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TWENTY FIRST CENTURY SCIENCE
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Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
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Paper 0608/01
Multiple Choice (Core)
Question
Number
Key
Question
Number
Key
1
2
3
4
5
D
C
D
A
D
21
22
23
24
25
A
D
C
C
A
6
7
8
9
10
B
B
C
A
B
26
27
28
29
30
B
C
B
A
B
11
12
13
14
15
C
D
A
D
D
31
32
33
34
35
A
B
C
B
A
16
17
18
19
20
D
C
A
C
A
36
37
38
39
40
D
C
D
B
D
General Comments
In broad terms, questions testing direct recall of knowledge were well answered.
Comments on Specific Questions
Candidates answered questions well relating to;
●
●
●
●
●
●
●
●
●
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location of genes in the cell (Question 1),
Wegener’s theory (Question 11),
the immune system (Question 13),
drug testing (Question 15),
heart disease (Question 16),
properties of materials (Question 17),
best estimates (Question 20),
life cycle assessment (Question 21),
evolution (Question 32),
extinction (Question 33),
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© 2011
Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
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use of fertilisers (Question 34),
radioactivity (Question 39).
Candidates struggled with the following questions.
Question 5
Many candidates thought that sulfur dioxide reacts with carbon dioxide and water to make acid rain.
Question 9
Candidates often chose the distracter that mentioned light travelling around the Sun.
Question 12
The answer which included white blood cells was a common choice. These are not a barrier.
Question 35
Most thought that emulsifiers stop the growth of microbes in food.
Question 37
Candidates were not aware that proteins are broken down into amino acids.
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© 2011
Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
TWENTY FIRST CENTURY SCIENCE
Paper 0608/02
Multiple Choice (Extended)
Question
Number
Key
Question
Number
Key
1
2
3
4
5
C
D
B
C
D
21
22
23
24
25
D
A
A
A
D
6
7
8
9
10
A
B
D
B
B
26
27
28
29
30
B
A
A
C
B
11
12
13
14
15
B
C
C
B
D
31
32
33
34
35
C
B
A
A
D
16
17
18
19
20
B
A
D
D
A
36
37
38
39
40
C
C
B
C
B
General Comments
In broad terms, questions testing direct recall of knowledge were well answered.
Comments on Specific Questions
Candidates answered questions well relating to;
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sex chromosomes (Question 4),
correlation and peer review (Questions 9 and 10),
drug testing (Question 18),
cross linked polymers (Question 23),
life cycle assessments for different materials (Question 25),
risk and benefit (Question 27),
the carbon cycle (Question 31),
variation (Question 32),
adaptations (Question 33),
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Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
●
power stations (Question 40),
Candidates found the following questions more difficult.
Question 6
Most chose reasons related to alleles for variation between identical twins.
Question 7
Candidates found it difficult to work out how many molecules of oxygen, carbon dioxide and water were
needed to make the numbers of atoms correct.
Question 8
Candidates were confused about what reacts with sulfur dioxide to form acid rain. All distracters were
popular choices.
Question 17
Most candidates thought that the mutation of the virus is the main reason that vaccines with low success
rates do not wipe out a disease.
Question 35
The most popular incorrect answer chosen was the one which discussed the intelligence of Homo sapiens.
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Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
TWENTY FIRST CENTURY SCIENCE
Paper 0608/03
Core Written
Key Message
To perform well in this paper, candidates need to have a knowledge of the syllabus that is both
broad and detailed, coupled with the ability to use this information in the context of the questions.
An understanding of concepts such as risk and benefit would help candidates to frame sensible
answers to relevant questions and it would help for candidates to know the meaning of the key
words used in the syllabus.
General comments
More able candidates showed knowledge and understanding in a number of areas of the syllabus
and some very good answers were seen. Weaker candidates evidenced patchy knowledge and
lacked a full understanding of key concepts. Some candidates clearly had difficulty in
understanding what was required by a number of the questions. More able candidates interpreted
data and performed simple calculations quite well. A number of candidates did not understand
some of the ‘ideas about science’ concepts, leading to answers that were not sufficiently relevant.
There was no evidence that candidates had insufficient time to complete the paper, and only a few
left blank spaces.
Comments on Specific Questions
Question 1
(a)
Most candidates were awarded full credit here. Where only partial credit was awarded,
there was no obvious pattern as to which number was given correctly.
(b)
More able candidates gave the correct number of atoms in the reactants, and most of
these realised that the number of atoms in the products must be the same as the number
of atoms in the reactants. A variety of incorrect combinations of numbers were seen from
weaker candidates.
