Cambridge IGCSE Sciences - Co-ordinated (Double) 0654 — 2012 May/June Paper 3 · Variant 3

This document consists of 27 printed pages and 1 blank page. IB12 06_0654_33/FP © UCLES 2012 [Turn over *7145091241* 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 0654/33 Paper 3 (Extended) 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 28. 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 © UCLES 2012 0654/33/M/J/12 For Examiner's Use 1 (a) Most atoms of metallic elements found in the Earth’s crust exist in compounds called ores which are contained in rocks. The chemical formulae of some metal compounds found in ores, together with the names of the ores, are shown below. argentite Ag2S chromite FeCr2O4 galena PbS scheelite CaWO4 (i) A binary compound is one that contains only two different elements. State which of the compounds in the list above are binary compounds. [1] (ii) State the ore from which the metallic element tungsten could be extracted. [1] (b) Fig. 1.1 shows an incomplete diagram of an atom of an element Q in which only the outer shell electrons are shown. Fig. 1.1 (i) Name element Q and explain your answer. name explanation [3]

3 © UCLES 2012 0654/33/M/J/12 [Turn over For Examiner's Use (ii) One atom of element Q combines with hydrogen atoms to form covalent molecules. Draw a diagram of one molecule of this compound to show how the bonding electrons are arranged. [3] (iii) Element Q may be extracted from its oxide, QO2, in a reaction with hydrogen, H2. In this reaction, hydrogen removes the oxygen from the oxide and forms water. Suggest a balanced symbol equation for this reaction. [2]

4 © UCLES 2012 0654/33/M/J/12 For Examiner's Use 2 (a) An athlete is training on a bicycle. He uses the bicycle to turn a generator that lights a lamp as he pedals. Fig. 2.1 shows the simple generator which he uses. N S magnet magnet slip ring brush coil axle lamp Fig. 2.1 Explain how the rotating coil causes the lamp to light. Include in your explanation a description of what the slip rings and brushes do. [4]

5 © UCLES 2012 0654/33/M/J/12 [Turn over For Examiner's Use (b) During his bicycle ride the athlete cools down by sweating. Describe and explain, in terms of the movement of water molecules, how evaporation cools down the athlete. [2]

6 © UCLES 2012 0654/33/M/J/12 For Examiner's Use 3 (a) Fig. 3.1 shows the effect of pH on the activity of an enzyme. rate of reaction 1 2 3 4 5 pH 6 7 8 9 10 11 12 0 Fig. 3.1 (i) Describe the effect of pH on the activity of this enzyme. [2] (ii) Explain why pH affects the enzyme in this way. [2] (iii) A protease enzyme works in the human stomach, where hydrochloric acid is secreted. This enzyme is adapted to work best in these conditions. On Fig. 3.1, sketch a curve to show how pH affects the activity of this protease enzyme. [1] (iv) After the food has been in the stomach for a while, it passes into the duodenum. Pancreatic juice, which contains sodium hydrogencarbonate, is mixed with the food in the duodenum. Explain why the protease enzyme stops working when it enters the duodenum. [2]

7 © UCLES 2012 0654/33/M/J/12 [Turn over For Examiner's Use (b) Explain how the protease enzyme enables body cells to obtain nutrients. [3] (c) Fig. 3.2 shows the structure of a villus. A B Fig. 3.2 (i) Name the structures labelled A and B. A B [2] (ii) Describe the role of villi in the human alimentary canal. [3]

8 © UCLES 2012 0654/33/M/J/12 For Examiner's Use 4 (a) A car tyre is inflated using a footpump. The mechanic using the footpump notices that the pump gets hot. (i) Explain how the air molecules in the tyre exert a pressure on the wall of the tyre. [2] (ii) The air going into the tyre is warmed up by the pumping. Describe what happens to the motion of the air molecules as the air warms up. [1] (iii) When the air in the tyre becomes hotter, the pressure rises. Explain in terms of the motion of the air molecules why the pressure rises. [2] (b) Car brake lights (stop lights) light up when the driver presses on the footbrake pedal. The pedal acts as a switch. Draw a circuit diagram including a battery to show how this works. Design your circuit so that if one brake light fails, the other still lights up. [2]

