GCSE Twenty First Century Additional
Science A (J242)
CANDIDATE STYLE
ANSWERS
Exemplar work illustrating the difference between
mark bands 5/6 and mark bands 7/8
Version 1
Oxford Cambridge and RSA
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
CANDIDATE STYLE ANSWERS
CONTENTS
S(a)
3
S (b)
7
C
10
A (graph)
11
A (Mathmatical)
12
E(a)
14
E(b)
15
R(a)
16
R(b)
19
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2
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
CANDIDATE STYLE ANSWERS
Task: Investigate how much energy is transferred as heat when acids react with alkalis
Mark Band
S(a)
criteria
Exemplar
5-6
7-8
Consider major factors and refer to scientific knowledge to make a testable hypothesis
about how one factor will affect the outcome. Information is effectively organised
with generally sound spelling, punctuation and grammar. Specialist terms are used
appropriately.
After consideration of all relevant factors, select one and propose a testable hypothesis
and quantitative prediction about how it will affect the outcomes. The report is
comprehensive, relevant and logically sequenced, with full and effective use of relevant
scientific terminology. There are few, if any, grammatical errors.
When an acid reacts with an alkali it transfers energy to the surroundings, this is
called an exothermic reaction. The energy is usually transferred as heat energy,
causing the reaction mixture and its surroundings temperature to increase. The
temperature increase can be detected using a thermometer. Other examples
of exothermic reactions are: burning and the reaction between Calcium oxide
and water. The reaction between acids and alkali’s like oxides, hydroxides and
carbonates are called neutralisation reactions. The general word equation for
a classic neutralisation reaction is: Acid +alkali -> salt +water. An example is
hydrochloric acid +sodium hydroxide >+ sodium chloride +water / HCl(aq) +
NaOH(aq) -> NaCl(aq)+ H2O(l). Here is a graph that shows what happens during an
exothermic reaction.
When an acid reacts with an alkali it transfers energy to the surroundings, this is
called an exothermic reaction. The energy is usually transferred as heat energy,
causing the reaction mixture and its surroundings temperature to increase. The
temperature increase can be detected using a thermometer. Other examples of
exothermic reactions are: burning and the reaction between Calcium oxide and
water. The reaction between acids and alkali’s like oxides, hydroxides and carbonates
are called neutralisation reactions. The general word equation for a classic
neutralisation reaction is: Acid +alkali -> salt +water. An example is hydrochloric acid
+sodium hydroxide >+ sodium chloride +water / HCl(aq) + NaOH(aq) -> NaCl(aq)+ H2O(l).
Here is a graph that shows what happens during an exothermic reaction.
The activation energy here is the amount of energy that is needed to start
the reaction. We can see in the graph that as the reactants react together the
products have a lower energy level. The energy difference between the reactants
and products in this reaction will always be -58 kJ mol-1, this is also known as the
delta H ( ∆ H) of the reaction. The delta H of a reaction is calculated by the energy
‘in the bonds of the reactants minutes the energy in the bonds of the products.
The delta H is always negative for an exothermic reaction.
In this investigation, I am going to investigate how much energy is transferred as
heat when acids react with alkalis.
The activation energy here is the amount of energy that is needed to start the
reaction. We can see in the graph that as the reactants react together the products
have a lower energy level. The energy difference between the reactants and
products in this reaction will always be -58 kJ mol-1, this is also known as the delta
H ( ∆ H) of the reaction. The delta H of a reaction is calculated by the energy ‘in the
bonds of the reactants minutes the energy in the bonds of the products. The delta
H is always negative for an exothermic reaction.
In this investigation, I am going to investigate how much energy is transferred as
heat when acids react with alkalis.
3
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
Mark Band
CANDIDATE STYLE ANSWERS
5-6
7-8
The factors that I could test in this investigation are:
The factors that I could test in this investigation are:
•
•
•
•
•
•
•
•
•
•
Concentration of acid
Concentration of alkali
Type of acid
Type of alkali
If I choose to change the concentration of acid/alkali in this investigation then
the higher the concentration of acid/alkali the higher the temperature of heat
energy given off will be. This is because as the acid/alkali is more concentrated
there are more particles to react with the other so more successful collisions
occur and more energy is given off as heat.
Changing the type of acid/the type of alkali could also be investigated. Different
acids have different properties and so they can give off different temperatures of
heat energy. The same could happen if I used different types of alkali.
The factor that I have decided to change for this experiment is the concentration
of acid. I have decided to use the concentration of add as my independent
variable because there is a variety of different concentrations I can test which will
able me to produce a good set of results and also a good graph can be produced
from this. The factors that I am going to control in this experiment are the type
of acid/alkali, the temperature of acid and the concentration of acid. These are all
my control variables.
