Cambridge IGCSE Twenty-First Century Science 0608 — 2013 May/June Paper 4 · Variant 1

This document consists of 17 printed pages and 3 blank pages. DC (LEG/CGW) 64752/3 © UCLES 2013 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education * 2 8 4 7 9 5 0 5 2 4 * TWENTY FIRST CENTURY SCIENCE 0608/04 Paper 4 May/June 2013 1 hour 30 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use a pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. Electronic calculators may be used. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. www.XtremePapers.com

2 0608/04/M/J/13 © UCLES 2013 For Examiner’s Use 1 Scientists measure the nitrogen dioxide concentration in the air in a city centre. They take their measurements over a period of 24 hours. Their results are shown in the bar chart. 130 120 110 100 90 80 70 60 concentration of nitrogen dioxide in the air in µg / m3 50 01 02 03 04 05 06 07 08 09 10 11 12 time of day in hours mean value for the day = 45 µg / m3 13 14 15 16 17 18 19 20 21 22 23 00 40 30 20 10 0 (a) What is the range of the measurements taken by the scientists on this day? range = from … to … µg / m3 [1] (b) The main source of nitrogen dioxide is from cars driving in the town. Suggest why the concentration reaches two peak levels each day. … … …[2]

3 0608/04/M/J/13 © UCLES 2013 [Turn over For Examiner’s Use (c) The fumes from car engines contain nitrogen monoxide, but they cause the air to be polluted with nitrogen dioxide. (i) Describe how nitrogen monoxide is formed in car engines. … … …[2] (ii) Explain how cars cause the air to be polluted with nitrogen dioxide. … …[1] [Total: 6]

4 0608/04/M/J/13 © UCLES 2013 For Examiner’s Use 2 Fibres made from a new polymer are tested using the apparatus shown below. stand loop of fibre weights A 20 cm loop of fibre is stretched by adding weights one at a time. The length of the loop is measured after each weight is added. The length of the loop of fibre just before it breaks is written down. This is used to calculate how much the fibre has stretched. The test is then repeated five more times and a best estimate is calculated. (a) The same diameter of fibre is used for each test. Explain why it is important to keep this variable constant. … … … …[2]

5 0608/04/M/J/13 © UCLES 2013 [Turn over For Examiner’s Use (b) Results of these tests on the new polymer are shown in Table 1. Table 1 sample number 1 2 3 4 5 6 stretch in mm 13 11 19 13 14 12 Show that the best estimate for the stretch of fibres made from the new polymer is 12.6 mm. [1] (c) A plasticiser is added to the new polymer. Fibres of the plasticised polymer are then tested in the same way as the unplasticised polymer. Results of these tests are shown in Table 2. Table 2 sample number 1 2 3 4 5 6 best estimate stretch in mm 21 20 22 21 23 22 21.5 (i) The results in Tables 1 and 2 show that there is a real difference between the properties of the fibres from the plasticised and unplasticised polymers. Explain how they show a real difference. … … …[1]

6 0608/04/M/J/13 © UCLES 2013 For Examiner’s Use (ii) Adding a plasticiser has changed the properties of the polymer. Explain how the plasticiser caused this change in properties. Use ideas about forces between molecules in your answer. … … … …[3] [Total: 7]

7 0608/04/M/J/13 © UCLES 2013 [Turn over For Examiner’s Use 3 (a) Complete these sentences about the digestion of food. During digestion large food molecules are broken down into small molecules. Starch is broken down into … Protein is broken down into … [1] (b) Eating too much of some food types can lead to health problems. For example, eating too much sugar can lead to diabetes. (i) The labels on many food packets give details of what is in the food. A person could use this information to avoid the health problems that may be caused by eating too much of some food types. Explain how. … … …[2] (ii) A high sugar intake can lead to the development of diabetes. Many people eat large quantities of foods that contain a lot of sugar. Use ideas of risk and consequence to discuss whether they should or should not do this. … … … … …[3] (c) Obesity is also associated with the development of diabetes. Use ideas about energy to explain why a person may become obese. … …[1] [Total: 7]