(c)
The most common correct answer was carbon monoxide, with fewer candidates gaining
credit for carbon. Many weaker candidates suggested sulfur dioxide or nitrogen dioxide.
Question 2
Most candidates demonstrated some understanding of Life Cycle Assessments.
(a)
Most candidates managed to tick two of the correct boxes to gain at least partial credit.
(b)
Weaker candidates thought that more trees could be burned rather than grown or that
wooden window frames are made from a less sustainable material.
(c)
Most candidates gained credit for realising that plasticised PVC would be too soft or
flexible for window frames. Fewer could explain why this would be a disadvantage.
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© 2011
Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
(d)
(i)
Only a minority of candidates knew that acid rain is caused by sulfur dioxide or
nitrogen dioxide, with the former being the most common correct answer. Even
fewer could give the correct formula. Common incorrect answers were carbon
monoxide and sulfur.
(ii)
Most candidates could describe an environmental problem caused by acid rain.
Correct answers relating damage to buildings and the death of plants or fish were
common. Some candidates incorrectly suggested air pollution.
Question 3
Most candidates showed a good understanding of organic farming methods.
(a)
(i)
Most candidates realised that synthetic pesticides would be too costly or not
available for these farmers. Some simply repeated information from the question
that they were in a developing country, which did not gain credit.
(ii)
Most candidates suggested practical methods such as picking off pests by hand,
crop rotation, insect predators or natural pesticides. Some weaker candidates
simply suggested that they use organic farming methods, which did not gain credit.
(iii)
Only a small number of candidates mentioned that attack by insect pests would
reduce crop yield. Many gained credit for suggestions related to damage to crops or
poor quality produce.
(i)
Most candidates realised that the crops would not grow as fast or as well. Some
weaker candidates thought that they would be better quality.
(ii)
More able candidates suggested crop rotation or adding manure. Many others
misunderstood the question, giving irrelevant answers such as ‘by using their
hands’.
(b)
Question 4
(a)
Most candidates gained at least partial credit here. A common error was to think that a
problem was that Wegener had no training in astronomy or chemistry rather than geology.
(b)
Only the most able correctly suggested mantle. The most common incorrect answer was
crust.
(c)
(i)
Most candidates correctly suggested F. Some weaker candidates suggested two
letters.
(ii)
Only a few candidates realised the answer is D.
(iii)
Most candidates gave the two correct letters A and E. Some gave only one letter.
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© 2011
Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
Question 5
Few candidates showed that they had the knowledge required to answer most of this question.
(a)
(i)
Only a few candidates correctly named two of the missing names. Fewer could give
all three names. Many made no attempt at the question.
(ii)
Again, many candidates missed out this question. Most of those who did answer
gave ticks in random fashion across the diagram. Only a few ticked two of the three
correct boxes without also ticking at least one incorrect box.
(b)
More able candidates expressed the idea that the benefits outweighed the risks involved.
Weaker candidates concentrated on the risks.
(c)
Many candidates realised that microwaves do not leak out because of the door
construction or wall material. Few stated that metal in the door or walls stops or reflects
the radiation. Some incorrectly thought that glass stops the radiation.
Question 6
(a)
(i)
Most candidates correctly named a renewable energy source.
candidates suggested crude oil.
Some weaker
(ii)
Most candidates realised that coal will one day run out too.
(i)
Most candidates gave the correct answer of 400.
answer was 140.
(ii)
Few candidates could explain that the 200 MJ transferred into heat energy is half of
the total.
(iii)
Few candidates performed the calculation but most gave a verbal description of this
subtraction to gain credit.
(iv)
More able candidates performed the calculation correctly. A common error was to
use the sum of the electrical energy and heat energy in steam in the calculation,
giving an answer of 85 %. A variety of other incorrect answers were seen.
(b)
The most common incorrect
Question 7
Most candidates used the information given to frame good answers.
(a)
Very few candidates knew that the unspecialised cells are called stem cells. A wide
variety of incorrect answers were seen, including embryo, unspecialised cells, genetic
cells and chromosomes. Many candidates did not attempt the question.
(b)
A common error here was to choose ‘nerve’ for the first gap.
(c)
(i)
Most candidates correctly chose at least two letters, with only a few choosing one
letter or including incorrect letters in their choice.
(ii)
The answers here followed a similar pattern to (i).
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Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
(d)
Most candidates gained at least partial credit here.
Question 8
Only the more able candidates showed good knowledge of virus diseases and vaccination against
them.
