cm away from the apparatus.
6. Start the stopwatch and record the number of bubbles of oxygen produced in
one minute.
7. Repeat the experiment with the lamp 10 cm, 15 cm, 20 cm, 25 cm and 30 cm from the
apparatus.
Analysis
1. Plot a graph of the distance against number of bubbles produced in 1 minute.
2. What conclusions can be reached from your results?
3. Evaluate your method and state how it could be improved.
Risk Assessment
Hazard
Lamps will
become hot
Risk
Control measure
Burning hand when moving lamp
45
Do not touch lamp until it has cooled
down.
Teacher/Technician notes
If the plant is not producing bubbles then the stem might have started to ‘heal’ up, cutting off the
end off may improve bubbling.
Begin the experiment with the lamp closer to the plant and move the plant further away as this
seems to give better results.
Cabomba caroliana (and Elodea crispa) are no longer available to buy. They have been banned
for culturing or sale under European regulations controlling invasive non-native plants. CLEAPSS
have worked with native plants (Hornwort and red Cabomba), and they are OK for use. The
CLEAPSS method (see the link below) overcomes the problems of the native aquatic plants
bubbling slowly.
http://science.cleapss.org.uk/Resource-Info/GL184-Using-video-recording-to-measure-the-rateof-photosynthesis.aspx
If students have any difficulty in obtaining results, the link below can be used.
http://www.reading.ac.uk/virtualexperiments/ves/preloader-photosynthesis-full.html
The method as stated does not include repeats, but students should be encouraged to carry out
an appropriate number, if time allows.
This experiment is ideal for a discussion of the limiting factors of photosynthesis and how they
are controlled variables in this experiment. There is also a clear opportunity to discuss the
limitations of the investigation such as the difficulty in controlling temperature.
Students should design their own table, but a suggested table format is shown below.
Number of bubbles produced in one minute
Distance
from plant
to lamp (cm)
Trial 1
Trial 2
46
Trial 3
Mean
Practical techniques covered
B1
Use of appropriate apparatus to make and record a range of measurements accurately,
including length, area, mass, time, temperature, volume of liquids and gases, and pH.
B2
Safe use of appropriate heating devices and techniques including use of a Bunsen burner
and a water bath or electric heater.
B3
Use of appropriate apparatus and techniques for the observation and measurement
of biological changes and or processes.
B4
Safe and ethical use of living organisms (plants or animals) to measure physiological
functions and responses to the environment.
B5
Measurement of rates of reaction by a variety of methods including production of gas,
uptake of water and colour change of indicator.
47
6 – ECOSYSTEMS
6.1 LEVELS OF ORGANISATION WITHIN AN ECOSYSTEM
Comment
Spec Statement
(a)
describe different levels of
organisation in an ecosystem
from individual organisms
through populations and
communities to the whole
ecosystem
The total number of organisms, of the same species,
in a given geographical area or location make up a
population. All the interacting populations of different
species within that location form a community. The
term ecosystem is used to describe a community of
organisms interacting with each other and with their
environment.
(b)
explain how some abiotic factors
affect communities as
exemplified by pH, light,
temperature and salinity
Abiotic (non-living) factors in a community are
constantly changing and these changes affect living
organisms. Plants in a community interact with each
other by competing for light, space and mineral ions.
(c)
explain how some biotic factors
affect communities as
exemplified by predation,
disease and food availability
Biotic (living) factors in a community are constantly
changing. A change in a biotic factor might affect a
community e.g. by a change in the availability of food
or the presence of a new predator or pathogen.
(d)
describe the importance of
interdependence and
competition in a community
(e)
describe photosynthetic
Radiation from the sun is the source of energy for
organisms as the main producers living organisms. Green plants capture only a small
of food and therefore biomass for percentage of the solar energy which reaches them.
life on Earth. Green plants, and
other photosynthetic organisms
such as algae use the light from
the sun to produce organic
materials
(f)
describe the differences between
the trophic levels of organisms
within an ecosystem including
producers; first, second and third
stage consumers; herbivores and
carnivores
Candidates should be aware that alternative terms for
the organisms in the trophic levels include: primary
consumers, secondary consumers and tertiary
consumers.
(g)
investigate data about food
chains and food webs and
explain that they show the
transfer of biomass between
organisms
Analyse data in terms of: efficiency of energy transfer,
numbers of organisms and biomass.
48
6.2 THE PRINCIPLE OF MATERIAL CYCLING
Spec Statement
Comment
(a)
recall that many different
materials cycle through the
abiotic and biotic components of
an ecosystem. Nutrients are
released in decay, e.g. nitrates
and phosphates and these
nutrients are then taken up by
other organisms resulting in
nutrient cycles. In a stable
community the processes which
remove materials are balanced
by processes which return
materials
Only the general principle of the cycling of elements is
required here (no detail of nitrate or phosphate cycles).
(b)
explain why it is important that
carbon is constantly cycled in
nature by the carbon cycle via
photosynthesis which
incorporates it and respiration
which releases it
Carbon is taken up by green plants in photosynthesis
and is passed to animals when they eat the plants.
Some of this carbon then becomes part of
carbohydrates, fats and proteins which make up their
bodies. Animals and plants release carbon dioxide
during respiration.
(c)
explain that microorganisms,
bacteria and fungi, feed on waste
materials from organisms and
that when plants and animals die
their bodies are broken down by
microorganisms bringing about
decay. These micro-organisms
respire and release carbon
dioxide into the atmosphere.
Burning fossil fuels releases
carbon dioxide
Micro-organisms digest materials from their
environment for growth and other life processes.
These materials are returned to the environment either
in waste products or when living things die and decay.
When decay is prevented, fossil fuels such as coal, oil
and gas are formed and these store energy in carbon
compounds.
(d)
explain the importance the water
cycle to living organisms
Water evaporates from large bodies of water (seas
and oceans) and condenses to form clouds.
Precipitation provides fresh water for plants and
animals on land. Water from the land drains into the
seas and oceans.
49
6.3 BIODIVERSITY
Spec Statement
(a)
describe how to use quadrats to
investigate the abundance of
species e.g. a comparison of
different sides of a hedge or
mown and unmown grassland
(b)
describe how transects can be
used to measure changes in the
abundance and distribution of
species e.g. seashore
(c)
describe the principles of
sampling, the need to collect
sufficient data and use of
appropriate statistical analysis.
(Details of statistical tests are
not required.) Describe the
principles of capture/recapture
techniques including simple
calculations on estimated
population size
Comment
Any suitable location could be used to show the effect
of different environmental factors. This should include
the use of line transects and random quadrat
distribution. An understanding that the number/
distribution of quadrats used should be enough to give
valid results.
Candidates should know how to use the equation:
population size =
number in 1st sample x number in 2nd sample
number in 2nd sample previously marked
When using capture-recapture data, assumptions
made include: there is no death, immigration or
emigration and that the marking technique does not
affect chances of survival.
Candidates will not be expected to recall the equation.
(d)
(e)
explain what is meant by
biodiversity, the variety and
number of different species in an
area, and why it is important.
Explain that indicator species
are an important set of
organisms whose numbers and
changing population can tell us a
lot about the changing state of
ecosystems
Biodiversity is important as it provides food, potential
foods, industrial materials, new medicines and for
human well-being.
describe both positive and
negative human interactions
within ecosystems and explain
their impact on biodiversity
An increase in the size of the human population results
in an increased demand for food, water and other
resources. These interactions, together with
urbanisation, industrialisation and globalisation, can
reduce biodiversity because ecosystems are
destroyed, reduced in area or damaged. The extreme
case is where populations die out or organisms
become extinct.
Indicator species and changes in pH and oxygen
levels may be used as signs of pollution in a stream
and lichens can be used as indicators of air pollution.
If the resources in an ecosystem are used in a
sustainable way the human interaction within the
ecosystem can be considered as positive.
50
(f)
describe the ways in which
biodiversity and endangered
species can be protected locally
and globally, including issues
surrounding the use of
legislation. Explain the need for
and issues associated with the
collection of reliable data and
ongoing environmental
monitoring
Biodiversity and endangered species can be
conserved and protected by the following:
• Convention on International Trade in
Endangered Species
• Sites of Special Scientific Interest
• captive breeding programmes
• national parks
• seed/ sperm banks
• local biodiversity action plans
(g)
explain the use of biological
control agents and the
introduction of alien species and
their effects on local wildlife.
Explain the issues surrounding
the use of biological control
agents and how the approach to
using this method of control has
changed as requirements for
detailed research and
scientifically based trials and
analysis are now more fully
understood
Candidates should know that some animals and plants
have been introduced, deliberately and accidentally,
into areas where they do not naturally occur and some
have become invasive and caused problems. Invasive
species may grow faster than native species and upset
the natural eco-system. Native species may not be
able to compete with them.
Research into the use of biological control agents
takes place, on a world-wide basis, in order to
understand how best to control alien species. During
the research, trials are needed to assess the effects of
biological control agents particularly on non-targeted
native species.
(h)
explain some of the benefits and
challenges of maintaining local
and global biodiversity
Maintaining biodiversity means that there is a greater
chance of the discovery of potential treatments for
many diseases and health problems. It ensures the
sustainable productivity of soils and provides genetic
resources for all crops, livestock and marine species
harvested for food.
Climate change, global warming and acidification of
the oceans all have a negative impact on biodiversity.
Controlling both climate change and global warming is
one of the greatest challenges facing mankind at the
present time.
SPECIFIED PRACTICAL WORK
•
BSP6.3 Investigation into factors affecting the abundance and distribution of a species
51
Investigation into factors affecting the abundance and distribution of a species
Introduction
Daisies are a common plant species that can be found on a school field. Using quadrats for
random sampling allows you to estimate the numbers of daisy plants growing in this habitat. This
technique also reduces sampling bias. A simple calculation can then be used to estimate the total
number of daisy species in the entire school field habitat.
Apparatus
2 × 20 m tape measures
2 × 20 sided dice
1 m2 quadrat
Diagram of Apparatus
52
Method
1.
2.
3.
4.
5.
Lay two 20 m tape measures at right angles along two edges of the area to survey.
Roll two 20 sided dice to determine the coordinates.
Place the 1 m2 quadrat at the place where the coordinates meet.
Count the number of daisy plants within the quadrat. Record this result.
Repeat steps 2-4 for at least 25 quadrats.
Analysis
1. Use the following equation to estimate the total number of daisy plants in the field habitat:
Total number of daisy plants in the habitat = total number in sample ×
Where:
total area = 400 m2
total sample area = number of 1 m2 quadrats used
total area �m2 �
total sample area (m2 )
Risk Assessment
Hazard
Some plants have
thorns, sting or are
poisonous
Biting and stinging
insects
Tripping
Risk
Control measure
Adverse skin response
Cover skin at all times
Cover skin at all times.
Use insect repellent.
Care where walking
Adverse skin response
Strains and sprains
Teacher/Technician notes
Students could compare data for mown and unmown areas.
This practical activity is effective at developing practical fieldwork skills. Students can discuss the
need for a large sample of data in ensuring that there is confidence in a valid conclusion. Also,
students can describe the importance of random sampling techniques in reducing/eliminating
bias.
Alternative methods of generating coordinates can be used, such as using a random number
generator or random number tables.
53
Practical techniques covered
B1
Use of appropriate apparatus to make and record a range of measurements accurately,
including length, area, mass, time, temperature, volume of liquids and gases, and pH.
B3
Use of appropriate apparatus and techniques for the observation and measurement
of biological changes and or processes.
B4
Safe and ethical use of living organisms (plants or animals) to measure physiological
functions and responses to the environment.
B6
Application of appropriate sampling techniques to investigate the distribution and
abundance of organisms in an ecosystem vis direct use in the field.
54
7 – INHERITANCE, VARIATION AND EVOLUTION
7.1 THE GENOME AND GENE EXPRESSION
Comment
Spec Statement
(a)
describe chromosomes as linear
arrangements of genes.
Chromosomes that are found in
pairs in body cells are strands of
DNA
DNA has a ladder-like structure, the bases forming the
rungs. They should have an understanding of
complementary base pairing - A pairs with T and that
C pairs with G
(b)
describe DNA as a polymer
made up of two strands forming
a double helix
(c)
describe how an organism's DNA The term genetic profiling should be used in place of
can be analysed by 'genetic
genetic fingerprinting to avoid confusion with
profiling' and how this can be
fingerprinting. No detail of process is required.
used to show the similarity
between two DNA samples. The
process involves cutting the DNA
into short pieces which are then
separated into bands. The
pattern of the bands produced
can be compared to show the
similarity between two DNA
samples
(d)
describe the genome as the
entire genetic material of an
organism
All the genetic material of an organism is known as its
genome. It is the organism’s complete set of DNA,
including all of its genes. Each genome contains all
the information to build and maintain that organism. In
humans, a copy of the entire genome – more than 3
billion DNA base pairs – is contained in all cells that
have a nucleus.
The entire genome of many organisms, including
humans, has now been studied. This will have
important medical significance in future.
(e)
discuss the potential importance
for medicine of our increasing
understanding of the human
genome
An understanding that the human genome is important
because it uses information from DNA to develop new
ways to treat, cure, or even prevent disease.
SPECIFIED PRACTICAL WORK
•
BSP7.1 Simple extraction of DNA from living material
55
Simple extraction of DNA from living material
Introduction
DNA is the hereditary material found in all living things. In this practical you will extract the DNA
from strawberries. Strawberries can have up to 8 copies of each chromosome and so contain a
lot of DNA. When extracted from the strawberry this DNA is visible.
Apparatus
re-sealable plastic bag
strawberry
10 cm3 washing up liquid (detergent)
1 g sodium chloride
100 cm3 water
2 × 250 cm3 beakers (one beaker will be used for the filtering apparatus below)
filter funnel
coffee filter paper
ice-cold 90 % alcohol
ice lolly stick or plastic coffee stirrer
Method
1. Remove the green top from the strawberry.
2. Put the strawberry into the plastic bag, seal it and crush for about 2 minutes.
3. In a beaker mix together the 10 cm3 of washing up liquid, 1 g of salt and 100 cm3 water. This
mixture is the DNA extraction liquid.
4. Add 10 cm3 of the extraction liquid to the bag with the strawberry.
5. Re-seal the bag and gently mix the extraction liquid with the strawberry for 1 minute.
6. Place the coffee filter inside the beaker and gently pour the strawberry mixture into it.
7. Pour 10 cm3 of ice-cold 90 % ethanol down the side of the beaker into the strawberry
mixture, do not mix or stir.
8. Within a few seconds you should see a white cloudy substance form in the clear layer
above the strawberry mixture. Use a lolly stick to pull strands of this out of the top layer, this
is the strawberry DNA.
56
Risk Assessment
Hazard
90% ethanol
could act as an
irritant
Risk
Inhalation could cause irritation of
the nose/throat
Ethanol could touch skin during the
experiment
Control measure
Use in well-ventilated area/wear safety
glasses.
Use gloves when pouring ethanol.
Teacher/ Technician notes
Chill the ethanol by keeping in the freezer for at least 2 hours or overnight. Keep on ice during the
experiment.
A variety of fruits can be used as an alternative to strawberries, such as kiwi or banana, but
check students have no allergies to the fruit used.
This experiment could be used as stimulus material to begin a piece of extended writing
describing what was observed in the experiment and linking it to what the student already knows
about the structure of DNA. It could also lead to a discussion of the ethical issues surrounding
DNA.
Practical techniques covered
B2
Safe use of appropriate heating devices and techniques including use of a Bunsen burner
and a water bath or electric heater.
B3
Use of appropriate apparatus and techniques for the observation and measurement
of biological changes and or processes.
B4
Safe and ethical use of living organisms (plants or animals) to measure physiological
functions and responses to the environment.
57
7.2 INHERITANCE
Spec Statement
(a)
explain the following terms:
gamete, chromosome, gene,
allele/variant, dominant,
recessive, homozygous,
heterozygous, genotype
phenotype
(b)
describe genes as sections of
DNA molecules that determine
inherited characteristics and that
are in pairs. Genes have
different forms, called alleles
(c)
explain single gene inheritance
and be able to complete Punnett
squares to show this
(d)
predict the outcomes of
monohybrid crosses including
ratios
(e)
recall that most phenotypic
features are the result of multiple
genes rather than single gene
inheritance
(f)
describe sex determination in
humans. In human body cells,
one of the pairs of
chromosomes, XX or XY, carries
the genes which determine sex.
These separate and combine
randomly at fertilisation
Comment
The terms gene and allele are not interchangeable.
An understanding of probability is also required.
The use of Punnett squares to show the inheritance of
sex chromosomes.
58
7.3 VARIATION AND EVOLUTION
Spec Statement
Comment
(a)
describe simply how the
genome, and its interaction with
the environment, influence the
development of the phenotype of
an organism. Variation may be
due to environmental or genetic
causes or a combination of the
two
The variation in height/length in organisms could be
used to show that individuals of the same species are
similar but they are never exactly the same.
Continuous and discontinuous variation should be
illustrated graphically – bell shaped curve for
continuous variation and discontinuous variation as
discrete groups.
(b)
state that there is usually
extensive genetic variation
within a population of a species
(c)
recall that all variants result from
changes, mutations, in existing
genes and that mutations occur
at random. Most mutations have
no effect on the phenotype but
some influence phenotype and
very few determine phenotype.
Mutation rates can be increased
by ionising radiation
The greater the dose/exposure to ionising radiation the
greater the chance of mutation.
(No reference to specific ionising radiation is required.)
(d)
describe evolution as a change
in the inherited characteristics of
a population over time through a
process of natural selection
which may result in the
formation of new species. Genes
which enable better adapted
individuals to survive are passed
on to the next generation. This
may results in new species
being formed. The process of
natural selection is sometimes
too slow for organisms to adapt
to new environmental conditions
and so organisms may become
extinct
The term natural selection should be understood. The
term ‘Survival of the fittest’ should only be used with
care as it must be qualified in the context of breeding
i.e. survival of the fittest to breed.
(e)
explain how individuals with
characteristics adapted to their
environment are more likely to
survive and breed successfully.
This results in evolution
59
(f)
describe that evolution is
ongoing as shown by the
development of resistance to
antimicrobial chemicals by
bacteria or Warfarin resistance
in rats and that evolution can
also be evidenced by fossils
(g)
describe the impact of
developments in biology on
classification systems; biological
classification systems continue
to be modified in the light of
ongoing research. Recently, the
three Domain system (based on
differences in RNA) proposes
two Domains of prokaryotes and
one further Domain containing
four main eukaryote kingdoms –
Protists, Fungi, Plants and
Animals
There is a need for a systematic scheme to divide the
variety of living organisms into groups in order to make
the understanding of the variety of living things
manageable and to understand trends and
relationships. The classification system maybe based
on morphological features or DNA analysis. A simple
understanding of possible groupings. The five
Kingdom classification using morphological features:
Bacteria, Single celled organisms, Plants, Fungi, and
Animals. The three Domain classification based on
analysis of DNA: Ancient bacteria, Bacteria and All
organisms with a nucleus. No features of these groups
required.