Hypothesis
My hypothesis is that if I increase the concentration of HCl then more energy
will be produced when reacting with NaOH. This means that the temperature
produced each time will increase. This happens because a more concentrated
acid means that there will be more acid particles to collide with the alkali to
create an exothermic reaction, this will release more heat as energy and will
cause the reactants to become hotter.
4
Initial Temperature
Concentration of acid
Concentration of alkali
Type of acid
Type of alkali
Volume of acid/alkali
If I choose to change the concentration of acid/alkali in this investigation then the
higher the concentration of acid/alkali the higher the temperature of heat energy
given off will be. This is because as the acid/alkali is more concentrated there are
more particles to react with the other so more successful collisions occur and more
energy is given off as heat.
Changing the type of acid/the type of alkali could also be investigated. Different
acids have different properties and so they can give off different temperatures of
heat energy. The same could happen if I used different types of alkali.
If I choose to change the temperature of the acid I would find out that; the higher
the temperature is the more heat energy will be given off. I know this because as
the temperature rises the acid particles have more energy and move around faster
which causes all the particles to collide more frequently. Also the faster the particles
move the more energy they have, so more of the collisions will have enough energy
to make the reaction happen and in this case, when the acid and alkali react the
temperature given off will rise quickly.
Lastly, another factor that I could choose to investigate for this investigation is to
test how much heat energy is given off when different volumes of add react with an
alkali. I know that if I increase the volume of acid more heat energy is produced. This
is because there are more acid particles to react together with the alkali and so the
heat energy will increase.
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
Mark Band
CANDIDATE STYLE ANSWERS
5-6
7-8
The factor that I have decided to change for this experiment is the concentration
of acid. I have decided to use the concentration of add as my independent variable
because there is a variety of different concentrations I can test which will able me
to produce a good set of results and also a good graph can be produced from this.
The factors that I am going to control in this experiment are the type of acid/alkali,
the temperature of acid and the concentration of acid. These are all my control
variables.
I chose not to change the type of acid/alkali because school has a limited supply of
them and it would be difficult for me to collect different acids/alkalis to use just for
the experiment this would limit my results I have chosen not to carry them further.
Therefore, I have just decided to use Hydrochloric Acid and Sodium Hydroxide as
my add and alkali.
I have also chosen not to change the temperature of the acid because keeping a
certain temperature is difficult to keep constant as it could drop or even increase
due to the temperature of the room. Temperature is hard to control and is
dangerous as the hot water can burn. I have decided to keep the temperature of my
acid at just room temperature.
I am also controlling the concentration of alkali in this experiment as school
only permits us to go up to 2M alkalis as more concentrated alkalis are corrosive.
Because there will not be enough molars of alkali for me to test it would limit the
amount of results I could achieve. For this experiment, I have decided to keep the
concentration of alkali constant at 2M.
I have decided that I am also going to keep the volumes of the acid and alkali
constant. I am going to test different volumes that will ensure the best results for
my experiment when I do my preliminary experiments and then decide how much
volume I will use of each acid and alkali. It is important for me to keep these factors
constant because this will make sure I keep the test fair to achieve accurate and
reliable results.
Hypothesis
My hypothesis is that if I increase the concentration of HCl then more energy will be
produced when reacting with NaOH. This means that the temperature produced
each time will increase.
5
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
Mark Band
CANDIDATE STYLE ANSWERS
5-6
7-8
Due to the tests that I did in my preliminary experiments, I found out that the
higher the volume of acid and alkali the wider the range of results I would get. As
you can see from my results tables the experiment at l0cm3 ranged from 22°C-36°C,
20cm3 ranged from 22°C-37°C, and the 50cm3 ranged the highest from 22°C-39°C.
I could have chosen the volume variable to change but I would have needed
large quantities of acid and alkali and the school could not provide me with such
amounts. Therefore, I decided to control this variable at 50cm3 of acid and alkali
so the volume of the two when reacting comes to 100cm3. I also noticed that
measuring the temperature every 5 seconds showed me exactly how much the
temperature was Increasing each time until it reached the optimum temperature.
The concentrations that I tested were 4M, 2M, 1M and 0.5. When I do my official
experiment, I think that I am also going to measure how much energy is given off
when using 3M acid too as this will give me more results to compare and see an
exact pattern of change.
Prediction
I predict that as the concentration of acid doubles, the temperature will increase
and when the range is identified, the difference in temperature will be doubled. An
example is shown in my preliminary results. When the molar of acid was at 0.5M the
difference in temperature was at 3° so when the concentration is doubled to 1M
the difference in temperature will be double the difference in temperature for 0.5M,
which will be 6°, This happens because a two times more concentrated acid means
that there will be twice as many acid particles to collide with the alkali particles to
create an exothermic reaction, this will release twice as much heat as energy and
will cause the reactants to become twice as hot.