(a)
Only the most able realised that influenza is caused by a virus or that antibiotics kill
bacteria. Many candidates gave answers that were too vague or not relevant.
(b)
(i)
Candidates had little idea that virus mutation necessitated repeated vaccination.
Many answers had the efficiency of the vaccination only lasting one year, which did
not gain credit.
(ii)
Most candidates knew that vaccination results in the formation of antibodies.
(c)
A variety of good answers were seen, based on ideas of safety and efficacy.
candidates gained credit here.
Most
(d)
Most candidates were awarded at least partial credit here. Incorrect answers showed no
obvious pattern.
Question 9
Few candidates showed a sound knowledge of nervous and hormonal communication.
(a)
Most candidates were awarded at least partial credit but very few received full credit.
There seemed to be little pattern in which of the four parts candidates chose correctly and
in which they made incorrect choices.
(c)
Only a few candidates could give an example of hormonal communication. Many gave an
example of nervous communication instead. A number did not attempt the question
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Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
TWENTY FIRST CENTURY SCIENCE
Paper 0608/04
Extended Written
Key Message
Candidates would benefit from looking back over past papers at the style of questions asked e.g.
talking heads, benefit versus risk, graph interpretation, so that they are aware of these and can
practise the style of answer required. Candidates are encouraged to read each question carefully
and address the question asked.
General Comments
Most candidates attempted all the questions on the paper and candidates appeared to have had
the time to answer all the questions equally well. Only a few questions were left blank Questions
5 and 7 proved to be more accessible to candidates, with Questions 6 and 8 causing more
difficulties. However, the performance across all the questions was generally much more
consistent than in previous sessions. Candidates seemed able to recall facts reasonably
competently, although there were still some areas where the key facts had not been learnt. Those
questions requiring analysis and evaluation skills appeared to be better answered than in previous
sessions. The questions requiring use of Ideas about Science showed that the candidates are
continuing to improve their understanding of this aspect of the syllabus. However, mistakes are
still being made when candidates do not read the rubric carefully enough and do not do what the
question asks.
Comments on Specific Questions
Question 1
(a)
Very few candidates answered this correctly with most suggesting that the biomass could
be reused, and that this is what makes it renewable. A few realised that the plants were
grown but were unable to explain that this growth was happening at the same rate as, or
faster than, the burning.
(b)
(i)
Many candidates gained credit here and it was pleasing to see more candidates
including their working out. It remains important to show all working as well as the
final answer. This will ensure that, for questions of this nature worth more than one
mark, credit can be awarded for the working even if the final answer given is
incorrect.
(ii)
This part of the question was also very well answered by most candidates. They
were able to substitute the correct values into the given formula and calculate the
percentage efficiency. Those that calculated it incorrectly included the ‘heat energy
in steam used in factory’ in their calculation.
(iii)
This question caused some difficulty. Those candidates who had correctly
answered (ii) were able to see their way through this part of the question, and
successfully included the ‘heat energy in steam used in factory’ to calculate an
efficiency of 85 %. Some candidates had already calculated 85 % for (ii) so they
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© 2011
Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
were unable to fully understand what was expected from them for this part question.
A few candidates consequently left this part of the question blank. The question
should have perhaps acted as a clue to the errors made in (ii) for these few
candidates.
(c)
Most candidates were able to interpret the graph and identify that as the power station
efficiency increases, the emissions of CO2 reduce. Unfortunately, this was not awarded
any credit as that idea is clearly stated in the stem of the question. Candidates needed to
say more to gain any credit. Some were able to recognise that the biomass emits less
CO2 than coal at the same efficiency, but very few made comment about the shape of the
curve, which indicates that the difference in the CO2 emissions is less significant at higher
efficiencies.
Question 2
(a)
(i)
Most candidates gained at least partial credit here. It was clear that some
candidates had not learnt the sequence of the electromagnetic spectrum.
(ii)
The majority of candidates correctly ticked the three boxes at the right-hand end of
the spectrum. A small number did this even if they had incorrectly labelled them in
(i).
(b)
This was generally quite poorly answered with few candidates able to describe the
precautionary principle, and even fewer then able to relate this to the question.
Candidates needed to be specific in their answer, ensuring that they considered the risk of
mobile phones and why the risk could be greater for children and therefore why the risk
should not be taken at all.
(c)
Most candidates were able to describe how the walls or door screen of the microwave
reflect or block the microwave radiation. Fewer commented that the walls and door
screen are made of metal and both points were needed for credit to be awarded.
