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Example Candidate Responses
(Standards Booklet)
Cambridge IGCSE®
Combined Science
0653
Cambridge Secondary 2
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permitted to copy material from this booklet for their own internal use. However, we cannot give permission
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® IGCSE is the registered trademark of Cambridge International Examinations.
© Cambridge International Examinations 2013
Contents
Introduction ........................................................................................................................... 2
Assessment at a glance ........................................................................................................ 3
Paper 2 – Core ...................................................................................................................... 4
Paper 3 – Extended ............................................................................................................54
Paper 5 – Practical test ......................................................................................................114
Paper 6 – Alternative to practical....................................................................................... 144
Introduction
Introduction
The main aim of this booklet is to exemplify standards for those teaching Cambridge IGCSE Combined
Science (0653), and to show how different levels of candidates’ performance relate to the subject’s
curriculum and assessment objectives.
In this booklet a range of candidate responses has been chosen to exemplify grades C and E for Paper
2, and grades A, C and E for Papers 3, 5 and 6. Each response is accompanied by a brief commentary
explaining the strengths and weaknesses of the answers.
For ease of reference the following format for each paper has been adopted:
For each question an extract from the mark scheme, as used by examiners, is followed by examples of
marked candidate responses, each with an examiner comment on performance. Comments are given to
indicate where and why marks were awarded, and how additional marks could have been obtained. In this
way, it is possible to understand what candidates have done to gain their marks and what they still have to
do to improve their grades.
Past papers, Examiner Reports and other teacher support materials are available on Teacher Support at
http://teachers.cie.org.uk
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Cambridge IGCSE Combined Science 0653
Assessment at a glance
Assessment at a glance
Candidates are awarded grades A* to G.
Candidates expected to achieve grades D, E, F or G study the core curriculum only and are eligible for
grades C to G.
Candidates expected to achieve grades C or higher should study the core and extended curriculum areas.
All candidates must enter for three papers.
Candidates take:
Paper 1
(45 minutes)
(30% of total marks)
A multiple-choice paper consisting of 40 items of the four-choice type.
and either:
or:
Paper 2
(50% of total marks)
(1 hour 15 minutes)
Core curriculum – Grades C to G available
Paper 3
(50% of total marks)
(1 hour 15 minutes)
Extended curriculum – Grades A* to G available
Core theory paper consisting of short-answer
and structured questions, based on the core
curriculum.
Extended theory paper consisting of shortanswer and structured questions. A quarter
of the marks available will be based on core
material and the remainder on the supplement.
and:
Practical assessment
either:
Paper 4
Coursework
or:
Paper 5
Practical test (1 hour 30 minutes)
or:
Paper 6
Alternative to practical (1 hour)
(20% of total marks)
Teachers are reminded that a full syllabus is available on www.cie.org.uk
Cambridge IGCSE Combined Science 0653
3
Paper 2 – Core
Paper 2 – Core
Question 1
Mark scheme
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
Example candidate response – grade C
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
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Paper 2 – Core
Examiner comments – grade C
(a) A clearly-written answer. The use of words in the formula ensures the correct data is taken from the
question. The fraction, as given, was a necessary part of the working. 2/2
(b) (i) The word ‘energy’ after ‘chemical’ was not necessary, nor was ‘potential’, before ‘chemical’. The
answer ‘potential’ on its own, would not have gained a mark. 1/1
(ii) This answer was considered good enough to gain the mark, although if the candidate had explained
where the heat energy was lost to, it would have been a better answer. 1/1
(c) This question was exploring the candidates’ knowledge of the expansion of metals in high temperatures
and the consequences of this expansion. This candidate’s use of ‘hot’ temperatures was considered just
good enough. The second part of the answer was a clear description of the consequences. 2/2
(d) Although this answer was often seen, it was not detailed enough. ‘Sulfur dioxide’ was necessary in any
answer referring to ‘pollution’. Similarly, a common answer referring to the ‘renewable’ nature of ethanol
had to be detailed. ‘Eco-friendly’, for example, did not gain a mark. 0/1
(e) (i) The data only suggested that some power would be generated below 5 km/h, so this answer gained
the mark. 1/1
(ii) The vast majority of candidates gave this correct answer. 1/1
(iii) This was a very full answer. Not only did it describe the unreliability of the wind, but the candidate
then went on to explain the consequences of a low wind speed. Some candidates misinterpreted
or misread the question, their answers referred to the low power output of ONE wind turbine being
insufficient. Other candidates referred to the ‘creation’ of electrical energy. Generally, these answers
did not gain a mark. 1/1
Total mark awarded = 9 out of 10
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
Example candidate response – grade E
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
Cambridge IGCSE Combined Science 0653
9
Paper 2 – Core
Examiner comments – grade E
(a) A correct answer in which the use of words, when the formula was written, ensured accuracy when
data was selected from the question. The fraction, as written, was a necessary part of the working. 2/2
(b) (i) The candidate has attempted the question, which is always preferable to leaving the line blank.
Should candidates, on re-reading their answer, decide to change a word, the original answer can be
deleted with one line through it. 0/1
(ii) The answer shows that the candidate knows that a discharge is made to the air, but this is not
sufficient. 0/1
(c) The candidate has misinterpreted the question. The answer is not relevant to the drawing, which gives
no indication of a curve. 0/2
(d) If this answer had explained in what way the air is damaged by the use of petrol, which is by the
emission of sulfur dioxide, it would have been awarded a mark. 0/1
(e) (i) The data only suggests that there is power generated at wind speeds less than 5 km/h, so this
answer gains the mark. 1/1
(ii) Many candidates gave this correct answer. 1/1
(iii) Neither attempt to answer the question are relevant. When two different answers are given, if one
is incorrect, the correct answer does not gain a mark. 0/1
Total mark awarded = 4 out of 10
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Paper 2 – Core
Question 2
Mark scheme
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Paper 2 – Core
Example candidate response – grade C
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
Examiner comments – grade C
(a) (i) The correct answer here is clearly written. Some candidates confused the word ‘nucleon’, which
was part of the question, with ‘nucleus’. 1/1
(ii) The explanation of how the number ‘18’ had been calculated is clearly given. It was insufficient to
give ‘37-17 = 18’, as some candidates wrote. 2/2
(iii) There was no mark given because the question had asked for the ‘name’ of the element. This was a
quite common error. 0/1
(b) (i) Although this is a correct statement, the question had asked for ‘properties’ which were different.
This was a quite common misinterpretation of the question. 0/1
(ii) This answer gained the mark because it referred to both elements. A common error was to only
state that, for example, ‘Z is a Noble gas’. 1/1
(c) (i) The inaccuracy of the statement and of the equation detracted sufficiently that no mark could be
awarded. If ‘carbon’ had been written instead of ‘calcium’, one mark would have been awarded for
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
reference to ‘oxygen’. If ‘joins with’ had been written instead of ‘gains’, both marks would have been
awarded. To clarify, ‘in this reaction, carbon joins with oxygen’ would have been a complete answer.
0/2
(ii) This question was exploring the candidates’ knowledge of the basicity of calcium oxide and calcium
carbonate and that some soils are too acidic. This candidate’s answer only referred to the need for
minerals in the soil. Many candidates confused the terms ‘increasing the fertility’ and ‘fertilising the
soil’. 0/2
Total mark awarded = 4 out of 10
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
Example candidate response – grade E
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
Examiner comments – grade E
(a) (i) The candidate has misread the question and failed to give the part of the atom where the particles
are found. 0/1
(ii) This is a very full answer. The statement at the side of ‘18’ is almost sufficient on its own. 2/2
(iii) A correct answer. The candidate did not make the mistake of some and give the symbol for
hydrogen. 1/1
(b) (i) The answer does not show any knowledge of the metallic/non-metallic nature of the elements
across the period. 0/1
(ii) The candidate gave a very full description of the element Z. If a brief note had been made that
element Y was reactive, the mark would have been gained. 0/1
(c) (i) The candidate mistook the words ‘oxidation’ and ‘exothermic’. 0/2
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
(ii) The question was exploring the candidates’ knowledge of acidic soils and the basicity of calcium
oxide and calcium carbonate. This answer does not indicate any such knowledge. 0/2
Total mark awarded = 3 out of 10
Question 3
Mark scheme
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Paper 2 – Core
Example candidate response – grade C
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Paper 2 – Core
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
Examiner comments – grade C
(a) Although the answer did not refer to getting energy from plants, the candidate showed sufficient
understanding of plants being the sole source of food, and therefore energy, that it was just enough to
gain both marks. If the answer had not referred to ‘not eating meat’, it would only have gained one mark.
