MINISTRY OF EDUCATION
NAMIBIA SENIOR SECONDARY CERTIFICATE
PHYSICAL SCIENCE
SPECIMEN PAPERS 1 – 2, PRACTICAL AND
MARK SCHEMES
HIGHER LEVEL
GRADES 11 – 12
(FOR TEACHERS)
THESE PAPERS AND MARK SCHEMES SERVE TO
EXEMPLIFY THE SPECIFICATIONS IN THE LOCALISED
NSSC PHYSICAL SCIENCE HIGHER LEVEL SYLLABUS
2006
Ministry of Education
National Institute for Educational Development (NIED)
Private Bag 2034
Okahandja
Namibia
© Copyright NIED, Ministry of Education, 2005
NSSCH Physical Science Specimen Paper Booklet Grades 11 - 12
ISBN: 99916-69-96-5
Printed by NIED
Publication date: 2005
TABLE OF CONTENTS
PAPER 1: SPECIMEN PAPER...............................................................................................1
PAPER 1: MARK SCHEME.................................................................................................13
PAPER 2: SPECIMEN PAPER.............................................................................................17
PAPER 2: MARK SCHEME.................................................................................................37
INSTRUCTIONS TO THE PRACTICAL PAPER.................................................................47
PRACTICAL PAPER..............................................................................................................51
PRACTICAL PAPER MARK SCHEME................................................................................57
MINISTRY OF EDUCATION
Namibia Senior Secondary Certificate (NSSC)
PHYSICAL SCIENCE: HIGHER LEVEL
PAPER 1:
SPECIMEN PAPER
TIME: 1h 30 minutes
MARKS: 70
INSTRUCTIONS TO LEARNERS
Write your Centre number and Learner number in the space at the top of this page.
Answer all questions.
Write your answers in the spaces provided on this question paper.
Use a sharp pencil for your drawings. Coloured pencils or crayons should not be used.
INFORMATION TO LEARNERS
The intended number of marks is given in brackets [ ] at the end of each question.
A copy of the Periodic Table is provided at the end of this paper.
1
Question 1
1.
Chlorine is the element with proton (atomic) number 17. It has two isotopes of nucleon
(mass) numbers 35 and 37.
(a) Explain the meaning of the word isotope in terms of the particles present in 35Cl
and 37Cl.
………………………………………………………………………………………
………………………………………………………………………..………
[2]
(b) The relative atomic mass (Ar) of chlorine is given on the Periodic Table as 35.5.
Explain why the relative atomic mass is not a whole number.
………………………………………………………………………………………
………………………………………………………………………..………
[2]
(c) On the diagram below, show the electron arrangement in an atom of chlorine.
[1]
(d) (i) Draw a 'dot and cross' diagram to show the bonding in potassium chloride
KCl, showing outer electrons only.
[3]
(ii) Name the type of bonding present in potassium chloride.
……………………………………………. [1]
2
(e) (i) Phosphorus forms a chloride, PClx, which contains 77.45% chlorine by mass.
Calculate the value of x.
…………….…………………… [3]
(ii) Suggest the type of bonding present in this chloride of phosphorus.
………………………………………..…
[1]
Total [13]
3
Question 2
2.
(a) Complete the following table.
name of compound
homologous series
displayed formula
Ethane
ethene
alkene
[4]
(b) (i) Give one chemical test by which you could distinguish between ethane and
ethene.
…………………………………………….……………………………………
……………………………………………………………………….….
[2]
(ii) Under what conditions does ethene react with water? What is the product of
this reaction?
Conditions ……………………………………………………………………
Product …………………………………………………………..…….
[2]
Total [8]
4
Question 3
3.
Lime (calcium oxide) is manufactured from limestone (calcium carbonate).
(a) How is limestone converted into lime?
………………………………………………………………………..………
[1]
(b) Suggest how lime is converted into slaked lime (calcium hydroxide).
………………………………………………………………………..………
[1]
(c) Explain why slaked lime is sometimes spread on farmers' fields.
………………………………………………………………………………………
………………………………………………………………………..………
[1]
(d) State two industrial uses of calcium carbonate, other than the manufacture of lime.
use 1 …………………………………………………………….………………….
use 2 …………………………………………………………………………. [2]
Total [5]
Question 4
4.
Magnesium and calcium are members of Group II of the Periodic Table. Chlorine and
iodine are members of Group VII.
(a) Give the symbols of the ions formed by
(i) magnesium, ………………………………………………………..…..………
(ii) iodine. …………………………………………………………………….
[2]
(b) Magnesium iodide can be made by the direct combination of magnesium with
iodine. Write the balanced chemical equation for this reaction.
………………………………………………………………………..………
[1]
(c) Predict what you would see if aqueous magnesium iodide was added to:
(i) aqueous silver nitrate, …………………………………….…………………...
(ii) aqueous sodium hydroxide. …………………………………..…………..
[2]
(d) Write an equation for the reaction between aqueous magnesium iodide and aqueous
silver nitrate.
………………………………………………………………………..………
[2]
Total [7]
5
Question 5
5.
A sky-diver (see Fig. 5.1) steps from an aircraft and drops vertically through 500 m,
reaching a terminal speed of 60 m s-1.
(a) Name the quantity represented by the symbol g.
………………………………………………………………………..………
[1]
The total mass of the sky-diver is 90 kg.
Fig 5.1
(b) Calculate
(i) the loss of gravitational potential energy of the sky-diver during the 500 m
drop,
…………………………………… [2]
(ii) the kinetic energy of the sky-diver at the end of this 500 m drop.
…………………………………… [2]
(c) Suggest why your answers to (b) (i) and (b) (ii) differ.
………………………………………………………………………………………
………………………………………………………………………..………
[1]
Total [6]
6
Question 6
6.
(a) Fig. 6.1 shows two rays of light from a distant object arriving at a spherical
concave mirror. The centre of curvature C of the mirror is shown.
.
Fig 6.1
(i) On Fig. 6.1, draw the path of these two rays after reflection.
[1]
(ii) What name is given to the point where these reflected rays meet?
……………………………………………………………………….….
7
[1]
(b) Fig. 6.2 shows a ray of light undergoing refraction at an air-glass surface. The
refractive index of the glass is 1.6.
Fig 6.2
(i) The angle of incidence is now increased to 45°. Calculate the angle of
refraction for this value.
[2]
(ii) State the value of the ratio
speed of light in air
speed of light in glass
for this refraction.
[1]
Total [5]
8
Question 7
7.
(a) Two light bulbs A and B, in series, form part of an electrical circuit (see Fig. 7.1).
The resistance of bulb A is to be determined by using a voltmeter and an ammeter.
Fig 7.1
Complete the circuit diagram of Fig. 7.1 to show the positions of the voltmeter and
of the ammeter.
[2]
(b) The filaments at A and B have equal lengths.
The cross-sectional area of the filament in B is twice that of the filament in A.
Assuming that the voltmeter draws negligible current, compare the following
quantities:
(i) the current at A with the current at B,
……………………………………………………………………….….
[1]
(ii) the potential difference across A with the potential difference across B.
…………………………………………………………………………………
……………………………………………………………………….….
[2]
(c) Which of the two bulbs, A or B, shines more brightly? Explain how you arrive at
your answer.
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………..………
[2]
Total [7]
9
Question 8
8.
