Cambridge IGCSE Sciences - Co-ordinated (Double) 0654 — 2012 May/June Paper 2 · Variant 1

This document consists of 28 printed pages and 4 blank pages. IB12 06_0654_21/4RP © UCLES 2012 [Turn over *4369159917* For Examiner's Use 1 2 3 4 5 6 7 8 9 10 11 12 Total UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education CO-ORDINATED SCIENCES 0654/21 Paper 2 (Core) May/June 2012 2 hours 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 soft pencil for any diagrams, graphs, tables or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. A copy of the Periodic Table is printed on page 32. 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

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3 © UCLES 2012 0654/21/M/J/12 [Turn over For Examiner's Use 1 Sugar cane is a food crop grown in Australia. It is harvested and then transported on small trains to the processing plant. Fig. 1.1 shows one of the trains carrying sugar cane. Fig. 1.1 (a) The train travels a distance of 25 km in 2 hours. Calculate the average speed of the train. State the formula that you use and show your working. formula used working km / h [2] (b) The engine is powered by oil. The oil is burned to change water into steam. The steam is used to make parts of the engine move. (i) What kind of energy is stored in the oil? [1] (ii) The engine is 30 % efficient in converting the energy stored in the oil into movement energy. The rest of the stored energy is lost in different ways. State one of these ways. [1]

4 © UCLES 2012 0654/21/M/J/12 For Examiner's Use (c) The track for the train is composed of short lengths of steel rail with small gaps left between them as shown in Fig. 1.2. gap steel rail Fig. 1.2 Suggest a reason for leaving these small gaps. [2] (d) Sugar can be fermented and turned into ethanol. Ethanol is now used as a fuel for cars. (i) Give one reason, other than cost, why people might use ethanol rather than petrol in their cars. [1] (ii) Sugar is a carbohydrate, but ethanol is not. Name the three chemical elements contained in both sugar and ethanol. [1]

5 © UCLES 2012 0654/21/M/J/12 [Turn over For Examiner's Use (e) The farm on which the sugar cane is grown uses a wind turbine to produce electrical power. Table 1.1 shows the electrical power generated for different wind speeds. Table 1.1 wind speed / km per hour 0 3 5 8 10 12 15 20 power generated / W 0 0 150 500 1000 1100 1200 1200 (i) Suggest the lowest wind speed needed to generate power. km / h [1] (ii) State the maximum power that this wind turbine can produce. W [1] (iii) State one disadvantage of using only a wind turbine as the source of electrical power. [1] (iv) Complete the sentence to show the energy transfer taking place when the wind turbine generates power. energy is transferred to energy. [2]

6 © UCLES 2012 0654/21/M/J/12 For Examiner's Use 2 The bar chart in Fig. 2.1 shows the approximate composition of unpolluted air. nitrogen … % oxygen … % other gases … % percentage in unpolluted air Fig. 2.1 (a) (i) Complete the bar chart in Fig. 2.1 by labelling the approximate percentages of nitrogen, oxygen and other gases. [2] (ii) Name one gaseous compound that exists in unpolluted air. [1] (b) Nitrogen and oxygen exist in the air in the form of the diatomic molecules, N2 and O2. When lightning passes through the air, the gaseous compounds nitric oxide, NO, and nitrogen dioxide, NO2, are formed. NO NO NO NO2 NO NO2 NO NO NO NO2 NO2 NO (i) Explain why nitrogen and oxygen are described as chemical elements. [1] (ii) Suggest and explain the type of chemical bonding in nitric oxide and nitrogen dioxide. type of bonding explanation [2]

7 © UCLES 2012 0654/21/M/J/12 [Turn over For Examiner's Use (iii) A student carried out an experiment to investigate what happened to the acidity of rainwater during a thunderstorm. His results are shown in Table 2.1. Table 2.1 description of sample pH pure water obtained in a science laboratory 7 rainwater collected when no thunderstorm was occurring 5 rainwater collected during a thunderstorm 4 What conclusions can the student make from these results? [3]

