GCSE
SCIENCE A (ROUTE 2)
SCA2HP
Report on the Examination
4406
June 2015
Version: v1.0
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REPORT ON THE EXAMINATION – GCSE SCIENCE A (ROUTE 2) – SCA2HP– JUNE 2015
General
There were 13 questions on the Higher Tier paper. Questions 1 - 7 targeted grades C-D; of these
questions, 1, 2, 4, and 6 were common with the Foundation Tier paper. Questions 8 - 13 targeted
grades B-A*.
The questions are always presented in the same order: biology at standard demand, followed by
chemistry and then physics at standard demand; biology at high demand, followed by chemistry
and then physics at high demand. It is likely that more marks will be gained from the questions at
the beginning of the paper, as these are at a lower demand than those in the second half of the
paper, so it is important that these are completed. However, students do not need to answer all the
questions in numerical order. A student whose strength lies in physics may benefit from doing the
physics questions first.
Many students cross out work that they do not want to be marked. Only the remaining or
replacement work is marked. However, if no replacement answer is written, the examiner will
attempt to mark the crossed out work, so it can be beneficial to the student to strike through the
work neatly, and leave it so it is still legible.
In the Science A combined exam papers fifty percent of the marks are for knowledge and
understanding, based on the content of the specification. Many students lose these marks because
they have not revised the basic facts. It is useful for all students to have a copy of the subject
content of the specification so they can check that they know this information.
Question 1 (Standard demand)
1(a)
Only a third of the students said that lichens are indicators of sulfur dioxide concentration in the
atmosphere. A wide range of incorrect organisms were given. These ranged from different birds,
fish, insects and mammals to trees, plants and bacteria.
1(b)
The dependent variable in the investigation was the number of seeds that grew in each bag. A
reference to both number, eg amount, and seeds was required. Incorrect responses generally
mentioned control variables or referred to the water and sodium metabisulfite solutions.
1(c)(i)
Just over half of the students correctly calculated the percentage of seeds that grew.
1(c)(ii)
Less than a tenth of the students gave a valid conclusion. The stem of the question made clear
that the investigation was to find out how sulfur dioxide gas affects the growth of cress seeds.
Many students simply referred to growth with the water or growth with the sodium metabisulfite
solution and did not add any value. They had to refer to sulfur dioxide in their answer. Some said
that sulfur dioxide stopped the seeds growing, which was incorrect.
Question 2 (Standard demand)
2(a)(i)
Two thirds of the students gained full marks for this question. 1 mark could be gained for correctly
reading 122 and 92 from the graph. Incorrect readings that were correctly added together could
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also gain 1 mark. This highlights the importance of showing working for all calculations, no matter
how simple they may appear to be.
2(a)(ii)
Only just over half of the students gained the mark for this simple calculation. Some made a
correct calculation but then tried to write out the number in full, or in standard form, but could only
gain the mark if they had deleted billion from the answer line.
2(b)(i)
Students were instructed to use information given in the graph to suggest why some scientists do
not think that burning fuels is the main cause of carbon dioxide in the atmosphere. Most students
said that respiration and decomposition released more carbon than burning fuels to gain the mark.
If figures were quoted, a comparison was needed.
2(b)(ii)
Students had to suggest how eating less food from animals or more food from plants could reduce
the amount of carbon dioxide in the atmosphere. Credit could not be gained just for mentioning
respiration or photosynthesis alone. Clear statements as to whether these processes would occur
more or less were needed, and how this would affect the amount of carbon dioxide absorbed or
released. Most students were unable to make the link that less meat would mean fewer animals
were required, or that more food from plants would mean that more crops needed to be grown.
Instead many answers related to more animals being alive because they weren’t being eaten, or
fewer plants being alive because they were being eaten. Other students linked their answer to the
idea of decomposition of dead organisms, which was ignored. Some spoke about carbon dioxide
being produced by the meat production processes, which was also ignored.
Question 3 (Standard demand)
3(a)
The question asked why a compost heap is useful to the chef, not how it is important
environmentally. Most students said that the compost heap would provide nutrients for the chef’s
plants or would help his plants grow. A few also said that it would dispose of his fruit peelings.