(a) Describe, using electromagnetic principles, the operation of an alternating current
transformer.
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………..………
[3]
(b) At a power generating station, the 3 000 V output from the generators is
transformed to 72 000 V before transmission along overhead lines.
(i) Assume the transformers used for this purpose have 100% efficiency.
Calculate the ratio Ns/Np, where Ns and Np are, respectively, the number of
turns on the secondary coil and on the primary coil.
Ns/Np = ………………………………..………………….
[1]
(ii) Explain the advantage of using a high voltage for the transmission of electrical
energy.
…………………………………………………………………………………
…………………………………………………………………………………
……………………………………………………………………….….
[2]
Total [6]
10
Question 9
9.
(a) State the composition of
(i) alpha particles, ……………………………….………….……………….
[1]
(ii) beta particles, ………………………………………………….…………
[1]
(iii) gamma rays. ………………………………………………………..……
[1]
(b) Americium is a radioactive nuclide that emits alpha particles. In the past, small
sources of americium were fitted into smoke detectors used in factories and homes.
The presence of smoke interrupts an electric current through the air which has been
ionized by the alpha particles. The interruption causes an alarm to sound.
(i) State the change that occurs in the nucleon (mass) number of an americium
nucleus when an alpha particle is emitted.
…………………………………………..…………..…………………….. [1]
(ii) Suggest two reasons why an americium source was used in smoke alarms in
preference to an isotope that produces gamma rays.
1.
……………………………………………………….………………….
2.
………………………………………………………………….…
[2]
(iii) The strength of the americium source does not diminish significantly with
long-term use. Predict what further information this suggest about americium.
……………………………………………………………………….….
[1]
Total [7]
Question 10
10. Ammonia can be manufactured from hydrogen and nitrogen in the Haber process.
(a) State the essential conditions used in this process.
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………..………
[2]
(b) Write a balanced chemical equation for this process.
………………………………………………………………………..………
[1]
Total [3]
11
Question 11
11. (a) Outline what is meant by
(i) a scalar quantity,
……………………………………………………………………….….
[1]
(ii) a vector quantity.
……………………………………………………………………….….
[1]
(b) Identify the scalar quantity(s) in the following list
mass,
velocity,
time,
acceleration,
speed
[1]
Total [3]
Acknowledgement
The Ministry of Education acknowledges the assistance of the University of Cambridge Local
Examination Syndicate, (UCLES), in granting permission to use resources and ideas towards
the production of these specimen questions, notably for questions 1 to 11.
12
MINISTRY OF EDUCATION
Namibia Senior Secondary Certificate (NSSC)
PHYSICAL SCIENCE: HIGHER LEVEL
PAPER 1:
MARK SCHEME
Question 1
1. (a) Same number of 17 protons but different number of neutrons
(one atom has 18 and the other 20 neutrons)
or
Same atomic number but different nucleon number
The one atom has 18 and the other 20 neutrons
[2]
[1]
[1]
(b) The relative atomic mass of an element or compound = (the average mass of one
atom of the element) ÷ 1/12 of mass of one atom of the carbon-12 isotope
[1]
The average mass of an atom depends on the percentage of each isotope
most elements have more than one isotope that have to be taken into account when
calculating the average mass
[1]
or
The relative atomic mass of an element is the average mass of its isotopes
compared with an atom of carbon-12 isotope
[2]
(c) for correct electron configuration
[1]
(d) (i) correct indication of electron transfer from K to Cl (arrow from K electron to
Cl or arrow from K to donated electron in Cl) Note: K’s donated electron
should not be indicated on both K and Cl
[1]
correct diagram of cation of K+ and anion Cl[1]
correct indication of attraction between ions of opposite charge
[1]
(ii) ionic
[1]
(e) (i) In 100 g of phosphorus chloride:
1 mole chlorine = 77.45 ÷35.5 = 2.18 mol
1 mole phosphorus = 22.55 ÷ 31 = 0.72 mol
Resulting in 1 : 3 ratio
Therefore PCl3
1 mark for use of 100 or 1000 g as start
1 mark for calculation of mole ratios
1 mark for answer
(ii) covalent
13
[3]
[1]
Total [13]
Question 2
2. (a) alkane; ethanol; alcohol; structure of ethene
(b) (i) bromine water / potassium manganate (VII)
solution goes from coloured to clear
(ii) conditions:
catalyst (phosphoric acid)
temperature above 300oC
pressure above 60 atmospheres
product: ethanol
[4]
[2]
[2]
Total [8]
Question 3
3. (a) heated
[1]
(b) slaked with water/ water added
[1]
(c) to change the pH in soil from acidic to slightly alkaline
[1]
(d) Any two: fertiliser / making of NaOH / neutralising acidic industrial waste
products (open memo)
[2]
Total [5]
Question 4
4. (a) (i) Mg2+
(ii) I(b) Mg + I2 → MgI2
(c) (i) yellow ppt
(ii) white ppt
(d) MgI2 + 2AgNO3 → 2AgI + Mg(NO3)2
Question 5
5. (a) gravitational constant / gravitational acceleration towards centre of earth
(b) (i) Potential Energy = mgh = 90 × 10 × 500 = 450 kJ
1
(ii) Kinetic Energy = mv 2 = 0.5 × 90 × 60 × 60 = 162 kJ
2
(c) friction/ air resistance
Question 6
6. (a) (i)
(ii)
(b) (i)
(ii)
rays should reflect to point F (half way between C and mirror)
(principal) focal point
26.2o
1.6
[2]
[1]
[2]
[2]
Total [7]
[1]
[2]
[2]
[1]
Total [6]
[1]
[1]
[2]
[1]
Total [5]
Question 7
7. (a) 1 mark for ammeter in series
1 mark for voltmeter in parallel
[2]
(b) (i) Current at B is the same as at A
[1]
(ii) Voltage across B is half of voltage across A
[2]
(c) B - although both have the same I, B has smaller V, which means it will have a
lower power since P = V I
[2]
Total [7]
14
Question 8
8. (a) a transformer transfers electrical energy or electrical power from one circuit to
another
[1]
alternating current in the primary coil causes the induced magnetic field to
change direction/ changing the potential difference
[1]
this will have an effect of an induced e.m.f. in the secondary coil (mutual
induction)
[1]
(b) (i) 24:1
[1]
(ii) Same power via high current with low voltage or high voltage with low
current
high voltage and low current will result in less heating effect
less energy converted to heat
[2]
Total [6]
Question 9
9. (a) (ii)
(ii)
(iii)
(b) (i)
(ii)
2p+ / naked Helium nucleus
[1]
e[1]
energy waves
[1]
decrease of 4 u (2 protons and 2 neutrons)
[1]
any two: short range/ strong ionisation / low energy compared with gamma
rays
[2]
(iii) relatively high half-life
[1]
Total [7]
Question 10
10. (a) high pressure (200 atm)
about 450 oC
iron as catalyst
(b) N2 + 3H2 = 2NH3
[2]
[1]
Total [3]
Question 11
11. (a) (i) magnitude without direction
(ii) value with magnitude and direction
(b) mass, speed, time
15
[1]
[1]
[1]
Total [3]
16
MINISTRY OF EDUCATION
Namibia Senior Secondary Certificate (NSSC)
PHYSICAL SCIENCE: HIGHER LEVEL
PAPER 2:
SPECIMEN PAPER
TIME: 2 hours
MARKS: 100
INSTRUCTIONS TO LEARNERS
Write your Centre number and Learner number in the space at the top of this page.