8 © UCLES 2012 0654/21/M/J/12 For Examiner's Use 3 Fig. 3.1 shows part of a section across a root from a radish plant, photographed through a microscope. Fig. 3.1 (a) On Fig. 3.1, use a label line to label a root hair cell. [1] (b) Root hair cells absorb substances from the soil. Name two substances that root hair cells absorb from the soil. 1 2 [2] (c) A complete radish plant was placed with the lower part of its root standing in water. A soluble red dye was added to the water. After a while, the veins in the leaves of the radish plant became red. (i) Name the tissue in the radish plant through which the coloured water was transported from the roots to the leaves. [1] (ii) On Fig. 3.1, write the letter A, to show the position of this tissue in the root. [1]

9 © UCLES 2012 0654/21/M/J/12 [Turn over For Examiner's Use (d) The cells in the radish root are plant cells. Complete Table 3.1 to show which structures are present in plant cells and which are present in animal cells. Use a tick ( ) to show that the structure is present. Use a cross ( ) to show that the structure is not present. You should place either a tick or a cross in every space in the table. Table 3.1 structure plant cells animal cells cell membrane cell wall nucleus vacuole containing sap [4]

10 © UCLES 2012 0654/21/M/J/12 For Examiner's Use 4 (a) A bat produces a sound wave with a frequency of 212 kHz and a wavelength of 0.0016 m. This sound is outside the audible frequency range for humans. (i) State the approximate audible frequency range for humans. Hz [1] (ii) State the meaning of the terms frequency and wavelength, when describing a wave. You may use a diagram if it helps your explanation. frequency wavelength [2]

11 © UCLES 2012 0654/21/M/J/12 [Turn over For Examiner's Use (b) A girl shouts and waves to another girl in the school playground. Fig. 4.1 The sound energy and the light energy both travel from one girl to the other by wave motion. (i) State whether sound waves and light waves are transverse or longitudinal. Sound waves are . Light waves are . [2] (ii) Explain why sound waves will not travel through a vacuum. [1] (iii) If the first girl now makes another sound with a smaller amplitude than the original sound wave, what change would the second girl notice? [1] (iv) The girls could have communicated with each other using their mobile phones (cell phones). Name the type of electromagnetic wave used to communicate between mobile phones. [1]

12 © UCLES 2012 0654/21/M/J/12 For Examiner's Use 5 Marmots are herbivorous mammals. Fig. 5.1 shows a marmot. Fig. 5.1 (a) Define the term herbivore. [2] (b) A study has been carried out on the marmots living in Colorado, USA. The winters in this part of Colorado are very cold. The marmots hibernate (sleep) in burrows in winter. They do not eat while they are hibernating. They wake up in spring. Before they hibernate, marmots build up large fat stores beneath their skin. (i) Suggest and explain what marmots must do in order to build up large fat stores in their bodies. [2]

13 © UCLES 2012 0654/21/M/J/12 [Turn over For Examiner's Use Fig. 5.2 shows the percentage of marmots with different body masses that survive through the winter. 100 80 60 40 percentage of marmots surviving body mass / kg 2 3 4 5 Fig. 5.2 (ii) Describe the relationship between a marmot's body mass and its chance of surviving the winter. [2] (iii) Suggest how a layer of fat beneath the skin can reduce heat transfer from a hibernating marmot's body to its surroundings. [1] (c) In the last twenty years, spring has been arriving earlier in the year in Colorado. This is a result of global warming. Name two gases that contribute to global warming. 1 2 [2]

14 © UCLES 2012 0654/21/M/J/12 For Examiner's Use (d) Fig. 5.3 shows the mean body mass of the marmots on the first day of August (summer) between 1976 and 2006. 3.5 3.0 2.5 2.0 mean body mass / kg 1976 1986 1996 2006 Fig. 5.3 (i) Describe the general trend shown in Fig. 5.3. [1] (ii) Suggest how the earlier arrival of spring could be responsible for this trend. [1]