2/2
(b) The first two marking points were not matched; the term ‘enough’ did not indicate that food in excess
of the animals’ normal requirements must be eaten. The third marking point was not awarded since the
candidate did not clearly enough show that nutrients other than fats are converted to fat stores. 0/2
(c) (i) Only the first marking point was matched. The candidate gave no indication that they had
understood the implications of levelling off the graph. 1/2
(ii) The candidate had misread the question which was exploring their understanding of the insulating
effects of the layer of fat. The question had referred to keeping the marmot ‘warm’, not ‘alive’. It
also referred to cold weather, which should have guided candidates to the issue of prevention of
heat transfer. Some candidates, having read the question correctly, missed the mark by referring to
‘stopping the cold getting in’. 0/1
(d) Only the first answer gained a mark. 1/2
(e) (i) The candidate’s response was sufficient to indicate that they had seen the overall increase in body
mass. Some candidates only referred to the repeated increase and decrease in body mass. 1/1
(ii) This answer was just good enough to match the second marking point. It could have been improved
by using ‘earlier in the year’ rather than ‘early’. Also, if they had added to the phrase ‘by using up
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
their fat layer’, ‘ they had lost less weight’, a correct answer that would also have improved the
answer. 1/1
Total mark awarded = 6 out of 11
Example candidate response – grade E
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Paper 2 – Core
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Paper 2 – Core
Examiner comments – grade E
(a) The candidate did not indicate that a herbivore gets all its energy from plants. Only the first marking
point was matched. If the answer had been ‘it ONLY eats plants’, that would have been sufficient for
both marks. 1/2
(b) The answer does not stress that a lot of plants must be eaten. If they had added to the second part, the
idea that ‘more energy than they need’ must be provided by the plants, this would have matched the
second marking point. 0/2
(c) (i) Although the answer would have been improved by using ‘as’ rather than ‘and’, it was good enough
to match the first marking point. The candidate made no reference to the levelling off of the line at
high body mass values, so this mark was not given. 1/2
(ii) The candidate has taken phrases directly from the question and not explained the insulating effect of
the layer of fat. 0/1
(d) The candidate has misread the question and given means of electricity generation rather than the gases
contributing to global warming. 0/2
(e) (i) The candidate has only observed the rise and fall of the line and failed to see the, albeit slower,
overall rise. Other candidates made the same error. 0/1
(ii) This is a well-argued answer. Every statement is explained. The final bracketed point ensured
absolute clarity. 1/1
Total mark awarded = 3 out of 11
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
Question 4
Mark scheme
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Paper 2 – Core
Example candidate response – grade C
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Paper 2 – Core
Examiner comments – grade C
(a) Only the first marking point was matched. The candidate did not give sufficient detail of how the speed
of the bubbles should be measured. 1/3
(b) (i) This answer is correct. Some candidates thought that the volume of the acid would have an effect
on the rate of the reaction. 1/1
(ii) The candidate’s answer did not predict the difference in the results. However, since the statement
that the reaction would go faster is correct, the second marking point was awarded. 1/2
(c) (i) Although the statement is correct, the candidate has not explained the difference between an atom
and an ion, by stating that the atom is neutral, so no mark was awarded. 0/1
(ii) This is a correct answer. Some candidates wrote the formula equation for the reaction of
magnesium and hydrochloric acid. 1/1
(iii) This is the correct answer. This was another question where candidates were clearly asked to write
the word ‘hydrogen’ and the formula did not gain a mark. 1/1
Total mark awarded = 5 out of 9
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Paper 2 – Core
Example candidate response – grade E
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
Examiner comments – grade E
(a) The first two marking points were matched, but there was insufficient explanation of how the rate
of reaction should be measured. If they had written that the time was measured for the measuring
cylinder to fill with gas, that would have been enough to gain the third mark. No credit could be given to
‘repeating the experiment’. 2/3
(b) (i) Although the surface area of the magnesium is the actual variable, the ‘amount’ of magnesium was
sufficient to gain the mark. 1/1
(ii) The candidate has not predicted in what way the result would be different, so the first marking point
is not matched. The explanation, that the rate of reaction was greater, does match the other marking
point. 1/2
(c) (i) The candidate has given a good description of a magnesium atom, but the answer gives no
indication of their knowledge of the difference between atom and ion. The charged nature of the ion
was required. 0/1
(ii) Although the correct symbol for magnesium is given, the candidate has not made use of the
Periodic Table at the back of the examination paper to check the symbol for chlorine. 0/1
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
(iii) This is an incorrect answer. The candidate does not show experience of word equations. 0/1
Total mark awarded = 4 out of 9
Question 5
Mark scheme
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
Example candidate response – grade C
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
Examiner comments – grade C
(a) (i) The lower frequency was correct, but no mark was awarded because of the error in the upper limit
of the frequency range. 0/1
(ii) There were two omissions in the explanation of frequency, but the more important one was the
vague definition of the time period. If that had been given as ‘in a second’ then, with the quite good
diagrams which gave some indication of movement along the horizontal axis, the answer would
have gained the mark. In the second part, the two diagrams were sufficiently accurate to explain
wavelength. The written explanation was not precise enough on its own. 1/2
(b) (i) This answer shows a good understanding of the role of molecules in the propagation of sound
waves. 1/1
(ii) The use of the word ‘softer’ was sufficient to gain the mark. Some students referred to the difficulty
of hearing the sound, but these types of answers did not gain marks as there was no explanation of
why the sound would be difficult to hear. 1/1
(iii) This is the correct answer, although it proved a difficult question for many candidates. 1/1
(c) The two marks could have been gained by correct labelling at either one of the interfaces. This
candidate had initially focussed on the air/glass interface, but then deleted the associated angle of
refraction, possibly after observing that there was also refraction at the glass/air interface. The answer
could have been improved by drawing an arc around each angle. 1/2
Total mark awarded = 5 out of 8
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Paper 2 – Core
Example candidate response – grade E
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
Examiner comments – grade E
(a) (i) Although this frequency is within the range, no mark was awarded since both the lower and upper
limits were required. 0/1
(ii) Neither part was correct. The candidate has confused amplitude with frequency in the first part.
Many candidates have found it easier to answer both parts of the question by using diagrams. This
is advised at the end of the question. 0/2
(b) (i) The candidate has made a good attempt to answer a question, but lacks sufficient understanding of
the difference between light and sound waves. 0/1
(ii) Both parts of the answer were incorrect. However, if one of the answers given had been correct,
the presence of an incorrect answer would have lost the mark. 0/1
(iii) The second attempt only repeats information given in the question. This is quite a common error.
0/1
(c) The candidate has misread the question and has attached the label ‘r’ to the refracted ray. In ray
diagrams, candidates should be encouraged to draw an arc around angles, as is sometimes used in
mathematics. 0/2
Total mark awarded = 0 out of 8
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
Question 6
Mark scheme
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
Example candidate response – grade C
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
Examiner comments – grade C
(a) This is a well labelled answer; the line drawn with a ruler and an arrow for precision. 1/1
(b) These were the two expected answers although individual (correct) minerals would have gained marks.
2/2
(c) (i) This is the correct answer. Some candidates gave phloem here. 1/1
(ii) This answer was again well labelled. Some candidates did not draw the line and wrote ‘A’ in the
central area. These answers gained a mark, but were very difficult to see. It is always preferable to
draw a line to the outside of the diagram and write the label there. 1/1
(d) (i) This is the correct answer. The candidate did not make the error of some others and leave the boxes
blank where structures were not present; marks were not awarded for each row where there was a
blank. 4/4
(ii) The candidate has shown a good understanding of the necessity of light in photosynthesis. A few
answers were not so concise and gave, as the explanation for the lack of chloroplasts, the red colour
of the radish root. These did not gain marks. 1/1
Total mark awarded = 10 out of 10
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
Example candidate response – grade E
Cambridge IGCSE Combined Science 0653
39
Paper 2 – Core
Examiner comments – grade E
(a) The candidate has clearly labelled the diagram, using a ruler and writing outside the drawing area. It
would have been improved by adding the word ‘cell’. 1/1
(b) A mark is given for the first answer. The term ‘food’ is not sufficiently precise; ‘minerals’ or a named
(correct) mineral was needed for the second marking point. 1/2
(c) (i) This is the only occasion where this candidate has failed to attempt a question. In all other
questions, where the candidate lacked sufficient knowledge or understanding of the subject, they
have made an attempt and in some parts they have been successful. If no answer is given, there is
no chance of success. 0/1
(ii) Although correctly labelled, it would have been better if, as in part (a), the candidate had drawn a
line from the central area and written ‘A’ outside the drawing area. 1/1
(d) (i) These are the correct answers. The candidate did not make the error of some others and leave blank
the box where no structure is found in an animal cell. Marks were not awarded for rows containing
blank boxes. 4/4
(ii) The candidate has misread the question and not noticed that it is the root of the radish that is the
subject. The statement is correct, but gains no marks. 0/1
Total mark awarded = 7 out of 10
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
Question 7
Mark scheme
Cambridge IGCSE Combined Science 0653
41
Paper 2 – Core
Example candidate response – grade C
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
Examiner comments – grade C
(a) (i) Despite the neatness of the diagram and use of a ruler, because of the missing ammeter the
candidate was not awarded the first mark. 2/3
(ii) The candidate did not show a correct understanding of the use of a variable resistor. 0/1
(b) (i) The correct response. A few candidates used anode and cathode. 1/1
(ii) Here, the candidate has confused electrons with other charged particles, namely ions. 0/1
(iii) This is correct. A wide variety of metals and alloys gained marks here. 1/1
Total mark awarded = 4 out of 7
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
Example candidate response – grade E
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
Examiner comments – grade E
(a) (i) This is a neat drawing of the circuit with good use of a ruler, but only the first marking point has
been matched. The voltmeter is not in parallel and there is no variable resistor in the circuit. 1/3
(ii) If the candidate had written ‘lamp’ instead of ‘current’, the mark would have been awarded. 0/1
(b) (i) The candidate shows some knowledge of the experiment described in the question, but does not
sufficiently understand the difference in the charges, which causes the effects in their answer. 0/1
(ii) An answer was attempted, but was incorrect. 0/1
(iii) The answer shows knowledge of the difference between insulator and conductor. 1/1
Total mark awarded = 2 out of 7
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
Question 8
Mark scheme
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
Example candidate response – grade C
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
Examiner comments – grade C
(a) (i) The candidate showed a good knowledge of the composition of the air’s main components and an
understanding that the % figures should add up to 100. 2/2
(ii) This erroneous answer was often given. 0/1
(b) (i) The candidate showed a good enough understanding of the difference, although the answer would
have been of a better quality if they had clarified the word ‘type’ by using ‘proton number’. 2/2
(ii) This answer was only just good enough, because the candidate did not use the term ‘elements’.