8 0608/04/M/J/13 © UCLES 2013 For Examiner’s Use 4 This question is about near-Earth asteroids. These are asteroids with orbits which cross the Earth’s orbit. (a) Some astronomers spend a lot of time looking for near-Earth asteroids. (i) Explain why it is important to discover near-Earth asteroids. … … … …[2] (ii) Detecting near-Earth asteroids is difficult. Suggest and explain why this is so. … … … …[2]

9 0608/04/M/J/13 © UCLES 2013 [Turn over For Examiner’s Use (b) The dinosaurs died out about 65 million years ago. In 1980, scientists suggested that this happened when an asteroid crashed into the Earth. This idea was supported by asteroid dust found in rocks of that age. In 1990, the remains of a large crater was discovered near Chicxulub, in Mexico. Evidence in the rocks suggested that this crater was about 65 million years old. Pacific Ocean Mexico City Chicxulub Gulf of Mexico Caribbean Sea Explain why the discovery of this crater was important to the scientists developing the theory of extinction of dinosaurs. … … …[2] [Total: 6]

10 0608/04/M/J/13 © UCLES 2013 For Examiner’s Use 5 (a) The table below shows how the mean surface temperature of the Earth changed between 1900 and 2000. year 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 mean surface temperature in °C 13.75 13.65 13.70 13.80 13.95 13.90 14.00 13.95 14.05 14.20 14.40 (i) Seven points from the data in the table have been plotted on the grid below. Plot the remaining points. 1900 13.5 13.6 13.7 13.8 13.9 14.0 14.1 14.2 14.3 14.4 1920 1940 1960 year mean surface temperature in °C 1980 2000 1910 1930 1950 1970 1990 [2] (ii) Draw a smooth best-fit curve through the data. [1]

11 0608/04/M/J/13 © UCLES 2013 [Turn over For Examiner’s Use (b) Two scientists have different descriptions of the graph. Dr Chang The results show a definite trend. This is global warming. Dr Hussein The results are very variable. They do not show a definite trend. (i) Write down a scientific explanation Dr Chang would give for the rise in temperature. … … … … … …[3] (ii) Dr Chang and Dr Hussein are both scientists. Explain why they can have different interpretations of the graph. … … …[1] [Total: 7]

12 0608/04/M/J/13 © UCLES 2013 For Examiner’s Use 6 Nuclear power stations produce radioactive waste. (a) Radioactive waste must be processed before disposal. There are plans to build a new waste processing plant. Some people who live nearby are very worried about the possible risks. I don’t want a nuclear waste plant anywhere in my region. Radioactive materials may leak out and get into the environment. I don’t want my children to be poisoned! Aras (i) Give one benefit of having the processing plant built in the region. …[1] (ii) Give one way in which the risk could be kept as small as possible. … …[1] (b) Radioactive waste becomes less active with time. One part of the radioactive waste, plutonium, has a half-life of 24 000 years. Calculate the time that the plutonium must be kept securely before its activity drops to one quarter of its initial value. Show your working clearly. time = … years [2]

13 0608/04/M/J/13 © UCLES 2013 [Turn over For Examiner’s Use (c) The following table shows the properties of three different radioactive elements present in nuclear waste. element radiation emitted half-life in years caesium-137 gamma 30 strontium-90 beta 29 americium-241 alpha 400 (i) Suggest and explain how you could tell which element was which if you were given a sample of each. Use information from the table in your answer. … … … … …[2] (ii) The radioactive waste needs to be stored safely until it is no longer hazardous. Both americium-241 and caesium-137 pose problems in storage. Explain why. americium-241 … … caesium-137 … …[1] [Total: 7]

14 0608/04/M/J/13 © UCLES 2013 For Examiner’s Use 7 A newborn baby cannot produce antibodies. (a) A baby begins to make her own antibodies when she is about 12 weeks old. Many babies are vaccinated at this age. (i) Suggest why a baby is not usually vaccinated before 12 weeks. … …[1] (ii) Parents are encouraged to get their babies vaccinated. Explain why it is important that as many babies as possible are vaccinated. … …[1] (iii) Some people think it should be compulsory for all babies to be vaccinated. In many countries it is not compulsory to vaccinate all babies, even though it would be possible. Suggest reasons why vaccination remains optional in these countries. … … …[2]