Answer all questions in Section A
Write your answers in the spaces provided on this question paper.
Answer one question of the Chemistry section and one question of the Physics section in
Section B of the paper.
Answer Section B on the separate papers provided.
Use a sharp pencil for your drawings. Coloured pencils or crayons should not be used.
INFORMATION TO LEARNERS
A copy of the Periodic Table is provided at the end of the question paper.
The intended number of marks are given in brackets [ ] at the end of each question.
17
SECTION A:
Answer All Questions in this Section
Question 1
1.
Figure 1.1 shows an arrangement for measuring the temperature in a large oven.
Fig 1.1
The steel cylinder contains air. The pressure gauge indicates the pressure of this air in
kilopascals (kPa). At 20°C, the gauge reading is 100 kPa.
(a) On Fig. 1.2, draw a graph to show how the reading p of the pressure gauge varies
as the temperature of the oven is raised from 20°C to 220°C. Assume that the
expansion of the steel cylinder can be neglected and that the temperature of the air
in the cylinder is the same as that in the oven. Enter the final value of the pressure
on the vertical axis of the graph.
[3]
18
Fig 1.2
(b) For the air in the cylinder, assume that
the volume = 5.0 × 10-4 m3,
the density = 1.2 kg m-3
the specific heat capacity = 400 J kg-1K-1
Calculate
(i) the mass of air in the cylinder,
the mass of air = ………………………………. kg
[2]
(ii) the thermal energy absorbed by the air as its temperature rises from 20°C to
220°C.
thermal energy absorbed = ………………………..J
19
[2]
(c) Observations of the gauge readings in (a) could be used to determine the absolute
zero of temperature.
(i) Explain how this value would be obtained.
…………………………………………………………………………………
…………………………………………………………………………………
……………………………………………………………………….….
[2]
(ii) What would you expect this value to be on the Celsius temperature scale?
………………………………………….…………………...°C
20
[1]
Total [10]
Question 2
2.
Figure 2.1 shows part of the pattern and dimensions of circular ripples created on a water
surface by two oscillating beads.
Fig 2.1
(a) The beads oscillate 8.0 times per second. Calculate the speed of the ripples on the
water surface.
speed = …………………………….. m s-1
[2]
(b) Interference effects are observed at various points within the ripple pattern. These
effects can be either destructive or constructive.
(i) Outline what is meant by constructive interference
…………………………………………………………………………………
……………………………………………………………………….….
[1]
(ii) On Fig. 2.1 mark and label one point C where constructive interference occurs
and one point D where destructive interference occurs.
[2]
21
(c) Sketch an experimental arrangement to demonstrate interference effects with light
waves. Label the components of the apparatus used. Describe the interference
pattern obtained.
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………..………
[5]
Total [10]
22
Question 3
3.
Figure 3.1 shows a vertical cross-section of a loudspeaker and a horizontal axis through
the centre of the loudspeaker.
Fig 3.1
The principal components of the loudspeaker are a magnet and a paper cone with a coil
of fine copper wire glued to it.
(a) (i) In the space to the right of Fig. 3.1, draw a cross-section of the magnet of the
loudspeaker as seen from X, a point on the horizontal axis in front of the
loudspeaker. Use the same scale for your drawing as that of Fig. 3.1.
(ii) Add lines and arrows to your diagram in (i) to represent the magnetic field of
the loudspeaker magnet.
[3]
23
(b) Explain how the loudspeaker converts a suitable electrical signal into sound waves.
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………..………
[3]
(c) The graph Fig. 3.2 shows the displacement of the cone from its mean position
plotted against time t during two complete oscillations.
Fig 3.2
(i) State the frequency of the sound wave produced.
……………………………………………………..…………… Hz
[1]
(ii) Distinguish if this sound wave is a transverse wave or a longitudinal wave.
Give a reason for your answer.
…………………………………………………………………………………
……………………………………………………………………….….
[2]
(d) The frequency of the electrical signal is changed to 30 kHz. State, with a reason,
whether you would expect the loudspeaker to produce an audible sound.
………………………………………………………………………………………
………………………………………………………………………..………
[1]
Total [10]
24
Question 4
4.
For the following molecules, draw the shape of the molecule and explain why it has this
shape.
(a) Methane CH4
Shape
Explanation …………………………………………………………………………
…………………………………………………………………………..
[2]
(b) Water H2O
Shape
Explanation …………………………………………………………………………
…………………………………………………………………………..
[2]
Total [4]
Question 5
5.
Using the Periodic Table on the last page, write the symbol for:
(a) a p block element,
……………………………………………………………………………..………….
(b) two elements in the same period which have similar atomic radii and first
ionisation energies,
……….…………………………….. and ………………………….………………
[3]
Total [3]
25
Question 6
6.
The reaction between copper(II) ions and iodide ions may be represented by the
following equation.
(a) Describe the oxidation and reduction processes which take place in terms of
electron transfer.
………………………………………………………………………………………
………………………………………………………………………..………
[2]
(b) Use oxidation numbers to explain that oxidation and reduction have taken place.
………………………………………………………………………………………
………………………………………………………………………..………
[2]
(c) State the colour changes that are observed during this reaction. (Cu2I2 is a white
solid).
………………………………………………………………………………………
………………………………………………………………………..………
[1]
Total [5]
26
Question 7
7.
The diagram shows a simple cell connected to a light bulb.
(a) Write an ionic equation to represent the change taking place at the zinc electrode.
………………………………………………………………………..………
[3]
(b) On the diagram, draw an arrow to show the direction of the electron flow in the
external circuit.
[1]
(c) Name another metal which, if used in place of zinc, would produce a higher
voltage. Give a reason for your choice of metal.
………………………………………………………………………………………
………………………………………………………………………..………
[2]
(d) Other than higher voltage, suggest two advantages of commercial batteries over
simple cells such as those shown above.
………………………………………………………………………………………
………………………………………………………………………..………
[2]
Total [8]
27
Question 8
8.
Pollution of rivers by phosphates and nitrates is a serious problem, particularly if the
rivers are slow moving. This can cause a decrease in the amount of oxygen dissolved in
the water.
(a) State the most common source of river pollution by
(i) phosphates: …………………………………………..…………….…………
(ii) nitrates: ……………………………………………………….………...
[2]
(b) Explain briefly how this pollution decreases the amount of dissolved oxygen in the
water.
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………..………
[4]
(c) Pollution is also a factor in global warming and ozone depletion.
Ozone, O3, is a form of oxygen found naturally in the ozone layer of the upper
atmosphere. Chlorofluorocarbons, CFC's, destroy ozone in the upper atmosphere.
One example of a CFC is the compound CFC-113, an inert, synthetic compound
used in the electronics industry. It has the formula C2F3Cl3 .
Once the CFC vapour reaches the upper atmosphere the following reactions occur
in the following order:
Reaction 1: CFC
Reaction 2: Cl* + O3
Reaction 3: ClO + O
UV light
→
→
→
CFC fragment + Cl*
ClO + O2
Cl + O2
(i) State the characteristics of this CFC that allows its vapour to reach the upper
atmosphere chemically unchanged.