References to saving money on fertiliser or improving soil structure were rarely seen.
3(b)
To gain full marks references to both earthworms and the plastic sheet had to be attempted. Many
students gained at least 1 mark for saying that the plastic sheet trapped heat or moisture. A few
thought that it prevented air or sunlight reaching the compost heap. Although students attempted to
explain how the earthworms helped to speed up the decay process, only a few mentioned that they
would allow more air to enter the soil, or that they would break the wastes into smaller pieces. Just
saying that they would break down the wastes was insufficient, and suggested that they did not
fully understand the term ‘decay’. Many students gave responses linked to faeces from the
earthworm providing nutrients. Few students made any reference to microorganisms in their
response. A lot of students repeated information given in the question and focused their entire
response on the fact that the worms were not being eaten by the birds.
Question 4 (Standard demand)
4(a)
Less than a third of the students gained full marks for this question. Some did not know how to
calculate the thickness of the mantle and gave an answer of 2900 km which was ignored. For the
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core some said ‘inner core’ or ‘outer core’. These were incorrect, but students could gain the mark
if they said ‘both inner and outer core’.
4(b)
In this QWC question students were asked to describe changes in the position of continents over
the last 250 million years, using information given in a diagram. They then had to describe the
processes that caused these changes. In order to reach Level 3 both parts of the question had to
be answered. Some students either only described the changes, or only described the processes.
A good tip for students is to underline important instructions and words in the question, and use
these to check that they have answered the question fully.
Some students gave very well written descriptions of the changes and detailed descriptions of the
processes involved. Weaker responses did not refer clearly to the continents, and many thought
that the maps were showing the positions of the tectonic plates. There were quite a lot of answers
that went into detail about earthquakes and volcanoes, but this did not answer the question.
Question 5 (Standard demand)
5(a)
This question was very poorly answered with hardly any students being able to give the correct
word equation for the fermentation of sugar, which is detailed in the specification. Many equations
were badly written, and students did not appear to know the basic rules. For example, an equals
sign was used instead of an arrow; a sequence of reactions were presented with arrows between
each stage; reactant(s) and products were not on the correct sides of the equation. Many students
added yeast and water to the reaction. If these were written on both sides of the equation they
were ignored, as they would cancel each other out. However, they were usually just added as
reactants. The most common error, for those students who made a reasonable attempt at the word
equation, was to omit carbon dioxide as a product. They just gave ethanol. Others gave a correct
equation for the hydration of ethene. Students should be taught the difference between a word
equation and a symbol equation, and be discouraged from combining the two.
5(b)(i)
Filtration would be used to separate the yeast from ethanol and water. Some said ‘distillation’ or
‘evaporation’ which were both ignored. Many students displayed a lack of knowledge of technical
terms. The equipment to be used was often named as a sieve and words such as ‘colander’ were
also seen. Others suggested using a funnel but made no reference to filtering. Others gave
descriptions of decanting but did not name the process.
5(b)(ii)
The question asked how ethanol could be separated from the mixture of ethanol and water. There
were many references to evaporating the ethanol, but to gain the mark students had to also say
how the ethanol would be collected. Many thought that boiling the mixture would evaporate the
water first and leave the ethanol behind.
5(c)
Marks could not be gained from copying information directly from the table. Students should be
taught that they need to add value to any information provided in order to gain credit. The most
commonly obtained marks were for saying that sugar cane is a renewable resource for the
advantage and that fermentation is a slower process for the disadvantage. Students did find it
more difficult to express a disadvantage. Just saying ‘only 15% ethanol was produced’ was
insufficient. They had to say that the ethanol produced was impure or that it would have to be
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purified. Similarly stating that the fermentation vessel had to be emptied and refilled did not gain a
mark, but saying that fermentation is a batch process did, as value was added to the information
they were provided with.
Question 6 (Standard demand)
6(a)
The letter R was often written so that it overlapped areas of rarefaction and compression, so did
not gain credit. Those who knew the answer wrote the letter R very clearly in a correct position.
6(b)
Less than a third of the students gained the mark. Many thought that vibrations in a sound wave
can travel.
6(c)
The majority of students gained full marks for the calculation of the speed of sound.