Commentary
Major factors are considered in selecting a factor and scientific knowledge is used
to generate a testable hypothesis. Quality of written communication is good with
appropriate use of scientific terms. 6 marks
6
A wide range of major factors are considered in selecting a factor and generating a
testable hypothesis with a quantitative prediction. Work is logically sequenced with
good use of scientific terminology. 8 marks
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
CANDIDATE STYLE ANSWERS
Task: Focal length of Lens
Mark Band
S(b)
criteria
Exemplar
5-6
7-8
Select and use techniques and equipment appropriate for the range of data required,
and explain the ranges chosen. Identify any significant risks and suggest some
precautions.
Justify the choice of equipment and technique to achieve data which is precise and valid.
Complete a full and appropriate risk assessment, identifying ways of minimising risks
associated with the work.
Risk
Hazard
Precaution
Justification
Risk
Hazard
Precaution
Justification
The power pack
falling off the
desk
It could land on
someone’s foot,
injuring them.
It could pull out
the cables and
damage the
equipment
Ensure the power
pack is not near
the edge of the
desk.
We do this so
that the power
pack doesn’t get
knocked off the
edge of the desk
accidentally.
The power pack
falling off the
desk
It could land on
someone’s foot,
injuring them.
It could pull out
the cables and
damage the
equipment
Ensure the power
pack is not near
the edge of the
desk.
We do this so
that the power
pack doesn’t get
knocked off the
edge of the desk
accidentally.
Hot light bulb
It could burn
someone’s skin
with the light
bulb glass as it
can get very hot
when left on for
a long period of
time.
Don’t touch the
light bulb when it
is on. Make sure it
has cooled down
before handling
the light bulb.
We do this so that
no one gets burnt
on the hot light
bulb.
Hot light bulb
It could burn
someone’s skin
with the light
bulb glass as it
can get very hot
when left on for
a long period of
time.
Don’t touch the
light bulb when it
is on. Make sure it
has cooled down
before handling
the light bulb.
We do this so that
no one gets burnt
on the hot light
bulb.
Light bulb/lens
smashing
The broken
jagged glass
could cut
someone’s skin.
Make sure the
light bulb/lens
isn’t near the
edge of the desk
so it doesn’t fall
off. Make sure
people handle
the light bulb/
lens with care so
they don’t drop it
We do this so that
it won’t smash
into lots of sharp
pieces that could
potentially injure
someone
Light bulb/lens
smashing
The broken
jagged glass
could cut
someone’s skin.
Make sure the
light bulb/lens
isn’t near the
edge of the desk
so it doesn’t fall
off. Make sure
people handle
the light bulb/
lens with care so
they don’t drop it
We do this so that
it won’t smash
into lots of sharp
pieces that could
potentially injure
someone
Getting an
electric shock
Someone could
get electrocuted
from the power
sock or damaged
wired.
Use correct
equipment and
make sure it is
undamaged.
Be cautious
when using the
equipment in the
investigation.
We do this so
as to not shock
ourselves from
the equipment
and cause
ourselves harm.
Getting an
electric shock
from power pack
Someone could
get electrocuted
from the power
sock or damaged
wired.
Use low voltage
equipment and
make sure it is
undamaged.
Check when last
PAT tested.
We do this so
as to not shock
ourselves from
the equipment
and cause
ourselves harm.
7
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
Mark Band
CANDIDATE STYLE ANSWERS
5-6
7-8
Risk
Hazard
Precaution
Justification
Risk
Hazard
Precaution
Justification
Tripping up
Someone could
trip up and injure
themselves when
in a dark room
as they may not
be able to see
properly.
Remove any
items on the floor
that are tripping
hazards. Don’t
walk around
in the dark
room carrying
delicate pieces
of equipment
as it could get
dropped and
damaged.
We do this to
prevent anyone
getting injured
by tripping up on
loose wired that
aren’t visible in a
dark room.
Tripping up
Someone could
trip up and injure
themselves when
in a dark room
as they may not
be able to see
properly.
Remove any
items on the floor
that are tripping
hazards. Don’t
walk around
in the dark
room carrying
delicate pieces
of equipment
as it could get
dropped and
damaged.
We do this to
prevent anyone
getting injured
by tripping up on
loose wired that
aren’t visible in a
dark room.
Staring into the
lens
Someone could
get blinded by
the intensified
rays.
Don’t look directly
through the lens,
especially when
a light source is
shone through it.
We do this so as
to not cause any
damage to our
eyes.
Staring into the
lens
Someone could
get blinded by
the intensified
rays.
Don’t look directly
through the lens,
especially when
a light source is
shone through it.
We do this so as
to not cause any
damage to our
eyes.
Most of this risk assessment is based on the science department laboratory rules,
there was no need to use other sources.
My preliminary results showed that the range gave a suitable set of results, any
closer to the light source was too hot any further away the image was becoming
faint.
8
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
Mark Band
CANDIDATE STYLE ANSWERS
5-6
Item
Description
7-8
What It Is Used For
Lens
A round glass object
It is used as a magnifier.
that converges light rays.