9 © UCLES 2012 0654/33/M/J/12 [Turn over For Examiner's Use (c) A car which is moving has kinetic energy. The faster a car goes, the more kinetic energy it has. The kinetic energy of the car is 1 120 000 J when the car is travelling at 40 m / s. Calculate the mass of the car. State the formula that you use and show your working. formula used working [2] (d) A driver is accompanied by four other passengers and their heavy luggage. Explain how the addition of the passengers and luggage affects the braking of the car compared to when the driver is alone in the car. [2] (e) A car is moving along a road. The mass of the car is 1200 kg and the resultant force acting on it is 1500 N. Calculate the acceleration of the car. State the formula that you use and show your working. formula used working [2]

10 © UCLES 2012 0654/33/M/J/12 For Examiner's Use 5 In hydrocarbons, carbon atoms are joined in chains of various lengths. Table 5.1 shows information about some hydrocarbons. Table 5.1 alkanes molecular structure boiling point / °C C H C C C H H H C H H H H H H H H 36 C H C C H H H C H H H H H H 0 C H C H H H C H H H H –42 C H H H H C H H –87 alkenes molecular structure boiling point / °C 30 –6 –47 C H C H H C H H H C H C C H H C H H H H H C H C C C H H C H H H H H H H C H H C H H –104 (a) Table 5.1 contains examples of both saturated and unsaturated hydrocarbons. (i) State how the bonding in an unsaturated hydrocarbon molecule differs from that in a saturated hydrocarbon molecule. [1] (ii) Describe a chemical test that is used to show whether a hydrocarbon is saturated or unsaturated. [2]

11 © UCLES 2012 0654/33/M/J/12 [Turn over For Examiner's Use (b) The alkanes in Table 5.1 occur naturally in deposits of petroleum (crude oil) and natural gas. Petroleum is brought to an oil refinery where the mixture of alkanes is separated into simpler mixtures by fractional distillation. Some of the simpler mixtures are processed further to produce alkenes. (i) Fractional distillation relies on differences in the boiling points of hydrocarbons. State two trends shown in the boiling points of the alkanes and alkenes in Table 5.1. trend 1 trend 2 [2] (ii) Explain, in terms of forces between molecules, the trend in the boiling points of the alkanes in Table 5.1. [2]

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13 © UCLES 2012 0654/33/M/J/12 [Turn over For Examiner's Use 6 (a) Describe how sex is inherited in mammals. [2] Hawksbill turtles are an endangered species. Adults spend most of their lives at sea, but the females come ashore to lay their eggs. They bury their eggs in nests in the sand, either on a beach or in the vegetation that grows just behind the beach. sand sea Unlike mammals, the sex of hawksbill turtles is determined by the temperature of the sand in which the eggs develop. • At 29 °C, equal numbers of males and females develop. • Higher temperatures produce more females. • Lower temperatures produce more males. There is concern that in recent years too many female turtles have been produced, and not enough males.

14 © UCLES 2012 0654/33/M/J/12 For Examiner's Use (b) Researchers measured the temperature, at a depth of 30 cm, in four different parts of a beach, on Antigua, where hawksbill turtles lay their eggs. The results are shown in Fig. 6.1. The tops of the bars represent the mean temperatures. 30.0 29.0 28.0 27.0 open sand low vegetation part of beach edge of forest forest mean temperature / °C Fig. 6.1 With reference to Fig. 6.1, describe the effect of the presence of trees on the temperature of the sand. [2] (c) The researchers counted the proportion of male and female turtles hatching from nests in the four different parts of the beach. The results are shown in Table 6.1. Table 6.1 part of beach nests producing more males than females nests producing more females than males nests producing equal numbers of females and males open sand 0 16 0 low vegetation 31 24 6 edge of forest 61 0 11 in forest 36 0 0

15 © UCLES 2012 0654/33/M/J/12 [Turn over For Examiner's Use (i) State the part of the beach in which most female hawksbill turtles chose to lay their eggs. [1] (ii) Use the information in Fig. 6.1 to explain the results shown in Table 6.1. [2] (d) Tourism is an important industry in Antigua. The vegetation on many beaches has been cut down to make the beaches more attractive to tourists. With reference to the results of this research, suggest how deforestation of beaches could affect hawksbill turtle populations. [2] (e) Describe two harmful effects to the environment, other than extinction of species, that may result from deforestation. 1 2 [4]