……………………………………………………………………….….
[1]
(ii) State why the CFC will only react in the upper atmosphere.
………………………..…………………………………………………………
……………………………………………………………………….….
28
[1]
(iii) Describe and explain what has happened in Reaction 2 in terms of the process
of an oxidation and reduction reaction.
………………………..…………………………………………………………
……………………………………………………………………….….
[1]
(iv) Suggest reasons why the CFC is decomposed by UV light to form chlorine
atoms rather than fluorine atoms.
………………………..…………………………………………………………
……………………………………………………………………….….
[1]
Total [10]
29
SECTION B
Chemistry: Answer either Question 1 or 2.
Question 1a
(a) Ethyl ethanoate is an example of an ester
(i) Name the three chemicals needed to make a small quantity of ethyl ethanoate
in the laboratory.
[3]
(ii) This reaction is rather slow. Suggest how the rate of the reaction could be
increased.
[1]
(iii) Ethyl ethanoate is a liquid. Suggest what method would be used to obtain a
sample of ethyl ethanoate from the reaction mixture.
[1]
(b) Fats are esters. In one important process fats are boiled with aqueous sodium
hydroxide. This causes the fats to break down.
(i) What type of chemical reaction is this?
[1]
(ii) Name the two important materials which this process produces.
[2]
(c) Terylene is polyester. Draw a diagram to show the structure of Terylene.
[2]
Total [10]
Question 1b
(See syllabus 7.3.1 Extraction of metals page 49)
The concentrates produced by the different Ongopolo mines are all transported to the Tsumeb
Smelter for further processing.
(a) Name two predominant Namibian copper ores smelted at the Tsumeb Smelter. [2]
(b) Name the substances used in the smelter to extract copper from its ore.
[2]
(c) Describe the main chemical reactions that occur in the smelting process to reduce
the copper to the metal. Include some equations.
[3]
(d) Explain why this method cannot be use to extract aluminium from purified
aluminium oxide.
[1]
(e) Outline the method that is used to extract aluminium from purified aluminium
oxide.
[2]
Total [10]
30
Question 2a
The following ionisation constants are given:
Chemical
H3PO 4
HCl
H2O
NaOH
Constant
Ka
Ka
Kw
Kb
Value
7.1 × 10 -3
1.0 × 10 -14
-
(a) Define pH
[1]
(b) The pH of 0.1 mol/dm3 hydrochloric acids is 1. The pH of 0.1 mol/dm3 phosphoric
acid is 3. Which of these is a strong acids ? Give reason for your answer.
[2]
(c) What is the concentration of the hydrogen ions in the 0.1 mol/dm3 hydrochloric
acid and the phosphoric acid ?
[2]
(d) What is the pH of 0.1 mol/dm3 sodium hydroxide solution ?
[2]
(e) Write a word equation for the reaction of between HCl and NaOH.
[1]
(f) Predict the pH of the final products in (e) and the reaction between H3PO 4 and
NaOH. Give a short explanation of your prediction.
[2]
Total [10]
Question 2b
(a) Describe how either magnesium or calcium reacts with water, stating clearly what
is seen. Include in your answer the condition under which the reaction occurs and
give a balanced equation for the reaction.
[4]
(b) The compound of magnesium oxide and sodium fluoride contains ions which all
have identical electronic structures. Arrange these ions in order of increasing size,
explaining your answer.
[3]
(c) The bonding in magnesium oxide is stronger than in sodium fluoride. Give a
reason for the increased strength of bonding in magnesium oxide and state one
physical property of the compound which would reflect this difference.
[3]
Total [10]
31
Physics: Answer either Question 3 or 4.
Question 3a
A solar panel is connected to a voltmeter to determine the e.m.f. of the panel when exposed to
three different light sources. The light sources are:
Infrared
(frequency of 10 × 1012 Hz)
Ultraviolet
(frequency of 10 × 1016 Hz)
Red (visible range)
(frequency of 4 × 1014 Hz)
When the infrared light source is exposed to the solar panel no reading is registered on the
voltmeter while the other two produce a reading.
(a) State what an e.m.f is.
[1]
(b) State the process that produces the e.m.f.
[1]
(c) State what the above phenomenon implies about the nature of light.
[1]
(d) Explain why the infrared light source produces no reading. Will an increased
intensity produce a different reading?
[2]
(e) State which of the other two frequencies will produce the higher reading and
supply an explanation for your choice. Will an increased intensity produce a
different reading?
[3]
(f) If the solar panel is replaced with a thin piece of metal with a work function of
1.6 × 10-19 J, calculated the kinetic energy of an electron ejected from the thin piece
of metal by the red light source (use h = 6.6 × 10-34 J·s.).
[2]
Total [10]
32
Question 3b
Two blocks in the above figure are resting on a board AB
(a) The board is raised at B. As the height is increased, state which block falls
over first. State one reason for above.
[2]
(b) Each block has a weight of 20 N. If the difference in height (as measured from the
ground) of the centres of mass of each block is 4 cm, calculate the difference in
potential energy of the blocks.
[2]
(c) If BC has a perpendicular height of 3 m, and the horizontal distance between A and
C is 4 m, calculate the work done to move a block from position A to position B.
(d) Assuming a frictionless board, calculate the velocity of a block starting from rest at
position B (3 m above the ground) and sliding to position E, 1 m above the ground.
Total [10]
33
Question 4a
Two identical tuning forks are set up on a sound box, as illustrated in the figure above. The
first tuning fork (fork A) is set to vibrate. The vibration in the sound box is transferred by air
to a microphone. The microphone is connected to an oscilloscope. The screen of the
oscilloscope displays the following:
1.0 volt /div
1.0 ms/div
(a) Calculate at what frequency fork A is vibrating.
[1]
(b) State the value that represents the maximum displacement of the vibrating fork A.
Outline how the maximum displacement could be increased.
[2]
(c) After a while the second fork (B) will also start to vibrate due to resonance.
Explain the phenomenon of resonance in terms of natural frequency, natural
vibration and forced vibration.
[3]
(d) Explain what will happen if a piece of plasticine or presstick is placed on one of the
prongs of the fork, and the experiment is repeated.
[2]
(e) Discuss the use of resonance in electrical circuits when tuning a radio or television
to a particular station.
[2]
Total [10]
34
Question 4b
The model below is built to represent the action of a human arm. The elbow behaves like a
simple hinge. The mass (m = 8.0 kg) represents a load held in the hand. Assume that the mass
of the forearm and hand is small compared with m.
muscle
300 mm
m=8.0 kg
300 mm
30 mm
(a) With a diagram, draw arrows clearly showing the direction of the effort and load.
Label the fulcrum.
[3]
(b) Calculate the tension in the muscle when the forearm is horizontal and the muscle
itself is vertical as shown in the diagram.
[2]
(c) If the mass on the forearm is jerked upwards with quick motion the tension in the
muscle will be slightly higher than calculated in (b) - state a reason for this.
[1]
(d) Define momentum and explain how the change in momentum of a body is related
to the resultant force acting on it and the time for which this force acts.
[2]
(e) Suggest how you could demonstrate the principle of conservation of momentum in
a school science laboratory.
[2]
Total [10]
Acknowledgement
The Ministry of Education acknowledges the assistance of the University of Cambridge Local
Examination Syndicate, (UCLES), in granting permission to use resources and ideas towards
the production of these specimen questions, notably for the questions in Section A and
question 1 in Section B.