However, there were no inaccuracies, only omissions, so both marks were awarded. 2/2
(iii) The first statement in the answer is incorrect. The second statement is correct, so one mark was
given. Candidates were expected to convert pH values into comparisons of acidity. 1/2
Total mark awarded = 7 out of 9
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Cambridge IGCSE Combined Science 0653
Paper 2 – Core
Example candidate response – grade E
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
Examiner comments – grade E
(a) (i) The candidate gained full marks for the question, showing good knowledge of the percentages of
the main gases and that the amounts needed to add up to 100%. 2/2
(ii) The candidate showed good judgement in adding the name of the gas, since that was asked for in
the question. 1/1
(b) (i) The explanation of the term compounds is very full, but the brief reference to nitrogen and oxygen
are not sufficient explanation of why they are termed elements. 1/2
(ii) The type of bonding is wrong. Also the explanation, which was a separate marking point, is not
sufficiently detailed. Reference needed to be made either to the elements being non-metals or the
compounds being gases. 0/2
(iii) The first marking point is just matched by the last sentence. The answer needed to compare the
acidity of the two samples of rain water, by using the pH values, not by quoting them. 1/2
Total mark awarded = 5 out of 9
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Paper 2 – Core
Question 9
Mark scheme
Cambridge IGCSE Combined Science 0653
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Paper 2 – Core
Example candidate response – grade C
Examiner comments – grade C
(a) This was a good answer, where the correct terms were used. Some candidates included ‘sensitivity’,
others used descriptions of the characteristics. These were often not sufficiently accurately explained
and did not gain marks. 2/2
(b) (i) The expected answer and correctly spelt. 1/1
(ii) The two answers were good enough to gain the marks. However, the term ‘sugar’ should have been
more precisely ‘glucose’. 2/2
(c) The answer could have been slightly improved by using the phrase ‘in the blood’ rather than ‘by blood’.
Some candidates did not gain the mark by giving ‘in red blood cells’. 1/1
Total mark awarded = 6 out of 6
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Paper 2 – Core
Example candidate response – grade E
Examiner comments – grade E
(a) The descriptions of the characteristics were insufficiently precise to match any of the marking points.
0/2
(b) (i) The candidate attempted the question, but was incorrect. 0/1
(ii) The first answer shows the body’s resultant ability, following the effects of the hormone. If the
candidate had explained what happens to enable the body’s ‘fast reactions’, both marking points
could have been matched. 0/2
(c) The candidate has shown sufficient knowledge of the transportation of hormones to gain the mark. 1/1
Total mark awarded = 1 out of 6
Cambridge IGCSE Combined Science 0653
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Paper 3 – Extended
Paper 3 – Extended
Question 1
Mark scheme
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Paper 3 – Extended
Example candidate response – grade A
Cambridge IGCSE Combined Science 0653
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Paper 3 – Extended
Examiner comment – grade A
(a) (i) Only one compound has been given in the answer. This is a correct choice, but the candidate has
failed to notice that the question uses the plural verb ‘are’, indicating that at least two compounds
are binary compounds. No mark was awarded. 0/1
(ii) It appears that the candidate has failed to read the introduction to the question, in which the word
‘ore’ is explained, and where information about four ores is provided. The formulae provided can be
used to find the answer to this question. 0/1
(b) (i) This is an excellent answer. The element has been correctly identified as silicon, with a full
explanation. The candidate has explained the evidence that shows that the element belongs in
Period 3 and in Group 4. 3/3
(ii) This is all correct. The candidate has used the symbol for silicon rather than Q, but this is perfectly
acceptable. All four shared pairs of electrons are clearly shown. 2/2
(iii) The equation is entirely correct. Once again, the candidate uses Si rather than Q; either is
acceptable. 2/2
Total mark awarded = 7 out of 9
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Paper 3 – Extended
Example candidate response – grade C
Cambridge IGCSE Combined Science 0653
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Paper 3 – Extended
Examiner comment – grade C
(a) (i) The candidate correctly identifies both binary compounds in the list. 1/1
(ii) The ore of tungsten is correctly identified. 1/1
(b) (i) The element is correctly identified as silicon. A mark is also awarded for the explanation of how it
can be deduced that the element is in Group IV, but there is no mention of how it can be determined
which element in Group IV is shown. 2/3
(ii) The bonding diagram does not show any shared pairs of electrons, so no marks are awarded. 0/2
(iii) No marks are awarded for this attempt at a balanced symbol equation. There is no Si on the right
hand side, and the equation does not balance. 0/2
Total mark awarded = 4 out of 9
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Paper 3 – Extended
Example candidate response – grade E
Cambridge IGCSE Combined Science 0653
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Paper 3 – Extended
Examiner comment – grade E
(a) (i) Both binary compounds are correctly identified. The candidate has chosen to use the formulae
rather than the names; either is acceptable here. 1/1
(ii) The wrong ore has been chosen, perhaps because the candidate did not know the symbol for
tungsten. This could have been found on the Periodic Table printed on the back cover of the
examination paper. Candidates should be aware that the Periodic Table is always provided, and
should get into the habit of making use of it. 0/1
(b) (i) This answer suggests that the candidate does not know the meaning of the term ‘element’. There is
also confusion about what is represented in the diagram. The explanation states that the atom has
“4 outer shell”, which is not correct; the diagram shows that it has four outer electrons. 0/3
(ii) The diagram shows four shared pairs of electrons. However, the extra pairs of electrons on each
atom are incorrect, and prevent the second mark from being awarded. 1/2
(iii) The candidate appears not to understand the difference between an equation and a formula. 0/2
Total mark awarded = 2 out of 9
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Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Question 2
Mark scheme
Cambridge IGCSE Combined Science 0653
61
Paper 3 – Extended
Example candidate response – grade A
62
Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Examiner comment – grade A
(a) The axes are the right way round, and are fully labelled with the correct units. The scales on both axes
are suitable. The line is carefully drawn using a ruler, and shows the motion of the athlete as described
in the question. This is a good answer. 3/3
(b) (i) The formula for calculating speed is correctly shown, using recognised symbols for each quantity.
The substitution is correct, as is the calculation. The final answer is given with the correct unit. 2/2
(ii) The formula for calculating kinetic energy is not correct. The candidate appears to have shown
velocity squared, but then crossed out the superscript 2. The calculation is therefore incorrect. 0/2
(c) (i) This answer is not at all clear. The candidate does not appear to understand that, when evaporation
occurs, the fastest-moving molecules are lost from the surface of a liquid, so that the molecules
remaining in the liquid have a lower average speed (less kinetic energy), which means that the
temperature is lower. The first sentence of the answer mentions that the ‘water molecules move
out to the skin’, which does not help to explain the cooling effect of evaporation. The rest of that
sentence simply repeats the question. It is most important to read the question and identify exactly
what it is asking. Here, the candidate needs to concentrate on the movement of water molecules,
and how evaporation has a cooling effect. 0/3
(ii) Both of these factors are correct. 1/1
Total mark awarded = 6 out of 11
Cambridge IGCSE Combined Science 0653
63
Paper 3 – Extended
Example candidate response – grade C
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Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Examiner comment – grade C
(a) The axes of the graph are correctly orientated, both are labelled with units, and both have suitable
scales. The line has been carefully drawn; it is acceptable for the acceleration between 0 and 10 s not to
be constant, as the description does not state that it is. 3/3
(b) (i) The formula is correct and clearly shown, using acceptable symbols. The calculation is correct, and
units are given with the answer. 2/2
(ii) The formula for calculating kinetic energy is not correct. The answer is incorrect but – even if the
number had been correct – no units are given, so no mark would have been awarded. 0/2
(c) (i) The answer does not provide any correct information about how evaporation produces a cooling
effect. 0/3
(ii) Neither answer is correct. 0/1
Total mark awarded = 5 out of 11
Cambridge IGCSE Combined Science 0653
65
Paper 3 – Extended
Example candidate response – grade E
66
Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Examiner comment – grade E
(a) The axes are correctly orientated, but neither is labelled correctly and no units are given. The choice of
scale on the x-axis is not good, as less than half of the grid is used. The line, however, is carefully and
correctly drawn. 1/3
(b) (i) The formula for calculating speed is correct, as is the calculation. The correct unit is given with the
answer. 2/2
(ii) The formula for kinetic energy is incorrect. 0/2
(c) (i) This is a weak answer. The candidate has been given benefit of the doubt and is awarded a mark for
the idea that heat is transferred from the body to the water (in sweat). 1/3
(ii) The first answer “Drink water” is not correct. The second answer “Sun (heat)” shows that the
candidate is thinking along the right lines, but as the question asks for factors that would increase
the rate of evaporation, this should state ‘increased temperature’. 0/1
Total mark awarded = 4 out of 11
Cambridge IGCSE Combined Science 0653
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Paper 3 – Extended
Question 3
Mark scheme
Example candidate response – grade A
Examiner comment – grade A
(a) The syllabus provides a definition of respiration, and this is what candidates are expected to use. This
answer correctly states that respiration involves the breaking down of glucose molecules, but there is
no mention of releasing energy. The reference to taking in oxygen and giving out carbon dioxide is not
entirely correct, as this is gas exchange rather than respiration and applies only to aerobic respiration.