16 © UCLES 2012 0654/33/M/J/12 For Examiner's Use 7 (a) The isotope radon-220 is radioactive. A sample was investigated to find its half-life. The activity of the isotope was measured every minute for 6 minutes. The results are shown in Fig. 7.1. Fig. 7.1 (i) Use Fig. 7.1 to calculate the half-life of the isotope. Show your working on the graph. [2] (ii) Describe the differences in the structure of the nucleus of a radon-220 atom before and after the emission of an alpha particle. [2] 0 50 100 150 200 250 300 350 48 000 44 000 40 000 36 000 32 000 28 000 24 000 20 000 16 000 12 000 8000 4000 0 activity / counts per s time / s

17 © UCLES 2012 0654/33/M/J/12 [Turn over For Examiner's Use (iii) Explain why alpha radiation is affected by an electric field. [2] (b) The three types of nuclear radiation are alpha, beta and gamma. They can be identified by their different penetrating powers. Alpha radiation cannot penetrate paper. (i) Explain how you could identify beta and gamma radiations by their penetrating powers. beta radiation gamma radiation [2] (ii) Explain how radiation ionises an atom to make a positive ion. [1] (c) Gamma radiation is an electromagnetic wave with a short wavelength. Explain the meaning of the term wavelength. You may draw a diagram if it helps you to answer this question. [2]

18 © UCLES 2012 0654/33/M/J/12 For Examiner's Use 8 (a) Water is a compound which contains the elements hydrogen and oxygen. Describe one difference, other than physical state, between the compound water and a mixture of the elements hydrogen and oxygen. [2] (b) Table 8.1 shows information about water and three compounds that can form mixtures with water. Table 8.1 compound melting point / °C boiling point / °C solubility in water water 0 100 – sodium chloride 801 1413 soluble silicon dioxide 1650 2230 insoluble hexane –95 69 insoluble (i) State which compound in Table 8.1 could be separated from a mixture with water by filtration. [1] (ii) Explain why the other two compounds cannot be separated from a mixture with water by filtration. [2]

19 © UCLES 2012 0654/33/M/J/12 [Turn over For Examiner's Use (iii) A student looked at a magnified image of some sodium chloride crystals through a microscope. sodium chloride crystals Fig. 8.1 shows what she observed through the microscope. sodium chloride crystals Fig. 8.1 Draw a simple diagram of the structure of sodium chloride. Your diagram should clearly show the nature and arrangement of the particles involved and should show why the crystals have the shape shown in Fig. 8.1. [3]

20 © UCLES 2012 0654/33/M/J/12 For Examiner's Use (c) The student is asked to use the reaction between the insoluble compound copper carbonate and dilute sulfuric acid to make some crystals of copper sulfate. Describe the main steps of a method the student should use to carry out this task. You may draw labelled diagrams if it helps you to answer this question. [4]

21 © UCLES 2012 0654/33/M/J/12 [Turn over For Examiner's Use 9 Fig. 9.1 is a photograph of a cross-section of a leaf, taken through a microscope. Fig. 9.1 (a) On Fig. 9.1, use a label line to label a palisade cell. [1] (b) There are small gaps in the lower surface of the leaf, called stomata. Explain the role of stomata in photosynthesis. [2] (c) If a plant is deficient in magnesium, its leaves lose their green colour. (i) On Fig. 9.1, use a label line and the letter A to indicate a part of the leaf that would lose its green colour. [1] (ii) Explain why the part you have labelled would lose its green colour. [2]

22 © UCLES 2012 0654/33/M/J/12 For Examiner's Use 10 (a) Radio waves are electromagnetic waves. Sound waves are not. State three other ways in which radio waves differ from sound waves. 1 2 3 [2] (b) Visible light is another type of electromagnetic wave. The frequency of green light is 5 x 1014 Hz. The wavelength of green light is 6 x 10-7 m. Calculate the speed of green light. State the formula that you use and show your working. formula used working [2]