15 © UCLES 2012 0654/21/M/J/12 [Turn over For Examiner's Use 6 Fig. 6.1 shows some of the apparatus and substances a student used to investigate the rate of reaction between magnesium and dilute hydrochloric acid. In this reaction hydrogen gas is given off. water measuring cylinder dilute hydrochloric acid stopwatch bung magnesium Fig. 6.1 (a) Fig. 6.1 shows the apparatus just before the student started his experiment to measure the rate of reaction. Describe briefly how the student should proceed and the measurements he should make. [3] (b) The student repeated the experiment using hydrochloric acid which had a higher concentration. He kept all of the other variables which could affect the rate constant. Predict and explain briefly how the measurements the student made in the second experiment would be different from those he made in the first. [2]

16 © UCLES 2012 0654/21/M/J/12 For Examiner's Use (c) The reaction between magnesium and dilute hydrochloric acid also produces the ionic compound magnesium chloride. In crystals of this compound, two chloride ions combine with one magnesium ion. (i) Describe, in terms of electrons, what happens when a metal atom such as magnesium is converted into an ion. [1] (ii) State the chemical formula of magnesium chloride. [1] (d) (i) In the early days of photography, a mixture of chemicals including magnesium powder was burned to provide a flash of brilliant white light. Suggest why the magnesium had to be in the form of a fine powder. [2] (ii) Some alloys of aluminium contain magnesium. Describe two properties of aluminium alloys and explain why these properties make them suitable materials for making aircraft parts. property 1 reason property 2 reason [4]

17 © UCLES 2012 0654/21/M/J/12 [Turn over For Examiner's Use 7 (a) State and describe one use of radioactive isotopes in medicine. [2] (b) Alpha, beta and gamma radiations are three types of radioactive emission. State which of these radiations is described by each statement below. This form of radiation can pass through lead. This form of radiation consists of nuclei of helium atoms. This form of radiation is part of the electromagnetic spectrum. This form of radiation is the most ionising. [2] (c) Describe how ionising radiation can be dangerous to humans. [2]

18 © UCLES 2012 0654/21/M/J/12 For Examiner's Use 8 An element is a substance that is made of atoms which have the same proton number. Most atoms contain protons, neutrons and electrons. The elements are shown in the Periodic Table. (a) The chemical symbol of an atom of the element chlorine is shown below. Cl 35 17 The nucleon number of this atom is 35. (i) Name the part of an atom that contains the protons and neutrons. [1] (ii) State the number of neutrons in this chlorine atom. [1] (iii) Explain whether or not the nucleon number of all chlorine atoms is also 35. [2] (iv) Name the element whose atoms do not usually contain any neutrons. [1] (b) Table 8.1 shows Period 2 of the Periodic Table. Table 8.1 X Period 2 I II III IV V VI Y VII Z 0 The element represented by X is a solid at room temperature, and the elements represented by Y and Z are gases. (i) Suggest one difference, other than physical state at room temperature, between the properties of elements X and Y. [1]

19 © UCLES 2012 0654/21/M/J/12 [Turn over For Examiner's Use (ii) Suggest one difference between the chemical properties of elements Y and Z. [1] (c) Fig. 8.1 shows a simple lime kiln which is used to produce lime (calcium oxide) from limestone (calcium carbonate). waste gases air calcium carbonate carbon burns to provide heat energy Fig. 8.1 (i) Suggest two reasons why the mixture of waste gases from the lime kiln contains a large amount of carbon dioxide. 1 2 [2] (ii) Suggest and explain why a farmer would add lime to soil. [2]