Question 3
(a)
The rubric of this question caused some difficulty. Candidates were being asked to give
two reasons why the initial ideas that Wegener proposed in 1912 were not accepted. Few
candidates read it in this way and most instead suggested why his ideas were accepted
50 years later, i.e. they described the new evidence that now suggests he was correct.
Candidates needed to come up with two separate ideas in order to be awarded credit.
(b)
The very able candidates gave some excellent descriptions of how the magnetic patterns
occur on the seafloor. Many candidates however did not really seem to understand these
ideas, although they were able to make some reference to seafloor spreading to gain
partial credit.
(c)
(i)
Many candidates answered this question correctly, using the diagram to help them.
(ii)
Many candidates were able to identify two of the movements causing sea floor
spreading, but three were needed for credit to be awarded.
(iii)
It was clear that the majority of candidates knew how earthquakes are caused but
their answers were poorly expressed and lacked details. This meant that few
candidates were awarded full credit. Many described movements of the tectonic
plates without detailing the direction of the movement. Few candidates described
how the stresses build up and that the plates suddenly slip.
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© 2011
Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
Question 4
(a)
(b)
(i)
The majority of candidates correctly described the use of natural predators here.
Some gave specific examples which were credited.
(ii)
This question was quite poorly answered. Few candidates described that the yield
would reduce and instead said that the yield would be affected, without describing
how the yield would be affected. Other vague answers were given with little
relevance to yield.
Questions of this type have appeared in previous sessions and it was pleasing to see a
larger number of candidates correctly describing the balance between benefit and risk. In
addition some candidates made specific reference to the context of this question and gave
examples of a benefit and a risk. It is important to answer questions in the context they
are set if full credit is to be achieved.
Question 5
(a)
Only the most able candidates could correctly balance the equation and recognise that the
number of atoms of each element in the reactants and the products remains unchanged.
(b)
Most candidates could correctly show the number of molecules in one or two of the boxes,
but far fewer could complete the whole table correctly. Candidates would have perhaps
found it useful to write the equation out on the paper to help them answer this question.
This is allowed even if it is not asked for.
(c)
A large number of candidates were correctly able to identify carbon dioxide or carbon as
another product in the reaction. A few wrote down sulfur dioxide even though there was
no sulfur included in the reaction.
Question 6
(a)
Most candidates were able to correctly interpret the data in the table to answer this
question. It was clear that some candidates did not fully appreciate that they were
expected to use the table and a very small number of candidates misinterpreted the data
and gave the answers the opposite way round.
(b)
This question was poorly answered. A few of the most able candidates described the use
of the paint and recognised that it would use more energy and create more pollution to
make the paint. This directly links with the LCA as the question asks. The majority of
candidates instead talked incorrectly about the sustainability of the wooden and plastic
windows.
(c)
This question also caused some difficulty. Candidates often repeated the stem of the
question in their responses, stating that the longer chains affect the melting point, but then
not explaining how. A few described stronger forces of attraction but there is still a
common misconception that this relates to the bonds between atoms within a molecule
whereas in fact it relates to the attractions between the molecules. This needs to be
made clear to the candidates when this part of the syllabus is taught.
(d)
(i)
The majority of candidates were able to correctly write down the equation, although
some wrote a word equation instead of a symbol equation. Candidates are
reminded to read the question carefully and to do as the question asks.
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© 2011
Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
(ii)
Most candidates were aware that acid rain results from a reaction with water. Far
fewer described the reaction with oxygen. A small number of candidates referred to
mixing rather than reacting and this was not credited. Candidates need to ensure
that they use the correct terminology in their answers and that they avoid vague
references to processes without including specific details.
(iii)
Despite the fact that many candidates understood the damaging effects of acid rain,
a surprisingly large number of candidates were not able to describe these effects in
sufficient detail. Vague references to pollution were not credited.
Question 7
(a)
Most candidates recognised that antibiotics are only effective against bacteria or fungi.
Equally, a large number of candidates identified influenza as a virus. Therefore this
question was generally well answered. An answer stating ‘antibiotics don’t kill viruses’
was not awarded credit unless the influenza was clearly identified as the virus and the
candidate made reference to the antibiotics’ ability to kill bacteria as well.
(b)
(c)
(i)
This question was also well answered by the majority of the candidates, many of
whom were able to use the term mutated in the correct context.
(ii)
A significant number of candidates recognised that the vaccination stimulates the
body to produce antibodies. A few thought that the vaccine actually was the
antibodies and did not appreciate the idea that it triggers the body to produce them.