35
36
MINISTRY OF EDUCATION
Namibia Senior Secondary Certificate (NSSC)
PHYSICAL SCIENCE: HIGHER LEVEL
PAPER 2:
MARK SCHEME
Section A:
Question 1
1. (a) 1 mark for 168.2 (±1) kPA (calculated with pV/T and temp in K)
1 mark for correct plotting
1 mark for straight line graph
(b) (i) 6 × 10-4 kg
(ii) Q = c m ∆T
400 J/kg K × 6 × 10 -4kg × 200 K
= 48 J
(c) (i) change x-axis to full Kelvin scale
extrapolate backwards
(ii) - 273 (no unit required as stated in question paper)
[3]
[2]
[2]
[2]
[1]
Total [10]
Question 2
2. (a) λ = 0.5 cm or 0.005 m and f = 8 Hz
v = 0.005 m × 8 Hz = 0.04 m/s
(b) (i) waves interfering [maximum effect if waves are in phase], two crests or
troughs meet to produce a larger amplitude
(ii) 1 mark for C and
1 mark for D
[2]
[1]
[2]
(c) 1 mark for monochromatic source / single slit/
1 mark for double slit
1 mark for screen
1 mark for wave fronts
1 mark for description of superposition on interference where beams overlap
-1 mark for no labels
[5]
Total [10]
37
Question 3
3. (a) (i) small circle with N [or S] and larger concentric circle with S [or N]
[2]
(ii) arrows going from N to S
[1]
(b) when current passes through coil
depending on direction and magnitude of current
the coil is pulled into or pushed out of magnetic field
which causes the cone to vibrate
[3]
(c) (i) 0.5 Hz
[1]
(ii) Longitudinal - pulse or displacement is in the same direction as the wave
propagation
[2]
(d) No, the upper limit of audible range for humans is about 20 kHz
[1]
Total [10]
Question 4
4. (a) tetrahedral with bond angle 109o
due to electron electron repulsion
(b) bend with bond angle 105o
due to electron electron repulsion between lone pairs
Question 5
5. (a) element from p-block
(b) Na/Mg or P/S
[2]
[2]
Total [4]
[1]
[2]
Total [3]
Question 6
6. (a) oxidation loss of electrons
reduction gain of electrons
(b) Copper goes from plus II to I
Iodine goes from minus I to 0
(c) blue to brown
[2]
[2]
[1]
Total [5]
Question 7
7. (a) Zn(s) → Zn 2+(aq) + 2 e(b) [direction from Zn to Cu]
(c) Al or Mg (should be a higher redox potential)
(d) Any two: more ampere hour/ size/ dry/ efficiency
[3]
[1]
[2]
[2]
Total [8]
Question 8
8. (a) Any two: fertilisers /animal manure /industry (acid plants) /sewage /detergents [2]
(b) phosphates and nitrates are plant nutrients
process called eutrophication/
nutrients support algae growth / die and rot / bacteria live off dead algae
bacteria use oxygen
[4]
(c) (i) inert / unreactive
[1]
(ii) Light (hν) in upper atmosphere is composed of more ultraviolet light with
higher energy
[1]
(ii) Chlorine goes from 0 to negative I (oxidation)
Oxygen goes from negative I to 0 (reduction)
[1]
(iv) more reactive / less electronegative
[1]
Total [10]
38
Section B:
Chemistry
Question 1a
(a) (i) ethanol, ethonoic acid and sulphuric acid
(ii) slow heating
(iii) add water / then use separating funnel
(b) (i) alkali hydrolysis/saponification
(ii) sodium salt, fatty acid and glycerol
(c) correct structure of Terylene
[3]
[1]
[1]
[1]
[2]
[2]
Total [10]
Question 1b
(a) Chalcopyrite (CuFeS2), Bornite (Cu5FeS4) or Chalcocite (Cu2S)
[2]
(b) (pulverised bituminous) coal and SiO2
[2]
(c)
The first step is to ensure sulphidization of all oxides in the ore
FeS tends to sulphidize virtually all non-sulphudic copper /change all oxide ores to
1 mark
Cu2S
FeS + Cu2O (slag) → FeO (slag) + Cu2S
(all in liquid at high temperature)
(in the process the remaining FeS + O2 + SiO2 → FeOySiO2 + SO2 is removed as
slag)
1 mark
Molten metallic copper is formed via Cu(I) compounds through a combination of
the reactions:
Cu2S + O2 → Cu2O + SO2
Cu2S + Cu2O → Cu + SO2
1 mark
[3]
(except also CuS + O2 → Cu + SO2)
(d) Aluminium is too reactive to be produced via the oxidation
[1]
(e) electrolysis of molten aluminium oxide
aluminium formed at cathode
[2]
Total [10]
Question 2a
(a) negative log of the hydrogen ion (H3O)+ concentration
[1]
+
(b) pH is a measurement of the amount of dissociated hydrogen ion (H3O) in solution
the more acid dissociated the higher concentration of hydrogen ion, the stronger it
is considered.
results in lower pH - so HCl is the stronger acid
[2]
(c) Get [OH ]
since no Kb value given will take [OH-] as 0.1 mol/d m3
(reason: strong base will dissociate completely)
can assume that [NaOH] = [OH-] = 0.1 mol/dm3
Kw = [OH-][H3O+]
[H+] = 1 × 10-13 mol/dm3
(d) pH = 13
[2]
(e) hydrogen chloride + sodium hydroxide gives sodium chloride + water
[1]
(f) sodium chloride has pH = 7 while sodium phosphate will have pH slightly higher
than 7 - due to a combination of a strong base with a weak acid
[2]
Total [10]
39
Question 2b
(a) Calcium
cold or hot water
gas given off - hydrogen
colourless or slightly milky solution
Ca + 2H2O ⇐ Ca(OH)2 + H2
Magnesium
steam
white / bright flame
powder
allow MgO or Mg(OH)2 with equation if hot water is clearly stated
(b) Mg2+, Na+,O 2-, FMg /Na are in the same period (Mg is smaller)
since Mg has an extra positive charge
greater effective nuclear charge / affinity for electrons
electrons are pulled closer
[4]
O /F have bigger radii due to electron - electron repulsion of extra electron(s)
F is smaller due to higher electronegativity
[3]
(c) MgO higher since
closer together (smaller ionic radii)
cation anion attraction of order 2
resulting in melting and boiling point being higher
[3]
Total [10]
Physics
Question 3a
(a) An e.m.f. is defined in terms of work per charge supplied by a source in driving
charge
round a complete circuit.
[1]
(b) Photo-electric effect
[1]
(c) Provides evidence that energy comes in packages of energy (part of the dual nature
of light)
[1]
(d) The emission is frequency dependent. The lowest frequency which will cause
electrons to be ejected is called the threshold frequency. The frequency of the
incident light must be equal to or greater than this threshold frequency in order for
electrons to be ejected. Since the emission is frequency dependent increasing the
intensity will have no effect.
[3]
(e) The light with the higher frequency will have the higher e.m.f.