20 © UCLES 2012 0654/21/M/J/12 For Examiner's Use 9 (a) One of the characteristics of living organisms is sensitivity, which is the ability to respond to changes in the environment. List four other characteristics of all living things. 1 2 3 4 [2] (b) In many organisms, hormones help them to respond to changes in their environment. Define the term hormone. [3] (c) Adrenaline is sometimes called the 'fright, flight or fight' hormone. It is produced when a person is frightened. One effect of adrenaline is to increase a person's pulse rate. This means that oxygen and glucose are delivered more rapidly to their leg muscles. Explain how this could help a person to run away from the thing that has frightened them. [2]

21 © UCLES 2012 0654/21/M/J/12 [Turn over For Examiner's Use (d) Plants are able to respond to light. Name and describe the response of a plant shoot to light that is coming from only one side. name of response description [2]

22 © UCLES 2012 0654/21/M/J/12 For Examiner's Use 10 (a) A student investigated how the change in potential difference across a lamp affected the current flowing through it. She used wires to connect the components shown in Fig. 10.1 to make a suitable circuit. A V Fig. 10.1 (i) Using the correct symbols from Fig. 10.1, draw a diagram to show the circuit she made. [3] (ii) Explain why a variable resistor is used in the circuit. [1]

23 © UCLES 2012 0654/21/M/J/12 [Turn over For Examiner's Use (iii) During the investigations, she measured the voltage across the lamp as 3.0 V and the current passing through the lamp as 0.3 A. Calculate the resistance of the lamp. State the formula that you use and show your working. formula used working Ω [2] (b) Table 10.1 shows some information about six pieces of wire, all at room temperature (20 °C). Table 10.1 wire metal composition length / cm cross-sectional area / mm2 A copper 10 0.5 B nichrome 10 0.5 C copper 20 0.5 D nichrome 20 0.5 E copper 10 1.0 F copper 20 1.0 (i) Which wire, B or D, will have the greater resistance? Explain your answer. [1] (ii) Which wire, A or E, will have the greater resistance? Explain your answer. [1]

24 © UCLES 2012 0654/21/M/J/12 For Examiner's Use (c) A plastic rod is rubbed with a cloth. The rod becomes charged. There are two types of electric charge. (i) State the names of these charges. 1 2 [1] (ii) Charged particles are transferred between the rod and cloth. Name the charged particles transferred. [1]

25 © UCLES 2012 0654/21/M/J/12 [Turn over BLANK PAGE Please turn over for Question 11.

26 © UCLES 2012 0654/21/M/J/12 For Examiner's Use 11 (a) Fig. 11.1 shows part of the human gas exchange system. A B C Fig. 11.1 Name the structures labelled A, B and C. A B C [3] (b) State two ways in which the composition of expired air differs from the composition of inspired air. 1 2 [2] (c) A person with cystic fibrosis makes very thick mucus. This can form a thick covering over the inner surfaces of the alveoli in the lungs. This makes it difficult for oxygen to move from the alveoli into the blood. (i) Name the process by which oxygen moves from the alveoli into the blood. [1] (ii) Name the blood vessel that transports blood from the lungs to the heart. [1]

27 © UCLES 2012 0654/21/M/J/12 [Turn over For Examiner's Use (d) Cystic fibrosis is caused by a recessive allele f. The normal allele, F, is dominant. A couple who were both heterozygous for cystic fibrosis wanted to have children. (i) State the probability that their first child would have cystic fibrosis. [1] (ii) Complete the genetic diagram to explain your answer to (i). genotype of parents gametes Ff and … and gametes from woman gametes from man [4]

28 © UCLES 2012 0654/21/M/J/12 For Examiner's Use 12 Millions of tonnes of hydrocarbons are burnt every year to provide energy. (a) Name the raw material that provides hydrocarbons. [1] (b) Fig. 12.1 shows apparatus a student used to investigate the products of complete combustion of the gaseous hydrocarbon methane, CH4. U-tube pump draws gases through apparatus limewater cold water colourless liquid forms inside U-tube methane gas Fig. 12.1 Before the methane gas is ignited, the limewater appears as a colourless solution and the U-tube contains no liquid. (i) Describe how the appearance of the limewater changes after the methane is ignited, and name the compound that causes this change. change in appearance name of compound [2] (ii) Name the colourless liquid that forms inside the U-tube. [1] (iii) State and explain briefly whether or not the observations made in the experiment shown in Fig. 12.1 would be different if ethanol was burned instead of methane. [1]