Some also talked about antibodies ‘remembering’ the illness or the infection and this
is how it helps provide protection. Very few candidates described how it is important
that the body has made the antibodies before the infection occurs, so that the
response can be quick enough so that symptoms do not show.
Many of the candidates were able to correctly place the letters into the correct columns.
This is again a common style of question on these exam papers and candidates are
advised to practise the skills required by discussing these ethical issues and considering
both sides of the argument carefully.
Question 8
(a)
The majority of candidates described stem cells as unspecialised but very few were able
to give the full description, recognising that they are able to develop into any type of cell.
This full description was required for the award of credit.
(b)
(i)
It appeared that the candidates’ knowledge of the use of stem cells from cloned
embryos was generally not very good. Answers given here were very vague without
any clear idea of the uses of stem cells in treating diseases.
(ii)
More candidates seemed to be aware of the problems with cloning embryos,
although again a large number of responses were not specific enough.
(i)
Candidates understood this question but unfortunately very few candidates wrote
down all of the statements that gave reasons why parents might store their
children’s baby teeth. The majority only wrote down one or two letters and therefore
were not awarded credit.
(c)
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Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
(ii)
(d)
As with the previous question, a large number of candidates received no credit as
they only gave one of the correct statements. In these types of question, candidates
need to be aware that there is often more than one response required.
There was a wide range of answers given to this question. The most able candidates had
a clear understanding of the difference between natural and artificial clones. They gave
detailed and correct descriptions of how they are both formed, especially the artificial
clones. Some candidates were very confused about this process and unsure which cells
were used and how they were used. Most candidates identified identical twins as an
example of natural clones. However, some candidates talked incorrectly about asexual
reproduction here.
Question 9
(a)
Despite this being a direct definition from the syllabus, a large number of candidates left
this blank or gave an incorrect definition. Homeostasis is the maintenance of a constant
internal environment.
(b)
(c)
(i)
Most candidates were able to correctly identify D as the effector cells.
(ii)
Most candidates were able to correctly identify B as the sensor cells.
A significant number of candidates were able to correctly describe two differences
between hormonal and nervous communication but very few could give a clear example of
hormonal communication. Both of these things were needed to be awarded full credit.
The syllabus states that candidates should be able to recall two examples of hormonal
communication and so it was perhaps surprising that candidates found this so difficult.
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© 2011
Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
TWENTY FIRST CENTURY SCIENCE
Paper 0608/05
Analysis and Interpretation
Key message
To ensure continued success next year, Centres should ensure that Candidates realise that
Section A is a test of scientific comprehension of the science in the article(s) provided, while
Section B questions concern scientific procedures and the analysis of data. In particular, in
Section B, Candidates need to read instruments and scales, and to suggest apparatus and
techniques that could be used. They should be able to identify the variables which must be
controlled, the factor which is being changed (the independent variable) and the way
measurements are made upon the factor which changes as a consequence (the dependent
variable). In analysing the results, candidates need to be able to find best estimates from repeated
values (which may or may not contain outliers) and to process data graphically.
General comments
It was noticeable that standards were higher than in previous sessions, and that candidates had
been well prepared by their Centres for aspects of the examination specific to Twenty First Century
Science, particularly the central nature of ‘Ideas about Science’. They were also well prepared to
answer questions tackling assessment objectives 2 (in Section A) and 3 (in Section B). Less
successful candidates tried, particularly in Section B, to write what they could recall about the
topic areas from which the questions were drawn, but responses of this type were far less frequent
than in previous sessions.
Centres should read the following detailed comments together with the question paper and the
published mark scheme.
Comments on Specific Questions
Question 1
(a)
Most candidates could name at least two lifestyle factors associated with cardiovascular
disease, but some quoted ‘obesity’ instead of ‘poor diet’.
(b)
Most candidates could explain the stages in a heart attack.
(c)
The process of peer review in (i) and (ii) was understood by few candidates, and the
difference between peer review and replication in (iii) was not clear.
(d)
Nearly all candidates could calculate the number of people who ate dark chocolate in (i).
Most candidates were awarded partial credit in (ii) for comparing the flavanol content of
dark and milk chocolate and the effect on blood pressure, but it was rare to see the
complete link; flavanols ⇒ reduced blood pressure ⇒ reduced damage to blood vessels.
(e)
‘Correlation’ was generally well understood and the sketch graphs were usually clear and
correct.
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Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
(f)
Most candidates were able to suggest a variable which should be controlled in the study.
(g)
In (i) most candidates realised that the longer time and/or the greater number of
participants made the data in the first part of the study more reliable. More able
candidates realised that the significant aspect was ‘monitored more closely’ with an
associated increase in reliability of the data obtained for the answer to (ii).