Lens holder
A wooden block with a
shape cut out to hold a
lens stably.
It is used to hold the lens
so that the lens stably so
it doesn’t move or all out
and smash.
A large metal pole
attached to a base.
It is used to hold the
screen, where the light
rays will focus.
Stand
Screen
A piece of blank card.
Light bulb
A glass bulb which
It is used to produce the
lights up when an
light rays needed for the
electric current is passed experiment.
through it.
Power Pack
Item
It is used to supply
electricity to the light
source (bulb) from the
socket.
Calliper
A metal object that has
measurement marking
on.
Used to measure the
thickness of the lens.
Metre Ruler
A metre long plastic
thin object that has
measurement markings
on.
It is used to measure the
focal length.
9
What It Is Used For
Precision
Lens
A round glass object It is used as a
that converges light magnifier.
rays.
Lens holder
A wooden block
It is used to hold the n/a
with a shape cut out lens so that the lens
to hold a lens stably. stably so it doesn’t
move or all out and
smash.
Stand
A large metal pole
attached to a base.
It is used to hold the n/a
screen, where the
light rays will focus.
Screen
A piece of blank
card.
White allows the
image to be seen
clearly
Light bulb
A glass bulb which
lights up when an
electric current is
passed through it.
It is used to produce n/a
the light rays
needed for the
experiment. It is
easily portable
Power Pack
An object that,
when plugged in
and turned on,
produces an electric
charge at a chosen
voltage.
It is used to supply
low voltage
electricity to the
light source (bulb)
from the socket.
1/2 volts
Calliper
A metal object that
has measurement
marking on.
Used to measure
the thickness of the
lens.as precisely as
possible
It is precise to the
0.01 millimetre.
Metre Ruler
A metre long plastic
thin object that
has measurement
markings on.
It is used to measure It is precise to one
the focal length. No millimetre.
greater precision is
needed
It is used to focus the
light rays.
An object that, when
plugged in and turned
on, produces an electric
charge at a chosen
voltage.
Description
n/a
n/a
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
CANDIDATE STYLE ANSWERS
Mark Band
Commentary
5-6
7-8
(Equipment and technique appropriate). (Values of control variables determined
by preliminary work) but no explanation of range of independent variable.
Equipment has its use described not justified. Risk assessment considers
significant hazards and suggests some precautions, but lacks detail e.g. use of
low voltage supply and PAT testing check. Criteria at 5-6 partially met. 5 marks.
(Equipment and technique appropriate).The choice of equipment and technique
are appropriately justified. The choice of range is explained. Risk assessment
considers significant hazards and suggests some precautions, and gives some
indication of the sources of information. 8 marks.
Task: The dissolving of a solid ionic compound
Mark Band
C
criteria
Exemplar
5-6
7-8
Collect and correctly record data to cover the range of relevant cases/situations, with
regular repeats or checks for repeatability. Data is of generally good quality
Temperature
of solvent 0C
700C
600C
500C
400C
300C
Test 1
9.85
seconds
10.29
seconds
11.99
seconds
14.83
seconds
22.22
seconds
Test 2
Time
taken Test 3
8.95
seconds
10.84
seconds
11.44
seconds
11.89
seconds
17.29
seconds
9.00
seconds
9.09
seconds
11.20
seconds
15.68
seconds
21.87
seconds
Test 4
9.296
seconds
10.073
seconds
11.543
seconds
14.13
seconds
20.45
seconds
Choose an appropriate range of values to test across the range, with regular repeats and
appropriate handling of any outliers. Checks or preliminary work are included to confirm
or adapt the range and number of measurements to ensure data of high quality
Temperature
of solvent 0C
700C
600C
500C
400C
300C
Test 1
9.85
seconds
10.29
seconds
11.99
seconds
14.83
seconds
22.22
seconds
Test 2
Time
taken Test 3
8.95
seconds
10.84
seconds
11.44
seconds
11.89
seconds
17.29
seconds
9.08
seconds
9.09
seconds
11.20
seconds
15.68
seconds
21.87
seconds
Test 4
9.29
seconds
10.073
seconds
11.54
seconds
14.13
seconds
20.45
seconds
I repeated each value 4 times and found no outliers, so there was no need to repeat
any readings.
My results show a clear trend which confirms my range is suitable.
Commentary
Data covers a suitable range with regular repeats. However there is inconsistency
in the precision of recording of data (number of sig figs), so the data is not
correctly recorded. Quality of data is fine. 5 marks.
10
Data is correctly recorded in a suitable table. Quality of data is good for this
experiment. Repeats are included. An appropriate range has been selected, with
regular repeats and a check. A statement about no outliers is correct and also
demonstrates the candidate knows that outliers should be repeated. 8 marks.
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
CANDIDATE STYLE ANSWERS
Task: TBC
Mark Band
A (graph)
criteria
5-6
7-8
Correctly select scales and axes and plot data for a graph, including an appropriate
line of best fit or construct complex charts or diagrams eg species distribution maps.