60
7.4 SELECTIVE BREEDING AND GENE TECHNOLOGY
Spec Statement
(a)
explain the impact of the
selective breeding of food plants
and domesticated animals
Comment
Humans have been carrying out selective breeding of
plants and animals for many thousands of years.
Parents, of the same species, with desirable genetic
features are bred together. Offspring, which have
inherited the desirable features, are selected and also
bred together. This continues over many generations
until all the offspring show the desirable features.
Examples of these desirable features include:
• wheat plants with large seed grains
• sheep with fine wool
• cattle with high milk yields
• horses with fine features and a very fast pace
However, selective breeding can result in the
inheritance of undesirable characteristics. This is
‘inbreeding’ and can lead to breeds becoming
particularly sensitive to disease or inherited defects
such as hip dysplasia in domestic dogs.
(b)
describe genetic engineering as
a process which involves
modifying the genome of an
organism to introduce desirable
characteristics
The genome of an organism is modified by introducing
into it a gene from another organism. The introduced
gene would allow the required desirable characteristic
to be expressed in the genetically engineered
organism.
Crops that have had their genomes modified in this
way are known as genetically modified (GM) crops.
(c)
describe the main steps in the
process of genetic
engineering
The steps include:
• the gene for the desirable feature is
identified in an host organism
• enzymes are used to cut out the required
gene from the DNA of the host organism
• the gene is inserted into a vector, either a
bacterial plasmid or a virus.
• the vector is used to insert the genes into
cells of animals, plants or microorganisms
at an early stage in their development
• organism develops the desirable features.
(d)
explain some of the possible
benefits and risks, including
practical and ethical
considerations, of using gene
technology in modern agriculture
and medicine
Concerns include the risks of the spread of inserted
genes to other organisms and moral and ethical
concerns about modifying genomes.
Benefits include the possible use of genetic
engineering to treat or overcome inherited human
diseases.
61
COMPONENT 2 – Concepts in Chemistry
1 – PURE SUBSTANCES AND MIXTURES
Spec Statement
Comment
(a)
explain what is meant by the
purity of a substance,
distinguishing between the
scientific and everyday use of the
term 'pure'
A pure substance (element or compound) contains only one
component. 'Pure' orange juice is not pure in the scientific
sense.
(b)
use melting point data to
distinguish pure from impure
substances
A pure substance melts at a fixed temperature. The
presence of impurities always lowers the melting point of a
substance. The melting point of a pure substance is sharp
and impure substances tend to melt over a small
temperature range.
(c)
explain the differences between
elements, compounds and
mixtures
Elements are substances made up of only one type of atom.
Compounds are substances made of two or more different
types of atom that are chemically joined. They have
completely different properties to their constituent elements.
Mixtures consist of two or more substances not chemically
joined. The properties of the substances in a mixture
remain unchanged.
(d)
explain that many useful
materials are formulations of
mixtures, e.g. food and drink
products, medicines, sunscreens,
perfumes and paints
Many everyday products are mixtures in which each
chemical has a particular purpose. Formulations are made
by mixing the components in measured quantities to ensure
that the product has the required properties.
(e)
describe, explain and exemplify
the processes of filtration,
crystallisation, simple distillation
and fractional distillation
(f)
recall that chromatography
involves a stationary and a
mobile phase and that separation
depends on the distribution
between the phases
Candidates should know that different components travel
through the stationary phase at different rates because of
different distribution between phases. In the case of paper
chromatography this is due to differences in solubility; the
more soluble a component, the further it travels on the
chromatogram.
(g)
interpret chromatograms,
including measuring R f values
Candidates are expected to recall the expression used to
calculate R f values.
(h)
suggest chromatographic
methods for distinguishing pure
from impure substances
Candidates should know that gases can be analysed by gas
chromatography (where the mobile phase is a gas) and
liquids can be analysed by paper chromatography (where
the mobile phase is a liquid).
62
(i)
suggest suitable purification
techniques given information
about the substances involved
SPECIFIED PRACTICAL WORK
•
CSP1.1 Separation of liquids by distillation, e.g. ethanol from water, and by paper
chromatography
63
Separation of liquids by distillation, e.g. ethanol from water, and by paper
chromatography
Introduction
A mixture of liquids can be separated by distillation as each liquid will have a different boiling
point. In this experiment, you will separate ethanol from water. Ethanol has the lower boiling point
(78 ºC) and will therefore boil at a lower temperature than water. The vapour will travel into the
condenser where, in the cooler tube, it will condense back into a liquid and is collected in a
separate flask.
Apparatus
distillation apparatus
mixture of ethanol and water
anti-bumping granules
Bunsen burner
clamp stand, clamp and boss
thermometer
2 × watch glasses or evaporating basins
250 cm3 beaker
Diagram of Apparatus
64
Method
1. Add anti-bumping granules to the round bottomed flask (the distilling flask).
2. Add approximately 50 cm3 of the mixture of ethanol and water into the distilling flask.
3. Make sure there is a steady stream of water running through the condenser (from the
bottom to the top).
4. Heat the mixture, so that it boils gently.
5. Collect 5 cm3 of the liquid produced, stop heating and allow to cool.
6. Test the liquid with a lighted splint.
Risk Assessment
Hazard
Risk
Control measure
Ethanol is
flammable
Large volumes of ethanol coming in
to contact with naked flame and
igniting during the distillation
When not distilling, Bunsen burner
should be off
Broken glass is
sharp
Glassware could break when placing
in clamp stand and cause a risk of
cutting
Make sure all parts of apparatus are
clamped securely.
Care to not overtighten
Teacher / Technician notes
Reagents:
 Ethanol - Refer to CLEAPSS Hazcard 40A
A mixture of 80:20, water:ethanol should be used.
Care should be taken not to boil the mixture too vigorously as there is risk of it splashing into the
condenser and it may even crack the flask. Monitor the temperature in the neck and take care
that it doesn’t go higher than approximately 85 ºC.
The ethanol will evaporate due to its lower boiling point (78 ºC) then condense in the cold
condenser back to a liquid which is then collected in the beaker.
Practical techniques covered
C2
Safe use of appropriate heating devices and techniques including use of a Bunsen burner
and a water bath or electric heater.
C4
Safe use of a range of equipment to purify and/or separate chemical mixtures
including evaporation, filtration, crystallisation, chromatography and distillation.
65
2 – PARTICLES AND ATOMIC STRUCTURE
Spec Statement
Comment
(a)
recall and explain the main
features of the particle model in
terms of the states of matter and
changes of state, distinguishing
between physical and chemical
changes
(b)
use data to predict states of
substances under given
conditions
Candidates are expected to recall the melting point (0°C)
and boiling point (100°C) of water but data will be given for
all other substances.
(c)
explain the limitations of the
particle model in relation to
changes of state when
particles are represented by
inelastic spheres
This model provides no explanation as to why different
substances have different melting and boiling points.
This being the case, there must be some difference
between the particles of different substances.
(d)
describe how the particle model
does not explain why atoms of
some elements react with one
another
The explanation of why some elements react with others of
course requires the proton, neutron and electron model of
the atom and an understanding of electronic structure.
(e)
recall that experimental
observations suggest that atoms
are mostly empty space with
almost all the mass in a central
nucleus
Candidates should be familiar with the Geiger-Marsden
experiment and how this led to a new model of the atom.
Detailed recall of the experiment is not required.
(f)
describe the atom as a positively
charged nucleus surrounded by
negatively charged electrons,
with the nuclear radius much
smaller than the atomic radius
(g)
recall that the nucleus includes
protons and neutrons (except in
the case of 1H)
(h)
recall that atoms and small
molecules are typically around
10‒10 m or 0.1 nm in diameter
(i)
recall the relative charges and
approximate relative masses of
protons, neutrons and electrons
Charges need only be described in terms of positive (+1),
neutral (0) and negative (‒1). Protons and neutrons are
considered to have the same mass. That mass is given a
value of 1 atomic mass unit (amu). Electrons have a
negligible mass of approximately 2000 times less than that
of a proton/neutron.
66
(j)
explain why atoms as a whole
have no electrical charge
Candidates should be able to build upon this idea to
explain the charges found on simple ions e.g. Na+, Mg2+,
Cl– and O2–.
(k)
calculate numbers of protons,
neutrons and electrons in atoms
and ions, given atomic number
and mass number of isotopes
Candidates are expected to recall the definitions for atomic
number and mass number. They should use them to give
the numbers of protons, neutrons and electrons present in
any given atom/ion. Question papers in Chemistry will not
refer to proton number or nucleon number.
(l)
describe the electronic structure
of the first 20 elements
(m)
explain how the position of an
element in the Periodic Table is
related to the arrangement of
electrons in its atoms and hence
to its atomic number
Candidates should understand that an element's group
number corresponds to the number of electrons in the
outer shell of its atoms and that the period number is the
number of occupied electron shells.
(n)
describe what is meant by
isotopes and an element’s
relative atomic mass
Candidates should be able to describe the difference
between the atoms of different isotopes, in terms of the
numbers of neutrons present. They should be able to
calculate the relative atomic mass of elements with more
than one isotope.
(o)
explain that the arrangement
proposed by Mendeleev was
based on ‘atomic weights’; in
some cases the order was not
quite correct because different
isotopes have different masses
Early periodic tables placed the elements in strict order of
atomic weight. This resulted in gaps and some elements
being placed in the wrong group. Mendeleev overcame
some of the problems by leaving gaps for elements not yet
discovered. The discovery of isotopes made it possible to
explain why the order based on atomic weights was not
always correct.
67
3 – CHEMICAL FORMULAE, EQUATIONS AND AMOUNT OF SUBSTANCE
Spec Statement
Comment
(a)
use chemical symbols to write the
formulae of elements and simple
covalent and ionic compounds
Recall of common formulae such as H 2 O and CO 2 is
assumed.
(b)
deduce the empirical formula of a
compound from the relative
numbers of atoms present or
from a model or a diagram and
vice versa
(c)
recall and use the law of
conservation of mass
The law of conservation of mass states that no atoms are
lost or made during a chemical reaction so the total mass of
the products equals the total mass of the reactants.
Candidates will be required to use their understanding of this
law to solve numeric problems based on chemical equations.
(d)
use the names and symbols of
common elements and
compounds and the law of
conservation of mass to write
formulae and balanced chemical
equations and half equations
Only higher tier candidates will be required to write half
equations.
(e)
deduce the charge on ions of
elements in groups 1, 2, 3, 6 and
7
Assessment of this point will be in the context of ions not
appearing in the table given in the examination paper, e.g.
Rb+, Sr2+ or S2‒.
(f)
use the formulae of common ions
to deduce the formula of a
compound and write balanced
ionic equations
A table of formulae for common ions (including compound
ions) will be included in all examination papers. Candidates
should be able to apply their understanding in any context.
Only higher tier candidates will be required to write ionic
equations.
(g)
describe the physical states of
products and reactants using
state symbols (s, l, g and aq)
Candidates will be told to include state symbols in questions
where a specific mark is allocated for this skill.
(h)
calculate relative formula mass of
species separately and in
balanced chemical equations
Candidates should be able to calculate relative formula
masses using A r values.
(i)
use a balanced equation to
calculate masses of reactants
or products
Candidates should think of this as a progression from a
balanced symbol equation – and appreciate that
considering the masses of reactants and products is a
good opportunity to check that an equation is correctly
balanced. They will usually be given the balanced
equation in examination questions on this section.
68
(j)
calculate the empirical formula
of a compound from reacting
mass data
(k)
deduce the stoichiometry of an
equation from the masses of
reactants and products and
explain the effect of a limiting
quantity of a reactant
(l)
recall and use the definitions of Candidates should know that one mole of a substance
the Avogadro constant (in
contains the same number of particles as one mole of
standard form) and of the mole any other substance. The number of particles in a mole
of a given substance is the Avogadro constant. The
value of the Avogadro constant is 6.02 × 1023 per mole.
There is no requirement to recall this value.
(m)
explain how the mass of a
given substance is related to
the amount of that substance
in moles and vice versa
Candidates will not be expected to recall the methods
used to collect this type of data but they should show an
understanding of the principles involved when a
description is provided. They should be able to deal
with questions where the percentage composition of the
compound is given, as well as examples where actual
masses are provided. Candidates must show their
working in questions of this type and should be made
aware that data collected may possibly suggest a
formula different to that which they know to be correct,
e.g. incomplete reaction of magnesium with oxygen
could provide data that gives Mg 2 O as the formula for
magnesium oxide.
Candidates are expected to recall the relationship
between number of moles and mass in grams.
69
4 – THE PERIODIC TABLE AND PROPERTIES OF ELEMENTS
Spec Statement
(a)
explain how the reactions of
elements are related to the
arrangement of electrons in their
atoms and hence to their atomic
number
(b)
recall the trends in melting
point/boiling point of elements in
Groups 1, 7 and 0
(c)
recall the reactions of Group 1
elements with Group 7 elements,
with oxygen and with water
Comment
Candidates should understand that elements with the
same number of electrons in their outer shell undergo
similar chemical reactions e.g. as seen in Group 1 and
Group 7.
Candidates are expected to recall observations made
during the reactions of lithium, sodium and potassium
in each case:
• Halogens – flame colours, white products
• Air/oxygen – tarnishing of freshly cut surface
• Burning in air/oxygen – flame colours, white
products
• Water – metals floating, movement on the water
surface and whether or not a ball is formed,
hissing sound, potassium only begins to burn (lilac
flame), lithium doesn't melt as it reacts with water.
Observation includes sounds e.g. fizzing/hissing, but
‘hydrogen formed’ is not an observation.
The tarnishing in air and reaction with water can be
easily demonstrated in the laboratory but burning and
reaction with halogens are best observed through
video clips.
In common with all specified reactions, candidates
should be able to name products and write word and
balanced symbol equations describing those
reactions.
Candidates should know that the elements of Group 1
are known as the alkali metals.
(d)
recall the reactions of Group 7
elements with Group 1 elements
and with iron, and the
displacement reactions of
halogens
Candidates should recall the colours of chlorine,
bromine and iodine in their room temperature states.
Recall of the observations made during the reactions
with iron is not required but candidates should know
that it is the iron(III) salt formed in each case.
Candidates should appreciate that displacement
reactions provide stronger evidence for the decreasing
reactivity down Group 7 than that gained from the
elements’ reactions with iron. Factors such as the
70
halogens’ different states at room temperature can
make it difficult to make a fair comparison of their
reactivities by observation of their reactions with iron
but they compete directly against one another in
displacement reactions.
Candidates should know that solutions of halides are
colourless and that displacement of bromine and
iodine results in the formation of an orange-brown
solution.
Candidates should know that the elements of Group 7
are known as the halogens.
(e)
recall that Group 0 elements are
completely unreactive
Candidates should know that the elements of Group 0
are known as the noble gases.
(f)
explain the reactivities (or
otherwise) of these elements in
terms of their electronic
structures and the desire to
attain/retain a full outer electron
shell
Candidates should understand that elements with
atoms containing full outer electron shells (Group 0)
are unreactive and that other elements react in order
to try to attain the same state. They should
understand, for example, that the atoms of Group 1
metals lose one electron to do so, while those of
Group 7 elements gain one electron.
(g)
explain the trend in reactivities of
elements on descending Group 1
and Group 7
Group 1 metals become more reactive down the
group. The increasing size of the atom/distance from
the positively charged nucleus makes it easier for the
outer electron to be lost.
Group 7 elements become less reactive down the
group. The increasing size of the atom/distance from
the positively charged nucleus results in a smaller
force attracting the additional electron.
(h)
predict properties from trends
within groups
(i)
predict possible reactions and
probable reactivity of elements
from their positions in the
Periodic Table
71
(j)
describe tests to identify
hydrogen, oxygen and chlorine
gases
When a lit splint is placed into a jar/tube containing
hydrogen gas, a squeaky pop is observed.
When a glowing splint is placed into a jar/tube
containing oxygen gas, it re-lights. (Please note that
reference to a flame glowing more brightly
is not acceptable as a test for oxygen gas.)
When damp blue litmus paper is placed in a jar/tube
containing chlorine gas, the paper first turns red and is
then bleached white.
(k)
describe metals and non-metals
and explain the differences
between them on the basis of
their characteristic physical and
chemical properties
(l)
explain how the atomic structure
of metals and non-metals relates
to their position in the Periodic
Table
Candidates should recall the general physical
properties of metals and non-metals. They should
also know that metals form basic oxides while nonmetals form acidic oxides.
72
5 – BONDING, STRUCTURE AND PROPERTIES
Spec Statement
Comment
(a)
describe and compare the nature
and arrangement of chemical
bonds in ionic compounds, simple
molecules, giant covalent
structures, polymers and metals
(b)
explain ionic bonding in terms of
electrostatic forces and the
transfer of electrons
(c)
construct dot and cross diagrams
to show ionic bonding in simple
ionic substances
It should be emphasised to candidates that the dot/cross
notation should be used to ensure that it is completely
clear which electrons have been transferred in forming ions
and that no electrons should appear to be in two places at
once.
(d)
explain the physical properties of
ionic compounds in terms of their
lattice structure
Candidates should use this model to explain why ionic
compounds have high melting/boiling points, are soluble in
water and conduct electricity when dissolved or in molten
form.
(e)
explain covalent bonding in terms
of the sharing of electrons
(f)
construct dot and cross diagrams
to show covalent bonding in
simple molecules
Use of the dot/cross notation to show from which atom a
given electron has come should again be emphasised.
(g)
explain the physical properties of
simple covalent substances in
terms of intermolecular bonding
Candidates should use this model to explain why simple
molecular substances have low melting/boiling points.
They should also explain why simple covalent substances
do not conduct electricity, even in molten form.
(h)
explain metallic bonding in terms
of electrostatic forces between
the ‘sea’ of electrons/lattice of
positive ions
(i)
explain the physical properties of
metals in terms of the above
model
Candidates should use this model to explain why, in
general, metals have high melting/boiling points, are good
conductors of heat and electricity and are malleable and
ductile. Higher tier candidates should be able to
explain the trend in melting/boiling point from sodium
to magnesium to aluminium, in terms of the numbers
of electrons lost by each atom and the charges on the
ions.
73
(j)
describe the limitations of the
different representations and
models of bonding, including dot
and cross diagrams, ball and
stick models and two and three
dimensional representations
(k)
recall that carbon atoms can form
four covalent bonds
(l)
explain that the huge number of
natural and synthetic organic
compounds we use today occur
due to the ability of carbon to
form families of similar
compounds, chains and rings
Different models are useful in explaining different ideas but
none of them capture all the important details. The
strengths and weaknesses of each model should be
considered, e.g. a dot and cross diagram shows exactly
which atom in a molecule has contributed each electron to
a bond but it does not show the shape of the molecule; a
ball and stick model shows the molecular shape but little
about the nature of the bond.
(m)
explain the properties of
diamond, graphite, fullerenes and
graphene in terms of their
structure and bonding
Candidates should recognise each of these as giant
structures containing covalent bonds. Candidates should
know that the very high melting points of diamond and
graphite are a result of the strong covalent bonding
present. Their differing hardness, brittleness, lubricating
and conducting properties are a result of each carbon atom
in diamond being strongly bonded to four others whilst
each one in graphite forms only three strong bonds.