1/2
(b) The equation is entirely correct. 2/2
(c) The answer correctly states that oxygen diffuses into red blood cells, but there is no reference to
haemoglobin. 1/2
Total mark awarded = 4 out of 6
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Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Example candidate response – grade C
Examiner comment – grade C
(a) This is a wrong answer. Respiration does not ‘create’ energy; the energy is already present in the
molecules that are broken down during respiration, for example, glucose. Candidates should be
encouraged to learn the definitions that are provided within the syllabus. 0/2
(b) The equation is entirely correct. 2/2
(c) Once again, the answer correctly described the carriage of oxygen within red blood cells, but does not
refer to haemoglobin. 1/2
Total mark awarded = 3 out of 6
Cambridge IGCSE Combined Science 0653
69
Paper 3 – Extended
Example candidate response – grade E
Examiner comment – grade E
(a) This definition of respiration is correct. The candidate has written ‘in other’ instead of ‘in order’, but this
is accepted as the meaning is otherwise clear. 2/2
(b) The formulae for glucose and oxygen are both incorrect, and an incorrect formula is also given for one of
the products. 0/2
(c) There is a mention of blood in this answer, but not of red blood cells. The reference to a valve indicates
considerable misunderstanding. 0/2
Total mark awarded = 2 out of 6
70
Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Question 4
Mark scheme
Cambridge IGCSE Combined Science 0653
71
Paper 3 – Extended
Example candidate response – grade A
72
Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Examiner comment – grade A
(a) The first answer is clearly stated and correct. The second is not correct. 1/2
(b) The uses of infra-red and X-rays have been correctly identified, but the lines for gamma and microwaves
are incorrect. 1/2
(c) The formula is correct, and uses recognised symbols. The substitution is right, and the correct answer is
given with units. 2/2
(d) This description is accurate, except that it does not state how the mass of the tooth would be
measured. 2/3
Total mark awarded = 6 out of 9
Cambridge IGCSE Combined Science 0653
73
Paper 3 – Extended
Example candidate response – grade C
74
Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Examiner comment – grade C
(a) Neither answer is correct. 0/2
(b) Each radiation has been correctly matched to its use. 2/2
(c) No answer has been attempted. 0/2
(d) This answer is entirely correct. It would have been better if it had stated how the mass of the tooth
would be found, but the list of apparatus mentions a balance, so benefit of doubt has been given for
this. Otherwise, the answer is very clearly organised. 3/3
Total mark awarded = 5 out of 9
Example candidate response – grade E
Cambridge IGCSE Combined Science 0653
75
Paper 3 – Extended
76
Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Examiner comment – grade E
(a) One mark is awarded for the statement that radio waves ‘are faster’ than sound waves. 1/2
(b) This is entirely correct. 2/2
(c) The candidate does not know the formula relating velocity, frequency and wavelength. 0/2
(d) It is difficult to guess what the candidate means by the first sentence. The method of finding the volume
of the tooth is correctly described. However, the final sentence is incorrect; the mass should be divided
by the volume. 1/3
Total mark awarded = 4 out of 9
Cambridge IGCSE Combined Science 0653
77
Paper 3 – Extended
Question 5
Mark scheme
78
Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Example candidate response – grade A
Cambridge IGCSE Combined Science 0653
79
Paper 3 – Extended
Examiner comment – grade A
(a) The candidate has written ‘chloride’ instead of ‘chlorine’. Although spelling is not generally taken into
account, in this case it is important, as the word chloride has a different meaning from chlorine. Adding
chloride to water would not remove bacteria. 0/1
(b) Candidates often have difficulty in explaining the differences between compounds and mixtures, and it
is a good idea to ensure that they are equipped with suitable language to enable them to answer such
questions with confidence. Here, the first sentence incorrectly states that compounds can be separated
whereas mixtures cannot – a correct idea, but completely the wrong way round. The second sentence
refers to charge, which is irrelevant. 0/2
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Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
(c) (i) Silicon dioxide is correctly identified. 1/1
(ii) The first part of the explanation is correct, noting that sodium chloride is soluble in water. The
candidate is thinking along the right lines when attempting to explain why hexane cannot be
separated from water by filtration, but has wrongly deduced that it is a gas, not a liquid, at room
temperature. 1/2
(d) (i) The first step of the process, adding the carbonate to the sulfuric acid, is correctly described.
However, there is no mention of adding excess carbonate, which is necessary to ensure that all of
the acid has reacted so that none is left in the solution. The candidate has also failed to notice the
information in the question that zinc carbonate is insoluble, which could have helped them to think of
separating the unreacted zinc carbonate from the zinc sulfate solution by filtration. 1/3
(ii) The word equation is entirely correct. 2/2
Total mark awarded = 5 out of 11
Cambridge IGCSE Combined Science 0653
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Paper 3 – Extended
Example candidate response – grade C
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Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Examiner comment – grade C
(a)
The reference to chlorine is correct. The incorrect grammar is ignored, because the meaning is clear.
1/1
(b)
The candidate has made an attempt to describe a difference between a compound of hydrogen
and oxygen, and a mixture of hydrogen and oxygen, but it is entirely incorrect. It focuses on the
difference in physical state, and wrongly suggests that the mixture would contain ‘one hydrogen and
one oxygen’. 0/2
(c) (i) Silicon dioxide is correctly identified as the compound that could be separated by filtration. 1/1
(ii) The solubility of sodium chloride is correctly used to explain why it cannot be separated from water
by filtration. The candidate is getting towards the right idea with the sentence about hexane, but
does not quite say that hexane is a liquid; the fact that its melting point is lower than water’s is not
relevant. 1/2
Cambridge IGCSE Combined Science 0653
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Paper 3 – Extended
(d) (i) No attempt has been made to answer this question. It is good to encourage candidates always to
attempt an answer, even if they are very unsure. Here, there was a mark for adding the carbonate to
the acid, which could easily have been worked out from the first two lines of the question. 0/3
(ii) The candidate has failed to read the question carefully. It asked for a word equation – a much easier
task than writing a balanced equation. The balanced equation that has been given is entirely correct,
but as this is not what was asked for, only one mark is awarded. 1/2
Total mark awarded = 4 out of 11
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Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Example candidate response – grade E
Cambridge IGCSE Combined Science 0653
85
Paper 3 – Extended
Examiner comment – grade E
(a)
Bacteria are very small, so normal filtration would not remove them from water. A mark would have
been awarded if the candidate had specified ultrafiltration. 0/1
(b)
Once again, the answer fails to provide correct statements about either a compound or a mixture. It
is important that candidates learn how to describe these important and fundamental concepts. 0/2
(c) (i) Sodium chloride is a wrong answer. 0/1
(ii) The answer here correctly states that sodium chloride is soluble in water, which makes it difficult
to see why this was given as an answer to (i). There is no specific statement about hexane, but it is
included in the idea that ‘other two compounds’ are insoluble in water – which is incorrect. 1/2
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Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
(d) (i) The answer is given in terms of the reaction that occurs, but the question asked for a description of
the method a student should use. The first two lines state that “the zinc carbonate will react with
dilute sulfuric acid”, but this will only happen if they are added to one another – which the candidate
has not stated. 0/3
(ii) The reactants are correct, and one mark is given for this. The inclusion of the word ‘effervescence’
in the products suggests that the candidate does not understand how to write a word equation. 1/2
Total mark awarded = 2 out of 11
Cambridge IGCSE Combined Science 0653
87
Paper 3 – Extended
Question 6
Mark scheme
88
Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Example candidate response – grade A
Examiner comment – grade A
(a) The answer states that the molecules will “vibrate” faster. ‘Vibrate’ means move back and forth about a
fixed position. The word ‘move’ would have been the appropriate term to use here. 0/1
(b) The second and third effects are correct, but the first one is a less specific description of these two. An
answer containing two correct responses gains one mark. 1/2
(c) The lamps are shown connected in parallel, the switch is positioned so that it would prevent current
flowing through either of them and all symbols are correct. 4/4
Total mark awarded = 5 out of 7
Cambridge IGCSE Combined Science 0653
89
Paper 3 – Extended
Example candidate response – grade C
Examiner comment – grade C
(a) As in the previous answer, this candidate has wrongly used the term ‘vibrate’ instead of ‘move’ to
describe the motion of the particles in the gas. 0/1
(b) The answer suggests that the candidate has not understood the question. The answer attempts to
name the forces acting on the car, rather than stating the possible effects of a force. 0/2
(c) The circuit is entirely correct, and appropriate symbols have been used. Here, the switch is shown in the
closed position. 4/4
Total mark awarded = 4 out of 7
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Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Example candidate response – grade E
Examiner comment – grade E
(a) This answer does not address the question, which asked what happens to the motion of the
air particles. The candidate does not mention this at all. (There is also an indication that there is
confusion between force and pressure.) 0/1
(b) The first statement contains the idea that a force could start an object moving, although this is not
really clear. The candidate has been given benefit of doubt, and one mark has been awarded. 1/2
Cambridge IGCSE Combined Science 0653
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Paper 3 – Extended
(c) Incorrect symbols have been used for the lamps, and the circuit does not place the lamps in parallel. No
mark is available for the switch unless the lamps are in parallel. One mark is given for the circuit being
complete. 1/4
Total mark awarded = 2 out of 7
Question 7
Mark scheme
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Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Example candidate response – grade A
Cambridge IGCSE Combined Science 0653
93
Paper 3 – Extended
94
Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Examiner comment – grade A
(a) The answer gives one correct effect of the trees, that they reduce the temperature of the sand.