6(d)(i)
Over two thirds of students correctly named the Doppler effect. ‘Red-shift’ was sometimes named,
which was incorrect.
6(d)(ii)
Generally students interpreted the information in the table correctly and wrote sensible
conclusions. Some confused volume with frequency, whilst others tried to give conclusions about
distance of the car from the person. As they were not given any information about how far away
the car was, they could not make these conclusions.
Question 7 (Standard demand)
7(a)(i)
Over half of the students correctly stated that the relationship between the angle of incidence and
the angle of reflection is that they are equal. Poorly phrased responses, such as the angles were
‘even’ or ‘symmetrical’, or that there was a ‘positive correlation’, were all ignored.
7(a)(ii)
Only a fifth of the students could correctly describe the image in a plane mirror. The fact that the
image in a plane mirror is virtual is clearly stated in the specification. The most common response
was that the image in a plane mirror is a reflection. Some students attempted to describe ‘laterally
inverted’, but phrases such as ‘back to front’, ‘reversed’ or ‘flipped’ were all ignored.
7(b)(i)
Ray diagrams are difficult to draw without a ruler. We do allow some tolerance, but the line must
look straight by eye. Rays were drawn in many directions – reflected from the top surface, reflected
internally at both possible and impossible angles, emerging directly down the normal and at very
large or very small angles. The easiest way to draw the refracted ray is to position a ruler along the
incident ray and then move it parallel to this until it meets the normal on the lower surface of the
block.
7(b)(ii)
Less than half of the students knew that the dashed line drawn on ray diagrams is called the
normal.
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7(c)(i)
In science a line of best fit may be a straight line or a curve. Many students drew a straight line,
rather than a smooth curve. Others did not include the point drawn at 0,0. The curve had to touch
at least some part of each point, and could not be constructed from a series of straight lines drawn
from point to point.
7(c)(ii)
Most students gained the first marking point for stating that as the angle of incidence increased,
the angle of refraction increased. The mark was not awarded if cause and effect were written the
wrong way round, ie as the angle of refraction increased, the angle of incidence increased. The
second marking point was rarely attempted.
Question 8 (High demand)
8(a)
Many students gave confused responses implying that the tiger intended to adapt in order to
survive. Very few referred to variation in fur pattern within the population, although a few said that a
mutation could have occurred to produce striped fur. Some wrote answers about the giraffe, which
did not explain how the tiger evolved to have stripes. Quite a lot mentioned natural selection, but
they had to explain what this meant in relation to the tiger in order to gain a mark.
8(b)
There were some very well expressed responses saying that the stripes were an acquired
characteristic, or a characteristic developed during the tiger’s lifetime, that were passed on to the
offspring. However, many students confused the theories of Lamarck and Darwin by referring to
mutations, genes and natural selection.
Question 9 (Standard and High demand)
9(a)
Just under half of the students answered the question correctly giving ‘genetic engineering’ or
‘genetic modification’ as their response. Common incorrect terms included ‘cloning’, ‘asexual
reproduction’, ‘gene transplant’ and ‘genetic variation’.
9(b)
The most common points that gained credit were related to an increase in yield and that the
tomatoes could be poisonous if eaten. Students often said that the tomatoes could be grown in
cold conditions but did not relate this to a longer growing period. Others did not understand that
different genes affect different properties and thought that adding a gene from a fish would also
alter the taste. Both advantages and disadvantages had to be given in order to gain full marks.
Question 10 (High demand)
10(a)(i)
A surprising number of students did not mention that the wolf cubs were produced by sexual
reproduction, although most students gained a mark for saying that the cubs would have different
genes or chromosomes. The question referred to the biological parents, but many missed this and
gave answers that related to a surrogate mother.
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10(a)(ii)
Most students gave the response ‘cloning’, which was ignored unless they said ‘adult cell cloning’
which was incorrect.
10(a)(iii)
Students who obtained the mark usually did so by explaining that it would be better to produce
wolves that were different from each other because then there would be less chance of the
population being wiped out by a disease.
Question 11 (High demand)
11(a)(i)
Many students said there was a high demand for petrol, but this was not enough to gain the mark.