23 © UCLES 2012 0654/33/M/J/12 [Turn over For Examiner's Use (c) A thin beam of white light is shone onto two glass blocks. On Fig. 10.1, complete the diagrams to show what happens to the light passing through each block and after it emerges from the block. rectangular block triangular block (prism) Fig. 10.1 [4]

24 © UCLES 2012 0654/33/M/J/12 For Examiner's Use (d) A student carried out an experiment to find the speed of sound in air by watching and listening to a bell being rung. He stood 500 m from the bell. bell tower student 500 m The sound took 1.5 s to travel from the bell to the student. Calculate the speed of sound. State the formula used and show your working. formula used working [2]

25 © UCLES 2012 0654/33/M/J/12 [Turn over For Examiner's Use 11 Fig. 11.1 shows apparatus a student used to investigate temperature changes that occurred during chemical reactions. insulated beaker thermometer reaction mixture Fig. 11.1 The student added reactants to the insulated beaker and stirred the mixture. She recorded the final temperature of each mixture. At the start of each experiment, the temperature of the reactants was 22 °C. Table 11.1 contains the results the student obtained. Table 11.1 experiment reactant A reactant B final temperature / °C 1 dilute hydrochloric acid sodium hydrogencarbonate 16 2 dilute hydrochloric acid potassium hydroxide solution 26 3 magnesium copper sulfate solution 43 4 copper magnesium sulfate solution 22 (a) (i) Explain which experiment, 1, 2, 3 or 4, was a reaction involving an alkali. experiment explanation [1] (ii) State and explain which experiment, 1, 2, 3 or 4, was an endothermic reaction. experiment explanation [1]

26 © UCLES 2012 0654/33/M/J/12 For Examiner's Use (iii) Suggest and explain a reason for the result obtained in experiment 4. [2] (b) The student carried out two further experiments, 5 and 6, to investigate the reaction between zinc and copper sulfate solution. In experiment 5 the student used 3.25 g of zinc powder, and in experiment 6 she used a single piece of zinc which also had a mass of 3.25 g. The student observed the readings on the thermometer over five minutes during each experiment. Predict and explain any difference in the way that the temperature would change between experiments 5 and 6. [3] (c) In the reaction in (b), zinc atoms react with copper ions. This chemical change may be represented by the symbolic equation below. Zn (s) + Cu2+ (aq) → Zn2+ (aq) + Cu (s) Explain, in terms of the transfer of electrons, why this reaction is an example of oxidation and reduction (redox). [1]

27 © UCLES 2012 0654/33/M/J/12 For Examiner's Use (d) In both of the experiments in (b) the solution at the start of the experiment contained 0.08 moles of copper ions, and the zinc had a mass of 3.25 g. (i) Calculate the number of moles of zinc that are contained in 3.25 g. The relative atomic mass (Ar) of zinc is 65. Show your working. [1] (ii) Use your answer to (i) and the equation in (c) to explain whether or not the amount of copper ions is sufficient to react with all of the zinc. [2] 12 (a) Define the term respiration. [2] (b) (i) State the word equation for anaerobic respiration in yeast. [1] (ii) Describe how anaerobic respiration in yeast is used in bread-making. [3]