Candidates should explain these differences in terms of the
graphite carbon atoms’ fourth ‘delocalised’ or ‘free’
electron. Candidates should know that fullerenes are cage
structures made entirely of carbon atoms.
Buckminsterfullerene is the most widely-known fullerene.
Its molecules are spherical and contain 60 carbon atoms.
Research into the use of fullerenes as drug delivery
systems in the body, in lubricants and as catalysts is ongoing. Graphene has been shown to be the strongest
material ever tested and also the best electrical conductor
but although claims have been made that it will transform
technology in the future, there are as yet no commercially
available 'graphene products'.
(n)
use ideas about energy transfers
and the relative strength of
chemical bonds and
intermolecular forces to explain
the different temperatures at
which changes of state occur
The lower the amount of energy required to break bonds/
overcome forces between particles, the lower the
temperature required to cause a change of state.
74
(o)
recognise that individual atoms
do not have the same properties
as bulk materials as
demonstrated by the different
properties of diamond, graphite,
fullerenes and graphene, which
all contain carbon atoms only,
and by nano-scale silver particles
exhibiting properties not seen in
bulk silver
(p)
recall the multiplying factors milli(10‒3), micro- (10‒6) and nano(10‒9)
75
6 – REACTIVITY SERIES AND EXTRACTION OF METALS
Spec Statement
Comment
(a)
explain how the reactivity of
metals with water or dilute acids
is related to the tendency of the
metal to form its positive ion
(b)
investigate the relative reactivities
of metals by displacement (e.g.
iron nail in copper(II) chloride
solution) and competition
reactions (e.g. thermit reaction)
(c)
deduce an order of reactivity of
metals based on experimental
results
(d)
explain that the method used to
extract a metal from its ore is
linked to its position within the
reactivity series in relation to
carbon
Gold and silver are examples of metals that are found native.
Candidates should know that the most reactive metals are
extracted by electrolysis while those towards the middle of the
reactivity series can be chemically reduced. They may be
required to use information such as, “X is more/less reactive
than carbon…” to suggest a method of extraction for any
metal. Candidates should have an awareness of the
approximate position of common metals (and carbon and
hydrogen) in the reactivity series but detailed recall is not
required.
(e)
explain reduction and oxidation in
terms of loss or gain of oxygen,
identifying which species are
oxidised and which are reduced
e.g. during thermit reaction and in
the blast furnace
Candidates should be able to recognise loss or gain of
oxygen in any given reaction. They should be precise in their
descriptions e.g. iron(III) oxide – not iron – is reduced in the
blast furnace.
(f)
explain reduction and
oxidation in terms of gain or
loss of electrons, identifying
which species are oxidised and
which are reduced e.g. during
displacement reactions and
electrolysis
Candidates should be able to recognise gain or loss of
electrons in any given reaction e.g. Pb2+ ions are reduced
during the electrolysis of lead(II) bromide because they
gain electrons to form Pb atoms; Br‒ ions are oxidised
because they lose electrons. Defining reduction and
oxidation in terms of electrons is useful when reactions
do not involve oxygen.
The emphasis is on the understanding of the processes and
not on recall of colours of elements, compounds or solutions,
although information of this nature these may be given in a
question.
76
(g)
explain the principles of
extraction of iron from iron ore in
the blast furnace, including
reduction by carbon monoxide
and the acid/base reaction that
forms slag
Candidates are expected to name each of the raw materials
that are added to the furnace and to explain why they are
needed:
• Iron ore – source of iron
• Coke – as a fuel and to produce carbon monoxide for the
reduction
• Limestone – to remove impurities (slag formation when
limestone breaks down and reacts with sand from the
rocks)
• Hot air – provides oxygen so that coke can burn
Candidates should be able to write word and balanced symbol
equations for the combustion of carbon, reduction of iron(III)
oxide by carbon monoxide, decomposition of calcium
carbonate and the neutralisation reaction between calcium
oxide and silicon dioxide.
(h)
describe electrolysis of molten
ionic compounds, e.g. lead(II)
bromide, in terms of the ions
present and reactions at the
electrodes
(i)
recall that metals (or hydrogen)
are formed at the cathode and
non-metals are formed at the
anode in electrolysis using inert
electrodes
(j)
predict the products of
electrolysis of binary ionic
compounds in the molten state
(k)
explain why and how electrolysis
is used to extract reactive metals
from their ores
Candidates should know that for electrolysis to proceed,
compounds must be melted to release their ions. They
should explain electrolysis in terms of positive ions moving
towards the cathode where they gain electrons forming metal
atoms, and negative ions moving towards the anode where
they lose electrons forming molecules of the non-metal.
Higher tier candidates should be able to write half
equations for the processes taking place at the
electrodes.
Reactive metals like sodium and aluminium are extracted by
electrolysis. Electrolysis is required because carbon cannot
displace metals higher than it in the reactivity series. This
process uses vast amounts of electricity.
77
(l)
explain the principles of
extraction of aluminium from
aluminium ore (bauxite), including
the use of cryolite
Candidates should know that aluminium oxide (from bauxite)
dissolves in molten cryolite at a temperature much lower than
its melting point, therefore saving energy. Candidates should
know that aluminium ions travel to the cathode and that they
gain electrons and form aluminium atoms, whilst oxide ions
travel to the anode and lose electrons forming oxygen gas.
They should be able to write a balanced equation for the
overall reaction taking place.
Higher tier candidates should be able to write half
equations for the processes occurring at the cathode and
the anode.
Al3+ + 3e– → Al
2O2– → O 2 + 4e–
Candidates at both tiers should know that the oxygen formed
reacts with the carbon anodes, forming carbon dioxide gas
and requiring these to be replaced frequently.
(m)
evaluate the methods of
bacterial metal extraction and
phytoextraction
Higher tier candidates should be familiar with the
following methods of copper extraction but detailed recall
is not required.
Copper ores are becoming scarce and new ways of
extracting copper from low-grade ores include bacterial
extraction (bioleaching) and phytoextraction.
Bioleaching
• bacteria absorb copper compounds to form a solution
called a leachate
Phytomining
• plants absorb copper compounds through their roots
whilst growing
• plants are cropped
• cropped plants are burned to produce ash
• ash mixed with water to form a solution containing
copper compounds
Copper can be obtained from both solutions by either
displacement or electrolysis.
Both methods avoid the usual disadvantages associated
with mining and traditional extraction methods.
Advantages include: low cost, less environmental impact
than traditional methods
Disadvantages include: extremely slow process, toxic
chemicals formed
78
(n)
describe electrolysis of water in
terms of the ions present and
reactions at the electrodes
Candidates should know that hydrogen ions travel to the
cathode and that they gain electrons and form hydrogen gas,
whilst hydroxide ions travel to the anode and lose electrons
forming oxygen gas. They should be able to explain why the
volume of hydrogen formed is twice that of oxygen. They
should be able to write a balanced equation for the overall
reaction.
Higher tier candidates should be able to write a half
equation to show the reaction taking place at the cathode
and to balance the equation (atoms and charges) for the
reaction taking place at the anode. They are not required
to recall this equation.
2H+ + 2e– → H 2
2OH– → O 2 + 2H+ + 4e‒
(o)
describe competing reactions in
the electrolysis of aqueous
solutions, e.g. copper(II) chloride,
sodium chloride and sulfuric acid,
in terms of the different species
present
Candidates should know that there are H+ and OH‒ ions
present in an aqueous solution as well as the ions from the
dissolved salt. They should know that metals lower in the
reactivity series than hydrogen are formed at the cathode. In
the case of copper(II) chloride solution, the products are
copper metal and chlorine gas. They should be able to write
a balanced equation for the overall reaction.
Higher tier candidates should be able to write half
equations for the processes occurring at the cathode and
the anode e.g.
Cu2+ + 2e– → Cu
2Cl– → Cl 2 + 2e–
Candidates at both tiers should know that when the dissolved
salt contains ions of metals higher in the reactivity series than
hydrogen, it is hydrogen gas rather than the metal that forms
at the cathode. Electrolysis of sodium chloride solution
therefore gives hydrogen gas and chlorine gas.
Electrolysis of sulfuric acid gives hydrogen gas and oxygen
gas. In this case candidates are not expected to explain the
reaction taking place at the anode.
Higher tier candidates should again be able to write half
equations showing the formation of hydrogen and
chlorine.
(p)
recall the properties of aluminium,
copper, iron and titanium
(q)
explain how the properties of
metals are related to their uses
and select appropriate metals
given details of the usage
required
79
SPECIFIED PRACTICAL WORK
•
•
CSP6A Determination of relative reactivities of metals through displacement
reactions
CSP6B Investigation into electrolysis of aqueous solutions and electroplating
80
Determination of relative reactivities of metals through displacement reactions
Introduction
Some metals are more reactive than others. In this experiment, a piece of metal is added to a
solution of a compound of another metal. A more reactive metal displaces a less reactive metal
from its compound. By carrying out this experiment, you will be investigating the competition
reactions of metals and produce a reactivity series of the metals.
Apparatus
dimple tray
100 cm3 beaker
4 × dropping pipettes
5 cm3 of each of the following at 0.1 mol/ dm3
 zinc sulfate
 magnesium sulfate
 copper(II) sulfate
 iron(II) sulfate
Approximately 1 cm length/square sample of the following metals.
 zinc
 magnesium
 copper
 iron
Diagram of Apparatus
81
Method
1. Using a dropping pipette, put a little zinc sulfate in four of the depressions of the dropping
tile. Do this for each solution in turn. Do not overfill dimples.
2. Put a piece of metal in each of the solutions, using the apparatus diagram as a guide.
3. Observe and record the changes in the solutions or metal samples.
Analysis
1.
Use your results to construct a reactivity series for the metals used. Write equations for any
reactions that occurred.
Risk Assessment
Hazard
Salt solutions
are harmful
Risk
Whilst dispensing the solutions they
can be squirted into eyes or if spilt
onto hands, solutions can be
transferred to eyes
Control measure
Wear eye protection
Wash hands when solutions spilt on to
hands
Teacher / Technician notes
Reagents
 Zinc sulfate - Refer to CLEAPSS hazcard 108
 Magnesium sulfate - Refer to CLEAPSS hazcard 59B
 Copper(II) sulfate - Refer to CLEAPSS hazcard 27B
 Iron(II) sulfate - Refer to CLEAPSS hazcard 38
 Zinc foil - Refer to CLEAPSS hazcard 107
 Magnesium ribbon - Refer to CLEAPSS hazcard 59A
 Copper foil - Refer to CLEAPSS hazcard 26
 Iron(II) sulfate - Refer to CLEAPSS hazcard 38
Solutions may be dispensed in small beakers to each group of students or in small dropper
bottles.
Students may need two dimple trays per group, if trays do not contain 16 dimples.
Metals should be approximately 1 cm lengths/squares of ribbon or foil cleaned with an emery
cloth and as similar in size as possible.
Students will need to record which metals react with the solutions. A table may be useful. Use a
✓ to show reactivity and a ✗ to show no reaction. The metals with the most ticks are the most
reactive.
82
Students should design their own table, but a suggested table format is shown below.
Zinc
Magnesium
Copper
Iron
Zinc sulfate
Magnesium sulfate
Copper(II) sulfate
Iron(II) sulfate
You can point out to students that there is no need to carry out the zinc/zinc sulfate,
magnesium/magnesium sulfate reactions, etc or allow them to decide for themselves if these
reactions are likely to lead to a positive result.
Remind students that they are looking for metal displacement, some solutions are slightly acidic
so bubbles of hydrogen can be seen. Explain that this doesn’t count as displacement. Students
may need to be given guidance of the sort of observations they may expect to see.
It may be best to get the class to tell you what they think the order of reactivity is while they still
have the evidence in front of them, so that discrepancies can be resolved.
There are many ways of carrying out this series of reactions. The one described here uses a
dimple tray, but it can be adapted with test tubes. The advantages of the dimple tray are the
small amounts of chemical involved and the way the results are displayed.
Practical techniques covered
C5
Making and recording of appropriate observations during chemical reactions
including changes in temperature and the measurement of rates of reaction by a variety
of methods such as production of gas and colour change.
83
Investigation into electrolysis of aqueous solutions and electroplating
Introduction
In this experiment you will carry out the electrolysis of copper(II) sulfate solution and link your
findings to industrial copper purification and copper plating.
Apparatus
250 cm3 beaker
2 × graphite electrodes (about 5 mm diameter)
clamp stand, boss and clamp
12 V d.c. power supply
leads and crocodile clips
200 cm3 copper(II) sulfate, about 0.5 mol/dm3
Diagram of Apparatus
Method
1.
2.
3.
4.
Measure 200 cm3 of copper(II) sulfate into the beaker.
Set up the apparatus as in the diagram.
Switch on the power supply.
After 2 minutes record any observations seen at the electrodes.
84
Risk Assessment
Hazard
Copper sulfate
is harmful
Risk
Control measure
Copper sulfate splashed onto hands Wear eye protection
whilst pouring could be transferred to Wash hands if copper sulfate spilt on
eyes
them
Teacher / Technician notes
•
Copper sulfate solution - Refer to CLEAPSS hazcard 26
There are several ways of securing the graphite electrodes. Using a clamp stand and clamp is
probably the most convenient. They can also be fixed on to a small strip of wood or cardboard
resting on the top of the beaker.
A lamp can be included in the circuit to indicate that there is a flow of current.
As an extension to the basic experiment, strips of copper can be used in place of the graphite
rods.
After setting up the cell as shown students can observe changes to each of the electrodes. They
should see a deposit of copper forming on the cathode. This will often be powdery and uneven. It
can be explained that, if the current used is much lower, then the solid coating is shiny,
impermeable and very difficult to rub off; this process forms the basis of electroplating.
Bubbles of gas (oxygen) are formed at the anode.
Cathode
Cu2+(aq) + 2e-
Anode
2H 2 O(l)
Cu(s)
O 2 (g) + 4H+(aq) + 4e-
With copper electrodes, the copper anode dissolves. The reaction is the reverse of the cathode
reactions.
With graphite electrodes, the oxygen usually reacts with the anode to form CO 2 .
The results can lead to a discussion about electroplating and the electrolytic purification of
copper. It is useful to allow students to copperplate metal objects supplied by the school and
previously tested for their suitability. Personal items should not be used. In many cases, an
alternative redox reaction often takes place before any current is actually passed.
85
After doing the electrolysis as described above, the electrodes can be interchanged. Students
can then see the copper disappearing from the surface of the copper-coated anode.
Cu(s)  Cu2+(aq) + 2eThis leads to a discussion as to why, during electrolysis, the:
-
anode consists of an unrefined sample of the metal.
cathode is made of pure copper or a support metal such as stainless steel.
Practical techniques covered
C3
Use of appropriate apparatus and techniques for conducting and monitoring chemical
reactions, including appropriate reagents and/or techniques for the measurement of
pH in different situations.
C5
Making and recording of appropriate observations during chemical reactions
including changes in temperature and the measurement of rates of reaction by a variety
of methods such as production of gas and colour change.
C6
Safe use and careful handling of gases, liquids and solids, including careful mixing of
reagents under controlled conditions, using appropriate apparatus to explore
chemical changes and/or products.
C7
Use of appropriate apparatus and techniques to draw, set up and use electrochemical
cells for separation and production of elements and compounds.
86
7 – CHEMISTRY OF ACIDS
Spec Statement
Comment
(a)
recall that acids react with some
metals and with bases (including
alkalis) and carbonates
When an acid reacts with a metal, a solution of the
metal salt and hydrogen gas are produced. Metal
oxides and metal hydroxides are known as bases and
an alkali is a soluble base.
(b)
write equations predicting
products from given reactants
(c)
describe a test to identify carbon
dioxide gas
When carbon dioxide gas is passed through limewater
the solution turns milky. (Please note that reference
to extinguishing a lit splint or flame is not acceptable
as a test for carbon dioxide gas.)
(d)
describe a test to identify
carbonate ions using dilute acid
Effervescence (fizzing) is observed when an acid
reacts with a carbonate. Note that ‘carbon dioxide
formed’ is not an observation.
(e)
recall that acids form hydrogen
ions when they dissolve in water
and solutions of alkalis contain
hydroxide ions
(f)
recall that acidity and alkalinity
are measured by pH and how to
measure pH using pH indicator
chart and digitally
Acids and alkalis can be classified as being either
strong or weak. Universal indicator and the pH scale
are used to for this purpose. Candidates should recall
associated colours, approximate pH values and
acid/alkali strength e.g. orange > pH ~3/4 > weak
acid.
(g)
describe neutralisation as acid
reacting with base to form a salt
plus water (or with carbonate to
form a salt plus water and carbon
dioxide)
The reactions of acids with bases always produce a
metal salt and water and acids and carbonates
produce carbon dioxide gas in addition to a salt and
water. Neutralisation reactions are exothermic and
effervescence (fizzing) is observed when an acid
reacts with a carbonate.
(h)
prepare crystals of soluble salts
from insoluble bases and
carbonates
Candidates should know the method used to prepare
crystals of soluble salts from the reaction of acids with
insoluble bases and carbonates:
• excess base/carbonate to use up all acid;
• filtration to remove excess base;
• evaporation of water to form crystals.
They should know that small crystals can be formed
quickly by heating to evaporate until about ⅓ of the
solution remains and leaving to cool. Allowing the
filtered solution to evaporate slowly over a period of
days results in the formation of larger crystals.
87
(i)
use a titration method to prepare
crystals of soluble salts and to
determine relative concentrations
of strong acids and strong alkalis
Candidates should know the method used to prepare
crystals of soluble salts from the reaction of acids with
alkalis:
• indicator and fixed volume of acid/alkali in flask;
• exact volume of alkali/acid needed for
neutralisation is measured and recorded;
• same fixed volume of acid/alkali in clean flask and
exact volume of alkali/acid needed for
neutralisation is added but with no indicator;
• evaporation of water to form crystals.
All candidates should be able to compare relative
concentrations of acid/alkali on the basis that if, for
example, 25cm3 of NaOH requires 30cm3 of HCl to
neutralise it, the alkali must be of higher concentration
than the acid.
(j)
recognise that aqueous
neutralisation reactions can be
generalised to hydrogen ions
reacting with hydroxide ions to
form water
H+ + OH‒ → H 2 O
Candidates at both tiers should know that
neutralisation reactions can be summarised by this
ionic equation.
(k)
use and explain the terms
dilute and concentrated
(amount of substance) and
weak and strong (degree of
ionisation) in relation to acids
Candidates should know that any acid (or any
solution) can be dilute or concentrated whilst any
given acid is either strong or weak, e.g.
hydrochloric acid is a strong acid (pH 1) and
ethanoic acid is a weak acid (pH 3). They should
understand that a strong acid is fully dissociated
whilst a weak acid is only partly dissociated.
(l)
describe the observed differences Candidates should know that weak acids, such as
between reactions of strong acids ethanoic acid, react with metals, bases (including
and weak acids
alkalis) and carbonates in the same way as strong
acids but that the reactions occur more slowly and are
less exothermic. They should know that ethanoic acid
forms salts called ethanoates, e.g. sodium ethanoate
is formed when it reacts with sodium hydroxide.