Once the threshold frequency is reached increasing the intensity will increase the
number of electrons being emitted per time unit.
so an increase in intensity will increase current from the panel
[2]
(f) Ek = hf - work function
Ek = 6.6 × 10-34 J s × 4 × 1014 Hz - 1.6 × 10-19 J
[2]
=1.04 × 10-19 J
Total [10]
40
Question 3b
(a) left block
higher centre of gravity relative to base/ base area less
(b) Potential Energy = 20 × 0.04
= 0.8 N m or 0.8 J
(c) Work done = potential energy
= mgh = 20 N × 3m
= 60 J
(d) v = 2gh = 2 × 10 × 2 = 40 = 6.32 m/s
1
or E P = mgh = 20 N × 2 m = 40 J = mv 2 = ∆E k
2
2 × 40
v=
= 40 = 6.32 m/s
2
[1]
[1]
[2]
[2]
[4]
Total [10]
Question 4a
(a) (1.0 ms/div × 5 div) ÷ 1000 ms will give period [T]
frequency = 1/T = 200 Hz
[1]
(b) 2 volts per division
by letting the fork vibrate more vigorously / hitting it harder
[2]
(c) resonance will occur if forcing frequency equals its natural frequency
natural frequency - object vibrate freely after single displacement
natural vibration - object vibrates at its natural frequency
forced vibration - object forced to vibrate at frequency of another source
[3]
(d) by adding the plasticine or presstick the natural frequency of the fork will change
two forks will be out of phase
forced frequency of A and natural frequency of B will no longer be the same
no resonance
second fork will not start to vibrate
[2]
(e) when we tune a radio we are selecting transmission at one particular frequency
detecting circuit is forced to conduct oscillating electrical current at frequencies of
all signals received
however by tuning in on one particular radio frequency the oscillating electrical
current is resonating with the selected radio frequency
allowing large current (compared with other radio frequencies) to flow at only one
frequency
[2]
Total [10]
Question 4b
(a) If both levers are to the left of the fulcrum, the load is downwards and the effort is
upwards
If diagram is "open", both load and effort are directed downwards
[3]
(b) moment = 80 N × 0.3 m = 24 N m
tension (force) = moment ÷ 0.03 m = 800 N
[2]
(c) inertia
[1]
(d) momentum = mass × velocity and the change in momentum = impulse = F ∆t [2]
(e) any experiment: trolley, etc.
[2]
Total [10]
41
ADDITIONAL INFORMATION TO QUESTION 1B OF SECTION B OF PAPER 2
(This is additional information and not for examination purposes)
Ongopolo Mining and Processing (Pty) Limited (OMPL):
As the ore is mined in its natural form it is crushed, milled and then by means of flotation the
valuable minerals are separated from the waste or “gangue” as called in metallurgical terms.
Flotation is a selective process and can be used to achieve specific separations from complex
ores such as lead-zinc, copper-zinc, etc. Initially developed to treat the sulphides of copper,
lead and zinc, the field of flotation has now expanded to include oxides.
Froth flotation utilizes the differences in physico-chemical surface properties of particles of
various minerals. After treatment with reagents, such differences in surface properties
between the minerals within the flotation pulp become apparent and, for flotation to take
place, an air-bubble must be able to attach itself to a particle, and lift it to the water surface.
The process can only be applied to relatively fine particles, as if they are too large the
adhesion between the particle and the bubble will be less than the particle weight and the
bubble will therefore drop its load.
In flotation concentration, the mineral is usually transferred to the froth, or float fraction,
leaving the gangue in the pulp or tailing. This is direct flotation as opposed to reverse
flotation, in which the gangue is separated into the float fraction.
The air-bubbles can only stick to the mineral particles if they can displace water from the
mineral surface, which can only happen if the mineral is to some extent water repellent or
hydrophobic. Having reached the surface, the air bubbles can only continue to support the
mineral particles if they can form a stable froth, otherwise they will burst and drop the
mineral particles. To achieve these conditions it is necessary to use the numerous chemical
compounds known as flotation reagents.
Typical copper minerals mined by Ongopolo Mining and Processing (Pty) Limited
(OMPL) :
1.
Kombat
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10
1.11
2.
Bornite
Chalcopyrite
Chalcocite
Malachite
Azurite
Galena
Cerussite
Native Copper
Pyrite
Sphalerite
Silver
Cu5FeS4
Cu FeS2
Cu2 S
Cu2(CO3)2(OH)2
Cu3(CO3)2(OH)2
Pb S
Pb CO3
Cu
FeS2
ZnS
Ag
Otjihase
2.1
2.2
2.3
2.4
Chalcopyrite
Pyrite
Silver
Gold
Cu FeS2
FeS2
Ag
Au
42
3.
Khusib Springs
3.1
3.2
3.3
3.4
3.5
3.6
4.
Cu10 (Cu, Fe)2 As4 S13
Cu FeS2
Cu5FeS4
Cu2 S
Pb S
Ag
Tschudi
4.1
4.2
4.3
4.4
4.5
5.
Tennantite
Chalcopyrite
Bornite
Chalcocite
Galena
Silver
Malachite
Azurite
Chalcocite
Chalcopyrite
Silver
Cu2(CO3)2(OH)2
Cu3(CO3)2(OH)2
Cu2 S
Cu FeS2
Ag
Tsumeb and Tsumeb West
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.10
5.11
5.12
5.13
5.14
Bornite
Chalcopyrite
Chalcocite
Malachite
Azurite
Galena
Cerussite
Native Copper
Pyrite
Sphalerite
Silver
Chonichalcite
Dioptase
Duftite
Cu5FeS4
Cu FeS2
Cu2 S
Cu2(CO3)2(OH)2
Cu3(CO3)2(OH)2
Pb S
Pb CO3
Cu
FeS2
ZnS
Ag
Ca Cu (AsO4) (OH)
Cu SiO2 (OH)2
Pb Cu (AsO4) (OH)
The concentrates produced by the different Ongopolo mines are all transported to the Tsumeb
Smelter for further processing.
Minerals as mined from underground are still in their natural form in the concentrate.
In the Smelter extraction of the copper is done by pyrometallurgical techniques. The process
basically consists of two steps :
1.
2.
Smelting of concentrate in the Copper Reverboratory Furnace, and
Cleaning of the Copper Matte produced during stage 1 in the Copper Converting
process.
43
A short description of the two steps:
1.
Smelting of concentrates
A mixture of concentrates are charged into the Reverboratory Furnace and heated with
pulverized butimunuous coal and hot air. The concentrates contain oxidic, as well as
sulphudic copper and iron minerals. The charge also contains oxides such as Al2O3,
CaO, MgO and principally SiO2, which are either present in the original concentrates or
added as fluxes if needed. It is the iron, copper, sulphur, oxygen and these oxides
which largely control the chemistry and physical constitution of the matte slag system.
The first purpose of concentrate smelting is to ensure sulphidization of all the
concentrate present in the charge so that it enters the matte phase. This is ensured by
the presence of FeS in the matte which tends to sulphidize virtually all non-sulphudic
copper of the charge by reactions of the type :
FeS (l) + Cu2O (l, slag) = FeO (l, slag) + Cu2 S (l)
Oxidized copper may be present in different forms in the charge eg. as Cu2 (CO3(OH)2,
Cu3 (CO3)2(OH)2, CuSO4 etc. These compounds also react to form Cu2S during
smelting. CuS and FeS2 are unstable at smelting temperatures due to their high sulphur
pressures to form Cu2S and FeS.