Indicate the spread of data (eg through scatter graphs or range bars) or give clear keys for
displays involving multiple data- sets.
(points plotted correctly) Axes labelled and scaled correctly, line of best fit OK, 6
marks
(points plotted correctly) Axes labelled and scaled correctly, line of best fit OK,
spread of data shown by (correctly plotted) range bars. 8 marks
Exemplar
Commentary
11
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
CANDIDATE STYLE ANSWERS
Task: The distribution of Plants
Mark Band
5-6
7-8
A
(Mathmatical)
criteria
Use mathematical comparisons between results to support a conclusion.
Use complex processing to reveal patterns in the data eg statistical methods, use of
inverse relationships, or calculation of gradient of graphs.
Exemplar
Statistical Analysis – chi squared
Chi-squared is a statistical test to see if there is a significant difference.
Statistical Analysis – chi squared
Chi-squared is a statistical test to see if there is a significant difference.
x2 = chi – squared value
∑ = the sum of
O= the observed results in investigation
e = the results you expect
x2 = chi – squared value
∑= the sum of
O= the observed results in investigation
e = the results you expect
Null Hypothesis
There is no difference in number of species in managed and unmanaged areas,
and semi-managed areas.
Comparing unmanaged, semi-managed(1m away) and managed (2m away)
areas
Null Hypothesis
There is no difference in number of species in managed and unmanaged areas, and
semi-managed areas.
Comparing unmanaged, semi-managed(1m away) and managed (2m away) areas
NUMBER OF SPECIES
Trial/site
unmanaged
NUMBER OF SPECIES
semi-unmanaged
(1m away)
Managed
(2m away)
Trial/site
unmanaged
semi-unmanaged
(1m away)
Managed
(2m away)
1
7
x2=1.46
4
x2=0.05
3
x2=0.04
1
7
x2=1.46
4
x2=0.05
3
x2=0.04
2
7
x2=1.46
4
x2=0.05
2
x2=1.3
2
7
x2=1.46
4
x2=0.05
2
x2=1.3
3
6
x2=0.54
4
x2=0.05
3
x2=0.04
3
6
x2=0.54
4
x2=0.05
3
x2=0.04
Total x2 = 1.46 + 1.46 + 0.54 + 0.05 + 0.05 + 0.05 + 0.47 + 1.35 + 0.47 + 1.35 +
0.47 = 5.9
x2 = 5.9
12
Total x2 = 1.46 + 1.46 + 0.54 + 0.05 + 0.05 + 0.05 + 0.47 + 1.35 + 0.47 + 1.35 + 0.47 =
5.9
x2 = 5.9
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
Mark Band
CANDIDATE STYLE ANSWERS
5-6
7-8
Critical value = 5.99 with 2 degrees of freedom at 5% level
5.9 < 5.99
The critical value is larger than the x2 value, with 2 degrees of freedom at a 5%
significance level, therefore we accept the null hypothesis and conclude that
there is no significant difference between the number of species in managed and
unmanaged areas, and semi-managed areas.
Comparing completely unmanaged and completely managed areas
Null hypothesis
There is no difference in the number of species in managed and unmanaged areas.
NUMBER OF SPECIES
Trial/site
unmanaged
Managed (2m away)
1
7
x =1.16
3
x2=0.60
2
7
x2=1.16
2
x2=1.53
3
6
x =0.39
3
x2=0.60
2
2
Total x2 = 1.16 + 1.16 + 0.39 + 0.60 + 1.53 + 0.60 = 5.44
x2 = 5.44
Critical value = 3.84 with 1 degree of freedom at a 5% level
5.44 > 3.84
The critical value is smaller than the x2 value with 1 degree of freedom at a 5%
significance level, therefore we reject the null hypothesis and conclude that there
is a significant difference between the number of species in only completely
managed and unmanaged areas.
Commentary
The calculation of Chi2 is correct, however it is not used to compare the two data
sets. 6 marks
13
The calculation of Chi2 is correct and its use to assess the significance of the results
matches the level 7-8 mathematical criteria. 8 marks
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
CANDIDATE STYLE ANSWERS
Task: The rate of enzyme activity
Mark Band
5-6
7-8
E(a)
Suggest (in outline) improvements to apparatus or techniques, or alternative ways
to collect the data; or explain why the method used gives data of sufficient quality to
allow a conclusion
Describe in detail improvements to the apparatus or techniques, or alternative ways to
collect the data, and explain why they would be an improvement; or explain fully why no
further improvement could reasonably be achieved.
Exemplar
After completing my experiment I can see how I could of improved it and made
it more accurate. There was some limitations from the equipment that we were
using. One of these limitations was the lack of spotting tiles owned by the school,
we could only examine a certain amount of amylase because we only had one
tile to work on. This stopped us from spotting anything that would have occurred
later on however this would be useless if the enzyme was denatured. Another
factor that may of slightly altered our results was that the change of colour was
hard to detect on the tiles. To stop this we could of made the same person check
for the change every time to eliminate the problem of different peoples opinions.
