Cambridge IGCSE Science - Combined 0653 — 2018 Oct/Nov Paper 3 · Variant 2

1 (a) The boxes in Fig. 1.1 contain the names of cells, diagrams of these cells, and their functions. Draw straight lines to connect each named cell with its correct diagram and function. One is done for you. diagram (not to scale) name of cell function carries out palisade cell photosynthesis red blood defends against cell disease root hair cell male gamete sperm cell transports oxygen white blood water uptake cell [4] Fig. 1.1 (b) One of the cells is shown in Fig. 1.2. Fig. 1.2 The actual diameter of the cell is 0.0070 mm. Calculate the magnification shown by the diagram. magnification = ...........................................................[2] (c) The list shows some substances that are found in living organisms. amino acids bile carbon dioxide enamel glycogen platelets starch Draw a circle around three substances which are transported by the blood plasma. [2] (d) (i) Describe the importance of chemical digestion in the body. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... .......................................................................................................................................[3] (ii) State one organ of the body which produces digestive enzymes. .......................................................................................................................................[1]

Mark scheme: 1(a) palisade cell carries out photosynthesis red blood cell defends against disease root hair cell male gamete sperm cell transports oxygen white blood cell water uptake 1 mark for each correct diagram / name / function ;;;; 4 1(b) diameter of red blood cell = 21 mm ; magnification = 21 / 0.007 = 3000 (times) ; 2 1(c) amino acid ; carbon dioxide ; platelets ; All 3 correct = 2 2 or 1 correct = 1 2 Question Answer Marks 1(d)(i) breaks down ; large / insoluble molecules ; into small / soluble molecules ; that can be absorbed ; Max 3 3 1(d)(ii) salivary glands / stomach / pancreas / ileum / small intestine ; 1

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2 (a) A student makes a salt using the apparatus shown in Fig. 2.1. process A process B powdered metal carbonate dilute sulfuric acid gentle heat Fig. 2.1 (i) Name process A and process B. process A .......................................................................................................................... process B .......................................................................................................................... [2] (ii) The student uses 1 g of the powdered metal carbonate. Describe the effect of using a single 1 g piece of the metal carbonate on the rate of this reaction. .......................................................................................................................................[1] (iii) Describe the effect of using the same volume of a more concentrated sulfuric acid on the rate of this reaction. .......................................................................................................................................[1] (iv) When the metal carbonate is mixed with dilute sulfuric acid, the temperature increases. State the name given to chemical reactions that cause the temperature to increase. .......................................................................................................................................[1] (b) The student mixes copper carbonate with dilute sulfuric acid. Copper(II) sulfate and a colourless gas and a colourless liquid are formed. (i) Complete the word equation for this reaction. copper + + +carbonate [2] (ii) Describe a test for aqueous copper(II) ions. State the observations that show copper(II) ions are present. test .................................................................................................................................... observations ...................................................................................................................... ........................................................................................................................................... [2] (iii) Copper is a transition metal. It forms coloured compounds. Describe one other property of a transition metal. .......................................................................................................................................[1]

Mark scheme: 2(a)(i) (process A) filtration / filtering / filter ; (process B) evaporation ; 2 2(a)(ii) decreases ; 1 2(a)(iii) increases ; 1 2(a)(iv) exothermic ; 1 2(b)(i) (copper carbonate) + sulfuric acid Î copper sulfate + carbon dioxide + water sulfuric acid LHS AND copper sulfate RHS ; carbon dioxide AND water RHS ; 2 2(b)(ii) (test) (add) aqueous sodium hydroxide OR aqueous ammonia ; (observations) (light) blue precipitate OR blue ppt (then deep blue solution) ; 2 2(b)(iii) high density / high melting point / (element or compound) act as catalysts ; 1

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3 Fig. 3.1 shows a farm tractor pulling a trailer. Fig. 3.1 (a) The tractor and trailer are moving across a level field. Fig. 3.2 shows the four forces W, X, Y and Z acting on the trailer. X Y W Z Fig. 3.2 (i) State the letter corresponding to the gravitational force acting on the trailer. ........................................... [1] (ii) The tractor and trailer are moving at a constant speed. Force W has a value of 2000 N. State the value of force Y. Explain your answer. value of force Y = ......................... N explanation ........................................................................................................................ ........................................................................................................................................... [2] (b) The tractor leaves the trailer in the field and drives to the farmyard. Fig. 3.3 shows a speed–time graph of the tractor as it travels from the field to the farmyard. 4 3 speed 2 m / s 1 0 0 10 20 30 40 50 60 time / s Fig. 3.3 (i) On Fig 3.3, label with a letter C a point in the journey when the tractor is travelling with changing speed. [1] (ii) The tractor travels 200 m from the field to the farmyard. Use information from the graph to calculate the average speed of the tractor on this journey in m / s. Show your working. average speed = .................................................. m / s [2] (c) (i) The tractor is powered by a diesel engine, which burns diesel oil. Complete the energy transfer that occurs to move the tractor. .............................................. energy in the diesel oil .............................................. energy of the tractor. [2] (ii) State the original source of the energy stored in diesel oil. .......................................................................................................................................[1] (iii) To keep the tractor moving at constant speed for 30 s, an energy input of 300 000 J from diesel fuel is needed. Only 60 000 J is required to do the work against forces resisting the motion. Describe what happens to most of the wasted energy. ........................................................................................................................................... .......................................................................................................................................[1]