29 © UCLES 2012 0654/21/M/J/12 For Examiner's Use (c) In the chemical industry, large quantities of ethanol are made from ethene. Name the compound that reacts with ethene to form ethanol. [1] (d) Ethene is a colourless gas. When ethene is heated and pressurised the white solid poly(ethene) is formed. (i) Name the type of reaction which occurs when poly(ethene) is formed from ethene. [1] (ii) Describe briefly how ethene molecules are converted into molecules of poly(ethene). You may use a diagram to help your explanation. [2]

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31 Copyright Acknowledgements: Question 3 Photograph © B23WP8 cross section of a radish root; Biodisc/Visuals Unlimited/Alamy. Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. © UCLES 2012 0654/21/M/J/12 BLANK PAGE

32 © UCLES 2012 0654/21/M/J/12 Group 140 Ce Cerium 58 141 Pr Praseodymium 59 144 Nd Neodymium 60 Pm Promethium 61 150 Sm Samarium 62 152 Eu Europium 63 157 Gd Gadolinium 64 159 Tb Terbium 65 162 Dy Dysprosium 66 165 Ho Holmium 67 167 Er Erbium 68 169 Tm Thulium 69 173 Yb Ytterbium 70 175 Lu Lutetium 71 232 Th Thorium 90 Pa Protactinium 91 238 U Uranium 92 Np Neptunium 93 Pu Plutonium 94 Am Americium 95 Cm Curium 96 Bk Berkelium 97 Cf Californium 98 Es Einsteinium 99 Fm Fermium 100 Md Mendelevium 101 No Nobelium 102 Lr Lawrencium 103 1 H Hydrogen 1 7 Li Lithium 3 23 Na Sodium 11 24 Mg Magnesium 12 40 Ca Calcium 20 45 Sc Scandium 21 48 Ti Titanium 22 51 V Vanadium 23 52 Cr Chromium 24 55 Mn Manganese 25 56 Fe Iron 26 59 Co Cobalt 27 59 Ni Nickel 28 64 Cu Copper 29 65 Zn Zinc 30 70 Ga Gallium 31 27 Al Aluminium 13 11 B Boron 5 12 C Carbon 6 14 N Nitrogen 7 16 O Oxygen 8 19 F Fluorine 9 28 Si Silicon 14 31 P Phosphorus 15 32 S Sulfur 16 35.5 Cl Chlorine 17 40 Ar Argon 18 20 Ne Neon 10 4 He Helium 2 73 Ge Germanium 32 75 As Arsenic 33 79 Se Selenium 34 80 Br Bromine 35 84 Kr Krypton 36 39 K Potassium 19 88 Sr Strontium 38 89 Y Yttrium 39 91 Zr Zirconium 40 93 Nb Niobium 41 96 Mo Molybdenum 42 Tc Technetium 43 101 Ru Ruthenium 44 103 Rh Rhodium 45 106 Pd Palladium 46 108 Ag Silver 47 112 Cd Cadmium 48 115 In Indium 49 119 Sn Tin 50 122 Sb Antimony 51 128 Te Tellurium 52 127 I Iodine 53 131 Xe Xenon 54 137 Ba Barium 56 139 La Lanthanum 57 * 178 Hf Hafnium 72 181 Ta Tantalum 73 184 W Tungsten 74 186 Re Rhenium 75 190 Os Osmium 76 192 Ir Iridium 77 195 Pt Platinum 78 197 Au Gold 79 201 Hg Mercury 80 204 Tl Thallium 81 207 Pb Lead 82 209 Bi Bismuth 83 Po Polonium 84 At Astatine 85 Rn Radon 86 Fr Francium 87 227 Ac Actinium 89 9 Be Beryllium 4 I II III IV V VI VII 0 85 Rb Rubidium 37 133 Cs Caesium 55 226 Ra Radium 88 The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.). a X b a = relative atomic mass X = atomic symbol b = proton (atomic) number Key *58-71 Lanthanoid series 90-103 Actinoid series DATA SHEET The Periodic Table of the Elements