Also a colour card could have been used to check, this would help the accuracy
of the experiment. It was also hard to measure how much of the solution was
dropped on to the iodine. To stop this we could of used a graduated pipette, this
tells us exactly how much solution is being put on and it makes the experiment
a bit more accurate. Another problem that limited us was the reaction time to
the ten second gaps. Sometimes the solution was added a bit to late which may
of slightly changed our results, to solve this we could have the same person
counting down and dropping in the solution to ensure it was more exact. The
final limitation was that we could only do the experiment at room temperature,
temperature can have a large effect on enzymes at doing at different ones may
of given us different results.
There was some limitations from the equipment that we were using. One of these
limitations was the lack of spotting tiles owned by the school, we could only
examine a certain amount of amylase because we only had one tile to work on.
This stopped us from spotting anything that would have occurred later on however
this would be useless if the enzyme was denatured. Another factor that may have
slightly altered our results was that the change of colour was hard to detect on the
tiles. This meant the exact time of the starch being broke down was not always
perfect. To stop this we could have used a colour card to check against, this would
help be more consistent in finding the end point and reduce the spread of the
repeats. It was also hard to measure how much of the solution was dropped on
to the iodine. To stop this we could have used a graduated pipette, this tells us
exactly how much solution is being put on and it reduces the spread of the repeats.
Another problem that limited us was the reaction time to the ten second gaps.
Sometimes the solution was added a bit too late which may have slightly changed
our results, by making our times to long. To solve this we could have the same
person counting down and dropping in the solution to ensure it was more exact.
The final limitation was that we could only do the experiment at room temperature,
temperature can have a large effect on enzymes a higher temperature will speed up
the reaction and reduce the measured time, at lower temperature will slow down
the reaction and increase our times. We could improve this by doing the experiment
in a water bath which will give a constant temperature and reduce any variations in
our results.
Commentary
Limitations identified and outline improvements given, but lacks detail of effect
of improvements on experimental results. 6 marks
Limitations identified and improvements described, the effect of each improvement
is clearly described. 8 marks
14
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
CANDIDATE STYLE ANSWERS
Task: The motion of a falling object
Mark Band
5-6
7-8
E(b)
criteria
Use the general pattern of results or degree of scatter between repeats as a basis for
assessing accuracy and repeatability and explain how this assessment is made.
Consider critically the repeatability of the evidence, accounting for any outliers.
Exemplar
Evaluation of primary data:
In my experiment, I believe that we were very accurate and precise. This is
because we used a phone stopwatch which was accurate to 0.01seconds, this
was very accurate because it was the most precise we can get to, as we can’t get
any more accurate. We were also accurate because we could not get it any more
accurate. Both these accuracy levels will make our result more reliable because
we can get everything to the most precise point.
In our experiment, I believe that our results are quite repeatable.
with small range bars. This shows our result is very repeatable because it’s within
a very short time scale between all of the results, which makes this result very
repeatable. The range bars were small and did not overlap which means they are
accurate and the line of best fit is clearly correct.
Evaluation of primary data:
In my experiment, I believe that we were very accurate and precise. This is because
we used a phone stopwatch which was accurate to 0.01seconds, this was very
accurate because it was the most precise we had access to, as we can’t get any
more accurate. We were also accurate because the data all fitted very well with
the line of best fit, which passed through all the range bars. I addition there was
no overlap between the range bars of any points, which means that we can be
confident in the accuracy of the results. Both these accuracy levels will make our
result more reliable because we can get everything to the most precise point.
In our experiment, I believe that our results are quite repeatable.
First of all, at 0.53g our results were within 0.17 seconds of each other. This shows
our result is very repeatable because it’s within a very short time scale between all
of the results, which makes this result very repeatable.
At 1.11g, our results were even more accurate within a range of 0.09 seconds, this
shows the result is very repeatable because it’s a very tiny range and if the range
is small it shows our results are very repeatable and therefore reliable. Although, I
did get one outlier at 1.11g. This result was a lot faster than the others at this mass
probably because the height was too short or it was given a small push when being
released.
Commentary
(An outlier was identified on the results table). The general scatter between
repeats and the general pattern of results are used to consider repeatability and
accuracy, however there is some confusion. 5 marks
Outliers are correctly identified and accounted for. Uses scatter and general pattern
of results to assess accuracy and repeatability. Spread is critically considered. 8
marks
15
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
CANDIDATE STYLE ANSWERS
Task: The distribution of Plants
Mark Band
5-6
7-8
R(a)
criteria
Describe and explain the extent to which the secondary data supports, extends and/
or undermines the primary data, and identify any areas of incompleteness. A range of
relevant secondary data is collected from several fully referenced sources.