15 0608/04/M/J/13 © UCLES 2013 [Turn over For Examiner’s Use (b) The graph shows what happens to the concentration of antibodies in a baby’s bloodstream after vaccination at time A and then after exposure to the disease at time B. 0 10 20 30 40 A B 50 concentration of antibodies time in days 60 (i) Describe two differences between the increases in antibody concentration after the vaccination at time A and after exposure to the disease at time B. … … … …[2] (ii) Explain these differences. … … … …[2] [Total: 8]

16 0608/04/M/J/13 © UCLES 2013 For Examiner’s Use 8 Our bodies have communication systems that allow us to respond to changes in our environment. (a) (i) Write down two examples of nervous communication in humans. … … …[2] (ii) The nervous system consists of nerve cells, receptor cells and effector cells. Explain how these cells work together to respond to a stimulus. … … …[2] (iii) The speed of nerve impulses is different in different animals. Look at the table of data. animal speed of impulse in m / s vertebrate or invertebrate human 30.4 vertebrate crab 6.4 invertebrate frog 12.2 vertebrate horse 18.3 vertebrate lugworm 3.1 invertebrate Write down a conclusion that can be made about the speed of impulses in vertebrate and invertebrate animals. Use data in your answer to support your conclusion. … … …[2]

17 0608/04/M/J/13 © UCLES 2013 For Examiner’s Use (b) The effect of hormonal communication in humans is more widespread through the body than the effect of nervous communication. Explain why. … … …[2] [Total: 8] 9 Read the article about stem cells. First stem cell trial in stroke patient A British man has had stem cells injected into his brain to replace the cells damaged by a stroke. A stroke is a serious medical condition that occurs when the blood supply to part of the brain is cut off. The stem cells used in this clinical trial were taken from embryos. Many people support this step forward in the treatment of stroke patients. Others are worried about the ethical issues it raises. (a) Explain why stem cells can be used to replace damaged cells. … … …[2] (b) Stem cell therapy has the potential to save many lives. It may help to treat or cure some serious illnesses. Despite this potential benefit of stem cell therapy, some people believe it should never be carried out. Suggest two reasons why. 1 … 2 … [2] [Total: 4]

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CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education MARK SCHEME for the May/June 2013 series 0608 TWENTY FIRST CENTURY SCIENCE 0608/04 Paper 4 (Extended Written), maximum raw mark 60 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the May/June 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components. www.XtremePapers.com

Page 2 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0608 04 © Cambridge International Examinations 2013 1 (a) 10 to 120 [1] allow 120 to 10 (b) more cars driving in town at these times (1); people going to and from work (1) [2] both to and from needed (c) (i) reaction of nitrogen with oxygen (1); nitrogen from air (1) [2] (ii) nitrogen monoxide reacts with oxygen in air (1) [1] Total: [6] 2 (a) Different diameters will stretch different amounts for same weight (1); Best estimate would be unreliable / cannot average different quantities (1) [2] Can give example, e.g. if it were thinner (1); it would stretch more (1) (b) (13 + 11 + 13 + 14 + 12)/5 (1) [1] allow 63/5 (c) (i) the mean for unplasticised is outside the range for plasticised / the mean for plasticised is outside the range for unplasticised (1) [1] accept ‘the ranges do not overlap’ as that implies both alternative marking points in this case (ii) plasticiser makes the polymer softer / more flexible (1); plasticiser gets between polymer molecules (1); forces are lower (1); molecules / chains slide over each other more easily (1) [3] Any three points. Total: [7]