A liquid slag system at a 1 250 ° C enables a proper separation between slag and copper
matte. Matte is tapped on the one side of the furnace for further processing, whereas
slag is tapped on the other end of the furnace, granulated with high pressure water and
discarded.
2.
Cleaning of the Copper Matte
Molten matte from smelting contains copper, iron, lead and sulphur as its major
components and in addition minor amounts of impurity metals, eg. arsenic, nickel,
antimony as well as silver and gold.
The purpose of converting is to remove iron, sulphur, lead and other impurities from
matte, thereby producing liquid metallic copper in a crude blister copper form (98 – 99
% Cu). This is achieved by oxidizing the molten matte at a high temperature, 1 150 – 1
250 ° C, with air. The Blister Copper is subsequently fire refined and electro refined,
which is not done by Ongopolo. The Blister Copper is exported for further refining.
The converting of the copper matte is carried out in a cylindrical Pierce Smith
converter. Air is blown into the liquid matte via tuyeres along the length of the vessel.
The products are Slag and Blister Copper. Large volumes of hot, So2-bearing gases
are also produced during converting and these are collected, cooled down and cleaned
in the baghouses. The converting reactions are exothermic and the process is
autogenous.
44
2.1
Stages of the Converting Process
Converting takes place in two chemically and physically distinct stages, both of
which involve blowing air into the molten sulphide stage :
2.1.1 The Slag Forming stage in which FeS is oxidized to FeO and Fe3O4
(magnetite).
2FeS + 3O2 + SiO2 = 2FeO◦SiO2 + 2SO2
The slag forming stage is completed when the FeS in the matte has been
almost completely oxidezed, i.e. to a point when the matte contains less
than 1 % FeS.
2.1.2 The Copper Making stage in which the remaining sulpher is oxidized to
SO2. Copper is not appreciably oxidized by air until it is almost devoid of
sulphur and thus the Blister Copper product of converting is low in both
sulphur and oxygen.
Molten metallic copper is formed in the converter by a combination of the
reactions:
Cu2S (l) + 3/2 O2 = Cu2O (s) + SO2
Cu2S (l) + 2 Cu O (s) = 6 Cu (l) + SO2
Cu2S (l) + O2 = 2 Cu2O (l) + SO2
The final Blister Copper produced also contains the silver and gold which
is received in the different concentrates.
A typical analysis of Blister Copper:
Cu
98.5 %
Pb
0.2 %
As
0.1 %
Sb
0.05 %
Ni
0.01 %
S
0.02 %
Ag
1 000 g/t
Au
7 g/t
Remainder
O2
Environmental
Due to the fact that the Smelter treats concentrates containing lead and
arsenic, it is extremely important to have the necessary environmental
precautions in place. Smelting facilities (furnaces, converters, etc.) have
the following equipment available:
1.
All furnaces, as well as tapping systems are equipped with gas
extraction fans. The hot gases from the reverboratory furnace are
cooled down from ± 1 200 ° C to 110 ° C through a waste heat boiler
system (electricity generation system with steam), air heaters as well
as an evaporative gas cooler. This is done to ensure that all arsenic,
as well as lead particles which fumed off during the smelting process
are condensed and in the solid form again. The cool gases ± 110 ° C
are filtered through glass-fibre bags (98 % efficient to a size of less
than 5 µ m particles) before vented to the atmosphere. The filtered
dust containing various lead and arsenic oxides and sulphates are
treated in the Arsenic Plant. Here a final product, Arsenic Trioxide
45
(As2O3) is produced, which is sold to South Africa and overseas for
the production of herbicides, insecticides, etc.
The residue or slag from the process is dumped on a disposal site,
specially designed to take care of toxic waste.
The hot gases from the converter process are also cooled down to ±
120 ° C, before filtered and vented to the atmosphere. The filtered
dust contains high amounts of lead oxides and sulphates and are
bagged and sold overseas for further processing.
All circulating materials in the smelter are either retreated, sold or
dumped onto the disposal site in order to protect the environment.
Ongopolo has implemented a new environmental monitoring
program a year ago which was recommended by International
Environmental Consultants.
Twelve sites in and around Tsumeb have been established. The sites
have been equipped with state of the art equipment which enables us
to continuously measure stack emissions regarding heavy metal and
SO2 pollutions. A weather station continuously monitoring wind
speeds, wind directions, humidity as well as rainfall is also used to
accumulate data to help to interpret data obtained from the
monitoring stations. Results obtained from these stations are
published on a seasonable basis (summer, autumn, winter, spring)
and sent to the necessary governmental authorities for scrutiny.
It is the aim of Ongopolo to strive to the improvement of
environmental conditions for ourselves, as well as future generations.
46
MINISTRY OF EDUCATION
Namibia Senior Secondary Certificate (NSSC)
PHYSICAL SCIENCE: HIGHER LEVEL
INSTRUCTIONS TO THE PRACTICAL PAPER
47
Chemistry
More material may be issued if required, without penalty, but this should not be necessary.
Safety spectacles may be provided if considered necessary.
Learners will require the following.
1.
Approximately 2.0 mol dm-3 hydrochloric acid, labelled P.
Allow each Learner approximately 150 cm3
2.
Approximately 1.1 mol dm-3 sodium hydroxide, labelled Q.
Allow each Learner approximately 100 cm3.
Notes: Some variation in the above concentrations is acceptable, but it is essential that
50.0 cm3 of Q reacts with between 26.5 cm3 and 28.5 cm3 of P when titrated
separately with an indicator in the normal manner.
P and Q should each be at laboratory temperature at the start of the examination.
It is essential that Learners accept the descriptions of these solutions on the
question paper.
The following apparatus should be provided for each Learner:
A 50 cm3 burette, a 50 cm3 or 100 cm3 measuring cylinder, an expanded polystyrene (or other
light plastic) cup of at least 150 cm3 capacity supported in a suitable beaker, a 0 °C to 100 °C
or 0 °C to 50 °C thermometer graduated at 1 °C.
The Supervisor is asked to perform the experiments in the questions and to record the results
on a spare copy of the question paper clearly labelled 'Supervisor's Results', followed by the
number of the Centre. This must be enclosed with the scripts. Unless this is done, Learners
may be unavoidably penalised.
If Learners from more than one Centre are taking the examination, it is essential that a copy
of the Supervisor's Results should be sent with the scripts for each Centre.
48
Physics
In addition to the usual equipment, each Learner will require the apparatus specified. If a
Learner breaks any of the apparatus, or loses any of the material supplied, the ammeter
should be rectified and a note made in the report.
Question
Apparatus required (per set of apparatus, unless otherwise specified):
two small wooden beams of about 1 cm × 1 cm cross-section, one of length 0.35 m, the other
of length 0.55 m;
4 screw eye rings, each of about 12 mm (or ½ inch) external diameter;
two threads, each of minimum length of 0.75 m;
two drawing pins;
one retort stand of at least 0.6 m height, boss and clamp;
one G-clamp;
one half-metre rule with millimetre graduations;
stopwatch or stop clock.
Fig. 1.1
Fig 1.2
49
The equipment as used by the Learners is shown in Fig. 1.1; Fig. 1.2 shows part of the
equipment in more detail.