Assess the levels of confidence that can be placed on the available data, and explain the
reasons for making these assessments. Comment on the importance of any similarities or
differences.
Exemplar
a) Ecological succession
Kent, M, (2009), A2 biology, Oxford University press, 15BN 978-0-19-915270-4
(pages 80-83)
a) http://www.marz-kreations.com/Photos/065-BennasSummer2004_0.html
(BENNAS (SUMMER 2004)-04 :
Summer vacation in Finland 2004 - Bennas, Turku, Larsmo, Jakobstad, Vasa, etc)
Pictures are objective (what you see is factual and unarguable) so it’s reliable data.
b) Graph showing mean number of species for Crop field and Field margin.
Found on 17/10/13
http://repository.lib.ncsu.edu/ir/bitstream/1840.16/1419/1/etd.pdf (JELINEK,
SUSAN THERESA. The Association of Weed Species Richness and Abundance
with Field Margin Type in Crop Fields. (Under the direction of Dr. J. Paul Mueller
and Dr. Nancy G. Creamer).)
Picture of a man cutting long grass with a motorised rotary blade.
b) The OCR secondary data sheet is very reliable because we can assume the
data has been gathered by and peer reviewed by experts, as OCR are a wellrecognised exam board for GCSE and A-level students.
Comparing results with secondary data
a)“human management of habitats to maintain communities at an early
succession stage”
“To prevent secondary succession occurring on arable land, the field would
need to be ploughed regularly. {managed}”.
The supports my results because it explains why there are less plant species
in managed areas; because management keeps plant areas at an “early
successional stage”. Furthermore, the source is similar and supports my data as
it claims to prevent secondary succession, i.e. development of plant areas into
woodland etc., you need to plough (managed) the area.
This source differs from my results as it is explaining the science behind
ecological succession and isn’t actually from an investigation.
b)This source is similar to my results because it shows that at one site, the field
margin, there are more types of species in the unmanaged area than in the
managed area. However, it’s different to my results because at the other site,
the crop field, there were less species variety in the unmanaged area, whereas
my results consistently showed that there are less species in managed areas.
16
You can clearly see the managed
areas are predominantly grass, and
have less variety of species.
The unmanaged areas clearly have
more species; from trees to broad
leaf grass, to cow parsley and
buttercups.
b) Ecological succession 11
Kent, M, (2009), A2 biology, Oxford University press, 15BN 978-0-19-915270-4
(pages 80-83)
This is a very reliable source because Oxford University Press is a recognised
publisher in the field of scientific textbooks, and Michael Kent is a recognised
author in the field of A-level biology (however he isn’t necessarily an expert in
ecology). The scientific explanations are fully agreed by almost everyone which
increases the reliability of the data.
c) Graph showing mean number of species for Crop field and Field margin.
Found on 17/10/13
http://repository.lib.ncsu.edu/ir/bitstream/1840.16/1419/1/etd.pdf (JELINEK,
SUSAN THERESA. The Association of Weed Species Richness and Abundance
with Field Margin Type in Crop Fields. (Under the direction of Dr. J. Paul Mueller
and Dr. Nancy G. Creamer).)
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
Mark Band
CANDIDATE STYLE ANSWERS
5-6
7-8
c) This source has data similar to my results as it shows that different factors e.g.
light intensity and trampling have an effect on the number of plant species.
However, it is also very different to my results because it is only investigating
light, trampling, water, and plants under a tree: there isn’t any results on how
managing an area affects plant distribution. Therefore, it partially supports
my results because it shows that different factors can affect plant distribution,
however it isn’t that useful because it doesn’t show the effect of managing an
area.
The source is quite reliable because it was undertaken by scientists working in the
field, however they aren’t recognised experts. It seems like the data is based on a
study with small samples, which decreases the data’s reliability. Furthermore, you
can’t tell if the investigation has been peer reviewed/where it was published so
reliability is uncertain.
d)Three paragraphs of text included from
http://en.wikipedia.org/wiki/Ecological_succession
Wikipedia isn’t a very reliable source because anyone, with varying degrees of
expertise, can write and upload information so the information is unlikely to have
been peer reviewed which decreases the reliability of the data. However, authors of
the website are often experts in the field but you can’t be certain from reading the
information.
Comparing results with secondary data
a) Our results are similar to source A because source A clearly shows the majority of
managed areas are grass and have fewer plant species than the unmanaged area.
My chi-squared statistical analysis shows there is a significant difference between
the number of species in managed areas, therefore my results and source are
similar. However, we accurately measured the number of species in managed/
unmanaged areas and statistically proved there is a significant difference whereas
you can only infer/estimate from the photograph that there are more species in
the unmanaged area. Therefore, source A supports my results.
b) “human management of habitats to maintain communities at an early succession
stage”
“To prevent secondary succession occurring on arable land, the field would need
to be ploughed regularly. {managed}”.