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education MARK SCHEME for the May/June 2012 question paper for the guidance of teachers 0654 CO-ORDINATED SCIENCES 0654/21 Paper 2 (Core Theory), maximum raw mark 120 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 must be read in conjunction with the question papers and the report on the examination. • Cambridge will not enter into discussions or correspondence in connection with these mark schemes. Cambridge is publishing the mark schemes for the May/June 2012 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses. www.XtremePapers.com

Page 2 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0654 21 © University of Cambridge International Examinations 2012 1 (a) (speed) = distance / time ; = 25 / 2 = 12.5 (km / h) ; [2] (b) (i) chemical ; [1] (ii) heating engine / heating surroundings / light / sound ; [1] (c) metal track expands in summer / hot weather ; metal can expand into gap ; prevents track from buckling / bending / being damaged / becomes unsafe for trains to move ; [max 2] (d) (i) ethanol is renewable source / no sulfur dioxide produced / does not deplete fossil fuel supplies ; [1] (ii) carbon, hydrogen, oxygen ; [1] (e) (i) 5 (km / h) ; (accept 4 / reference to greater than 3, but equal to or less than 5) [1] (ii) 1200 (W) ; [1] (iii) dependent on wind / wind speed unreliable or variable / owtte ; [1] (iv) kinetic ; electrical ; [2] [Total: 13] 2 (a) (i) nitrogen 78% oxygen 21% others 1% ;; [2] (all three correct 2 marks, two correct 1 mark) (ii) carbon dioxide / water (vapour) ; [1] (b) (i) contain only one type of atom / all atoms have same proton number ; [1] (ii) covalent ; bonded elements are both non-metals / compounds are gases ; (iii) pure water is neutral ; rain water (generally) is more acidic (than pure water) ; rainwater during thunderstorm is the most acidic ; likely to be caused by nitrogen oxides ; which have reacted with the rain to form an acid ; [max 3] [Total: 9]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0654 21 © University of Cambridge International Examinations 2012 3 (a) label to root hair cell ; [1] (b) water ; minerals / ions / named mineral ion ; [2] (c) (i) xylem ; [1] (ii) A in central area of root ; [1] (iii) structure plant cells animal cells cell membrane

cell wall
 nucleus

vacuole containing sap
 one mark for any row correct ;;;; [4] [Total: 9] 4 (a) (i) between 10 and 20 Hz to between 20 000 and 25 000 Hz ; [1] (ii) frequency – number of waves produced / passing a point per second ; wavelength – distance between two consecutive peaks / troughs on two consecutive waves ; [2] (b) (i) sound – longitudinal ; light – transverse ; [2] (ii) no medium / material for waves to travel through ; [1] (iii) quieter ; [1] (iv) microwaves ; [1] [Total: 8]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0654 21 © University of Cambridge International Examinations 2012 5 (a) (an animal that) eats plants ; only plants / not meat ; reference to getting energy from, its food / plants ; [max 2] (b) (i) eat a lot ; eat / take in, more energy than they use ; excess, carbohydrate / protein, converted to fat ; [max 2] (ii) the greater the body mass, the greater the chance of survival ; idea that effect is greater at lower body masses / levels off at higher body masses ; use of figures ; [max 2] (iii) insulator / poor conductor / reduces conduction ; [1] (c) carbon dioxide ; methane ; [2] (d) (i) mean body mass is increasing ; [1] (ii) marmots have more time to feed (from spring onwards) ; marmots lose less weight during hibernation (as winters are shorter) ; reference to more food available ; [max 1] [Total: 11] 6 (a) add magnesium to acid ; insert bung ; measure time for known volume of gas to collect ; measure volume of gas at fixed intervals ; [max 3] (b) time for (same volume) of gas to collect is shorter ; because rate of reaction is greater / greater collision frequency / faster reaction / more vigorous ; [2] (c) (i) (atom) loses electrons / achieves complete outer shell ; [1] (ii) MgCl2 ; [1] (d) (i) to increase reaction / burning rate ; (powder has) large surface area ; high rate needed to get all light at once / so brighter ; [max 2] (ii) light / low density ; reduces weight of aircraft / less energy or fuel needed for flight ; strong ; reference to maintenance of the integrity of airframe / safety ; [4] [Total: 13]