However, this is not enough for two marks, and the candidate should have recognised that they need
to give more information in order to get the second mark. Here, the question asks for the answer to be
given “with reference to Fig. 7.1”, which is a clue that data from the graph should be used, either by
quoting figures directly, or by giving a quantitative comparison between the temperature in areas with
and without trees. 1/2
(b) (i) This question requires the addition of the total numbers of nests in each part of the beach. The
candidate has incorrectly identified low vegetation, which in fact has fewer nests than the edge of
the forest. 0/1
(ii) This answer successfully brings together the information about temperature, provided in the graph,
and the data in the table. The candidate relates the production of females in sand to the higher
temperature there. However, the second statement gives no extra information; it is essentially the
converse of the first one. The second mark was available for stating that it is temperatures above
29 ºC that produce more females, a temperature that is only reached in open sand. 1/2
(c) This answer is again successful in combining information from different sources, correctly stating that
the deforested beaches would be hotter, and therefore would give rise to more females than males. The
answer goes on to say that the population will decrease, “because of the differences”. Although this
is not entirely clear, the candidate is thinking along the right lines, and the second mark has also been
awarded. 2/2
(d) The first answer is correct, but the description is incomplete as it does not link to deforestation in any
way. The second answer about “natural disasters” is not well expressed; benefit of doubt has been
given because more sandstorms might well arise because of exposure of soil, and one mark has been
awarded for this. 2/4
Total mark awarded = 6 out of 11
Cambridge IGCSE Combined Science 0653
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Paper 3 – Extended
Example candidate response – grade C
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Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Examiner comment – grade C
(a) The first few words of this answer correctly state that the trees make the sand cooler. However, the rest
of the answer then tries to explain why this happens. The question asked the candidate only to describe,
not explain, and they were also guided to refer to Fig. 7.1, which this answer does not do. 1/2
(b) (i) The answer correctly identifies the edge of the forest as the area in which most nests were made.
1/1
(ii) This question requires information from three areas – the bullet points near the beginning of the
question which show that a temperature of above or below 29º C is critical, the data in the graph
and also the data in the table – to be brought together. This is a high-level task, and this candidate
has done quite well to link the production of nests with more females than males in the open sand
to the high temperature there. (The wording of the sentence is not clear, and requires reading more
than once to be sure of its meaning.) However, the information in the bullet points has not been
used in the answer, so no specific temperature is mentioned. 1/2
(c) The answer mentions lack of shade on the deforested beaches, and states that the turtles will lay fewer
eggs there. However, the rest of the answer is about nutrients, which is irrelevant. 1/2
(d) The candidate is still thinking about turtles, and has not recognised that this question is a general one.
Neither answer is correct. 0/4
Total mark awarded = 4 out of 11
Cambridge IGCSE Combined Science 0653
97
Paper 3 – Extended
Example candidate response – grade E
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Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Examiner comment – grade E
(a) This answer indicates a misunderstanding of the data provided in the graph. It suggests that the
differences in the vegetation are caused by differences in temperature, rather than the other way
round. 0/2
(b) (i) The answer suggests that the candidate has not realised they need to find the total number of nests
in the area. Low vegetation had only 61 nests, compared with 72 at the edge of the forest. 0/1
(ii) The answer gives the mean temperatures in open sand and in forest, taken from the graph. These
are read correctly, but this is the only the first step in providing a suitable answer to this question,
and does not provide an explanation for the results shown in the table. 0/2
(c) This answer refers to “respiration” from trees, which suggests that this candidate has little
understanding of the context of this question. 0/2
(d) The first statement makes no sense. The reference to ‘pollution’ is too general, and it also seems to
suggest that there would be more species diversity. The second statement does mention erosion, and
one mark has been given for this. 1/4
Total mark awarded = 1 out of 11
Cambridge IGCSE Combined Science 0653
99
Paper 3 – Extended
Question 8
Mark scheme
100
Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Example candidate response – grade A
Cambridge IGCSE Combined Science 0653
101
Paper 3 – Extended
Examiner comment – grade A
(a) The candidate correctly identifies experiment 2 (for which there is no mark), and also states that
potassium hydroxide is an alkali. 1/1
(b) The experiment is correctly identified as 1, but the rest of the sentence is not quite clear enough to gain
a mark. There is no reference to actual evidence in the results, which is that the temperature decreased.
0/1
(c) This is correct. A colour of brown/red to describe copper is acceptable. ‘Red’ alone would not be
credited. 1/1
(d) This is a simple, clearly stated and entirely correct answer. 1/1
(e) The statement that there would be no reaction is correct, and is given one mark. “No change” could
possibly mean that there was no change in temperature, but the candidate needs to actually say this in
order for a mark to be awarded. 1/2
Total mark awarded = 4 out of 6
102
Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Example candidate response – grade C
Cambridge IGCSE Combined Science 0653
103
Paper 3 – Extended
Examiner comment – grade C
(a) The correct experiment (2) has been identified, but the explanation is not sufficient. There needs to be
some statement identifying potassium hydroxide as an alkali. 0/1
(b) The answer shows that this candidate does not understand the term ‘endothermic’, so does not
recognise that in an endothermic reaction temperature decreases. 0/1
(c) The candidate appears not to understand what is meant by an ‘observation’. 0/1
(d) The answer wrongly states that copper sulfate, rather than copper, is more reactive than magnesium.
0/1
(e) Although it is not well expressed, this answer successfully conveys two correct ideas – firstly that the
temperature did not change, and secondly that no reaction took place. 2/2
Total mark awarded = 2 out of 6
104
Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Example candidate response – grade E
Cambridge IGCSE Combined Science 0653
105
Paper 3 – Extended
Examiner comment – grade E
(a) Neither the experiment nor the reason is correct. 0/1
(b) The candidate has wrongly chosen an experiment in which the temperature increased. The explanation
indicates a misunderstanding of the term ‘endothermic’. 0/1
(c) This answer suggests that this candidate is not familiar with displacement reactions, and perhaps is also
not entirely sure of the meaning of the term ‘observation’. 0/1
(d) This answer suggests that the candidate may be looking at the wrong experiment, as experiment 3
does not involve either an acid or an alkali. 0/1
(e) As with the answer to (d), there is no mention of relative reactivity of magnesium and copper. Overall, it
appears likely that this candidate has no knowledge or understanding of displacement reactions. 0/2
Total mark awarded = 0 out of 6
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Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Question 9
Mark scheme
Cambridge IGCSE Combined Science 0653
107
Paper 3 – Extended
Example candidate response – grade A
108
Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Examiner comment – grade A
(a) (i) The first statement is incorrect because it refers to temperature, whereas the graph shows pH. This
is corrected in the second sentence, where a statement is made about the lack of activity below a
pH of 4 and above pH 9. It is most important that candidates read the axes of graphs carefully, and
the questions relating to them, and do not make assumptions that they are the same as those they
have seen before. 1/2
(ii) Once again, there is confusion between pH and temperature, so no mark can be given for the first
idea. The second sentence is again changed from temperature to pH, and a correct statement about
denaturation of the enzyme at high and low pH is made. 1/2
(iii) A suitable curve is drawn on the graph, with a similar shape to the first curve, and with an optimum
pH at a much lower value. 1/1
(iv) The answers states that the conditions are neutralised. However, there is no clear reference to this
resulting in a pH that is unsuitable for this enzyme to work. 1/2
(b) This answer has all three ideas required by the mark scheme. It clearly states that digestion involves
breaking down large molecules to small ones, which can then be absorbed. 3/3
Total mark awarded = 7 out of 10
Cambridge IGCSE Combined Science 0653
109
Paper 3 – Extended
Example candidate response – grade C
110
Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Examiner comment – grade C
(a) (i) The first sentence correctly identifies the pH range in which the enzyme has no activity, and the
second states the range over which the activity is greatest. Both marks are awarded. 2/2
(ii) This answer makes no correct statements. The statement that “temperature, which is related
to pH” indicates confusion. Most candidates appeared to be more familiar with the effect of
temperature on enzyme activity than with the effect of pH, and commonly attempted to answer in
terms of temperature. The candidate also appears to think that if something is a catalyst then this
makes it sensitive to pH. 0/2
(iii) The curve drawn on Fig. 9.1 is not correct, showing a very broad activity with the same optimum
pH as the first enzyme. 0/1
(iv) There are no correct statements within this answer. The term ‘catalyst’ appears in a context that
suggests this candidate does not fully understand the meaning of the term. 0/2
(b) More misunderstanding is displayed here. The references to stomach acid are irrelevant. The
first statement refers to the breaking down of “food”, ignoring the term ‘nutrients’ that is used in
the question. There is nothing in the answer that suggests the candidate understands that large
molecules are broken down to small ones, which can subsequently be absorbed. 0/3
Total mark awarded = 2 out of 10
Cambridge IGCSE Combined Science 0653
111
Paper 3 – Extended
Example candidate response – grade E
112
Cambridge IGCSE Combined Science 0653
Paper 3 – Extended
Examiner comment – grade E
(a) (i) The description is entirely incorrect. Firstly, it is worded as though rate of reaction causes the
changes in pH, rather than the other way round. Secondly, it states that when one increases the
other increases, which is not what is shown on the graph. 0/2
(ii) The candidate uses the term ‘denatured’ in relation to a pH above 7, and one mark is awarded for
this despite the unclear wording. 1/2
(iii) A line is drawn on the graph, rather than a curve. It may be that this is intended to represent an
optimum pH of just above 5, which would have been accepted if shown using a curve. 0/1
(iv) No correct information is given in this answer. 0/2
(b) The reference to partially permeable cell membranes suggests that perhaps the candidate is thinking
along the right lines, and could possibly appreciate that nutrients need to pass through these in order to
enter a cell. However, there is not enough in this answer to award a mark. 0/3
Total mark awarded = 1 out of 10
Cambridge IGCSE Combined Science 0653
113
Paper 5 – Practical test
Paper 5 – Practical test
Question 1
Mark scheme
114
Cambridge IGCSE Combined Science 0653
Paper 5 – Practical test
Example candidate response – grade A
Cambridge IGCSE Combined Science 0653
115
Paper 5 – Practical test
Examiner comment – grade A
(a) The candidate obtained a realistic time for tube B and this was clearly recorded in seconds. 3/3
(b) There was no discussion about the fatty acid neutralising the alkali. There was a slightly awkward yet
adequate attempt to state that the solution was acidic. Simply saying that fatty acids are acidic was not
generally credited. 1/2
(c) The first sentence obtained the second mark for denaturing of the enzyme. The first mark was not
awarded as there was nothing linking this process to the boiled lipase giving ‘no change’. 1/2
(d) The difficulty in maintaining a constant temperature was credited and the wrong spelling of ‘constant’
was ignored here. 1/1
(e) The candidate completed the table correctly. 2/2
Total mark awarded = 8 out of 10
116
Cambridge IGCSE Combined Science 0653
Paper 5 – Practical test
Example candidate response – grade C
Cambridge IGCSE Combined Science 0653
117
Paper 5 – Practical test
Examiner comment – grade C
(a) Clearly this candidate carried out the experiment correctly but recorded the time in minutes rather than
seconds so the third mark was not awarded. Note that a time greater than 600 seconds (10 minutes)
would have been wrong. 2/3
(b) There was no discussion about the fatty acid neutralising the alkali. It was stated clearly that the solution
becomes acidic, so one mark was awarded for this part. 1/2
(c) The candidate understood that high temperature denatured the enzyme but this was not related to tube
A having no activity. 1/2
(d) The candidate’s discussion of temperature as an error was not worthy of a mark because it was
not specific enough. This may have scored a mark if there had been a reference to the difficulty in
maintaining the required temperature range or to the fact that it was the temperature of the water bath.