(m)
recall that as hydrogen ion
concentration increases by a
factor of ten the pH value of a
solution decreases by one
For example a solution with a hydrogen ion
concentration of 0.01 mol / dm3 has a pH of 2. A
0.1 mol / dm3 solution of hydrogen ions is 10 times
as concentrated and has a pH of 1.
(n)
describe neutrality and relative
acidity and alkalinity in terms
of the effect of the
concentration of hydrogen ions
on the numerical value of pH
(whole numbers only)
For example if the hydrogen ion concentration of a
solution of pH 2 is reduced by a factor of 10 then
its pH will be 3. If it reduced by a further factor of
10 it will be 4 and so on.
88
(o)
explain how the mass/number
of moles of a solute and the
volume of the solution is
related to the concentration of
the solution
Candidates are required to recall the relationship
between mass/number of moles, volume and
concentration and be able to use it appropriately.
SPECIFIED PRACTICAL WORK
•
•
SP7A Preparation of crystals of a soluble salt from an insoluble base or carbonate
SP7B Titration of a strong acid against a strong base using an indicator
89
Preparation of crystals of a soluble salt from an insoluble base or carbonate
Introduction
In this experiment you will make crystals of copper sulfate. This can be done using either copper
carbonate or copper oxide.
copper
carbonate
CuCO 3 (s)
+
sulfuric
acid
+ H 2 SO 4 (aq)
copper
+ water + carbon
sulfate
dioxide
CuSO 4 (aq) + H 2 O(l) + CO 2 (g)
copper
oxide
CuO(s)
+
copper
sulfate
CuSO 4 (aq)
sulfuric
acid
+ H 2 SO 4 (aq)
Apparatus
100 cm3 beaker
stirring rod
filter funnel and paper
evaporating basin
50 cm3 measuring cylinder
0.5 mol/dm3 H 2 SO 4
copper(II) oxide or copper carbonate
spatula
indicator paper
Access to:
electronic balance ± 0.1 g
Diagram of Apparatus
90
+
water
+
H 2 O(l)
Method
1. Measure 50 cm3 of sulfuric acid and pour into the beaker.
2. Measure approximately 4 g copper (II) oxide or 5 g copper(II) carbonate. (This does not need
to be precise as the solid will be in excess.)
3. Add the solid to the acid and stir thoroughly.
4. To ensure all the acid has reacted, touch the glass rod onto a piece of indicator paper. If it
is acidic continue stirring.
5. If the solution is neutral, pour the mixture into the filtration apparatus above the evaporating
basin.
6. Allow to evaporate for several days until dry.
Risk Assessment
Hazard
Sulfuric acid is
corrosive
Copper sulfate is
harmful
Risk
Risk of splashing into eyes
whilst stirring
Risk of splashing into eyes
whilst stirring
Control measure
Take care whilst stirring and wear eye
protection
Take care whilst stirring and wear eye
protection
Hot tripod and
evaporating basin
can burn
Risk of burning hands when
touching hot tripod / basin
Leave apparatus to cool before moving.
Teacher / Technician notes
Reagents:
•
•
•
•
Copper(II) oxide - Refer to CLEAPSS hazcard 26
Copper(II) carbonate - Refer to CLEAPSS hazcard 26
Sulfuric acid - Refer to CLEAPSS hazcard 98A
Copper sulfate solution - Refer to CLEAPSS hazcard 26
50 cm3 of copper sulfate solution requires medium to large evaporating basins. Quantities can be
reduced to suit available equipment. However it is vital that the solid is always in excess.
It can be emphasised that the reason for adding the insoluble base in excess is to ensure all of
the acid has reacted and that a pure sample of the salt can thus be obtained.
At method point 6, it is possible to heat the evaporating basin to reduce the volume of copper
sulfate solution by approximately a third using a Bunsen burner. This will reduce the time needed
to reach dryness.
There is also scope for extension work – the mass of the base added could be weighed
accurately and recorded. The mass of excess could then be obtained and thus the number of
moles of copper sulfate produced could be calculated.
91
Practical techniques covered
C2
Safe use of appropriate heating devices and techniques including use of a Bunsen burner
and a water bath or electric heater.
C4
Safe use of a range of equipment to purify and/or separate chemical mixtures
including evaporation, filtration, crystallisation, chromatography and distillation.
92
Titration of a strong acid against a strong base using an indicator
Introduction
In this experiment sodium hydroxide is neutralised with hydrochloric acid to produce the soluble
salt, sodium chloride in solution. An indicator is used to show when neutralisation has occurred.
The solution could then be concentrated and crystallised to produce sodium chloride crystals.
Apparatus
burette
measuring cylinder
100 cm3 conical flask
small filter funnel
white paper
dilute sodium hydroxide
dilute hydrochloric acid
indicator
clamp stand, boss and clamp or burette stand
Diagram of Apparatus
93
Method
1.
Use the small funnel to fill the burette with acid. Run a little acid out into a waste beaker to
fill the part of the burette that is below the tap. Record the starting volume of acid in the
burette.
Accurately measure 25 cm3 of sodium hydroxide solution into a conical flask.
Add 2 drops of indicator.
Add 0.1 cm3 of acid at a time, swirl the flask after each acid addition. Keep adding acid
until the indicator changes colour. Record the final volume of acid in the burette.
Repeat steps 1-4 twice more.
2.
3.
4.
5.
Analysis
1.
2.
Calculate the volume of acid that was needed to neutralise the alkali in each repeat.
Calculate the mean volume of dilute hydrochloric acid needed to neutralise 25 cm3 sodium
hydroxide solution.
What do your results tell you about the concentration of the alkali?
3.
Risk Assessment
Hazard
Hydrochloric
acid and
sodium
hydroxide are
corrosive
Burette and
pipette made
from glass
which is brittle
and is sharp if
broken
Risk
Hydrochloric acid or sodium
hydroxide spilling onto hands when
filling burette or measuring volume of
liquids
Control measure
Wear gloves
Wash hands immediately after contact
with solutions
Hydrochloric acid or sodium
hydroxide splashing into eyes when
filling burette
Wear goggles
Burette breaking when clamping
giving danger of cuts.
Take care when clamping burette not to
overtighten
Pipette breaking when being
handled giving danger of cuts.
Take care when using pipette
Teacher / Technician notes
Reagents:
•
•
Hydrochloric acid – Refer to CLEAPSS hazcard 47A
Sodium hydroxide – Refer to CLEAPSS hazcard 31
94
Sodium hydroxide and hydrochloric acid solutions do not need to be made up to a high degree of
accuracy, but should be reasonably close to the same concentration and less than 0.5 mol/dm3.
Burette stands and clamps are designed to prevent crushing of the burette by over-tightening,
which may happen if standard jaw clamps are used.
A white tile can be used to go under the titration flask, instead of white paper.
Students need training in using burettes correctly, including how to clamp them securely and fill
them safely. You should consider demonstrating burette technique, and give students the
opportunity to practise this. Students do not need the acid volume to start on zero in the burette,
but must ensure that the reading is not above zero.
In this experiment, a pipette is not essential and measuring cylinder is acceptable. However, a
pipette and filler could be used to increase accuracy if desired.
There is an opportunity here with more able students to do quantitative measurements, leading to
calculations, but the primary aim is to introduce students to the titration technique to produce a
neutral solution.
Indicators you can use include screened methyl orange (green in alkali, violet in acid) and
phenolphthalein (pink in alkali, colourless in acid).
At the end of the experiment the solution can be left to crystallise slowly in a warm room to
produce large crystals or heated to half the volume of solution with a Bunsen burner and allowed
to cool.
Students should design their own table, but a suggested table format is shown below.
1
Trial
2
Final volume of
acid in burette
(cm3)
Initial volume
of acid in
burette (cm3)
Titre (volume
added) (cm3)
95
3
Mean
Practical techniques covered
C1
Use of appropriate apparatus to make and record a range of measurements accurately,
including mass, time, temperature and volume of liquids and gases.
C3
Use of appropriate apparatus and techniques for conducting and monitoring chemical
reactions, including appropriate reagents and/or techniques for the measurement of
pH in different situations.
C6
Safe use and careful handling of gases, liquids and solids, including careful mixing of
reagents under controlled conditions, using appropriate apparatus to explore
chemical changes and/or products.
96
8 – ENERGY CHANGES IN CHEMISTRY
Spec Statement
Comment
(a)
distinguish between endothermic
and exothermic reactions on the
basis of the temperature change
of the surroundings
The emphasis here should be on interpretation of
experimental data to identify exothermic and endothermic
reactions. There is no requirement for candidates to recall
examples of endothermic reactions but they do need to
know that combustion and neutralisation reactions are
exothermic.
(b)
draw and label a reaction profile
for an exothermic and an
endothermic reaction, identifying
activation energy
(c)
explain activation energy as the
energy needed for a reaction to
occur
Candidates should know that this is the minimum amount
of energy required to start a reaction.
(d)
calculate energy changes in a
chemical reaction by
considering bond making and
bond breaking energies
Candidates should be able to calculate the total
amount of energy required to break bonds and the
total amount released in forming bonds during a given
reaction, and use those values to find the overall
energy change for the reaction. They should explain
that a reaction is exothermic because more energy is
released in forming bonds than is required to break
bonds, rather than by stating simply that the overall
energy change has a negative value. They should be
able to apply their understanding to more complex
questions, e.g. where the given data is used to
calculate a bond energy value.
SPECIFIED PRACTICAL WORK
•
CSP8 Determination of the amount of energy released by a fuel
97
Determination of the amount of energy released by a fuel
Introduction
Fuels react with oxygen when they burn, releasing energy. You will burn four different alcohols
and compare the energy they give off.
Alcohol + oxygen
carbon dioxide + water
Apparatus
clamp stand, clamp and boss
250 cm3 conical flask
100 cm3 measuring cylinder
thermometer
Access to:
electronic balance ± 0.01 g
4 × spirit burners containing methanol, ethanol, propanol, butanol
Diagram of Apparatus
98
Method
Measure 100 cm3 of water into the conical flask.
Clamp the flask at a suitable height so the spirit burner can be placed below it (as shown
in the diagram - make sure that the thermometer does not touch the bottom of the flask).
Record the temperature of the water.
Record the mass of the spirit burner (including the lid and alcohol).
Place the spirit burner under the conical flask and light it.
Allow the burner to heat the water until the temperature rises by about 40 °C. Record the
temperature of the water.
Extinguish the flame carefully and record the mass of the burner.
Repeat steps 1-7 with each of the other alcohols.
1.
2.
3.
4.
5.
6.
7.
8.
Analysis
1. Calculate the temperature rise for each fuel.
2. Calculate the mass of each alcohol burnt.
3. Calculate the energy released for each alcohol using the following equation.
Energy released from alcohol per gram (J) =
mass of water (g)×temperature increase (°C)×4.2
mass of alcohol (g)
Risk Assessment
Hazard
Methanol is harmful
and highly
flammable
Ethanol is highly
flammable
Propanol is highly
flammable and an
irritant
Butanol is highly
flammable and
harmful if swallowed
Risk
May set light to / burn
individuals or equipment.
Vapour can cause irreversible
damage
May set light to / burn
individuals or equipment
May set light to / burn
individuals or equipment
Vapour may irritate respiratory
system and may irritate skin if
spilt
99
Control measure
Work in a well ventilated lab. Wear eye
protection and ensure work station is
clear
Work in a well ventilated lab. Wear eye
protection and ensure work station is
clear
Work in a well ventilated lab. Wear eye
protection and ensure work station is
clear
Work in a well ventilated lab. Rinse
immediately if spilt on skin
Teacher / Technician notes
Methanol - Refer to CLEAPSS hazcard 40B
Ethanol - Refer to CLEAPSS hazcard 40A
Propanol - Refer to CLEAPSS hazcard 84A
Butanol - Refer to CLEAPSS hazcard 84B
Pentanol should not be used as a fume cupboard is needed - Refer to CLEAPSS hazcard 84C.
Spirit burners should not be used for more than one alcohol. Make sure that the wick fits tightly in
the holder and the holder sits tightly in the container.
Students should not fill or refill spirit burners.
An extension activity could be to plot a graph of the number of carbon atoms in the alcohol
against the energy released per gram.
No repeats are planned in this experiment, but can be carried out if time allows. Alternatively,
groups can compare results to discuss reproducibility.
Students should design their own table, but a suggested table format is shown below.
Alcohol
Initial
mass
of
burner
(g)
Final
mass
of
burner
(g)
Change
Initial
in mass
temperature
of burner
(ºC)
(g)
Final
temperature
(ºC)
Temperature
increase
(ºC)
Energy
released
per gram
(J)
Practical techniques covered
C1
Use of appropriate apparatus to make and record a range of measurements accurately,
including mass, time, temperature and volume of liquids and gases.
C5
Making and recording of appropriate observations during chemical reactions
including changes in temperature and the measurement of rates of reaction by a variety
of methods such as production of gas and colour change.
C6
Safe use and careful handling of gases, liquids and solids, including careful mixing of
reagents under controlled conditions, using appropriate apparatus to explore
chemical changes and/or products.
100
9 – RATE OF CHEMICAL CHANGE AND DYNAMIC EQUILIBRIUM
Spec Statement
Comment
(a)
suggest practical methods for
determining the rate of a given
reaction – from gas collection,
loss of mass and precipitation
(including using data-logging
apparatus)
Candidates should recognise that a rate measures a
change over a given time. They should be familiar
with gas collection and mass loss methods of studying
the rates of reactions such as acids and
metals/carbonates, as well as the precipitation
reaction of dilute hydrochloric acid and sodium
thiosulfate.
(b)
explain any observed changes in
mass in non-enclosed systems
during a chemical reaction using
the particle model
(c)
interpret rate of reaction graphs
Candidates should be able to draw a tangent to a
curve and use this to calculate rate at a given point.
(d)
describe the effect of changes in
temperature, concentration
(pressure) and surface area on
rate of reaction
The rate of reaction is increased by increasing
temperature, concentration (pressure) and surface
area. Candidates should appreciate that decreasing
solid particle size increases surface area.
(e)
explain the effects on rates of
reaction of changes in
temperature and concentration
(pressure) in terms of frequency
and energy of collision between
particles
Candidates should understand that particles of
reactants must collide in order for a reaction to occur
and that these collisions must have energy greater
than the activation energy to be 'successful'. The
greater the number of successful collisions in a given
time, the faster the reaction/higher the rate.
(f)
explain the effects on rates of
reaction of changes in the size of
the pieces of a reacting solid in
terms of surface area to volume
ratio
(g)
describe the characteristics of
catalysts and their effect on rates
of reaction
A catalyst is a substance that increases the rate of a
reaction while remaining chemically unchanged.
(h)
identify catalysts in reactions
Candidates are not expected to recall the names of
specific catalysts other than those named in other
parts of the specification, e.g. iron in the Haber
process. They should know that a catalyst does not
appear as a reactant in a chemical equation.
(i)
explain catalytic action in terms of
activation energy
Catalysts increase the rate of a reaction by lowering
the minimum energy required for successful collisions.
101
(j)
recall that enzymes act as
catalysts in biological systems
Candidates should understand what is meant by an
enzyme’s optimum temperature and that enzymes are
denatured at high temperature e.g. over about 60°C.
No explanation of how enzymes work, i.e. the lock and
key idea, is expected.
(k)
recall that some reactions may be
reversed by altering reaction
conditions
Candidates should know that a reversible reaction is
one that can go in either direction. Certain conditions
may favour the forward reaction whilst others favour
the backward reaction. The ⇌ symbol is used to
represent a reversible reaction.
(l)
recall that dynamic equilibrium
occurs when the rates of forward
and reverse reactions are equal
When a reversible reaction occurs in a closed system,
dynamic equilibrium is reached when the forward and
backward reactions occur at exactly the same rate.
Once equilibrium is reached, the concentrations of the
reactants and products remain constant (but not
necessarily equal).
(m)
predict the effect of changing
reaction conditions
(concentration, temperature
and pressure) on equilibrium
position and suggest
appropriate conditions to
produce a particular product
Candidates should recall Le Chatelier's principle
and be able to apply it to any given example.
SPECIFIED PRACTICAL WORK
•
•
•
CSP9A Investigation into the effect of one factor on the rate of a reaction using a gas
collection method
CSP9B Investigation into the effect of one factor on the rate of the reaction between dilute
hydrochloric acid and sodium thiosulfate
CSP9C Investigation into the effect of various catalysts on the decomposition of hydrogen
peroxide
102
Investigation into the effect of one factor on the rate of reaction using a gas
collection method
Introduction
Magnesium reacts with dilute hydrochloric acid to produce hydrogen. The equation for the
reaction is as follows:
Magnesium
Mg(s)
+ Hydrochloric
acid
+
2HCl(aq)
Magnesium
chloride
+
Hydrogen
MgCl 2 (aq)
+
H 2 (g)
The rate at which the hydrogen gas is produced can be used to determine the rate of the
reaction.
In this experiment you will study the effect of changing the concentration of the hydrochloric acid
on the rate of the reaction.
Apparatus
250 cm3 conical flask
single-holed rubber bung
delivery tube to fit conical flask
trough or plastic washing-up bowl
100 cm3 measuring cylinder
250 cm3 measuring cylinder
clamp stand, boss and clamp
stopwatch
magnesium ribbon in 3 cm lengths
1 mol/dm3 hydrochloric acid
103
Diagram of Apparatus
Method
1.
2.
Set up the apparatus as shown in the diagram.
Measure 20 cm3 of 1 mol/dm3 hydrochloric acid using the 25 cm3 measuring cylinder. Pour
the acid into the 250 cm3 conical flask.
Fill the other measuring cylinder with water, make sure that it stays filled with water when
you turn it upside down and clamp above the trough.
Add a 3 cm strip of magnesium ribbon to the flask, put the bung into the flask and start the
stopwatch.
Record the volume of hydrogen gas given off every ten seconds. Continue timing until no
more gas appears to be given off.
Repeat steps 2-5 using 10 cm3 of the hydrochloric acid and 10 cm3 of water to make the
total volume used 20 cm3.
3.
4.
5.
6.
Analysis
1.
Plot a graph of volume of hydrogen gas (y-axis) against time (x- axis),for both
concentrations of hydrochloric acid and label the lines appropriately.
Risk Assessment
Hazard
Hydrochloric
acid is an
irritant
Risk
Hydrochloric acid could get onto the
skin when adding to measuring
cylinder
Hydrochloric acid could get
transferred from the hands to the
eyes
104
Control measure
Wash hands immediately if any
hydrochloric acid gets onto them / wear
laboratory gloves.
Wear eye protection.
Teacher / Technician notes
The magnesium ribbon should be clean and free from obvious corrosion or oxidation. Clean if
necessary by rubbing lengths of the ribbon with an emery board to remove the layer of oxidation.
To ensure that most of the magnesium surface is under the surface of the acid, it should be
folded into a zigzag shape.
The bungs in the flasks need to be rubber. Corks are too porous and will leak. The tube through
the bung should be a short section of glass, and then a flexible rubber tube can be connected.
These can be pre-prepared before the reaction so all the student has to do is push the bung into
the flask.