Page 5 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0654 21 © University of Cambridge International Examinations 2012 7 (a) use – cancer treatment / tracers / kill bacteria / sterilising surgical equipment ; correct description ; [2] (b) gamma alpha gamma alpha (2 marks for four correct, 1 mark for two or three correct) ;; [2] (c) destroys / damages cells ; caused cancer ; mutations / damages DNA ; [max 2] [Total: 6] 8 (a) (i) nucleus ; [1] (ii) 18 ; [1] (iii) (no) – no mark reference to isotopes ; which are atoms of same element with different number of neutrons ; [2] (iv) hydrogen ; [1] (b) (i) any typical metal property for X and corresponding non-metal for Y ; [1] e.g. X conductor Y insulator X malleable Y not malleable X forms positive ions Y forms negative ions X high fixed points Y low fixed points (ii) Y is more reactive / Z is less reactive / unreactive / specific example ; [1] (c) (i) combustion of carbon ; (thermal) decomposition / breakdown of calcium carbonate ; [2] (ii) soil is acidic ; lime reacts with acid / reduces acidity / neutralises ; to increase fertility ; [max 2] [Total: 11]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0654 21 © University of Cambridge International Examinations 2012 9 (a) nutrition excretion respiration reproduction growth movement (1 mark for any two correct) ;; [2] (b) chemical ; produced by a gland ; carried by the blood ; affects (specific) target organs ; destroyed by the liver ; [max 3] (c) more respiration ; more energy (for muscles) ; muscles can work, harder / faster ; [max 2] (d) (positive) phototropism ; grows towards the light ; [2] [Total: 9] 10 (a) (i) ammeter in series ; voltmeter in parallel ; all else correct ; [3] (ii) to change voltage across, current through lamp ; [1] (iii) R = V / I ; = 3 / 0.3 = 10 (Ω) ; [2] (b) (i) D it’s longer (resistance proportional to length) ; [1] (ii) A smaller cross-sectional area ; [1] (c) (i) positive and negative ; [1] (ii) electron ; [1] [Total: 10]

Page 7 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0654 21 © University of Cambridge International Examinations 2012 11 (a) A larynx ; B trachea ; C bronchus / bronchiole ; [3] (b) more carbon dioxide ; less oxygen ; more water vapour ; [max 2] (c) (i) diffusion ; [1] (ii) pulmonary vein ; [1] (d) (i) 1 in 4 / one quarter / 0.25 ; [1] (ii) (parents’ genotypes) both Ff ; gametes F and f from both parents ; offspring genotypes FF, Ff, Ff and ff ; ff identified as having cystic fibrosis ; [4] [Total: 12] 12 (a) petroleum / crude oil ; [1] (b) (i) goes cloudy / milky / opaque / white ; carbon dioxide ; [2] (ii) water ; [1] (iii) (no) – no mark ethanol’s combustion products are the same as methane’s ; [1] (c) water / steam ; [1] (d) (i) polymerisation / addition / self addition ; [1] (ii) link together ; into long chains / into chain molecules ; [2] [Total: 9]