0/1
(e) The candidate completed the table correctly. 2/2
Total mark awarded = 6 out of 10
118
Cambridge IGCSE Combined Science 0653
Paper 5 – Practical test
Example candidate response – grade E
Cambridge IGCSE Combined Science 0653
119
Paper 5 – Practical test
Examiner comment – grade E
(a) Clearly this candidate carried out the experiment correctly but recorded the time in minutes rather than
seconds so the third mark was not awarded. 2/3
(b) There was no discussion about the fatty acid neutralising the alkali. It was stated clearly that the solution
was acidic. 1/2
(c) The candidate’s second attempt at the bottom of the page simply repeated the answer in (b) and there
was no explanation of boiling causing enzymes to denature and hence tube A having no activity. 0/2
(d) The statement was not an accepted source of error in this experiment. 0/1
(e) The candidate completed the table correctly. 2/2
Total mark awarded = 5 out of 10
120
Cambridge IGCSE Combined Science 0653
Paper 5 – Practical test
Question 2
Mark scheme
Cambridge IGCSE Combined Science 0653
121
Paper 5 – Practical test
Example candidate response – grade A
122
Cambridge IGCSE Combined Science 0653
Paper 5 – Practical test
Cambridge IGCSE Combined Science 0653
123
Paper 5 – Practical test
124
Cambridge IGCSE Combined Science 0653
Paper 5 – Practical test
Examiner comment – grade A
(a) The candidate recorded the mass and dimensions of the pipe appropriately to one decimal place and
within 20% of the supervisor’s value for (i). The substitutions and calculations in parts (iii), (iv) and (v)
were all correct. 6/6
(b) The volumes were recorded and calculated correctly. Part (iv) is an accuracy mark and required this
density value to be within 0.05 of the value calculated in (a)(v). In this case the difference was 0.054 so
it was just outside the accepted range. 3/4
Total mark awarded = 9 out of 10
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Paper 5 – Practical test
Example candidate response – grade C
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Paper 5 – Practical test
Cambridge IGCSE Combined Science 0653
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Paper 5 – Practical test
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Cambridge IGCSE Combined Science 0653
Paper 5 – Practical test
Examiner comment – grade C
(a) The candidate did not record the mass to one decimal place as requested in the question. Even if it
was found to be exactly 5 it should have been recorded as 5.0.
The mark was awarded in (ii) as the candidate had clearly recorded the dimensions in centimetres and
di = 2 was assumed to be exactly 2.
The substitutions and calculations in the remaining parts were all correct. It was good practice to show
all working as this candidate did. 5/6
(b) The two volumes were recorded correctly. The difference between the two values had not been
calculated in (iii). No accuracy mark was awarded in (iv): the density was calculated (5.0/5 = 1.0) by
the examiner and found to be more than 0.05 greater than the value in (a)(v) which was 0.63. 2/4
Total mark awarded = 7 out of 10
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Paper 5 – Practical test
Example candidate response – grade E
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Paper 5 – Practical test
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Paper 5 – Practical test
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Paper 5 – Practical test
Examiner comment – grade E
(a) The candidate did not record the mass of the pipe to one decimal place as requested in the question.
Even if it was found to be exactly 4 it should have been recorded as 4.0.
The mark was awarded in (ii) as the candidate clearly recorded the dimensions in centimetres; l = 7 was
assumed to be exactly 7 and de = 2 was assumed to be exactly 2.
The substitutions and calculations in (iii) and (iv) were all correct. It was good practice to show all
working as this candidate did. The candidate rounded the calculation for (v) to one significant figure
which produced no decimal places; at least 1 decimal place was required for this mark. 4/6
(b) Both volumes were recorded correctly but they were then added rather than subtracted to find the
volume of the pipe. No accuracy mark was awarded in (iv): the density was calculated (4.0/2 = 2.0) by
the examiner and found to be more than 0.05 greater than the value in (a)(v) which was 0.95. 2/4
Total mark awarded = 6 out of 10
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Paper 5 – Practical test
Question 3
Mark scheme
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Paper 5 – Practical test
Example candidate response – grade A
Cambridge IGCSE Combined Science 0653
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Paper 5 – Practical test
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Paper 5 – Practical test
Examiner comment – grade A
(a) (i) The candidate recorded the start temperature as 31. To be recorded to the nearest half a degree,
readings ended in .0 or .5 so the mark was not awarded. 0/1
(ii) Although the readings were not recorded appropriately this was not penalised a second time. The
maximum temperature in the table was achieved no more than a minute beyond the supervisor’s
time for the maximum temperature and so scored the second mark. It was important that the
supervisor provided a carefully obtained set of results for the examiner. 2/2
(iii) Suitable colours were recorded in Table 3.2. 2/2
(b) (i) The candidate scored the plotting mark. The line mark was not awarded because this was not a
smooth curve; it did have just one maximum but it was not appropriate to draw a curve through
every point. Experimental error and the distribution of the points here suggested that the best
smooth curve should not have passed through every point. 1/2
(i) The maximum temperature rise was recorded correctly. 1/1
(ii) The calculation of the value of E is correct. 2/2
Total mark awarded = 8 out of 10
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Paper 5 – Practical test
Example candidate response – grade C
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Paper 5 – Practical test
Cambridge IGCSE Combined Science 0653
139
Paper 5 – Practical test
Examiner comment – grade C
(a) (i) The candidate recorded the start temperature as 30. To be recorded to the nearest half a degree,
readings ended in .0 or .5 so the mark was not awarded. 0/1
(ii) Although the readings were not recorded appropriately this was not penalised a second time. The
maximum temperature in the table was achieved no more than a minute beyond the supervisor’s
time for the maximum temperature and so scored the second mark. 2/2
(iii) The colour of solid A was correct but solution B could not have been black as well. 1/2
(b) (i) The candidate scored the plotting mark. The line mark was not awarded because this was not a
smooth curve: there was sketching between the first and second points which may have been
overlooked if the curve had not been discontinuous as it passed through the second point. The curve
did have only one maximum but it was not appropriate to draw a curve through every point during
the cooling phase. Experimental error and the distribution of the points here suggested that the best
smooth curve should not have passed through every point. 1/2
(ii) The maximum temperature rise recorded by the candidate was incorrect; it should have been 35.
0/1
(iii) The wrong value of the temperature rise was then substituted correctly so ‘error carried forward’
was applied and the candidate scored both marks. 2/2
Total mark awarded = 6 out of 10
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Paper 5 – Practical test
Example candidate response – grade E
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Paper 5 – Practical test
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Paper 5 – Practical test
Examiner comment – grade E
(a) (i) The candidate recorded the start temperature as 20.5, to the nearest half a degree, and so gained
the mark. 1/1
(i) The other readings were not recorded appropriately, for example 44 should have been 44.0, so this
mark was not awarded. However, the maximum temperature in the table was achieved no more
than a minute beyond the supervisor’s time for the maximum temperature and so scored the second
mark. 1/2
(iii) The colour of solid A was correct but solution B could not have been black also. 1/2
(b) (i) The candidate scored the plotting mark as there were at least 5 points plotted correctly in the first
3 minutes. The line mark was not awarded as the curve had more than one maximum and was not
smooth. Experimental error and the distribution of the points here suggested that the best smooth
curve should not have passed through every point. 1/2
(ii) The temperature rise was given as 23.5 when the rise from the table was 34 and from the graph
was 29.5. 0/1
(iii) The candidate used a wrong value for the volume of solution B (20 instead of 25) but this was then
calculated correctly so one mark was given for the calculation as an ‘error carried forward’. 1/2
Total mark awarded = 5 out of 10
Cambridge IGCSE Combined Science 0653
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Paper 6 – Alternative to practical
Paper 6 – Alternative to practical
Mark scheme
144
Cambridge IGCSE Combined Science 0653
Paper 6 – Alternative to practical
Example candidate response – grade A
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Paper 6 – Alternative to practical
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Paper 6 – Alternative to practical
Examiner comments – grade A
(a) (i) The candidate has correctly identified chlorophyll as the green substance from the leaf that has
dissolved in the alcohol. 1/1
(ii) The candidate has realised that iodine has been used to test for starch and remembered the relevant
colours. 4/4
(b) (i) Four correct volume readings for two marks. 2/2
(ii) A glowing splint relights showing the gas to be oxygen. 1/1
(iii) Tube F had been kept in the dark, therefore the plant was unable to photosynthesise. Therefore the
gas was carbon dioxide produced by respiration. 2/2
Total mark awarded = 10 out of 10
Cambridge IGCSE Combined Science 0653
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Paper 6 – Alternative to practical
Example candidate response – grade C
148
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Cambridge IGCSE Combined Science 0653
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Paper 6 – Alternative to practical
Examiner comments – grade C
(a) (i) The candidate has correctly identified chlorophyll as the green substance dissolved in the alcohol.