They had to be more specific and say that the demand for petrol was greater than the supply.
11(a)(ii)
Just under half the entry selected kerosene as the fraction most suitable to be cracked to produce
petrol. Only slightly fewer selected diesel.
11(a)(iii)
Most responses were poorly expressed. Students who had selected kerosene in part (a)(ii)
struggled to give two reasons why kerosene is cracked to give petrol, although both marking points
were seen in roughly equal proportions in creditworthy responses. Students who selected diesel in
part (a)(ii) could only gain the second marking point for saying it had larger molecules than petrol.
11(b)
There was much confusion between cracking, hydrogenation, fractional distillation and
polymerisation. Many students referred to heating the hydrocarbon, but needed to say that it
vaporised in order to gain this mark. Students did not need to know the name of the catalyst,
although some did give correct examples such as ‘aluminium oxide’. They did, however, have to
say that it was hot in order to gain the mark. Those who referred to a hot nickel catalyst were not
credited as they were confusing the process with hydrogenation.
Question 12 (High demand)
12(a)
Just under half of the students gained full marks for an answer of 40%. An answer of 60% could
gain 1 mark, but only if they had shown their working. They had used the mass of all the other uses
of polymers, 27 megatonnes, but correctly worked out a percentage. There were many addition
errors, with students unable to correctly add figures given to 2 decimal places.
12(b)(i)
Students had to draw the displayed structure of ethene. Common errors were to draw a single
bond instead of a double bond between the carbon atoms, or to show open bonds sticking out from
either side of the molecule as in a polymer. Some students did not take enough care when writing
the symbols, which should have been roughly the same height as each other.
12(b)(ii)
To gain full marks students had to refer to many monomers joining together to form a polymer or a
very large molecule. The number of monomers and size of the molecule formed were important.
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Some good responses went on to explain how the double bond in the alkene broke to allow the
molecules to join together. Some students confused polymerisation and cracking.
12(c)
Students had to evaluate the use of plastic bags made from cornstarch instead of poly(ethene), so
both advantages and disadvantages were required for full marks. Many students said that
cornstarch is biodegradable and produced from a renewable source. A lot of students also gave a
disadvantage related to land use. There were many responses that referred to properties of the
bags, such as strength. These were ignored, along with references to cost and recycling.
Question 13 (High demand)
13(a)
The question asked for similarities and differences between generating power using nuclear fuels
and using fossil fuels. A lot of students gave information about how the fuels had formed, how they
are mined and aspects of commissioning and decommissioning the power stations, none of which
answered the question. Quite a lot of students thought that both fuels were burnt. The marking
points that were seen most were that fossil fuels are burnt and that they release carbon dioxide, or
another named gas.
13(b)(i)
A few responses were very comprehensive and covered all the points in the mark scheme.
However, a lot of students had not interpreted the graph correctly, and had not read the question
carefully. They thought the graph compared how much power could be generated from a given
mass of fuel, so gave ‘fossil fuels release more energy’ as a reason why nuclear fuels are used
less than fossil fuels to generate power. Many said that nuclear fuels are less readily available and
cost more, even though they were directed to give different reasons from these in the question.
13(b)(ii)
Most students gained 1 mark for saying that fossil fuels are running out. Some had misunderstood
the question and said there would be an increase in demand for electricity.
13(c)
Some students gave very good answers to this question about the use of step-up transformers in
the National Grid. A few confused voltage and current, and some said that step-up transformers
stop energy losses in the cables, rather than reducing it. However, the terms ‘power’, ‘electricity’,
‘current’ and ‘voltage’ were often poorly used and are obviously not understood.
13(d)
Fracking is a topical issue, but students did not have to know anything about the process in order
to answer the question. The majority of responses just included statements copied from the report,
without adding any value, so did not gain credit. A few students said that the earth tremors might
damage houses, or that habitats would be destroyed, both of which were creditworthy.
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Mark Ranges and Award of Grades
Grade boundaries and cumulative percentage grades are available on the Results Statistics
page of the AQA Website.
Converting Marks into UMS marks
Convert raw marks into Uniform Mark Scale (UMS) marks by using the link below.
UMS conversion calculator
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