(h)
More able candidates were able to suggest how this test could be carried out.
(i)
This part was generally done well. Most could suggest at least one reason why people
choose to eat large amounts of chocolate.
(j)
Most candidates realised what ‘components’ of a balanced diet referred to, although some
had not read the question and included carbohydrates and fats.
Question 2
A number of candidates had difficulty in interpreting the schematic diagrams in this question.
Although most could identify the 1 kg mass in (a), many could not then identify why the named
factors in (b) needed to be constant. In a similar way, a number of candidates could not make
measurements of the diameter of the grey ‘dents’ in (c). In (d), most could identify the harder
polymer (or, alternatively, the softer one) and understood the action of a plasticiser, but only the
most able candidates understood the idea of a real difference in data sets.
Question 3
This question proved the most accessible on the paper. Candidates clearly had some difficulty in
(a) and (b) in visualising the experiment (heating water for different times in a microwave oven, and
measuring its temperature periodically with a thermometer, mixing thoroughly each time).
However, in (c) the reading of data, plotting the graph and finding the gradient was well done by
most. Only the most able candidates understood the physical significance of the y-axis intercept of
the graph in (c)(ii).
Question 4
This proved the most difficult question on the paper. Only about half of the candidates could
suggest a variable to control in (a), although in (b) most could explain why measurements should
be repeated and could calculate the mean, even though weaker candidates did not exclude the
obvious outlier from their calculation. Many recognised, in (c), that the measurements lacked
accuracy, but few were able to justify it in terms of the wide variation of results. Even though many
could not suggest in (d) an extra piece of apparatus used to make a sound, most could describe
how to modify the experiment to measure the reaction time with a sound stimulus.
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Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
TWENTY FIRST CENTURY SCIENCE
Paper 0608/06
Case Study
Introduction
Although the number of Centres entered for this syllabus is relatively small, it was clear that some
encouraging and appropriate work had been performed by the candidates involved. Most Centres
provided a suitable stimulus for their candidates so that a range of Case Studies were presented
which were often adapted to reflect the local environment and so encourage ownership and
interest on the part of candidates. There has been a noticeable improvement in the quality of work
submitted over the last few years and in particular the performance levels shown in Strands A, B
and D have improved.
Administrative aspects
As a reminder the following key points regarding the administration of coursework samples are
described below.
●
●
●
●
●
The coursework assessment summary form should be completed showing the individual
Strand and total marks awarded for each candidate.
Candidates’ work should be fastened in the left-hand corner.
Details should be included about how each of the tasks used for assessment had been
introduced and presented to candidates.
Candidates’ work in the sample should be annotated showing where and why the marks
were awarded.
If appropriate, details of internal standardisation procedures should be described.
Marking procedures
The award of marks is based on the professional judgement of the science teacher, working within
a framework of performance descriptions which are divided into strands and aspects of
performance.
●
●
●
Each aspect of performance within each Strand should be considered in turn, comparing
the piece of work against the lowest performance description first, then each subsequent
higher one in a hierarchical manner until the work no longer matches the performance
description.
For Strand B or C, where candidate performance exceeds that required by one
performance description, but does not sufficiently match the next higher one, the
intermediate whole number mark should be given. Thus, the level of performance in each
aspect is decided.
The single, overall mark for the whole strand is determined as shown in more detail below.
If there is no evidence of achievement for an aspect, a mark of zero should be recorded
and included in the calculation of the overall strand mark.
Strands A and D
There are three aspects for each of these strands and the following examples illustrate how to
convert aspects of performance marks into Strand marks. The aspect marks are added together
for each Strand and divided by 3 to calculate the average mark and the answer is rounded to the
nearest whole number.
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Example
Marks for the three Formula
aspects in a strand
applied
to
be Mark to be awarded for the
strand
1
(a) = 4, (b) = 4, (c) = 3
[(a)+(b)+(c)] / 3
= 3.66 round up
=4
2
(a) = 3, (b) = 4, (c) = 3
[(a)+(b)+(c)] / 3
= 3.33 round down
=3
3
(a) = 4, (b) = 3, (c) = 1
[(a)+(b)+(c)] / 3
= 2.66 round up
=3
4
(a) = 3, (b) = 3, (c) = 0
[(a)+(b)+(c)] / 3
= 2.0
=2
5
(a) = 2, (b) = 3, (c) = 0
[(a)+(b)+(c)] / 3
=1.66 round up
=2
Strands B and C
There are only two aspects of performance for each of these strands.