Page 3 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0608 04 © Cambridge International Examinations 2013 3 (a) glucose AND amino acids (1) [1] both required (b) (i) look on label for food type they are trying to avoid (1); eat less of/do not eat if food type listed (1) [2] allow answers that use examples e.g. sugar/fat Credit answers which imply checking for chemicals in the food which could cause health problems (ii) Risk explained (1); Consequence explained (1); weighs up risk and consequence and comes to a judgement thereon (1) [3] Either: risk is low (may not get diabetes / diabetes only occurs late in life) Or risk is high (number of cases increasing); Either consequence is serious because life threatening/grave health problems Or consequence not serious due to good treatments now available; (c) if energy input in food exceeds energy used, person will gain weight (1) [1] allow arguments based on activity/exercise Total: [7] 4 (a) (i) to see if it is large / see if will collide with Earth (1); collision may result in climate change from dust clouds/serious local damage to cities/creation of tsunamis (1); [2] Allow ‘may be able to deflect/destroy asteroid’ as alternative (ii) small and dim so hard to see (1); movement rapid so appear suddenly (1); need many observations to establish it is near- Earth (1) [2] Any two points. Allow other valid suggestions. (b) crater caused by asteroid impact (1); gives more (independent) evidence about dinosaur extinction (1); shows that time of asteroid impact fits with time of extinction (1); this observation increases confidence in the asteroid impact theory (1) [2] Any two points. Total: [6]

Page 4 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0608 04 © Cambridge International Examinations 2013 5 (a) (i) 4 correctly plotted points = (2) 2 or 3 correctly plotted points = (1) [2] (ii) Smooth curve following trend (1) [1] Not a curve which slavishly goes through each point. Allow sensible straight line. (b) (i) Increased concentration of greenhouse gases, particularly CO2, in atmosphere (1); CO2 increase due to deforestation and increased burning of fossil fuels (1); absorbs radiation (emitted by warm Earth) so Earth as a whole absorbs more than it emits (1) [3] allow either ‘it’s global warming’ gets 0 unless developed 1 allow other reasoned suggestions, e.g. solar output fluctuation (ii) Same data allows different interpretations because of small range of time / variability of data / many variables involved in global warming (1) [1] Must qualify the reason for difference in interpretations Total: [7] 6 (a) (i) benefit: employment / revenue from tax / use of local facilities [1] allow any reasonable suggestion (ii) risk reduction: strict regular inspections / regulations about handling materials / secure containment at all stages (1) [1] allow any reasonable suggestion, e.g. workers wear protective clothing, waste stored in secure conditions, waste kept away from local people (b) 1⇒½⇒¼ in two half-lives (1); must be (longer than) 2 half-lives = (more than) 48 000 years (1) [2] (c) (i) 1) Cs: radiation would penetrate several mm of metal 2) Sr: radiation would penetrate paper, but stopped by couple of mm of metal 3) Am: radiation stopped by a sheet of paper [2] All 3 = (2); 1 or 2 = (1) Ignore any reference to half- life. (ii) Am-241: long half-life / very ionising and Cs-137: highly penetrating γ radiation (1) [1] Both needed or great range Total: [7]

Page 5 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0608 04 © Cambridge International Examinations 2013 7 (a) (i) won’t be able to produce antibodies (1) [1] (ii) to prevent epidemics of the disease (1) [1] (iii) people should be able to choose whether or not they are vaccinated (1); vaccination is against some peoples’ religious beliefs / would be an infringement of rights to make it compulsory (1) [2] allow ‘expensive’ only if qualified, e.g. for developing countries (b) (i) rise after exposure to disease is: quicker than rise after vaccination (1); to a higher concentration than after vaccination (1) [2] ora (ii) after vaccination body makes antibodies against microorganism (1); can make the antibody quicker on second exposure (1) [2] Ecf from (i) Total: [8] 8 (a) (i) any two correct examples of nervous communication [2] one mark for each example (ii) receptor cells detect stimulus (1); passes impulse along nerve cells (1); to effector cells which respond to stimuli (1) [2] any two (iii) faster impulses in vertebrates (1); some correct data quoted to support conclusion (1) [2] ora ignore units (b) nervous communication is via nerve cells from one specific place to another (1); hormonal communication is via blood which travels all over body (1) [2] Total: [8] 9 (a) stem cells are unspecialised cells (1); can develop into any type of cell (1) [2] (b) unnatural (1); against religious beliefs (1); expensive (1); uses cells from embryos (1); embryos produced only for stem cells (1); unused embryos are discarded (1) [2] Any two Do not allow ‘unethical’ unless qualified Total: [4] v