Gas syringes can be used instead of troughs of water and measuring cylinders. Syringes should
not be allowed to become wet, or the plungers will stick inside the barrels. The apparatus set up
for this procedure is shown in the diagram below:
Reagents:
•
•
Hydrochloric acid – Refer to CLEAPSS hazcard 47A
Magnesium ribbon – Refer to CLEAPSS hazcard 59A
A 3 cm length of magnesium ribbon has a mass of 0.04 g and should yield 40 cm3 of hydrogen
gas when reacted with this excess of acid.
If a graph of volume (y-axis) against time (x-axis) is drawn, the slope of the graph is steepest at
the beginning. This shows that the reaction is fastest at the start. As the magnesium is used up,
the rate falls. This can be seen on the graph, as the slope becomes less steep and then levels
out when the reaction has stopped (when no more gas is produced).
No repeats have been included in the method, but students can compare results with other
groups to make judgements on reproducibility.
105
Practical techniques covered
C1
Use of appropriate apparatus to make and record a range of measurements accurately,
including mass, time, temperature and volume of liquids and gases.
C3
Use of appropriate apparatus and techniques for conducting and monitoring chemical
reactions, including appropriate reagents and/or techniques for the measurement of
pH in different situations.
C5
Making and recording of appropriate observations during chemical reactions
including changes in temperature and the measurement of rates of reaction by a variety
of methods such as production of gas and colour change.
C6
Safe use and careful handling of gases, liquids and solids, including careful mixing of
reagents under controlled conditions, using appropriate apparatus to explore
chemical changes and/or products.
106
Investigation into the effect of one factor on the rate of reaction between dilute
hydrochloric acid and sodium thiosulfate
Introduction
Sodium thiosulfate reacts with hydrochloric acid to form a solid precipitate of sulfur. The formation
of this precipitate makes the solution become cloudy, and so the rate at which this cloudiness
appears can be used as a way to measure the rate of the reaction. The equation for this reaction
is as follows:
sodium
thiosulfate
+ hydrochloric
acid
Na 2 S 2 O 3 (aq) + 2HCl(aq)
sodium
chloride
+ water
+ sulfur + sulfur
dioxide
2NaCl(aq)
+ H 2 O(l) + SO 2 (g) + S(s)
The rate at which this precipitate forms can be changed by changing the conditions under which
the reaction is carried out.
In this experiment you will study the effect of changing the temperature of the sodium thiosulfate
solution.
Apparatus
10 cm3 measuring cylinder
25 cm3 measuring cylinder
250 cm3 conical flask
white paper with cross marked on it
stopwatch
1 mol/dm3 hydrochloric acid
thermometer
Access to:
40 g/dm3 sodium thiosulfate solution at 5 °C
40 g/dm3 sodium thiosulfate solution in a waterbath at 60 °C
107
Diagram of Apparatus
Method
1.
2.
Draw a cross on a square of white paper.
Measure 25 cm3 of hot sodium thiosulfate using the 25 cm3 measuring cylinder and pour
into the conical flask. Record the temperature of the solution.
Using the 10 cm3 measuring cylinder, measure out 5 cm3 of the hydrochloric acid.
Place the conical flask onto the cross and add the hydrochloric acid. Swirl the flask to mix
the contents and at the same time start the stopwatch.
Look down at the cross from above the mixture.
Stop the stopwatch as soon as the cross disappears.
Record the time taken for the cross to disappear.
Repeat steps 2 to 7 for different temperatures of sodium thiosulfate, made according to
the table below.
3.
4.
5.
6.
7.
9.
Volume of sodium thiosulfate solution at
60 °C (cm3)
25
20
15
10
5
0
Volume of sodium thiosulfate solution at
5 °C (cm3)
0
5
10
15
20
25
Analysis
1.
Plot a graph of the temperature of sodium thiosulfate against the time taken for the cross
to disappear.
108
Risk Assessment
Hazard
Risk
Hydrochloric acid is an
irritant.
Sodium thiosulfate is an
irritant
Sulphur dioxide gas
produced is an irritant
Hot water can scald/burn
Damage/irritation to skin.
There may be transfer from
the hands to the eyes
causing irritation.
Damage/irritation to skin.
There may be transfer from
the hands to the eyes
causing irritation.
Inhalation of gas may cause
damage/irritation to the lungs
Burns or scalds if the hot
sodium thiosulphate is
knocked over.
Control measure
Wash skin immediately if
contact made with
hydrochloric acid.
Wear safety goggles.
Wash skin immediately if
contact made with
sodium thiosulfate.
Wear safety goggles
Carry out in a well ventilated
space
Keep maximum temperature
to 60 oC.
Teacher / Technician notes
The crosses on the paper can be pre-prepared and laminated.
An alternative method can also be followed using the method set out on CLEAPSS card C195. It
reduces the volume of reactants used so enabling more sets of equipment to be created.
Reagents
•
•
Hydrochloric acid – Refer to CLEAPSS hazcard 47A
Sodium thiosulfate – Refer to CLEAPSS hazcard 95A
No repeats have been included in the method, but reproducibility can be checked by comparing
results with other groups. As temperatures will vary across groups, the whole class data could be
plotted onto one graph.
More able candidates could calculate and plot the rate of the reaction using
1
.
time (s)
Students should design their own table, but a suggested table format is shown below.
Recorded
temperature (°C)
Time taken for cross to disappear (s)
109
Practical techniques covered
C1
Use of appropriate apparatus to make and record a range of measurements accurately,
including mass, time, temperature and volume of liquids and gases.
C3
Use of appropriate apparatus and techniques for conducting and monitoring chemical
reactions, including appropriate reagents and/or techniques for the measurement of
pH in different situations.
C5
Making and recording of appropriate observations during chemical reactions
including changes in temperature and the measurement of rates of reaction by a variety
of methods such as production of gas and colour change.
C6
Safe use and careful handling of gases, liquids and solids, including careful mixing of
reagents under controlled conditions, using appropriate apparatus to explore
chemical changes and/or products.
110
Investigation into the effect of various catalysts on the decomposition of hydrogen
peroxide
Introduction
Hydrogen peroxide naturally decomposes to release oxygen. The equation for this reaction is as
follows:
hydrogen peroxide
2H 2 O 2 (aq)
water
2H 2 O(l)
+
+
oxygen
O 2 (g)
The rate at which this decomposition occurs is very slow. However the presence of a catalyst will
increase the rate at which the decomposition takes place. In this experiment you will study how
different catalysts affect the rate of decomposition.
The rate at which the oxygen gas is produced can be used to determine the rate of the reaction.
By changing the catalyst used, the rate at which the oxygen gas is produced can be changed.
Apparatus
250 cm3 conical flask
single-holed rubber bung
delivery tube to fit to conical flask
trough or washing up bowl
2 × 100 cm3 measuring cylinder
stopwatch
clamp stand, boss and clamp
Access to:
10 vol hydrogen peroxide
0.5 g pieces of various catalysts
111
Diagram of Apparatus
Method
1. Set up the apparatus as shown in the diagram.
2. Measure out 50 cm3 of hydrogen peroxide using a measuring cylinder and place it in the
conical flask.
3. Fill the other measuring cylinder with water and make sure that it stays filled with water
when you turn it upside down.
4. Connect the bung and delivery tube and place it under the measuring cylinder.
5. Add 0.5 g mass of a catalyst to the flask, put the bung back into the flask and start the
stopwatch.
6. Record the volume of gas given off every 10 seconds. Continue timing until no more oxygen
appears to be given off.
7. Repeat steps 2-6 for another two catalysts.
Method
1. Compare the results for the three catalysts and reach a conclusion.
Risk Assessment
Hazard
Hydrogen
peroxide is
corrosive
Risk
Hydrogen peroxide could get onto
the skin when adding to test tube
Hydrogen peroxide could get
transferred from the hands to the
eyes
112
Control measure
Wash hands immediately if any
hydrogen peroxide gets onto them /
wear laboratory gloves.
Wear eye protection.
Teacher / Technician notes
Reagents:
•
•
•
•
•
Hydrogen peroxide – Refer to CLEAPSS hazcard 50
Manganese(IV) oxide – Refer to CLEAPSS hazcard 60
Copper oxide – Refer to CLEAPSS hazcard 26
Zinc oxide – Refer to CLEAPSS hazcard 108B
Iron – Refer to CLEAPSS hazcard 55A
Students should be given the following catalysts to choose from – manganese(IV) oxide, iron
oxide, liver, potato, iron, copper oxide, yeast, zinc oxide.
In this experiment the students are to measure the volume of oxygen gas produced at various
time intervals. It is important that the concentration of the hydrogen peroxide is no greater than
10 vol, as this is safe for the students to use and creates a sufficient volume of gas to be
recorded.
It would save time if the masses of each catalyst were pre-weighed. Try to ensure with the liver
and potato options, that they are freshly prepared.
The bungs in the flasks need to be rubber. Corks are too porous and will leak. The tube through
the bung should be a short section of glass, and then a flexible rubber tube can be connected.
These can be pre-prepared before the experiment so all the student has to do is push the bung
into the flask.
No repeats are expected for this experiment and students can compare reproducibility by
comparing their results with those of other groups.
Gas syringes can be used instead of troughs of water and measuring cylinders.
Syringes should not be allowed to become wet, or the plungers will stick inside the barrels. The
apparatus set up for this procedure is shown in the diagram below.
113
In this experiment the students are expected to record the volume of oxygen gas produced at 10
second intervals for the three chosen catalysts.
Once the data from each experiment has been collected the students can construct a graph of
volume of oxygen gas (y-axis) against time in seconds (x-axis) for each of the catalysts on the
same axes.
Practical techniques covered
C1
Use of appropriate apparatus to make and record a range of measurements accurately,
including mass, time, temperature and volume of liquids and gases.
C3
Use of appropriate apparatus and techniques for conducting and monitoring chemical
reactions, including appropriate reagents and/or techniques for the measurement of
pH in different situations.
C5
Making and recording of appropriate observations during chemical reactions
including changes in temperature and the measurement of rates of reaction by a variety
of methods such as production of gas and colour change.
C6
Safe use and careful handling of gases, liquids and solids, including careful mixing of
reagents under controlled conditions, using appropriate apparatus to explore
chemical changes and/or products.
114
10 – CARBON COMPOUNDS
Spec Statement
Comment
(a)
recall that crude oil is a main
source of hydrocarbons and is a
feedstock for the petrochemical
industry
Candidates should know that crude oil is a complex
mixture of hydrocarbons that was formed over millions of
years from the remains of simple marine organisms.
(b)
describe and explain the
separation of crude oil by
fractional distillation
Candidates should know that crude oil is boiled/vaporised
before it enters the fractionating column and that the
hydrocarbons present condense at different heights in the
column. The lower the boiling point, the higher in the
column a compound is collected. They should know that
fractions are mixtures containing hydrocarbon compounds
that have similar boiling points and that these have similar
chain lengths. They are not expected to recall details such
as the range of chain lengths present in the constituent
hydrocarbons of different fractions but they should know
the uses of the following fractions: petroleum gases;
gasoline/petrol; naphtha; kerosene; diesel; lubricating oil;
fuel oil; bitumen.
Candidates should know that the longer the chain lengths
of the hydrocarbons present in a fraction, the higher its
boiling point range. They should also recall the effect of
increasing chain length on different fractions’ colour
(colourless – yellow – brown), viscosity, ease of ignition
and cleanliness of burn.
(c)
describe the fractions as largely a
mixture of compounds of general
formula C n H 2n+2 which are
members of the alkane
homologous series
(d)
describe the production of
materials that are more useful by
cracking
The cracking process involves heating fractions obtained
from crude oil to a high temperature in the presence of a
catalyst. This causes the hydrocarbon molecules present
to decompose forming smaller molecules, including an
alkene. There is greater demand for the smaller
hydrocarbons, and alkenes such as ethene, are the
starting material for the production of many plastics.
(e)
explain how modern life is
crucially dependent upon
hydrocarbons and recognise that
crude oil is a finite resource
Candidates should appreciate that hydrocarbon fuels are
vital for travel and electricity generation and that alkenes
produced by cracking are the basis for production of most
plastics. Without crude oil our lifestyles would be
unrecognisable. As crude oil reserves are used up,
governments will eventually have to decide between
burning the remaining oil and using it for other purposes.
115
11 – LIFE-CYCLE ASSESSMENT AND RECYCLING
Spec Statement
Comment
(a)
describe the basic principles in
carrying out a life-cycle
assessment of a material or
product
Candidates should know that a life-cycle assessment
(LCA) is carried out to assess the environmental impact
of products at each of the following stages:
• extraction and processing raw materials
• manufacture and packaging
• use, repair and maintenance during its lifetime
• disposal or recycling at the end of its useful life
(b)
interpret data from a life-cycle
assessment of a material or
product
Candidates should be able to carry out simple LCA
comparisons using numerical data (e.g. energy, water
consumption, waste) for a given material or product, e.g.
paper versus plastic shopping bags.
(c)
describe a process where a
material or product is recycled for
a different use, and explain why
this is viable
Aluminium, steel and glass can be recycled indefinitely
without losing quality so it is possible, for example, for
aluminium from drinks cans to be made into aircraft parts
and bicycle frames. Glass not suitable for re-melting can
be used as aggregate in concrete or ground down to
make building sand. Plastic bottles can be melted down
and made into any number of products, from garden
furniture to fleece jackets.
(d)
evaluate factors that affect
decisions on recycling
A number of factors have to be considered before the
recycling of a material becomes commonplace.
Economic viability is probably the most important one.
No private company will recycle a product if the costs are
greater than the return. This explains why some types of
plastic are not recycled. On the other hand, recycling
waste plastic reduces the amount of waste either ending
up in landfill or being burned. Equally important are the
benefits of conserving crude oil reserves and, because
recycling uses less energy than production, reducing
fossil fuel use.
Recycling metals conserves the raw materials and uses
much less energy. Recycling aluminium requires
approximately 5% of the energy used to extract the metal
from bauxite. The reduction in energy for recycling
means that less electricity is needed and so there are
smaller associated greenhouse emissions.
116
12 – THE EARTH AND ITS ATMOSPHERE
Spec Statement
Comment
(a)
interpret evidence for how it is
thought the atmosphere was
originally formed
Candidates should know that several theories have been
suggested to account for the formation of the Earth’s early
atmosphere, but many scientists agree that it is most likely
to have formed from gases expelled by volcanoes. Carbon
dioxide, water vapour and ammonia make up the greatest
proportion of volcanic gases.
(b)
describe how it is thought that the
an oxygen-rich atmosphere
developed over geological time
Candidates should know that the surface of the Earth cooled
over time and that water vapour present in the early
atmosphere condensed forming the oceans. They should
appreciate that this happened quickly, in geological terms,
and that other changes took far longer. The percentage of
carbon dioxide has decreased to a fraction of one percent as
a result of a number of processes, the most important being
photosynthesis. Photosynthesis began as green plants
evolved, using up carbon dioxide and releasing oxygen into
the atmosphere for the first time. The evolution of marine
animals followed over hundreds of millions of years and
much carbon dioxide was locked into limestone and chalk
formed from their shells. More still was locked into fossil
fuels formed many millions of years ago from the remains of
simple marine organisms (crude oil and natural gas) and
larger land plants (coal). Ammonia decomposed on reaction
with oxygen forming nitrogen, which became the most
abundant gas in the atmosphere. These changes occurred
over billions of years.
(c)
recall the approximate
composition of the present day
atmosphere
nitrogen 78%
oxygen 21%
argon (+ other noble gases) 0.9%
carbon dioxide 0.04%
(d)
describe the greenhouse effect in
terms of the interaction of
radiation with the Earth’s
atmosphere
Greenhouse gases (water vapour, carbon dioxide and
methane) in the atmosphere maintain temperatures on Earth
within a range that supports life. They allow short
wavelength radiation to pass through the atmosphere to the
Earth’s surface but absorb the outgoing long wavelength
radiation coming from the Earth's surface causing an
increase in atmospheric temperature. The greenhouse
effect is an entirely natural phenomenon.
(e)
explain global warming in terms
of an ‘enhanced greenhouse
effect’
Global warming is the result of an ‘enhanced greenhouse
effect’. It is the impact on the climate of the additional heat
retained due to the ever-increasing amounts of carbon
dioxide (and other greenhouse gases) released into the
Earth’s atmosphere since the industrial revolution.
117
(f)
evaluate the evidence for manmade causes of climate change,
including the correlation between
change in atmospheric carbon
dioxide concentration and the
consumption of fossil fuels, and
describe the uncertainties in the
evidence base
Candidates should appreciate that the overall trend over the
past 200 years shows a correlation between carbon dioxide
concentration and atmospheric temperature, although there
are anomalies over short time periods. They should be
aware that sunspot activity has been suggested as an
alternative cause for the observed temperature changes and
that this has been ruled out by the majority of scientists on
the basis of the available evidence.
(g)
describe the potential effects of
increased levels of carbon
dioxide and methane on the
Earth's climate and how these
may be mitigated, including
consideration of scale, risk and
environmental implications
Increased levels of carbon dioxide could cause:
• Climate change e.g. hotter summers in some parts of the
world (droughts) and increased rainfall (flooding) in
others
• Higher rate of melting of ice caps, polar sea ice, glaciers
• Rising sea levels
• Changes in food production capacity of some regions
• Impact on wildlife
Increases in carbon dioxide levels can be slowed and
eventually reversed by:
• Increasing use of alternative energy sources
• Improved energy conservation
• Carbon capture and storage
• Carbon off-setting e.g. tree planting
(h)
describe the major sources of
carbon monoxide, sulfur dioxide,
oxides of nitrogen and
particulates in the atmosphere
and explain the problems caused
by increased amounts of these
substances
Candidates should recall the main sources and effects of
atmospheric pollution.
• Carbon monoxide – incomplete burning of fossil fuels;
poisonous
• Sulfur dioxide – burning fuels containing sulfur; affects
the respiratory system, causes acid rain (see below)
• Nitrogen oxides – burning fossil fuels; affects the
respiratory system, causes acid rain
• Particulates (smoke and soot) – burning fossil fuels;
affects the respiratory system, reduces visibility,
damages the appearance of buildings
They should know that fossil fuels contain many impurities
including many sulfur-containing compounds and that these
produce sulfur dioxide on burning. Sulfur dioxide forms a
solution of sulfuric acid on contact with water in the
atmosphere and this falls as acid rain. Candidates should
know that ‘clean’ rain is weakly acidic (pH ~5.5) and that
acid rain has a pH in the range of about 2-4. They should
know that acid rain lowers the pH of lakes etc., damaging
aquatic life and damaging forests and vegetation. They
should know that it damages buildings (particularly those
made of limestone [calcium carbonate]) and increases the
rate of corrosion of metal structures such as bridges and
statues.
(i)
describe the principal methods for Candidates should know potable water is water that is safe
increasing the availability of
to drink, rather than 'pure' water.
potable water in terms of the
118
separation techniques used,
including ease of treatment of
waste water, ground water and
salt water
Candidates should know the stages in the treatment of the
public water supply using sedimentation, filtration and
chlorination.