1/1
(ii) The candidate has realised that iodine can test for starch. The “no colour” response could mean ‘no
colour change’ or the leaf had ‘no colour’, either way it is an incorrect answer. 3/4
(b) (i) The candidate has misread all four measuring cylinders. 0/2
(ii) The gas that relights a glowing splint is oxygen not hydrogen. 0/1
(iii) The gas produced in the dark that fails to relight a glowing splint is carbon dioxide. The candidate
gains a mark for recognising the process that occurs in the dark is respiration. 1/2
Total mark awarded = 5 out of 10
150
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Example candidate response – grade E
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Paper 6 – Alternative to practical
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Paper 6 – Alternative to practical
Examiner comments – grade E
(a) (i) The candidate has correctly identified chlorophyll as the substance that causes the green colouration
of the alcohol. 1/1
(ii) The candidate does not know the colour of iodine and its use as a test for starch. 0/4
(b) (i) The candidate has correctly read the scales and recorded the values in the table. 2/2
(ii) The candidate has not attempted this question. 0/1
(iii) The candidate has not attempted this question. 0/2
Total mark awarded = 3 out of 10
Question 2
Mark scheme
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Example candidate response – grade A
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Paper 6 – Alternative to practical
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Paper 6 – Alternative to practical
Examiner comments – grade A
(a) (i) The reading on the voltmeter is 2.22, with a tolerance of +/- 0.01; therefore the candidate’s
answer is out of the acceptable range. The ammeter reading is correct. 1/2
(ii) The candidate has correctly calculated the resistance of each length and recorded them to
two decimal places. When not specifically told, candidates are expected to complete tables
using the same number of decimal places as already shown. 2/2
(b) (i) The candidate has plotted the points correctly and the line of best fit is drawn with a ruler. 2/2
(ii) The candidate has shown (not very clearly) on the graph the points used to calculate the
gradient. The coordinates are also shown so the mark can be safely awarded. The subsequent
calculation is also correct. 2/2
(iii) The candidate has used the formula to correctly calculate the cross-sectional area of the
resistance wire. 1/1
(iv) The candidate has correctly predicted that the resistance of the wire will decrease if a wire
with a greater cross-sectional area is used. 1/1
Total mark awarded = 9 out of 10
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Paper 6 – Alternative to practical
Example candidate response – grade C
158
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Cambridge IGCSE Combined Science 0653
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Paper 6 – Alternative to practical
Examiner comments – grade C
(a) (i) The readings from the voltmeter and ammeter have been correctly recorded in the table. 2/2
(ii) The calculations of resistance are all correct for two marks. When candidates complete tables
they are expected to use the same number of decimal places in their answers to match the values
already printed. In this case, as there are no values printed in the resistance column, answers with
more than two decimal places were accepted. 2/2
(b) (i) The points have been plotted correctly but the line is not a single straight line. 1/2
(ii) This is not the method to calculate a gradient. 0/2
(iii) The candidate has used the value of the gradient found in (ii), but the calculation is incorrect. 0/1
(iv) A correct prediction. 1/1
Total mark awarded = 6 out of 10
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Paper 6 – Alternative to practical
Example candidate response – grade E
Cambridge IGCSE Combined Science 0653
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Paper 6 – Alternative to practical
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Paper 6 – Alternative to practical
Examiner comments – grade E
(a) (i) Both ammeter and voltmeter scales have been misread. The voltmeter is reading 2.22 (+/- 0.01) and
the ammeter reading is 0.21 exactly. 0/2
(ii) Candidates are expected to use the same number of decimal places as the values already printed.
The candidate has given three answers to only one decimal place so is only awarded one of the two
marks available. 1/2
(b) (i) The points are correctly plotted, but the line of best fit is not straight. 1/2
(ii) The candidate has found the gradient and has also shown their working. 2/2
(iii) The calculation of the cross-sectional area of the wire is incorrect. 1/1
(iv) The candidate has made a wrong prediction. The resistance would decrease if the cross-sectional
area is increased. 0/1
Total mark awarded = 5 out of 10
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Paper 6 – Alternative to practical
Question 3
Mark scheme
164
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Paper 6 – Alternative to practical
Example candidate response – grade A
Cambridge IGCSE Combined Science 0653
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Paper 6 – Alternative to practical
Examiner comments – grade A
(a) (i) The candidate has given the correct test and result to confirm the gas is carbon dioxide and
recognised that the anion present was a carbonate. 3/3
(ii) A blue precipitate is formed when the solution is tested with sodium hydroxide. Copper is therefore
the cation present. 1/1
(b) (i) The candidate has correctly identified that acidified barium nitrate solution is used to identify the
presence of sulfate ions and that no white precipitate would be formed if sulfate ions are not
present. 2/2
(ii) A white precipitate forms when acidified silver nitrate is added to the filtrate showing that chloride
ions are present. 1/1
(iii) The test described is the test for ammonium ions. The candidate has realised that as this was a
negative test ammonium ions are not present. 1/1
(c) Candidates were expected to use the information given to deduce that the other cation must be sodium
or potassium. The important piece of information was a lack of precipitate with sodium hydroxide
solution. As ammonium ions had been eliminated an alkali metal ion must be present. 0/2
Total mark awarded = 8 out of 10
166
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Paper 6 – Alternative to practical
Example candidate response – grade C
Cambridge IGCSE Combined Science 0653
167
Paper 6 – Alternative to practical
Examiner comments – grade C
(a) (i) A correct test and result for carbon dioxide. The correct anion that produces carbon dioxide with an
acid has been identified. 3/3
(ii) The candidate has identified the cation that produces a blue precipitate with aqueous sodium
hydroxide. 1/1
(b) (i) The test for the presence of sulfate ions is by adding acidified barium chloride solution, not as the
candidate suggests. 0/2
(ii) The test described in the question is for chloride ions not nitrate ions. 0/1
(iii) The test described is for the ammonium ion. 1/1
(c) The information in the question includes the fact that there is no precipitate formed when added to
aqueous sodium hydroxide. Ammonium has been eliminated therefore it must be a Group I metal, either
sodium or potassium being acceptable. 0/2
Total mark awarded = 5 out of 10
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Cambridge IGCSE Combined Science 0653
Paper 6 – Alternative to practical
Example candidate response – grade E
Cambridge IGCSE Combined Science 0653
169
Paper 6 – Alternative to practical
Examiner comments – grade E
(a) (i) The candidate has correctly given the test and result to identify carbon dioxide. The candidate has
stated carbonate and nitrate for the anion present. The incorrect response, nitrate, means that the
mark cannot be awarded for this part. 2/3
(ii) The cation that produces a blue precipitate with aqueous sodium hydroxide is copper(II). Correct.
1/1
(b) (i) The test for sulfate ions uses barium chloride or nitrate but not hydroxide. The result would be the
absence of a white precipitate not solution. 0/2
(ii) The white precipitate formed when acidified silver nitrate solution is added to the filtrate shows the
presence of chloride ions. 0/1
(iii) The candidate has crossed out the correct answer, ammonium and replaced it with the incorrect
nitrate ions. 0/1
(c) By reading the information, candidates would see that there is no precipitate formed by the addition of
aqueous sodium hydroxide. Therefore, candidates should realise that the filtrate contained ammonium,
sodium or potassium ions. Ammonium ions have already been eliminated so either of the other two ions
would be an acceptable answer. 0/2
Total mark awarded = 3 out of 10
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Question 4
Mark scheme
Cambridge IGCSE Combined Science 0653
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Example candidate response – grade A
172
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Cambridge IGCSE Combined Science 0653
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Paper 6 – Alternative to practical
Examiner comments – grade A
(a) (i) The oscilloscope trace shows that the volume of air inhaled in one breath is 0.5 dm3. 1/1
(ii) Candidates can see that there are 4 breaths in 20 seconds or 6 in 30 seconds, either way there are
12 breaths in one minute. 1/1
(iii) Using the answers to the two previous parts the total volume of air inhaled in one minute is 6 dm3.