The supports my results because it explains why there are less plant species in
managed areas; because management keeps plant areas at an “early successional
stage”. Furthermore, the source is similar and supports my data as it claims to
prevent secondary succession, i.e. development of plant areas into woodland etc.,
you need to plough (managed) the area.
This source differs from my results as it is explaining the science behind
ecological succession and isn’t actually from an investigation.
17
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
Mark Band
CANDIDATE STYLE ANSWERS
5-6
7-8
c) This source is similar to my results because it shows that at one site, the field
margin, there are more types of species in the unmanaged area than in the
managed area.
However, it’s different to my results because at the other site, the crop field,
there were less species variety in the unmanaged area, whereas my results
consistently showed that there are less species in managed areas.
Therefore, this source partially supports my results by showing some
unmanaged areas have more species, but also partially undermines my results
by not consistently showing unmanaged areas always have more plant species.
d) This source supports my results because it gives a scientific explanation for
my results, as it says the different stages of succession and that if there’s a
“disturbance”, “succession may be initiated by formation of new, unoccupied
habitat”.
The source differs from my results because it is explaining the science behind
ecological succession and isn’t actually results from an investigation.
Commentary
A suitable range of sources, however the OCR data is not referenced. The
comparison of secondary data with primary data is fine. no assessment of the
reliability of the sources. 5 marks
18
A suitable range of sources, fully referenced. The comparison of secondary data
with primary data is detailed. There is some assessment of the reliability of the
sources. 8 marks
Copyright © OCR 2016
GCSE TWENTY FIRST CENTURY ADDITIONAL SCIENCE A
CANDIDATE STYLE ANSWERS
Task: the motion of a falling object
Mark Band
R(b)
5-6
7-8
Explain the extent to which the hypothesis can account for the pattern(s) shown in
the data. Use relevant science knowledge to conclude whether the hypothesis has
been supported or to suggest how it should be modified to account for the data
more completely. Information is organised effectively with generally sound spelling,
punctuation and grammar. Specialist terms are used appropriately.
Give a detailed account of what extra data could be collected to increase confidence in
the hypothesis. The report is comprehensive, relevant and logically sequenced, with full
and effective use of relevant scientific terminology. There are few, if any, grammatical
errors
Exemplar
In my experiment my hypothesis said that when the mass is bigger resultant
force will be more powerful. By looking at my data I can say that my hypothesis
and prediction were supported to some extent. This data supports my
hypothesis and prediction because the object did fall faster when it had a larger
mass, although not by half the amount. The object will have fallen faster because
when an object falls it has a certain amount of air resistance which is an upwards
force, commonly known as drag because it pushes on the object. But it has a
force pulling it down called weight which is mass x gravity, which is a larger force
than the air resistance. As this weight force is higher than the air resistance it
has a resulting force pulling it down which is why it falls, because the forces are
unbalanced so the weight outweighs the air resistance. Therefore when the mass
is increased that increases the weight which means there is a larger force pulling
down, which means the resultant force is bigger, so the air resistance has less
effect.
In my experiment my hypothesis said that when the mass is bigger will the resultant
force will be larger and hence the time to fall would be less and I predicted that
when the mass was doubled the object would fall in half the time. By looking at my
data I can say that my hypothesis and prediction were supported to some extent.
This was because when the object had 1.11g mass it took on average 1.55 seconds
to fall whereas when the object was at 2.26g (slightly more than doubled) it fell
on average at 0,926 seconds. This data supports my hypothesis and prediction
because the object did fall faster when it had a larger mass, although not by half
the amount. The object will have fallen faster because when an object falls it has
a certain amount of air resistance which is an upwards force, commonly known
as drag because it pushes on the object. But it has a force pulling it down called
weight which is mass x gravity, which is a larger force than the air resistance. As this
weight force is higher than the air resistance it has a resulting force pulling it down
which is why it falls, because the forces are unbalanced so the weight outweighs
the air resistance. Therefore when the mass is increased that increases the weight
which means there is a larger force pulling down, which means the resultant force is
bigger, so the air resistance has less effect.
To increase confidence in my hypothesis first of all I would try increasing the weight
of other materials to see whether the mass increase has the same effect, because it
may not work the same with different materials.
Another way I could increase confidence in my hypothesis would be to use a bigger
range, we could use a range between 0g - 10g to see the effect that this amount
of weight has on the object, because how much time between weights may slow
down or even stop because it has reached terminal velocity.
Commentary
Comments on data supporting hypothesis/prediction Uses science to
explain how results support hypothesis. Generally good quality of written
communication. 6 marks
Comments on data supporting hypothesis/prediction Uses science to explain how
results support hypothesis. Insufficient detail of additional extra data (what different
material?). QWC is fine for level 7-8. 7 marks
criteria
19
Copyright © OCR 2016
ocr.org.uk/science
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