• Sedimentation – in reservoirs/tanks, larger solid particles
settle under gravity
• Filtration – through layers of sand and gravel, removes
smaller insoluble particles
• Chlorination – chlorine added to kill bacteria, prevents
disease/makes it safe to drink
Candidates should know that the simplest method for
desalination of sea water is distillation. This involves boiling
sea water which uses large amounts of costly energy,
preventing it from being a viable process in many parts of
the world. Candidates should be aware that other methods
are also used, e.g. the use of membrane systems, but they
are not required to know any details of such methods. They
should be able to discuss the potential of desalination as a
source of drinking water in different parts of the world in
terms of proximity to the sea, availability of ‘cheap’ energy
and a country’s wealth.
119
COMPONENT 3 – Concepts in Physics
1. ENERGY
1.1 ENERGY CHANGES IN A SYSTEM, AND IN THE WAYS ENERGY IS STORED BEFORE
AND AFTER SUCH CHANGES
Spec Statement
(a)
describe all the changes
involved in the way energy is
stored when a system changes,
for common situations: e.g. an
object projected upwards or up a
slope, a moving object hitting an
obstacle, an object being
accelerated by a constant force,
a vehicle slowing down, bringing
water to a boil in an electric
kettle, a change of state
Comment
Types of energy may include sound, internal,
chemical, kinetic, heat, electrical, light, nuclear, elastic
potential and gravitational potential.
Some of the ways in which energy is stored should be
known e.g. chemical (e.g. fuel and oxygen), kinetic (in
a moving object), gravitational potential (due to the
position of an object in a gravitational field), elastic
potential (e.g. in a stretched or compressed spring),
electrostatic (in two separated electric charges that
are attracting, or repelling) and heat (in a warm
object).
Know that energy is transferred mechanically (when a
force moves through a distance), electrically (when a
charge moves through a potential difference), by
heating (because of a temperature difference) or by
radiation (e.g. light, microwaves, sound).
(b)
describe how heating a system
will change the energy stored
within the system and raise its
temperature or produce changes
of state
In terms of bond breaking or bond formation during
changes of state. A smaller number of bonds are
broken during fusion than vaporisation so this means
more energy is required for vaporisation to occur.
The term internal energy should be known.
(c)
define the terms specific heat
capacity and specific latent heat
Define specific heat capacity as the amount of heat
energy required to increase the temperature of 1 kg of
a substance by 1 oC.
Define specific latent heat of fusion as the amount of
heat energy needed to change a mass of 1 kg of the
substance from a solid at its melting point into a liquid
at the same temperature.
The specific latent heat of vaporisation is the amount
of heat energy required to change 1 kg of a liquid at its
boiling point into a vapour without a change in
temperature.
Be able to relate the standard definitions to specific
examples e.g. water has a specific heat capacity of
4 200 J / kg oC this means that 4 200 J of energy is
required to increase the temperature of 1 kg of water
by 1 oC.
120
(d)
(e)
calculate the amounts of energy
associated with:
• a moving body (kinetic
energy = 0.5 × mass ×
(velocity)2 [ Ek = 12 mv 2 ]
•
a stretched spring (energy
transferred in stretching =
0.5 × spring constant ×
(extension)2 [ E = 12 kx 2 ]
•
object raised above
ground level (potential
energy = mass ×
gravitational field strength
× height [ E p = mgh ]
calculate the change in energy
involved when a system is
changed by heating (in terms of
temperature change, specific
heat capacity [∆Q = mc∆θ] and
specific latent heat [Q = mL])
Various contexts could be discussed, e.g. an
aeroplane, a falling object, a stretched rubber band, a
catapult etc.
Calculate the energy stored in a stretched material
from a force- extension graph i.e. area under the
graph.
Links with statement (f) in this section.
Values for specific heat capacities or specific latent
heat will be given or will be the object of a calculation.
Interpretation of a cooling / heating curve.
http://www.s-cool.co.uk/a-level/physics/temperatureand-thermal-properties/revise-it/specific-latent-heat
http://www.splung.com/content/sid/6/page/latentheat
Appreciation that latent heat does not increase the
temperature of matter – the energy is used for the
change of state to occur.
(f)
calculate the change in energy
involved by work done by forces:
work done = force × distance
(along the line of action of the
force) [ W = F x ]
Calculations will not be required where the force is at
an angle to the direction of motion.
Need to be able to recognise situations where no work
is done as there is no motion in the direction of the
force.
Need to be able to link W = Fd with changes in kinetic
or gravitational potential energy to calculate the mean
resistive force acting.
(g)
calculate the change in energy
involved by work done when a
current flows
Including the relationship between the units watts and
joules i.e. 1 W = 1 J/s and between volts and coulombs
i.e. 1 volt = 1 J/C.
Conversion between units will be required e.g.
minutes to seconds and kW to W.
See section 7.1 - current, potential difference and
resistance statements (b) and (e).
•
•
energy transferred =
power × time
energy transferred =
charge flow × potential
difference [ E = Q V ]
121
(h)
explain the definition of power as
the rate at which energy is
transferred e.g.
lifting an object, calculate values
for power using
work done
and
power =
time
describe the relationship between
the power ratings for domestic
electrical appliances and the
changes in stored energy when
they are in use e.g. in a kettle
how the power is related to the
increase in internal energy of the
water
This links to statement (e) above and could explore,
for example, the time taken to boil a given mass of
water (assuming 100% efficiency) i.e.
∆Q = mc∆θ = Pt
∆Q = mL = Pt
Alternative definition - energy transferred or work done
per unit time.
SPECIFIED PRACTICAL WORK
•
PSP1.1 Determination of the specific heat capacity of a material
122
Determination of the specific heat capacity of a material
Introduction
You will determine the specific heat capacity of metals by measuring the heat energy transferred
to the metal by an immersion heater and the temperature rise of the metal.
Apparatus
1 kg metal block
stopwatch
12 V d.c. power supply
connecting leads
50 W 12 V immersion heater
thermometer
Diagram of Apparatus
123
Method
1.
2.
3.
4.
5.
Ensure the power supply is switched off.
Place the immersion heater and thermometer in the holes provided in the metal block.
Record the initial temperature of the metal block.
Switch on the 12 V power supply.
Record the temperature of the metal block every minute for 10 minutes.
Analysis
1.
The heat energy transferred to the metal can be calculated from the equation:
Energy = Power × Time (seconds)
2.
The specific heat capacity (c) of the metal can be calculated from:
Q = mc∆θ
Where:
Q = Heat energy supplied
m = Mass of block
∆θ = Temperature rise of block
Calculate the specific heat capacity of the metal.
Risk Assessment
Hazard
Hot immersion
heater can burn
Risk
Control measure
Moving hot immersion heater
Do not switch on the immersion heater
unless in the metal block.
Allow to cool before touching
Technician / Teacher notes
Do not switch on the immersion heater outside the metal block.
Power supplies should be set at 12 V.
A variety of materials could be used by different groups, e.g. aluminium, copper or iron and the
results compared. In addition, students could be given the published value for the specific heat
capacity for each metal and then compare it with the value they have calculated.
124
Practical techniques covered
P1
Use of appropriate apparatus to make and record a range of measurements accurately,
including length, area, mass, time, volume and temperature.
Use of such measurements to determine densities of solid and liquid objects.
P5
Safe use of appropriate apparatus in a range of contexts to measure energy
changes/transfers and associated values such as work done.
125
1.2 CONSERVATION, DISSIPATION AND NATIONAL AND GLOBAL ENERGY SOURCES
Spec Statement
(a)
Comment
describe how in all system changes,
energy is dissipated, so that it is stored
in less useful ways
Understand that energy tends to spread from
more concentrated stores to more dispersed
stores such as heat in the environment, so it
is less useful for doing anything more.
Sankey diagrams may be a useful method to
display this information.
(b)
describe where there are energy
transfers in a system, that there is no
net change to the total energy of a
closed system e.g. mass oscillating on a
spring
Energy conservation for a complete closed
system must be applied.
Understand that for the mass on a spring the
total energy is the sum of the kinetic energy
and the energy stored in the stretched spring.
Numerical questions could be asked.
See section 1.1 – Energy changes statement
(d).
(c)
explain ways of reducing unwanted
energy transfer e.g. through lubrication,
thermal insulation; describe the effects,
on the rate of cooling of a building, of
thickness and thermal conductivity of its
walls (qualitative only)
Link method of heat transfer reduction to
each method of insulation.
Loft insulation and cavity wall insulation
reduce heat loss by both conduction and
convection. Cavity wall insulation also
reduces heat loss by radiation.
Be able to explain about the importance of
“trapped air.”
Be able to explain the role of silvered
surfaces in reducing heat transfer.
(d)
describe the processes of heat transfer
by conduction, convection and radiation
including the role of free electrons in
thermal conduction in metals
Free electrons, de-localised electrons, mobile
electrons are all suitable terms to use.
For example: “when a section of liquid (gas)
is heated the molecules gain energy and
move more vigorously. As a result this
section of the liquid increases in volume and
its density decreases. This less dense liquid
then rises and colder more dense liquid sinks
to takes its place. This process continues
until all of the liquid is heated.”
Learners need to be familiar with the term
convection currents.
Radiation is energy transfer by em waves
(infra-red).
126
(e)
calculate energy efficiency for any
energy transfer using:
efficiency =
Including drawing Sankey diagrams to scale.
Conversion between efficiency and
percentage efficiency is required.
An understanding that the maximum
efficiency of any energy transfer cannot
exceed 1.
Some systems described as being perfectly
efficient (e.g. transformers).
output energy transfer
input energy transfer
and describe ways to increase
efficiency
(f)
describe the main energy sources
available for use on Earth (e.g. fossil
fuels, nuclear fuel, bio-fuel, wind, hydroelectricity, the tides and the Sun),
compare the ways in which they are
used and distinguish between renewable
and non-renewable sources
Consider economic, environmental and
sustainablility issues as well as generating
capacities and start-up time.
Involves the interpretation of given data.
(g)
explain patterns and trends in the use of
energy resources
Involves the interpretation of given data.
Consideration of the different costs of energy
sources of vehicles and the range they allow:
e.g. the fuel efficiency of cars, the costefficiency of oil-fired heating etc
127
1.3 ENERGY TRANSFERS
Spec Statement
Comment
(a)
recall that, in the National Grid,
electrical power is transferred at
high voltages from power
stations, and then transferred at
lower voltages in each locality for
domestic use, and explain how
this system is an efficient way to
transfer energy
Step-up transformers increase voltage and decrease
current – reducing energy losses in transmission lines
making distribution more efficient.
Step-down transformers reduce voltage to safer levels
for consumers.
(b)
describe how, in different
domestic devices, energy is
transferred from batteries and
the a.c. mains to the energy of
motors or of heating devices
Understand that in electric circuits energy is
transferred electrically from stored chemical energy
from batteries or power stations to devices.
See section 1.2 – conservation, dissipation and
national and global energy sources statement (a).
128
2.
PARTICLE MODEL OF MATTER
Spec Statement
Comment
(a)
define density (i.e
mass
) and explain
density =
volume
the differences in density
between the three states of
matter in terms of the
arrangements of the atoms or
molecules
Be able to work in both g/cm3 and kg/m3 but no
conversions will be expected.
Density values decrease from solids → liquids →
gases due to increasing atomic or molecular
separation.
(b)
describe how, when substances
melt, freeze, evaporate,
condense or sublimate, mass is
conserved, but that these
physical changes differ from
chemical changes because the
substance recovers its original
properties if the change is
reversed
For example, ice → water → steam → water → ice
Be aware that physical changes are reversible.
An understanding of the terms boiling point and
melting point is required.
(c)
explain how the motion of the
molecules in a gas is related both
to its temperature and its
pressure: hence explain the
relationship between the
temperature of a gas and its
pressure at constant volume
(qualitative only)
Explanations using molecular model theory are
expected. As temperature increases the molecules
speed up so they hit the container walls faster which
increases the pressure i.e. p α T.
No knowledge of the assumptions of kinetic theory is
required.
SPECIFIED PRACTICAL WORK
•
PSP2 Determination of the density of solids and liquids
129
Determination of the density of liquids and solids
Introduction
The density of a substance measures the mass it contains in a given volume. Density is
calculated using the equation:
mass
density =
volume
Apparatus
2 × regular shaped solids
2 × irregular shaped solids
30 cm ruler
50 cm3 measuring cylinder
water
Access to:
electronic balance ± 0.1 g
Measuring the density of a regular shaped solid
Diagram of Apparatus
130
Method
1. Record the mass of the solid.
2. Record the length, width and thickness of the solid using a ruler.
3. Repeat for cubes of different material.
Analysis
1. Calculate the volume of the cube from: volume = length x height x width.
2. Calculate the density in g/cm3.
Measuring the density of an irregular shaped solid
Diagram of Apparatus
Method
1. Record the mass of the solid.
2. Fill the measuring cylinder with water up to 20 cm3 and record the volume.
3. Gently place the solid into the measuring cylinder and record the new volume.
Analysis
1. Calculate the volume of the solid by subtracting the original volume from the new volume.
2. Calculate the density in g/cm3.
131
Measuring the density of a liquid
Diagram of Apparatus
Method
1.
2.
3
Record the mass of the empty measuring cylinder.
Add 20 cm3 of water to the measuring cylinder.
Record the mass of the measuring cylinder with the water.
Method
1.
2.
Calculate the mass of the water by subtracting the mass of the measuring cylinder
(without water) from the mass of the measuring cylinder with the water.
Calculate the density in g/cm3.
Risk Assessment
Hazard
Risk
Control measure
There are no significant risks associated with this procedure
132
Teacher / Technician notes
Small pieces of Blu-Tack or plasticine or small stones can be used as irregular shaped solids.
Students should be provided with a range of regular shaped common materials, e.g. cork, wood,
steel, aluminium, polystyrene, rubber or plastic. However, care should be taken with the mass of
the blocks to ensure balances are not damaged.
As an extension students could investigate how the addition of a salt such as sodium chloride to
water changes its density.
This practical works well run as a circus of activities.
Practical techniques covered
P1
Use of appropriate apparatus to make and record a range of measurements accurately,
including length, area, mass, time, volume and temperature.
Use of such measurements to determine densities of solid and liquid objects.
133
3. FORCES
Spec Statement
Comment
(a)
recall examples of ways in which
pairs of objects interact by:
- gravity
- electrostatics
- magnetism and
- contact (including normal
contact force and friction)
and describe how such examples
involve forces on each object
using vector notation
Positive and negative forces may be used or required
in some situations e.g. cars in collision with one
another.
Vectors should be represented as lines with arrows to
show the direction.
Labelled diagrams or descriptive examples may be
used.
Links with statement (c) in this section.
(b)
define weight as the gravitational
force acting on an object,
describe how it is measured and
describe the relationship
between the weight of that body
and the gravitational field
strength (weight = mass ×
gravitational field strength [W =
mg])
That weight is the force of gravity acting on an object
whereas mass is the amount of matter in an object.
Candidates should know that mass is measured in kg
and weight is measured in N.
(c)
describe examples of the
forces acting on an isolated
solid object or system;
describe, using free body
diagrams, examples where
several forces lead to a
resultant force on an object
and the special case of
balanced forces when the
resultant force is zero: resolve
a force into components at
right angles
Be able to calculate the resultant force by
considering the forces acting on an object.
Be able to recognise direct or inverse proportion
from tabulated or graphical data.
Apply understanding to situations where mass is
not constant e.g. a rocket on take-off.
(d)
explain that to stretch, bend or
compress an object, more than
one force has to be applied e.g. a
stretched elastic band
Naming forces and the use of Newton’s 3rd Law would
be appropriate.
134
(e)
describe the difference between
elastic and inelastic distortions
caused by stretching forces;
calculate the work done in
stretching; describe the
relationship between force and
extension for a spring (force =
spring constant × extension [F =
kx]) and other simple systems;
describe the difference between
linear and non-linear
relationships between force and
extension, and calculate a spring
constant in linear cases
Simple systems could include springs connected
together (series or parallel) but not a combination.
Be able to predict the effect on the extension and
energy stored in a spring of different spring constant in
a given situation.
No explanation of the term spring constant is required.
Force plotted on the y-axis and extension on the xaxis.
(f)
use the relationship between
work done, force, and distance
moved (along the line of action
of the force) i.e. work done =
force × distance (along the line
of action of the force) [ W =
F x ] and describe the energy
transfer involved
Calculations will not be required where the force is at
an angle to the direction of motion.
Need to be able to recognise situations where no work
is done as there is no motion in the direction of the
force.
Need to be able to link W = Fd with changes in kinetic
or gravitational potential energy to calculate the mean
resistive force acting.
SPECIFIED PRACTICAL WORK
•
PSP3.1 Investigation of the force-extension graph for a spring
135
Investigation of the force-extension graph for a spring
Introduction
When a force is applied to a spring its length increases. The extension of the spring is found by
subtracting the original length of the spring from its length with the force applied. Hooke’s Law
states that the extension is directly proportional to the force applied provided that the elastic limit
is not exceeded. You will investigate if the spring obeys Hooke's law.
Apparatus
spring
100 g mass hanger
6 × 100 g masses
clamp stand, boss and clamp
metre ruler ± 1 mm
Diagram of Apparatus
Method
1.
2.
3.
4.
5.
6.
Record the original length of the spring.
Suspend the spring from the clamp and attach the 100 g mass hanger.
Record the new length of the spring.
Add a further 100 g to the spring and record the new length.
Repeat steps 2-3 until a total mass of 700 g has been added.
Repeat steps 1-5 once more.
136
Analysis
1.
2.
3.
4.
Calculate the mean length for each mass added.
Calculate the extension for each mass added.
Plot a graph of force (y-axis) against extension (x-axis). (100 g = 1 N)
Determine whether the spring obeys Hooke's law or not.
Risk Assessment
Hazard
Risk
Control measure
Ensure suitable orientation of the clamp
stand to reduce danger of toppling
Apparatus
toppling / falling
from the bench
Risk of injury (e.g. to foot) from
heavy, falling apparatus
Do not pull the masses down further
with your hand
Do not exceed the maximum load of
700 g (7 N)
Teacher / Technician Notes
Students may be asked to measure the length of the spring itself and not the loops at each end.
Including one, or indeed, both loops, will make no difference to their final values for extension.
However, students must be consistent in making the same measurement throughout the
investigation.
Students should be encouraged to measure and record each result to the nearest 0.1 cm (1 mm).
If the result is 9 cm they should write 9.0 in their table.
Students should be asked to gently place the masses onto the spring and to ensure that the
spring is stationary each time when measuring its new length.
Students should load the spring up to a limit of 700 g. This will ensure that the elastic limit is not
exceeded and the springs are not over-stretched. The teacher could demonstrate the effect of
further increasing the force applied.
A graph should then be plotted of force (y-axis) against extension (x-axis). The line of best fit
expected is a straight line through the origin. This proves that the spring obeys Hooke’s Law.
137
Students should design their own table, but a suggested table format is shown below.
Mass
(g)
Force
(N)
Length (cm)
1
2
Mean length
(cm)
Extension
(cm)
Practical techniques covered
P2
Use of appropriate apparatus to measure and observe the effects of forces including the
extension of springs.