1/1
(b) (i) A second oscilloscope trace is shown and candidates have to describe two differences between
them. This candidate has indicated that the second trace shows someone breathing deeper and
more times per minute. These are both proper comparisons and score full marks. 2/2
(ii) 1.6 dm3 is the correct answer. 1/1
(iii) The volume of air inhaled after exercise is increased as more oxygen is required and a greater
volume of carbon dioxide has to be removed. This candidate has also referred to the oxygen debt so
scores both marks. 2/2
(c) The reasons why it would be undesirable to breathe the exhaled air back in is because there is an
increased volume of carbon dioxide and a reduced volume of oxygen. This candidate has implied that all
the oxygen has been removed and only waste products such as carbon dioxide would be present. This
is too extreme so only scores one mark. 1/2
Total mark awarded = 9 out of 10
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Example candidate response – grade C
Cambridge IGCSE Combined Science 0653
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Paper 6 – Alternative to practical
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Paper 6 – Alternative to practical
Examiner comments – grade C
(a) (i) The candidate has correctly read the trace and given 0.5 dm3. 1/1
(ii) There are 12 breaths in one minute not 19. 0/1
(iii) Using the candidate’s figures, the total volume of air inhaled in one minute should have been
9.5 dm3. 0/1
(b) (i) A very weak answer but “more air” indicates a larger volume inhaled and “in less time” implies that
the rate of breathing is faster. 2/2
(ii) The candidate has correctly read the trace. 1/1
(iii) The candidate is correct by saying that the body needs more oxygen. There is no mention of
removing more carbon dioxide or the oxygen debt so one mark. 1/2
(c) The candidate has correctly stated that exhaled air contains more carbon dioxide but has not mentioned
the reduced volume of oxygen present. 1/2
Total mark awarded = 6 out of 10
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Paper 6 – Alternative to practical
Example candidate response – grade E
178
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Paper 6 – Alternative to practical
Cambridge IGCSE Combined Science 0653
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Paper 6 – Alternative to practical
Examiner comments – grade E
(a) (i) The candidate has correctly read the trace. The volume is 0.5 dm3. 1/1
(ii) There are 12 breaths in one minute. Correct. 1/1
(iii) Correct calculation, one mark. 1/1
(b) (i) Two differences between traces were required. This answer is confused, using incorrect terms and
implying the oscilloscope uses something. The volume of air inhaled is larger in trace two and the
rate of breathing is faster in trace two. 0/2
(ii) Correct answer. 1/1
(iii) No mention of more oxygen required, the need to remove more carbon dioxide or oxygen debt. No
marks. 0/2
(c) The candidate has stated that the exhaled air contains carbon dioxide. However, inhaled air also contains
carbon dioxide, and a mark could have been awarded for saying that exhaled air contains more carbon
dioxide, and a second mark could have been awarded for saying that it also contains less oxygen. 0/2
Total mark awarded = 4 out of 10
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Question 5
Mark scheme
Cambridge IGCSE Combined Science 0653
181
Paper 6 – Alternative to practical
Example candidate response – grade A
182
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Cambridge IGCSE Combined Science 0653
183
Paper 6 – Alternative to practical
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Paper 6 – Alternative to practical
Examiner comments – grade A
(a) (i)+(ii) Candidates can find the original lengths of the rods in the information given in the diagrams and
can read off the increase in length from the scales shown. 3/3
(b) (i) Candidates use the equation given to calculate the three coefficients of thermal expansion. All
correct 3 marks. 3/3
(ii) The unit can be found by putting the units into the equation and cancelling where possible. 0/1
(iii) Candidates should chose the metal with the smallest calculated E value, tungsten. 1/1
(c) (i) There are a number of occasions when expansion can be useful. Thermometers, thermostats,
fire alarms, fixing locomotive tyres and putting hoops on barrels are some common answers. The
candidates answer is too vague to be credit worthy. 0/1
(ii) The candidate has given a correct example of a case when expansion is a problem. 1/1
Total mark awarded = 8 out of 10
Cambridge IGCSE Combined Science 0653
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Paper 6 – Alternative to practical
Example candidate response – grade C
186
Cambridge IGCSE Combined Science 0653
Paper 6 – Alternative to practical
Cambridge IGCSE Combined Science 0653
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Paper 6 – Alternative to practical
Examiner comments – grade C
(a) (i)+(ii) The candidate has found the correct original lengths from the information and read the dials
correctly. 3/3
(b) (i) Three incorrect calculations. 0/3
(ii) The unit for E can be calculated using the equation given by entering the units into the equation and
cancelling them out. 0/1
(iii) The candidate should choose the metal with the smallest calculated E value. In this case, tungsten.
0/1
(c) (i) The candidate has not attempted this part. 0/1
(ii) The candidate has not attempted this part. 0/1
Total mark awarded = 3 out of 10
188
Cambridge IGCSE Combined Science 0653
Paper 6 – Alternative to practical
Example candidate response – grade E
Cambridge IGCSE Combined Science 0653
189
Paper 6 – Alternative to practical
190
Cambridge IGCSE Combined Science 0653
Paper 6 – Alternative to practical
Examiner comments – grade E
(a) (i)+(ii) This candidate has not read the question. It clearly says “increase in length” in the table and not
the new total length. 0/3
(b) (i) All three calculations are incorrect. The temperature rise is 100oC in each case. The other values
have been substituted correctly from (a) but the temperature rise has been altered from 100 to 1.
Candidates must use the information given to them and read the question carefully. 0/3
(ii) Units should be entered into the equation, and after cancelling out, the unit for the coefficient of
thermal expansion is found to be oC. 0/1
(iii) If the calculations in all the previous parts had been correct, the metal with the smallest value of
E, and hence the best choice for the instruments described, would be tungsten. However the
candidate has correctly chosen copper from the values of E in part (ii). 1/1
(c) (i) The candidate’s answer is unclear but does not mention the expected answer of thermometers,
thermostats, fire alarms etc. 0/1
(ii) A correct answer. Train tracks will buckle as the temperature rises in the summer, unless
precautions are taken. 1/1
Total mark awarded = 2 out of 10
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Paper 6 – Alternative to practical
Question 6
Mark scheme
192
Cambridge IGCSE Combined Science 0653
Paper 6 – Alternative to practical
Example candidate response – grade A
Cambridge IGCSE Combined Science 0653
193
Paper 6 – Alternative to practical
194
Cambridge IGCSE Combined Science 0653
Paper 6 – Alternative to practical
Cambridge IGCSE Combined Science 0653
195
Paper 6 – Alternative to practical
Examiner comments – grade A
(a) (i) A colour change was asked for. The candidate has given the original colour and the final colour and is
awarded the mark. 1/1
(ii) The candidate has calculated the volume of acid added in experiments 2 and 3 for one mark and the
average of all three experiments for a second mark. 2/2
(iii) The candidate has correctly calculated the concentration of sodium hydroxide in the first cleaner
used. 1/1
(b) (i) Two correct volumes of acid and a correct average of acid used in the second experiment. 2/2
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Cambridge IGCSE Combined Science 0653
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(ii) Another correct calculation shows the concentration of sodium hydroxide in the second experiment
using the second cleaner. 1/1
(c) The second cleaner has to be diluted before use. The candidate has correctly worked out the
concentration of the diluted cleaner. 1/1
(d) The more effective cleaner, when used as directed, is the first one as the sodium hydroxide is more
concentrated. 1/1
(e) Unfortunately the candidate does not know the chemical formula for sodium hydroxide and therefore
cannot write an equation for the reaction. 0/1
Total mark awarded = 9 out of 10
Cambridge IGCSE Combined Science 0653
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Paper 6 – Alternative to practical
Example candidate response – grade C
198
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Paper 6 – Alternative to practical
Cambridge IGCSE Combined Science 0653
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Paper 6 – Alternative to practical
Examiner comments – grade C
(a) (i) This is not a full answer. The candidate is asked for the colour change so the initial colour of indicator
should be given as well. 0/1
(ii) The calculations are all correct. One mark for the two volumes of acid added and one mark for
calculating the average. 2/2
(iii) A correct calculation of the concentration of sodium hydroxide in the first cleaner. 1/1
(b) (i) Again, the calculations are correct; one mark for the three volumes of acid added and one for the
average. 2/2
(ii) A correct calculation of the sodium hydroxide solution of the second cleaner. 1/1
(c) The second cleaner had to be diluted before use. The candidate was unable to calculate the
concentration of the sodium hydroxide in the second cleaner after it had been diluted. The concentration
found in (b)(ii) should have been divided by five. 0/1
(d) The candidate has chosen the name of the wrong cleaner. If the choice of cleaner had been correct but
with no explanation the candidate still would not have gained credit. 0/1
(e) The candidate does not know the formulae for sodium hydroxide, hydroxide or sodium chloride. 0/1
Total mark awarded = 6 out of 10
200
Cambridge IGCSE Combined Science 0653
Paper 6 – Alternative to practical
Example candidate response – grade E
Cambridge IGCSE Combined Science 0653
201
Paper 6 – Alternative to practical
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Examiner comments – grade E
(a) (i) This is an incorrect colour change. The solution is alkaline to start with and becomes neutral,
therefore the indicator changes from purple or blue to green. 0/1
(ii) The candidate has correctly worked out the volume of hydrochloric acid used in experiments 2 and
3; two answers for one mark. To calculate the average the candidate has added the three volumes
together but has failed to divide by 3. The shaded out areas of the table indicates spaces that are not
required and should not be filled in. 1/2
(iii) The candidate has used the incorrect value for the average to calculate the concentration of sodium
hydroxide. No further error therefore one mark awarded. 1/1
(b) (i) The candidate has made the same error as before, therefore awarded one mark for the three correct
volumes, but nothing for the average. 1/2
(ii) A correct answer using the wrong value for the average, one mark awarded. 1/1
(c) The second cleaner should be diluted before use. The answer from (b)(ii) should be divided by five. 0/1
(d) The candidate has not answered the question. Using the incorrect calculations the answer should be the
second cleaner as the sodium hydroxide is more concentrated. 0/1
(e) The candidate does not know the symbols for the elements or the formulae for the compounds and
therefore is unable to produce an equation. 0/1
Total mark awarded = 4 out of 10
Cambridge IGCSE Combined Science 0653
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