The eye rings in both beams are 0.300 m apart, inserted symmetrically with relation to the
ends of the beams. The rings in the upper and lower beams project horizontally and
vertically respectively. (If eye rings are unavailable, large bent solder tags, fixed with
drawing pins, may be substituted). The threads are anchored to the ends of the upper beam
by drawing pins.
A small saw-cut should be made at each end on the front face of the upper beam to act as a
guide for the thread.
The upper beam is to be supported horizontally by the retort stand, boss and clamp. This
stand should be secured rigidly to the bench by means of the G-clamp. There should be
sufficient clearances to allow the lower beam to execute torsional oscillations about a vertical
axis through its centre.
The initial lengths of the vertical threads between the eye rings should be about 0.55 m and
should differ slightly so that the lower beam is clearly not horizontal.
50
MINISTRY OF EDUCATION
Namibia Senior Secondary Certificate (NSSC)
PHYSICAL SCIENCE: HIGHER LEVEL
PRACTICAL PAPER
TIME: 2 hours
MARKS: 40
INSTRUCTIONS TO LEARNERS
Write your Centre number and Learner number in the space at the top of this page.
Answer all questions.
Write your answers in the spaces provided on this question paper.
Use a sharp pencil for your drawings. Coloured pencils or crayons should not be used.
INFORMATION TO LEARNERS
The number of marks is given in brackets [] at the end of each question or part question.
Practical notes are provided on last page.
51
CHEMISTRY
1.
The reaction between an acid and a base is exothermic. The end-point of an acid/base
titration can be found by measuring the changes in temperature which occur when the
acid is added to the base.
P is 2.00 mol/dm3 hydrochloric acid.
Q is aqueous sodium hydroxide of unknown concentration.
(a)
(i) Put P into the burette.
(ii) Use a measuring cylinder to transfer 50 cm3 of Q to a plastic cup. Measure
the temperature of Q to the nearest 0.5 °C and record this value (T0) in
column B of Results Table 1.
(iii) Add 5.0 cm3 of P, from the burette, to the sample of Q in the plastic cup. Stir
the mixture using the thermometer. Measure the highest temperature reached.
Record this value, (T1) in column B of Table 1.
(iv) Without delay, add another 5.0 cm3 portion of P to the mixture. Stir and
record the highest temperature reached (T2).
(v) Repeat the procedure in (iv) until you have added a total of 40.0 cm3 of P.
vi) Calculate the values of T1 - T0, T2 - T0, etc. to complete column C in Table 1.
Results Table 1
A
B
C
Temperature /
Total temperature
added/cm
°C
change/°C
0
T0 =
0
5
T1 =
T1 - T0 =
10
T2 =
T2 - T0 =
15
T3 =
T3 - T0 =
20
T4 =
T4 - T0 =
25
T5 =
T5 - T0 =
30
T6 =
T6 - T0 =
35
T7 =
T7 - T0 =
40
T8 =
T8 - T0 =
Total volume of P
3
[12]
(b)
Plot a graph of total temperature change (column C) against total volume of P
(column A) on the grid opposite. Draw two intersecting lines through these
points.
[3]
52
(c)
Use your graph to determine the maximum temperature change.
Maximum temperature change ……………………….. °C
(d)
[1]
From the graph, read the volume of P needed to cause the maximum temperature
change. This volume of P neutralises 50 cm3 of Q.
………………………………cm3 of P neutralises 50 cm3 of Q. [1]
(e)
P is 2.00 mol/dm3 hydrochloric acid.
Using your answer to (d), calculate the concentration, in mol/dm3, of sodium
hydroxide in Q.
Concentration of sodium hydroxide in Q = ……………mol/dm3 [2]
(f)
State one reason why the temperature rise in (d) is less than the value calculated
from theory.
…………………………………………………………..………………………. [1]
53
PHYSICS
Question 1:
1.
Fig. 1.1
You are to investigate how the period T of oscillation of a suspended wood beam varies with
the lengths l of the threads supporting it.
The apparatus shown in Fig. 1.1 is assembled for you, ready for use after adjustments.
All length measurements in this experiment should be stated in metres (m) and all timing
measurements in seconds (s).
(a)
(i) Adjust the vertical lengths l of the threads to be equal - about 0.400 m with the suspended beam horizontal. Measure l.
Set the suspended beam into small-angle torsional oscillations about a
vertical axis, so that when the left end of the beam swings away from you the
right end swings towards you. Make suitable measurements which will allow
you to determine a precise value of the period T of these oscillations.
(ii) Repeat the procedure in (i) for four more values of l in the range 0.300 m to
0.500 m. Ensure that at all times the suspended beam is horizontal.
54
(b)
Tabulate below all relevant measurements made. Include in your table your five
sets of values of l and T and the five corresponding values of T 2.
l /m
(c)
T2/s2
T/s
Justify the number of significant figures in your values of T.
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………
(d)
T and l are related by the expression
T2 k
=
l
g
where k is a constant and g is the acceleration of free fall. Take the value of g as
9.81 m s-2.
(i) Use your tabulated readings to find the mean value of
T2
.
l
mean value = ………………
(ii) Hence determine the value of k.
k = …………………………
55
(e)
Describe any difficulty encountered as you took readings. State how this
difficulty was overcome.
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………
[20 marks]
Acknowledgement
The Ministry of Education acknowledges the assistance of the University of Cambridge Local
Examination Syndicate, (UCLES), in granting permission to use resources and ideas towards
the production of these specimen questions, notably for questions 1 and 2.
56
MINISTRY OF EDUCATION
Namibia Senior Secondary Certificate (NSSC)
PHYSICAL SCIENCE: HIGHER LEVEL
PRACTICAL PAPER
MARK SCHEME
CHEMISTRY:
(a)
(b)
(c)
(d)
(e)
(f)
Table:
To recorded (sensible value)
To is recorded to nearest 0.5 oC (whole numbers have zero, e.g. 23.0)
all remaining temperatures show readings to nearest 0.5 oC
all B temperatures completed
all temperature changes completed
all temperature changes are correct
temperature change for vols. of P from 5 to 30 are ± 1 oC of Supervisor
Graph:
Best straight line drawn as temperature increase
Best straight line drawn as temperature decrease
two lines actually intersect
Correctly read from graph
Correctly read from graph
Suitable correct calculation
answer correct for candidate figures
Any acceptable answer e.g. heat loss
57
1
1
1
1
1
1
6
[12]
1
1
1
[3]
1
1
1
1
1
[5]
Total [20]
PHYSICS:
Table
(b)
(c)
(d)
Labels column 2 correctly
for measuring in metres (not cm)
5 measurements of l, s, and T
4 measurements allow 1 mark
a vertical length of 0.400 m ± 5 mm is used
4 further values of l suitably spread
uses 0.300 m
uses 0.500 m
takes more than one time for each length
T2 is correct for 4 values (judge by eye)
Justification of sig. figures
correct numbers
some explanation
1
1
[2]
(i) shows evidence of evaluating at least
one value for T2/l
calculation for all values
calculates the mean
(ii) Substitute correctly into equation
value of k for candidate’s figures
(e)
1
1
2
1
1
1
1
1
1
1
[10]
Any acceptable answer for difficulty
How it was overcome
1
1
1
[3]
1
1
[2]
2
1
[3]
Total [20]
58
The National Institute for Educational Development
P/Bag 2034
Okahandja
NAMIBIA
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