138
4. FORCES AND MOTION
4.1 SPEED AND VELOCITY, SPEED AS DISTANCE OVER TIME; ACCELERATION; DISTANCETIME AND VELOCITY-TIME GRAPHS
Spec Statement
Comment
(a)
explain the vector-scalar distinction as it
applies to displacement / distance and
velocity / speed
Vectors have both magnitude and direction
whilst scalars only have magnitude.
(b)
recall typical speeds encountered in
everyday experience for wind and sound,
and for walking, running, cycling and other
transportation systems; recall the
acceleration in free fall on Earth (10 m/s2)
and estimate the magnitudes of everyday
accelerations
Speed of sound = 330 m/s
Speed of wind – gentle breeze = 4 m/s
Strong breeze =12 m/s
Typical walking speed = 1.5 m/s
Running = 5 m/s
Cycling = 10 m/s
Typical acceleration for a car = 4.5 m/s2
(c)
explain with examples that motion in a
circular orbit involves a constant speed
but changing velocity (qualitative
responses only)
Understand that the velocity is constantly
changing because the direction changes
and hence the object accelerates.
Examples may include satellite motion or
an object moving in a circular orbit attached
to a piece of string.
(d)
recall and apply the relationships:
• distance travelled = speed × time
change in velocity
• acceleration =
time
Distances may include either km or m.
Time may include seconds (s) or hours (h).
Associated speed and acceleration units
would apply.
Conversions between m/s and km/h will not
be expected.
∆v 

a = t 


(e)
use motion graphs to describe and
determine the speed, acceleration and
distance travelled
Be able to describe the motion represented
by a motion graph including calculations
where appropriate such as speed or mean
speed for a distance-time graph and
acceleration or distance travelled (higher
tier only) for a velocity-time graph.
Calculations will be required for curved
sections of graphs as estimations and an
understanding of the motion of the object
will be expected.
139
(f)
apply the following equations to situations of
uniform acceleration only
•
final velocity = initial velocity +
acceleration × time [ v= u + at ]
•
distance = ½ (initial velocity + final
velocity) × time =
[ x 12 (u + v)t ]
•
(final velocity)2 = (initial velocity)2 + 2 ×
2
2
acceleration × distance [ v= u + 2ax ]
•
distance = initial velocity × time + ½ ×
acceleration × time2 [ x
= ut + 12 at 2 ]
140
Could include objects where velocity and
acceleration are in opposite directions, e.g.
a ball thrown upwards.
Distances may include either km or m.
Time may include seconds (s) or hours (h).
Associated velocity and acceleration units
would apply.
4.2 FORCES, ACCELERATIONS AND NEWTON’S LAWS OF MOTION
Spec Statement
Comment
(a)
recall Newton’s First Law and apply it
to explain the motion of objects
moving with uniform velocity and also
objects where the speed and/or
direction change
Recall Newton’s first law as:
An object will remain at rest or in uniform motion
in a straight line unless acted upon by an external
resultant force.
(b)
recall Newton’s Second Law and apply
it in calculations relating forces,
masses and accelerations: resultant
force = mass × acceleration [F = ma]
Recall Newton’s second law as:
Can be stated in words or as an equation.
resultant force = mass × acceleration [F = ma] /
The acceleration of an object is directly
proportional to the net force, in the same
direction as the net force, and inversely
proportional to the mass of the object.
Be able to calculate the resultant force by
considering the forces acting on an object.
Be able to recognise direct or inverse proportion
from tabulated or graphical data.
Apply understanding to situations where mass is
not constant e.g. a rocket on take-off.
(c)
explain that inertial mass is a
measure of how difficult it is to
change the velocity of an object
and that it is defined as the ratio of
force over acceleration
Understand that objects with greater mass
have greater inertia and so a greater resultant
force will be required to change its motion.
(d)
recall and apply Newton’s Third Law
Recall Newton’s third law as:
If a body A exerts a force on body B then body B
exerts an equal and opposite force on body A.
Be able to apply their knowledge of Newton’s
third law in different situations e.g. rocket
propulsion, gravitational force of the Earth on a
body and of the body on the Earth.
(e)
define momentum (i.e. momentum =
mass × velocity [ p = mv]), state the
principle of conservation of
momentum and apply it to one
dimensional interactions
The vector property of momentum (and
velocity) should be applied to give positive
and negative momentum values from a given
positive vector direction (usually to the right
in diagrams).
Need to recognise the directional property of
momentum.
SPECIFIED PRACTICAL WORK
•
PSP4.2 Determination of the acceleration of a moving object
141
Determination of the acceleration of a moving object
Introduction
An object moving down an inclined ramp will accelerate. The velocity of the object as it leaves
the ramp can be used to calculate the mean acceleration of the object using the formula:
acceleration =
change in velocity
time
Since the object starts from rest at the top of the ramp this means that:
acceleration =
velocity at bottom of ramp
time to reach bottom of ramp
The velocity at the bottom of the ramp can be calculated from the time the object takes to travel a
certain distance along the bench.
Apparatus
ramp
squash ball
metre ruler ± 1 mm
stopwatch
clamp stand, clamp and boss
Diagram of Apparatus
142
Method
1.
2.
3.
4.
5.
6.
7.
8.
Set the height of the ramp to 10 cm above the desk.
Measure a distance of 50 cm from the end of the ramp and mark this point.
Release the squash ball from the top of the ramp starting the stopwatch as you do.
When the squash ball reaches the bottom of the ramp press the lap button on the
stopwatch.
Stop the stopwatch when the squash ball reaches the 50 cm mark.
Record the time taken for the ball to travel down the ramp (lap time) and the total time.
Repeat steps 1-6 increasing the height in 5 cm intervals each time up to 25 cm.
Repeat the experiment twice more.
Analysis
1. Calculate the time taken for the ball to travel 50 cm along the bench;
this is the total time – the lap time.
2. Calculate the velocity at the bottom of the ramp using the formula:
velocity =
0.5
mean time taken to travel 50 cm along the bench
3. Calculate the acceleration using the formula:
acceleration =
velocity at bottom of ramp
mean time to reach bottom of ramp
4. Plot a graph of ramp height against acceleration.
Risk Assessment
Hazard
Risk
Control measure
There is no significant risk in carrying out this experiment.
Teacher / Technician notes
Self-adhesive trunking which is widely available in DIY stores can be stuck onto metre rules to
make effective ramps which work well with squash balls.
143
Students should design their own table, but a suggested table format is shown below.
Height
(cm)
Time to reach bottom of
ramp (s)
Trial 1 Trial 2 Trial 3
Mean time
to reach
bottom of
ramp (s)
Time to travel 50 cm
along bench (s)
Trial 1 Trial 2 Trial 3
Mean
time to
travel
50 cm
(s)
Velocity
(m/s)
Acceleration
2
(m/s )
This investigation is good for developing evaluation skills and students could be encouraged to
judge the repeatability and reproducibility of their results. Data could be compared against doing
the same experiment with data loggers and sources of error considered.
Practical techniques covered
P1
Use of appropriate apparatus to make and record a range of measurements accurately,
including length, area, mass, time, volume and temperature.
Use of such measurements to determine densities of solid and liquid objects.
P3
Use of appropriate apparatus and techniques for measuring motion, including
determination of speed and rate of change of speed (acceleration/deceleration).
144
4.3 SAFETY IN PUBLIC TRANSPORT
Spec Statement
Comment
(a)
explain methods of measuring human
reaction times and its effect on
thinking distances and recall values of
typical reaction times
Typical human reaction time is 0.20 – 0.25 s.
For any driver condition, the reaction time is
constant. Factors that increase a driver’s reaction
time include, for example, alcohol, tiredness, age.
(b)
explain the factors which affect the
braking distance required for road
transport vehicles to come to rest in
emergencies and the implications for
safety
Factors such as:
Speed
Road conditions (ice, wet)
Car conditions (quality of brakes, tyres, number
of passengers, total mass).
(c)
explain the dangers caused by large
decelerations and estimate the
forces involved in everyday
situations on a road e.g. vehicle
braking to a halt
A 1 000 kg car travelling at 30 mph requires a
force of 3 900 N to stop in a typical stopping
distance of 23 m.
See sections 1.1 – energy statement (d) and
section 3.1 – forces and their interactions
statement (f).
(d)
apply the principles of forces, motion
and energy to an analysis of safety
features of cars e.g. air bags and
crumple zones
Answer can be expressed in terms of work done:
i.e. an air bag and a crumple zone increase the
distance over which the energy is transferred, so
reducing the force.
Or in terms of momentum:
i.e. the same change in momentum happens over
a longer time so there is decreased deceleration
so the force decreases.
145
5. WAVES IN MATTER
Spec Statement
Comment
(a)
describe wave motion in terms
of amplitude, wavelength,
frequency and period i.e.

1
1
T = ;
period =

f
frequency 
define wavelength and
frequency and describe and
apply the relationship between
these and the wave velocity
(wave speed = frequency ×
wavelength [ v = f λ ] )
Define the term frequency as the number of cycles of a wave that occur in one
second.
Define the term wavelength as –
the distance between two adjacent points in a wave
that move in phase / in step.
Know that amplitude is the maximum displacement
from rest.
Describe the relationship between wavelength and
frequency as being inversely proportional for a wave
moving at constant velocity.
Describe the relationship between wavelength and
velocity as being directly proportional for a wave
moving at constant frequency (as for refracted waves
in a ripple tank).
Interpret displacement-distance and displacementtime graphs.
(b)
describe the difference between
transverse and longitudinal
waves
Include definitions of both types of waves with a
comparison of the direction of vibrations and the
direction of travel of the wave included.
Be able to give examples of a transverse wave and a
longitudinal wave.
(c)
describe how ripples on water
surfaces are examples of
transverse waves whilst sound
waves in air are longitudinal
waves; describe evidence that in
both cases it is the wave and not
the water or air itself that travels
Evidence such as motion of a boat / seabird at rest on
the ocean when a wave passes. It simply oscillates
up and down.
Demonstrating both transverse and longitudinal waves
using a slinky spring can assist students
understanding of this concept.
(d)
recall that sound requires a
medium for transmission
Bell jar demonstration is useful.
Solids, liquids and gases are included.
SPECIFIED PRACTICAL WORK
•
PSP5.1 Investigation of water waves
146
Investigation of water waves
Introduction
The speed of waves on the surface of water, created when the water is moved out of position,
depends only on the depth of the water and the gravitational field strength. To measure the
speed of the waves the time they take to travel a certain distance is measured and the following
equation is applied.
speed =
distance
time
The wavelength of water waves depends on their speed and frequency, as described by the
equation:
wave speed = frequency x wavelength
The wavelength of water waves can be observed using a ripple tank. The wavelength is the
distance between successive crests or troughs. When light is shone through the ripple tank the
wavefronts appear as dark and light lines, so the distance between successive dark or light lines
is the wavelength. The frequency of waves in the ripple tank is determined by the motor.
Apparatus – Method 1
rectangular apparatus tray with straight sides
stopwatch
large beaker
large measuring cylinder
Diagram of Apparatus
147
Method 1 – speed
1.
2.
3.
4.
5.
6.
7.
Measure the length of the tray and record the result.
Add water to the tray to give a depth of 0.5 cm and record the volume used.
Lift the end of the tray up a few cm and gently replace on the desk.
Start the stopwatch when the wave produced hits the end of the tray.
Record how long it takes the waves to travel three lengths of the tray.
Repeat steps 3-5 four more times.
Repeat steps 2-6 increasing the depth each time by 0.5 cm up to 3.0 cm.
Analysis
1.
Calculate the mean speed of the waves using:
mean speed =
2.
Plot a graph of depth against speed.
Apparatus – Method 2
ripple tank with plane wave dipper
motor mounted on beam, with beam support
hand stroboscope
metre rule
paper
lamp
148
distance
mean time
Diagram of apparatus
Method 2 - Wavelength
Water waves can be produced in a ripple tank. How will the depth of water affect the wavelength
of the waves produced? Use the results from your speed experiment to design a hypothesis to
be tested.
1. Set the ripple tank on the floor and ensure it is level.
2. Fill the ripple tank with a small volume of water.
3. Adjust until the plane wave dipper is just in contact with the surface of the water
4. Place the paper under the tank.
5. Switch on the motor as slowly as possible as possible to produce low frequency ripples.
6. Illuminate the ripple tank from above to produce a pattern on the paper.
7. Freeze the wave pattern using a stroboscope.
8. Observe the pattern produced and find the wavelength by measuring 10 wavelengths on
the paper on the floor and finding the mean.
9. Repeat for a greater depth of water.
Analysis
1. Do the results to the experiment agree with your hypothesis?
2. Make a conclusion; consider the accuracy of the measurements you made and how you
reduced the uncertainty in the measurements.
149
Risk Assessment
Hazard
Wet floors are
slippery.
Risk
Control measure
If water splashes on the floor during
the experiment people may slip and
be injured.
Do not overfill the trays.
Place down gently when producing
waves.
Mop up any spillages.
Teacher/ Technician notes
Photo-induced epilepsy
In all work with flashing lights, teachers must be aware of any student suffering from photoinduced epilepsy. This condition is very rare. However, make a sensitive inquiry of any known
epileptic to see whether an attack has ever been associated with flashing lights. If so, the student
could be invited to leave the lab or shield his/her eyes as deemed advisable. It is impracticable to
avoid the hazardous frequency range (7 to 15 Hz) in this experiment.
A drop of detergent in the water makes the pattern more easily seen.
If access to ripple tanks is limited, this experiment can be demonstrated to students.
Although straight sided trays are preferable, Gratnell trays work quite well in this experiment.
Students will need to be given the value for the volume of water required to fill the tray to a depth
of 0.5 cm – in cm3 this is numerically equal to half the surface area .
The data should give a smooth curve as the speed is proportional to �depth .
150
Students should plot a graph of depth against mean speed and be encouraged to plot a smooth
curve of best fit and to examine the quantitative relationship between the variables.
Students should be told that they need to use the length of tray × 3 in calculating the mean speed
for each depth.
It is interesting to investigate the factor by which the depth must change to double the speed of
the waves this could provide good extension opportunities for the more able.
Students should design their own table, but a suggested table format is shown below.
Depth of
water
(cm)
Length
of tray
(cm)
Time taken for waves to travel three lengths of the tray
(s)
Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Mean
Mean
speed
(cm/s)
Practical techniques covered
P4
Making observations of waves in fluids and solids to identify the suitability of
apparatus to measure speed/frequency/wavelength.
Making observations of the effects of the interaction of electromagnetic waves with
matter.
151
6
LIGHT AND ELECTROMAGNETIC WAVES
6.1 FREQUENCY RANGE OF THE SPECTRUM
Spec Statement
Comment
(a)
recall that light is an
electromagnetic wave
Expected to know the seven colours of the visible
light.
(b)
recall that electromagnetic waves
are transverse, are transmitted
through space where all have the
same velocity, and explain, with
examples, that they transfer
energy from a source to an
absorber
Examples of transferring energy from a source to an
absorber include emissions from the Sun – visible light
is absorbed by the retina in an eye, infra-red by the
surface of the Earth, ultraviolet by the atmosphere.
(c)
describe the main groupings of
the spectrum – radio, microwave,
infra-red, visible (red to violet),
ultraviolet, X-rays and gamma
rays, that these range from long
to short wavelengths and from
low to high frequencies, and that
our eyes can only detect a limited
range
Have knowledge of the order in which the regions are
arranged in terms of wavelength, frequency or energy.
In a question – speed of light in a vacuum,
c = 3 × 108 m s-1 will be given if needed.
No knowledge of alpha and beta is required here.
Higher frequencies transmit higher energies.
152
6.2 INTERACTIONS OF ELECTROMAGNETIC RADIATION WITH MATTER AND THEIR
APPLICATIONS
Spec Statement
Comment
(a)
recall that radio waves can be
produced by or can themselves
induce oscillations in electrical
circuits
Identify aerials as the devices that detect and
transform radio waves into electrical
oscillations.
The vibration of charged particles is expected
but knowledge of electric fields is not.
(b)
recall that the generation and
absorption of radiations over a wide
frequency range are associated with
changes in atoms and nuclei
When an atom absorbs em energy the electrons
or the nuclei may be excited and move to a
higher energy level. Electrons emit em energy as
they return to their original state. Nuclei emit
gamma rays when they return to their original
state.
The associated frequencies are not expected to
be known.
See section 9.2 – absorption and emission of
ionising radiation statement (a).
(c)
give examples of some practical uses
of electromagnetic waves in the radio,
microwave, infra-red, visible,
ultraviolet, X-ray and gamma ray
regions and describe how ultraviolet
waves, X-rays and gamma rays can
have hazardous effects, notably on
human bodily tissues
No knowledge of alpha and beta is required here.
Uses should include communications and
medical applications.
(d)
recall that different substances may
absorb, transmit, refract, or reflect
electromagnetic waves in ways that
vary with wavelength; explain how
some effects are related to
differences in the velocity of the
waves in different substances
X-ray photographs etc
Know that refraction involves a change in
velocity at the boundary of the media.
Learners may be expected to interact with
data that may be given.
(e)
use ray diagrams to illustrate reflection
and refraction at plane surfaces
Only at plane boundaries required.
Knowledge of the terms normal, angles of
incidence / reflection / refraction required.
Should know what happens to the speed /
frequency / wavelength / direction of water waves
as they move from deep to shallow water (and
vice versa).
SPECIFIED PRACTICAL WORK
•
PSP6.2 Investigation of refraction in a glass block
153
Investigation of refraction in a glass block
Introduction
When visible electromagnetic radiation interacts with matter it may be reflected, refracted or
absorbed. For light interacting with a transparent medium such as water or glass, it is refracted.
Refraction can be investigated using glass blocks and ray boxes.
Apparatus
rectangular perspex block
ray box
12 V d.c. power supply
protractor
plain A4 paper
Diagram of Apparatus
Note that the diagram is an illustration only so the angles are approximate
154
Method
1. Place the glass block on the paper and carefully draw round it.
2. Use a protractor to measure and mark the position of the normal and the incident rays at
20º, 40º, 60º and 80º as shown.
3. Shine an incident ray at 20º to the normal into the glass block.
4. Carefully mark with a pencil the path of the ray as it leaves the block.
5. Switch off the ray box and remove the glass block.
6. Using a ruler draw a straight line between the entry and exit points of the ray.
7. Measure and record the angle of refraction; this is the angle between the path of the ray in
the block and the normal.
8. Repeat steps 2 to 7 for incident rays at 40º, 60º and 80º.
Risk Assessment
Hazard
Hot ray box
lamp can burn
Risk
Control measure
If the lamp is touched when moving
it can cause burns to the skin.
Do not touch lamp
Switch off when not in use
Leave to cool before packing away
Teacher / Technician notes
If preferred a template could be produced and given to the students to use. If Perspex blocks are
not available, glass blocks can be substituted.
This experiment is good for developing careful measuring skills using a protractor. As an
extension students could investigate the angle at which the ray leaves the block and look for
patterns in their data. Repeat readings are not required.