28 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 0654/33/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 0654/33 Paper 3 (Extended 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 33 © University of Cambridge International Examinations 2012 1 (a) (i) argentite and galena (or formula or chemical name) ; [1] (ii) scheelite (or formula or chemical name) ; [1] (b) (i) germanium ; four outer electrons so in Group IV ; four shells so in fourth period ; [3] (ii) (does not have to be dots and crosses) at least one shared pair of electrons ; four shared pairs giving QH4 ; no extraneous electrons ; [3] (iii) QO2 + 2H2 → Q + 2H2O ;; [2] (balanced marked dependent on correct formulae) [Total: 10] 2 (a) coil / wire is moving in magnetic field / changing magnetic field / cuts lines of magnetic force ; e.m.f/voltage/current is, induced / produced (to light lamp) ; brushes / slip rings, form electrical connection ; stop connecting wires getting twisted ; [4] (b) heat absorbed from athlete’s body / heat transferred from body to sweat some molecules move faster than others / (kinetic) energy of the water molecules increases ; more energetic / faster molecules escape / leave the surface / break bonds / forces of attraction ; (average) energy (remaining) particles goes down ; [max 2] [Total: 6]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0654 33 © University of Cambridge International Examinations 2012 3 (a) (i) greatest activity / optimum pH at pH 6.5 / between 6 and 7 ; no activity, at / below, pH 4 AND at / above, pH 9 ; [2] (ii) pH changes the shape of the enzyme (molecule) ; changes shape of active site ; so substrate can no longer fit into it ; [max 2] (iii) curve of similar shape with peak at pH 4 or below ; [1] (iv) sodium hydrogencarbonate neutralises / reacts with the acid ; so pH rises (above optimum for enzyme) ; [2] (b) break down / digest, proteins ; to amino acids ; (amino acids) can be absorbed / can be taken into the blood / can pass through the wall of the gut / diffuse into cells ; [3] (c) (i) A capillary ; B lacteal ; [2] (ii) increase surface area ; in the small intestine / duodenum / ileum ; for absorption ; amino acids / glucose, absorbed into capillaries ; fats / fatty acids / glycerol, absorbed into lacteal ; [max 3] [Total: 15] 4 (a) (i) molecules collide with tyre wall ; force exerted causing pressure ; [2] (ii) they move faster / have more kinetic energy ; [1] (iii) particles collide with wall more often ; collisions, are harder / faster / have more energy ; [2] (b) symbols correct and all complete in complete circuit ; lamps in parallel and switch operates both lamps ; e.g. [2]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0654 33 © University of Cambridge International Examinations 2012 (c) KE = ½ mv2 OR (m) = 2 × KE / v2 ; m = (2 × 1 120 000) / (40 × 40) = 1400 kg ; [2] (d) mass increases so KE / momentum increases ; greater force needed (to reduce momentum) / longer braking time / distance needed (to reduce KE) ; (accept reverse arguments) [2] (e) force = mass × acceleration ; acceleration = 1500 / 1200 = 1.25 m / s2 ; [2] [Total: 13] 5 (a) (i) unsaturated molecule contains double / multiple bond OR saturated has only single bonds ; [1] (ii) add bromine (solution) ; if unsaturated colour changes from orange to colourless ; [2] (allow potassium manganate(VII) purple to colourless) (b) (i) as molecular size / number of C atoms / chain length / mass increases boiling point increases ; alkenes have lower boiling points than similar sized alkanes ; [2] (ii) (as molecular size / surface area increases) intermolecular / (attractive) forces between molecules increase ; so more (heat) energy needed to separate molecules / break forces/bonds ; [2] (accept reverse argument) [Total: 7] 6 (a) female is XX and male is XY ; each egg contains an X chromosome and each sperm contains either X or Y ; [2] (b) trees reduce the temperature / more trees lower temperature ; reference to figures from the graph / quantitative comparison ; [2] (c) (i) edge of forest ; [1] (ii) open sand is hotter so produced more females / OR in forest lower so produced more males ; reference to above or below 29 °C ; low vegetation is very close to 29 °C and so produced approximately equal males and females ; [max 2]