The average of the aspect marks may come to a whole number (N) or to N + ½.
●
●
If the average aspect marks of either B or C is a whole number and the other one is N + ½,
then the ½ should be rounded up.
If the average aspect marks of both B and C average to N + ½, then one should be
rounded up and the other rounded down.
This gives a “best fit” for the achievement overall for the two strands. For example,
Example
Marks for the two aspects
in a strand
Formula to be
applied
Mark to be awarded for the
strand
1
Strand B (a) = 6, (b) = 4
Strand C (a) = 6, (b) = 5
[(a)+(b)] / 2 = 5
[(a)+(b)] / 2 = 5.5
=5
=6
2
Strand B (a) = 7, (b) = 6
Strand C (a) = 6, (b) = 5
[(a)+(b)] / 2 = 6.5
[(a)+(b)] / 2 = 5.5
=7
=5
This general approach provides a balanced consideration of each aspect of performance involved
in each strand and allows the marker to build up a profile of strengths and weaknesses in the work.
Comparison of teacher and Moderator judgements in each aspect allows easy identification of
where a Centre marks too severely, too leniently or where marking is inconsistent. This allows
moderators to make far more constructive reports back to Centres.
Case Studies
General comments
The purpose of the Case Study is for candidates to gather together claims, opinions and evidence
about a controversial issue in science. Candidates should use their scientific knowledge and
understanding of the Ideas about Science (IaS) to compare and evaluate the evidence that they
have collected so that they can form their own conclusions and make appropriate
recommendations for future action. Where candidates use the language and concepts related to
IaS, such as ‘peer review’, ‘replication of evidence’, ‘correlation and cause’, ‘reasons why scientists
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disagree’, ‘precautionary principle’, ‘ALARA’, ‘risks and benefits’, ‘technical feasibility and values’ it
is easier to match the performance descriptions of the criteria and gain higher marks.
Case Studies are always best formulated in terms of a question to provide a focus in an area of
controversy. For example, ‘does air pollution cause asthma?’ rather than just ‘asthma’. A question
will encourage candidates to look for different opinions and views, and to consider the evidence on
which they are based and the reliability of sources. The Case Study is not a report on a topic but a
critical analysis of a controversial issue. Some topics are so uncontroversial that there are no valid
opposing views. The key point is that the Case Study question must invite debate and discussion
of both sides of the case and be firmly embedded in a scientific context so that candidates can use
their scientific knowledge and understanding and their understanding of IaS to produce a balanced
and informed account. It is this latter aspect which many candidates found the most difficult.
Assessment
Strand A: Quality of selection and use of information.
(a)
The key aspect here is for candidates to use sources of information to provide evidence for
both sides of their case study. If no sources are identified by the candidate then a
maximum of 1 mark will be allowed, unless annotation confirms that a suitable range of
sources were used. To meet the 3 mark performance description, candidates must select
sources which represent a variety of different views or opinions. It does not matter if all the
sources are from the internet although a balanced use of websites, textbooks and journals
is to be encouraged. Whatever sources are used by candidates they must assess their
sources in terms of reliability in a meaningful and appropriate way if 4 marks are to be
awarded.
(b)
If only one or two incomplete references e.g. website homepages, are given then one mark
should be awarded and of course if no references are given then zero marks. For 3 marks,
candidates must include a number of complete references to the exact URL address of the
webpage which would allow direct access to the source of information, and when
referencing books, title, author and page references would be required. Candidates
awarded 4 marks included the date that the site was visited and also some information
about the nature or sponsorship of the site.
(c)
Candidates may copy some, but reasonably short, material from their sources. However, it
is essential that they make this completely clear with the use of quotation marks, use of a
different font or colour highlighting etc. The more able candidates included references or
specific links within the text to show the source of particular quotations including details of
the author as well as the institution.
Strand B: Quality of understanding of the Case.
In simple terms this strand assesses candidates’ ability to describe and explain the underlying
relevant science and to recognise and evaluate the scientific evidence on which any claims are
based (IaS 1, 2 and 3).
(a)
Candidates often describe the relevant background science in the introduction to their case
studies, with the more able candidates going to a greater depth and detail. However, only
the most able link their scientific knowledge and understanding to the claims and opinions
that they had found from their sources. It is useful to look at the appropriate pages in the
C21 textbook about Science Explanations and the Ideas about Science that are appropriate
for each Case Study to give an indication as to what to expect before marking candidates’
work. For topics which are related to course modules, it can be taken as a general guide
that 6 marks requires all that is available in the candidate book. The 7th or 8th mark will
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come either for applying this correctly to the case, or for finding and explaining some more
specialised knowledge.