Practical techniques covered
P4
Making observations of waves in fluids and solids to identify the suitability of
apparatus to measure speed/frequency/wavelength.
Making observations of the effects of the interaction of electromagnetic waves with
matter.
155
7. ELECTRICITY
7.1 CURRENT, POTENTIAL DIFFERENCE AND RESISTANCE
Spec Statement
Comment
(a)
recall that current is the rate of
Current may also be described as the charge flow per
flow of charge, that for charge to
unit time.
flow, a source of potential
difference and a closed circuit are
needed and that a current has
the same value at any point in a
single closed loop
(b)
recall and use the relationship
between quantity of charge,
current and time (charge flow =
current × time [Q = It])
Charge measured in coulombs (C).
Recall that 1 amp = 1 coulomb flowing past a point in a
circuit in 1 second i.e. 1 A = 1 C/s
See section 1.1 – Energy changes statement (g).
(c)
recall that current (I) depends on
both resistance (R) and potential
difference (V) and the units in
which these are measured
Current (I), amperes =A
Resistance (R), ohms = Ω
Potential difference (V), volts = V
(d)
recall and apply the relationship
between I, R and V, and know
that for some components the
value of R remains constant but
for lamps it changes as the
current changes (potential
difference = current × resistance
[V = IR])
The qualitative and quantitative relationships should be
known.
1
If R is constant then I α V. If V is constant then I α
R
Circuits to investigate I-V characteristics could include a
variable resistor or a variable power supply.
Include knowledge of how:
• I varies with V for a resistor at constant
temperature. R remains constant
• R varies with V for a lamp because temperature
is not constant
• R varies with positive (forward bias) and
negative voltages (reverse bias) for a diode and
that normally a diode will not conduct until a
particular voltage is reached.
Current plotted on the y-axis and voltage on the x-axis.
156
(e)
(f)
explain how the power transfer in
any circuit device is related to the
p.d. across it and the current, and
to the energy changes over a
given time:
• power = potential
difference × current =
(current)2 × resistance
[P = IV = I2R]
energy transferred
• power =
time
and
• energy transferred =
charge flow × potential
difference
[E = QV]
explain the design and use of
circuits to explore the variation of
resistance – including for lamps,
diodes, ntc thermistors and LDRs
Including the relationship between the units watts and
joules i.e. 1 W = 1 J/s
V2
is not required
P=
R
Links with statement (b) in this section.
Include knowledge of how:
• R varies with T for a ntc thermistor
• R varies with light intensity for a LDR
A multimeter could be used as an ohmeter to
explore the variation of resistance in a thermistor and
LDR.
SPECIFIED PRACTICAL WORK
•
PSP7.1 Investigation of the current-voltage (I-V) characteristics of a component
157
Investigation of the current-voltage (I-V) characteristics of a component
Introduction
The voltage across and the current through a component can be measured and the results
plotted on a graph to show the I-V characteristic of the component.
Apparatus
12 V filament lamp
voltmeter ± 0.01 V
ammeter ± 0.01 A
connecting leads
12 V d.c. power supply
variable resistor
Diagram of Apparatus
158
Method
1.
2.
3.
4.
5.
6.
Connect the circuit as shown in the diagram.
Adjust the variable resistor until the voltmeter reads 1 V.
Record the readings of voltage and current.
Adjust the variable resistor to increase the voltmeter reading to 2 V.
Record the readings of voltage and current.
Repeat steps 4 to 5, increasing the voltage by 1 V each time, until the voltmeter reads 12 V.
Analysis
1. Plot a graph of current (y-axis) vs voltage (x-axis).
Risk Assessment
Hazard
Hot lamps can
burn
Risk
Control measure
Allow lamp to cool before touching
them.
Burning skin on hot lamps
Technician / Teacher notes
Ray box lamps are suitable to use instead of 12 V lamps.
d.c. voltmeters and ammeters must be used.
If variable resistors are not available then a variable power supply could be used. Students
should read the voltage directly from the voltmeter rather than using the settings on the power
supply.
If students are constructing the circuits, it is advisable they should be checked for short circuits
before use.
The graph should show a non-linear relationship.
More able students should be encouraged to discuss how the resistance of the filament changes
due to the heating effect.
Practical techniques covered
P6
Use of appropriate apparatus to measure current, potential difference (voltage) and
resistance, and to explore the characteristics of a variety of circuit elements.
P7
Use of circuit diagrams to construct and check series and parallel circuits including a
variety of common circuit diagrams.
159
7.2 SERIES AND PARALLEL CIRCUITS
Spec Statement
Comment
(a)
describe the differences
between series and parallel
circuits, including the
properties of currents and
potential differences
Including appreciation of types of household circuits e.g.
ring main, household lighting circuits.
(b)
explain why, if two resistors
are in series the net
resistance is increased, and
calculate the net resistance of
two resistors in series
No limit to the number of resistors in series.
Collision theory of mobile free electrons is an expected
explanation.
(c)
explain why, if two resistors
are in parallel the net
resistance is decreased and
calculate the net resistance
of two resistors in parallel
No limit to the number of parallel branches.
Learners should be encouraged to not express their
final answer in terms of a fraction.
(d)
calculate the currents,
potential differences and total
resistance in d.c. series
circuits, and explain the
design and use of such
circuits for measurement and
testing purposes; represent
them with the conventions of
positive and negative
terminals, and the symbols
that represent common circuit
elements, including diodes,
LDRs and thermistors
Know that an ammeter must be connected in series and a
voltmeter must be connected in parallel.
Be able to draw circuit diagrams.
160
SPECIFIED PRACTICAL WORK
•
PSP7.2 Investigation of the characteristics of series and parallel circuits
161
Investigation of the characteristics of series and parallel circuits
Introduction
Components (e.g. lamps) may be connected together in series or in parallel in electrical circuits.
This investigation explores the key differences between series and parallel circuits. How bright
are the lamps in each circuit? What happens when a bulb blows or is removed? How can we
explain our observations in terms of voltage and current values?
Apparatus
circuit board
approx. 6 × connecting wires [depending on apparatus used]
voltmeter ± 0.01 V
ammeter ± 0.01 A
12 V d.c. power supply
switch
Diagram of Apparatus
Method
Part 1 – Basic observations
1.
2.
3.
4.
5.
Set up the circuit shown on the left above with 2 bulbs in series.
Observe the brightness of the bulbs.
Remove (pull out / unscrew) one of the bulbs. Observe the effect on the other bulb.
Set up the circuit shown on the right above with 2 bulbs in parallel.
Repeat steps 2 and 3 with the parallel circuit.
162
Part 2 – Voltage measurements
1. Set up the circuit with 2 bulbs in series.
2. Connect a voltmeter across each of the bulbs (in turn) and then across the battery.
3. Record all of your measurements.
V
V
V
4. Set up the circuit with 2 bulbs in parallel.
5. Connect a voltmeter across each of the bulbs (in turn) and then across the battery.
6. Record all of your measurements.
V
V
V
Analysis
1. What conclusions can you draw from your measurements of voltage above.
•
•
•
•
What patterns can you see?
What happens to the voltage from the battery in a series circuit?
What happens to the voltage from the battery in a parallel circuit?
What is the link between the brightness of the bulb and the voltage across it?
163
Part 3 – Current measurements
1. Set up the circuit with 2 bulbs in series.
2. Connect an ammeter in each of the 3 positions (in turn) shown in the diagram below.
3. Record all of your measurements.
A
A
A
4. Set up the circuit with 2 bulbs in parallel.
5. Connect an ammeter in each of the 4 positions (in turn) shown in the diagram below.
6. Record all of your measurements.
A
A
A
A
Analysis
1. What conclusions can you draw from your measurements of current above.
•
•
•
•
What patterns can you see ?
What happens to the current from the battery in a series circuit?
What happens to the current from the battery in a parallel circuit?
What is the link between the brightness of the bulb and the current in it?
164
Risk Assessment
Hazard
Risk
Control measure
There is no significant risk in carrying out this experiment.
Teacher / Technician Notes
This investigation will take a series of lessons to complete. In Part 1 students will revise how to
set up series and parallel circuits and make simple observations of the key differences between
them. They may extend these circuits to 3 or 4 lamps in series/parallel. The ability to control
each lamp with its own switch in a parallel circuit may also be explored practically (and/or
discussed). Examples of each circuit could also be discussed, e.g. Christmas tree lights, house
lighting circuits.
Students will need to be taught (reminded) how to use a voltmeter correctly by connecting it in
parallel in Part 2. Although the potential difference across the battery will be less than its emf
(due to internal resistance) the sharing of the voltage between the lamps should be clearly
evident.
In Part 3 students will need to master the trickier task of connecting an ammeter in series in
various positions. This will involve “breaking the circuit” so that the ammeter may be inserted in
the gap created. Care is needed here so that ammeters are not “shorted” or the “fuses” blown in
digital meters by connecting them in parallel.
Students should be encouraged to discuss the patterns shown in their results and relate the
values obtained to the brightness of the lamps. They could write a full account (comparison) of
the characteristics of series and parallel circuits which incorporates all of their observations and
measurements in this series of lessons.
The work could be extended by determining the total resistance of the combination of 2 lamps in
series and in parallel. Also different components could be used, e.g. a resistor and a lamp, rather
than 2 identical lamps.
Simulation software is available (e.g. “Live Wire”).
characteristics of series and parallel circuits.
This could also be used to explore the
Practical techniques covered
P6
Use of appropriate apparatus to measure current, potential difference (voltage) and
resistance, and to explore the characteristics of a variety of circuit elements.
P7
Use of circuit diagrams to construct and check series and parallel circuits including a
variety of common circuit diagrams.
165
7.3 DOMESTIC USES AND SAFETY
Spec Statement
Comment
(a)
recall that the domestic supply in the
UK is a.c. at 50 Hz and 230 V, explain
the difference between direct and
alternating voltage
An alternating current (a.c.) is one that
continuously changes direction. Mains electricity
is an a.c. supply.
A direct current (d.c.) has a constant direction.
Cells and batteries provide d.c.
Graphical representation of a.c. and d.c. voltages
on CRO screens.
The UK mains supply is about 230 V and has a
frequency of 50 cycles per second (50 Hz).
(b)
recall the differences in function
between the live, neutral and earth
mains wires, and the potential
differences between these wires;
hence explain that a live wire may be
dangerous even when a switch in a
mains circuit is open, and explain the
dangers of providing any connection
between the live wire and earth
The structure and wiring of a 3 pin plug is
required.
The function of the live wire is to carry current to
the house/appliance at a high voltage.
The neutral wire completes the circuit and carries
current away at low/zero voltage.
The earth wire is a safety wire that can carry
current safely into the ground if a fault develops
in a metal framed appliance.
Appliances with metal cases are usually earthed.
Learners need to be aware of the symbol for
doubly insulated appliances and that these
appliances require no connection to earth.
If the casing becomes live, a large current can
flow along the low-resistance earth wire and this
high current will ”blow” a fuse.
Switches and fuses are placed into the live wire.
(c)
explain the function of a fuse and from
calculations select an appropriate
rating for a particular appliance
A selection of fuse ratings (for fitting in 3 pin
plugs) will be given.
166
8
MAGNETISM AND ELECTROMAGNETISM
8.1 PERMANENT AND INDUCED MAGNETISM, MAGNETIC FORCES AND FIELDS
Spec Statement
Comment
(a)
describe the attraction and
repulsion between unlike and like
poles for permanent magnets
and describe the difference
between permanent and induced
magnets
Be able to describe the effect as an example of a
“force acting at a distance”.
Knowledge of domain theory is not expected.
(b)
describe the characteristics of the To include magnetic field directions (N → S) and their
magnetic field of a bar magnet,
spacing to indicate magnetic field strength.
showing how strength and
direction change from one point
to another
(c)
explain how the behaviour of a
magnetic compass is related to
evidence that the core of the
Earth must be magnetic
To involve a horizontal compass only. Knowledge of
“angle of dip” and “angle of declination” are not
expected. No requirement to be able to draw the
magnetic field due to the Earth.
167
8.2 MAGNETIC EFFECTS OF CURRENTS AND THE MOTOR EFFECT
Spec Statement
Comment
(a)
describe how to show that an electric
current can create a magnetic effect
and draw the magnetic fields due to
currents in a straight conducting wire,
a plane coil and a solenoid, including
the relationship between the directions
of the current and field
To include magnetic field directions (N → S) and
their spacing to indicate magnetic field strength.
Application of Right Hand Grip Rule is required.
(b)
recall that the strength of the field
depends on the current and the
distance from the conductor, and
explain how solenoid arrangements
can enhance the magnetic effect
To include magnetic field directions (N → S) and
their spacing to indicate magnetic field strength.
Knowledge of the use of an iron core to enhance
magnetic field strength.
(c)
describe how a magnet and a
Application of Flemings Left Hand Rule is
current-carrying conductor exert a
required.
force on one another and apply
Fleming’s left-hand rule to the
relative orientations of the force,
the current in the conductor and the
magnetic field
(d)
apply the equation that links the
SI units only to be examined.
force on a conductor to the
Know that B-field is measured in Tesla (T).
strength of the field, the current and
the length of conductor to calculate
the forces involved i.e. force on a
conductor (at right angles to a
magnetic field) carrying a current =
magnetic field strength × current ×
length [F = BIl]
(e)
explain how this force is used to
cause rotation in electric motors
An understanding of quantitative
relationships between the stated variables is
required.
Appreciate the purpose of split rings and
carbon brushes.
SPECIFIED PRACTICAL WORK
•
PSP8.2 Investigation of the force due to the magnetic field of coils
168
Investigation of the force due to the magnetic field of coils
Introduction
The strength of an electromagnet can be varied by changing the number of turns on the
electromagnet.
Apparatus
iron ‘C’ core
flexible insulated wire
paper clips
d.c. power supply fixed at 4 V
Diagram of Apparatus
Method
1. Connect the circuit as shown in the diagram. Ensure that the power supply is initially off.
2. Wrap 10 turns of wire around the C-core then switch on the power supply.
3. Place the electromagnet into a pile of paper clips and record the number of paper clips
picked up. Switch off the power supply.
4. Add 10 more turns to the C-core and repeat step 3.
5. Repeat step 4 until the number of turns equals 70.
Analysis
1. Plot a graph to show how the number of paper clips picked up depends on the number of
turns on the electromagnet.
169
Risk Assessment
Hazard
Risk
Control measure
Do not exceed 4 V
Switch off the power supply after every
reading
Allow apparatus to cool before touching
Hot wires on the
Burning skin whilst handling
electromagnet
apparatus
can burn
Technician / Teacher notes
Power supplies should be set, fixed at 4 V.
To prevent the wires overheating the power supply should be switched off immediately after
taking readings.
Wire used should be flexible insulated wire and should be cut in lengths that allow 70 turns to be
wound around the iron core.
Approximately 2 cm of the insulation should be removed from each end of the wire.
Iron C-cores are preferred, however, large iron nails can be used but must be filed blunt.
Paper clips should be standard small metal clips – not covered in plastic.
Over time it is possible that the paper clips themselves will become magnetised. These should
not be used in this experiment.
170
Practical techniques covered
P2
Use of appropriate apparatus to measure and observe the effects of forces including the
extension of springs.
171
9.
ATOMIC STRUCTURE
9.1 NUCLEAR ATOM AND ISOTOPES
Spec Statement
Comment
(a)
describe how the model of the
atom has changed over time i.e.
plum pudding and Bohr models
The plum pudding model – the idea that an atom is a
sphere of positive charge, with negatively charged
electrons in it.
The Bohr model depicts the atom as a small, positively
charged nucleus surrounded by electrons that travel in
circular orbits around the nucleus with attraction
provided by electrostatic forces.
(b)
describe the atom as a positively
charged nucleus surrounded by
negatively charged electrons,
with the nuclear radius much
smaller than that of the atom and
with almost all of the mass in the
nucleus
The term nucleon refers to protons and neutrons.
Neutrons are not charged.
It is assumed that neutrons and protons have the
same mass.
(c)
recall the typical size (order of
magnitude) of nuclei, atoms and
small molecules
Typical diameter of a nucleus = 1 ×10-15 m
Typical diameter of an atom = 0.3 × 10-9 m
Typical diameter of a small molecule = 1 × 10-8 m
(d)
recall that atomic nuclei are
composed of both protons and
neutrons, that the nucleus of
each element has a characteristic
positive charge, but that atoms of
the same element can differ in
nuclear mass by having different
numbers of neutrons
Define isotopes of the same element as having equal
numbers of protons but differing numbers of neutrons
in their nuclei.
(e)
use atomic notation (i.e. 𝐴𝑍X) to
relate differences between
isotopes of the same and
different elements to their
charges and masses
Compare the nuclei of different elements in terms of
particles.
172
9.2 ABSORPTION AND EMISSION OF IONISING RADIATIONS AND OF ELECTRONS AND
NUCLEAR PARTICLES
Spec Statement
(a)
recall that in each atom its
electrons are arranged at
different distances from the
nucleus, that such
arrangements may change
with absorption or emission
of electromagnetic
radiation and that atoms
can become ions by loss of
outer electrons
Comment
Knowledge of basic orbit or energy levels of electrons is
required and the terms “excitation” and “ionisation”.
https://www.learner.org/interactives/periodic/elementary2.html
See section 6.2 – interactions of em radiation statement (b).
(b)
recall that some nuclei are
unstable and may emit
alpha particles, beta
particles, or neutrons, and
electromagnetic radiation
as gamma rays; relate
these emissions to
possible changes in the
mass or the charge of the
nucleus, or both
No credit will be given for stating that an alpha particle is
“helium” or a “helium atom” or a ”helium ion”.
Recognise an alpha particle as being a group of two neutrons
and two protons.
(c)
use names and symbols of
common nuclei and
particles to write balanced
equations that represent
radioactive decay
Express an alpha particle as 42He, an electron as −10e
neutron as 10n and a proton as 11p.
It is not expected that learners will recall nucleon and proton
numbers for different isotopes.
(d)
explain the concept of halflife and how this is related
to the random nature of
radioactive decay
Understand that small variations in count rate are to be
expected as radioactive decay is a random process.
Plot smooth curves of best fit when producing decay curves.
Be able to draw suitable horizontal and vertical construction
lines onto the decay curve in order to show a clear
determination of the half-life.
Define half-life as the time taken for the number of radioactive
nuclei / mass / activity to reduce to one half of its initial value.
An unstable nucleas becomes stable by losing energy or
mass.
173
(e)
calculate the net decline
in radioactive emission
as a ratio by using the
half-life
Be able to calculate the activity after a certain number of
half-lives, or calculate half-life from given data on
changes to activity.
(f)
recall the differences in the
penetration properties of
alpha particles, beta
particles and gamma rays
Understand the difference in risk for alpha, beta or gamma
sources outside or inside the body.
(g)
recall the differences
between contamination
and irradiation effects and
compare the hazards
associated with these two
effects
Understand that in contamination the radioactive isotope is
transferred and so the contaminated object will be exposed to
radiation whilst the isotope continues to decay. In irradiation
the object is exposed to ionising radiation e.g. to sterilise it,
so the exposure time is limited.
174