Page 5 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0654 33 © University of Cambridge International Examinations 2012 (d) deforestation will result in hotter sand / more open sand / more hot sand ; so more female turtles / fewer males produced ; which might make breeding difficult / might reduce number of young born or might increase number of eggs laid ; [max 2] (e) more carbon dioxide in the atmosphere / less absorption of carbon dioxide ; reference to global warming / effects of global warming / climate change / increase reaction between CO2 and seawater making it more acidic ; less oxygen in the atmosphere ; reference to possible harmful effects relating to respiration / less to breathe ; fewer roots to hold soil in place / fewer leaves to protect from rain ; more erosion / risk of landslide ; fewer trees to absorb rain water ; more flooding ; (any two pairs) [max 4] [Total: 13] 7 (a) (i) working ; 55 (± 2) s ; [2] (ii) contains two fewer protons and two fewer neutrons ; changed to, polonium / atom with 84 protons (in nucleus) ; [2] (iii) alpha particles contain 2 protons but no electrons ; therefore positively charged ; [2] (b) (i) beta radiation passes through paper / thin aluminium but is stopped by thick aluminium or (thin) lead ; gamma radiation able to pass through aluminium and thin lead / only stopped by thick lead / concrete; [2] (ii) the electrons are knocked out of / removed / lost from the atom ; [1] (c) distance between two waves ; distance between identical points on two successive waves ; [2] (or shown on diagram) [Total: 11]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0654 33 © University of Cambridge International Examinations 2012 8 (a) in water (molecules) hydrogen (atoms) are bonded to oxygen (atoms) ; in the mixture only like atoms are bonded ; in water the H:O ratio is 2:1 / formula is H2O ; in the mixture no fixed ratio ; water unreactive / puts out flame ; mixture burns / will react ; a mixture can be separated by physical means ; a compound can only be separated by chemical means ; a compound contains different elements that are chemically bonded / combined ; a mixture means two different substances that are not combined / chemically bonded ; the compound water is formed by chemical reaction ; the mixture of the elements hydrogen and oxygen is not formed by chemical reaction ; [max 2] (any one pair for 2 marks but needs statement about compound and mixture) (b) (i) silicon dioxide ; [1] (ii) sodium chloride forms solution (so all passes through the filter) ; hexane is (also) a liquid (at room temperature) and (so also passes through filter) ; [2] (iii) ions / charged particles shown alternating ; sodium and chloride correctly labelled ; reasonable square shape ; [3] (c) mix carbonate with acid ; keep adding carbonate until no more dissolves / reacts ; filter (and keep filtrate) ; (warm the filtrate) to evaporate (some) (water) ; [4] [Total: 12]

Page 7 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0654 33 © University of Cambridge International Examinations 2012 9 (a) label line to palisade cell ; [1] (b) allow carbon dioxide to enter (the leaf) ; allow oxygen to leave ; by diffusion ; [max 2] (c) (i) label line to any cell within mesophyll layers (not vein or air space) ; [1] (ii) magnesium needed to make / for chlorophyll / is in chlorophyll ; chlorophyll is green / labelled part contains chloroplasts ; [2] [Total: 6] 10 (a) transverse / longitudinal ; radio higher frequency ; radio has higher range of frequency ; different speed ; radio travels further ; radio can travel in a vacuum / sound cannot / needs a medium ; (2 marks for all three, 1 mark for one or two correct) [max 2] (b) v = f × λ ; = 6 × 10–7 × 5 × 1014 = 3 × 108 m / s ; [2] (c) rectangular block refraction towards normal on entry ; and refraction away from normal on leaving ; triangular block correct refraction and / or dispersion on entry ; correct refraction and / or dispersion on leaving ; [4] (d) speed = distance / time ; = 500 / 1.5 = 333 m / s ; [2] [Total: 10]

Page 8 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0654 33 © University of Cambridge International Examinations 2012 11 (a) (i) (expt. 2) potassium hydroxide is an alkali / contains hydroxide (ions) ; [1] (ii) (expt. 1) temperature decreased ; [1] (iii) no reaction occurred ; so there was no change in temperature / no energy was transferred ; copper is less reactive than magnesium (so no reaction) ; (accept reverse argument) [max 2] (b) in expt. 5 the temperature increased more quickly (than expt. 6) ; because the rate of reaction was greater / collisions more frequent ; so energy was transferred more quickly ; because powder has greater surface area ; [max 3] (c) reference to electron loss as oxidation / gain as reduction ; [1] (d) (i) 3.25 ÷ 65 = 0.05 ; [1] (ii) (copper is in excess) idea of 1:1 reacting ratio of Zn:Cu ; and greater number of moles of copper than zinc ; [2] [Total: 11] 12 (a) (chemical reactions that) break down glucose (molecules) / glucose reacts with oxygen ; to release energy ; [2] (b) (i) glucose → alcohol / ethanol + carbon dioxide ; [1] (ii) makes dough / bread rise ; yeast uses sugars (from flour) ; yeast produces carbon dioxide ; (carbon dioxide) trapped in the dough ; [max 3] [Total: 6]