(b)
Candidates were awarded 4 marks if they were able to recognise and extract relevant
scientific content and data in their sources. Candidates who were awarded 6 marks
referred to the evidence base of the various claims and opinions e.g. data from research
studies, a collection, survey or review of existing data, a computer simulation etc.
Candidates obtaining 7 or 8 marks look more critically at the quality of the evidence. They
used terms like ‘reliability’ and ‘accuracy’ when considering data, they looked at the design
of experiments and the issue of sample size and they also compared the reliability of data
between sources. The following table gives guidance as to the sort of aspects to consider
when assessing reliability of sources and data.
The further to the right, the more reliable the source is likely to be.
Publication
Nature of
the data
Website or
newsletter of
a private
individual or
a fringe
group
Based on
little or no
data
No support
Science
explanation within the
science
community
Status of
the author
Someone
who knows
little or no
science.
Someone
known to
have a
particular
point of view
A nonAuthor’s
affiliation or science
institute
institution
Respectable
pressure group
website or
newsletter
Based on some
data, but of
questionable
validity or
reliability, e.g.
small sample,
not
representative
of population.
New
explanation, but
with basis in
accepted
scientific ideas
An
inexperienced
scientist or
science
candidate
A scientific
institute or
company that
represents
particular views
only
‘Quality’ media
e.g. BBC, The
Times, The
Independent,
The Guardian,
Daily Mail
Based on just
one study (or
several small
studies). Little
information
about sample,
or procedures
followed.
School textbook
or science
magazine e.g.
New Scientist,
Focus, Catalyst.
Peer reviewed
science journal
or government
report
Valid and
reliable method
e.g. health study
with large
sample size,
carried out over
many years
Results
repeated by
different
scientific
studies, each
using a valid
and reliable
method
One among
several
explanations
discussed with
the science
community
A professional
scientist whose
expertise is in
a different field
Agreed by most,
but not all,
within the
science
community
Agreed by
everyone
within the
science
community
A scientific
institute with a
doubtful
reputation
A recognised
university or
scientific
institute
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A professional
A recognised
scientist working expert in this
in the area –
field of science
though not
regarded as a
top expert by
his/her peers
A leading
university or
scientific
institute, or the
research lab of
a major
company
© 2011
Cambridge International General Certificate of Secondary Education
0608 Twenty First Century Science November 2011
Principal Examiner Report for Teachers
Strand C: Quality of conclusions
In this strand candidates should consider aspects of IaS 5 about actual and perceived risks and the
ALARA principle and in IaS 6 about how society should respond.
The aspects for Strand C can be summarised in the following simple flowchart
Views ‘for’
evidence
evidence
evidence
Views ‘against’
evidence
evidence
evidence
Compare and evaluate
Conclusion stated and linked to evidence
Limitations to conclusion acknowledged
Alternative conclusions considered and
recommendations for action made
Most candidates could sort the information that they had gathered into views ‘for and against’,
sometimes in a tabular form if appropriate. Those who just listed it in this way were awarded 4
marks. More able candidates started to compare and balance arguments against one another in
both their ‘for and against’ list and were awarded 6 marks. The best candidates began to analyse,
compare and evaluate the claims and opinions, describing their own viewpoint or position in
relation to the original question and justifying this by reference to the sources. Alternative
conclusions should be considered where appropriate and recommendations for future action
should also be included.
Strand D: Quality of presentation
(a)
Most reports included headings and/or sub-headings to provide the necessary structure.
The more able candidates included a table of contents and numbered the pages in their
report to help guide readers quickly to particular sections and this matched the 3 mark
performance description. Those reports which were presented simply as PowerPoint
printouts achieved good marks in this aspect but often lacked sufficient detail for high
marks in the other strands.
(b)
Suitable diagrams and graphics should be incorporated as appropriate to clarify difficult
ideas and encourage effective communication but the visual impact was often variable. If
there are no decorative or informative images included then zero marks is awarded. If one
image is included, a decorative front cover or other low level attempt to add interest then 1
mark is appropriate. Two marks would be awarded for the inclusion of decorative images
only or perhaps for the minimal use of informative images. Three marks would be given for
including a variety of informative illustrations e.g. charts, tables, graphs, or schematic
diagrams and 4 marks if this is fully integrated into the text, referred to and used. Too often
downloaded images from the internet were not clear, too small and not referred to in the
text.
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