Mark scheme: 3(a)(i) Z 1 3(a)(ii) 2000 N ; constant speed / no acceleration, (so forces must balance) ; 2 3(b)(i) C on any point on graph line between 0 and 20 s, or between 50 and 60 s ; 1 3(b)(ii) (average) speed = (total) distance / (total) time ; = 200 / 60 = 3.3(3) (m / s) ; 2 3(c)(i) chemical ; kinetic ; 2 3(c)(ii) the Sun ; 1 3(c)(iii) converted / transformed into thermal energy ; 1

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4 (a) Fig. 4.1 shows a piece of potato in a solution of hydrogen peroxide. A reaction occurs and oxygen gas is produced. bubbles of oxygen gas hydrogen peroxide solution potato Fig. 4.1 The student thinks the reaction is caused by an enzyme in the potato. She repeats the experiment with potato that has been boiled first, and then allowed to cool. Predict what the student sees if an enzyme in the potato is responsible for the reaction. Explain your prediction. prediction .................................................................................................................................. explanation ............................................................................................................................... ................................................................................................................................................... [2] (b) A farmer has a field of potato plants near a river. Some untreated human sewage is spilled into the river. The river overflows and deposits some of the sewage onto the potato field. (i) Explain why the potatoes in the field are now unsafe to eat. ........................................................................................................................................... ........................................................................................................................................... .......................................................................................................................................[2] (ii) The concentration of oxygen in the river decreases after the sewage is spilled into the river. Suggest how this affects the animals living in the river. Explain your answer. ........................................................................................................................................... ........................................................................................................................................... .......................................................................................................................................[2]

Mark scheme: 4(a) no reaction ; the increased temperature / boiling has removed enzyme activity ; 2 4(b)(i) the water / river is polluted ; contains bacteria / viruses / microbes / pathogens ; that cause disease ; Max 2 2 4(b)(ii) animals / fish will die / move away ; due to suffocation / less oxygen for respiration ; 2

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5 (a) Natural gas and coal are fossil fuels. (i) Name one other fossil fuel. .......................................................................................................................................[1] (ii) Name the main constituent of natural gas. .......................................................................................................................................[1] (b) Ethane, C2H6, is an alkane. (i) Describe the chemical properties of alkanes. ........................................................................................................................................... .......................................................................................................................................[1] (ii) Complete the structure of a molecule of ethane. H C [2] (c) The atomic numbers and mass numbers of carbon and of hydrogen are shown in Table 5.1. Table 5.1 atomic number mass number carbon 6 12 hydrogen 1 1 (i) Define atomic number. ........................................................................................................................................... .......................................................................................................................................[1] (ii) Complete Table 5.2 to describe the particles in an atom. Table 5.2 particle position in atom relative charge relative mass electron –1 neutron in nucleus proton 1 [3]

Mark scheme: 5(a)(i) petroleum ; 1 5(a)(ii) methane ; 1 5(b)(i) unreactive / (only) burn / combust ; 1 5(b)(ii) C – C single bond ; All else correct ; 2 5(c)(i) number of protons (in an atom / nucleus) ; 1 5(c)(ii) 2 or 3 correct entries = 1 mark 4 or 5 correct entries = 2 marks All correct = 3 marks 3

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6 (a) (i) State one property that distinguishes a liquid from a solid. .......................................................................................................................................[1] (ii) Describe how this property is the result of the arrangement of molecules. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... .......................................................................................................................................[2] (b) When a liquid is heated, it expands. Name a measuring instrument that makes use of this property of liquids. ...............................................................................................................................................[1] (c) Fig. 6.1 shows a hot drink in a cup left to cool down. Fig. 6.1 The statements below describe ways in which the drink loses thermal energy as it cools. Put a tick (3) in the box alongside any correct statement. Put a cross (✗) in the box alongside any incorrect statement. conduction through the sides and base of the cup convection as air above the cup is heated and the warm air moves upwards ultraviolet radiation in all directions evaporation as the faster molecules escape from the surface of the liquid [2] (d) Astronomers use telescopes to study stars. Stars are extremely hot bodies that lose energy by emitting electromagnetic radiation into space. (i) Explain why stars can only lose energy by radiation, and not by conduction or convection. ........................................................................................................................................... ........................................................................................................................................... .......................................................................................................................................[1] (ii) Some stars can emit gamma radiation. Fig. 6.2 shows an incomplete electromagnetic spectrum. On Fig. 6.2 place gamma radiation in the correct box. ultra-violet infra-red microwaves Fig. 6.2 [1] (iii) Some telescopes use converging lenses. Light from a distant star arrives at a telescope as a beam of parallel rays. On Fig. 6.3 complete the ray diagram to show how a clear image of the star is formed on the screen by a converging lens. light from star screen converging lens Fig. 6.3 [1] (iv) On your ray diagram in Fig. 6.3, mark and label the focal length of the lens. [1]

Mark scheme: 6(a)(i) able to flow / takes up the shape of container / any appropriate property ; 1 6(a)(ii) (liquid) irregular / random arrangement ; molecules can move around one another ; molecules further apart ; (solid) regular / lattice arrangement ; molecules vibrate around fixed positions ; molecules tightly packed / closer together ; Max 2 2 6(b) thermometer ; 1 6(c) ticks in first, second and fourth boxes ; cross in 3rd box ; 2 6(d)(i) conduction and convection require a medium 1 6(d)(ii) gamma in left-hand end box ; 1 6(d)(iii) all three rays refracted to meet the screen at the same point ; 1 6(d)(iv) focal length correctly indicated as on above diagram ; 1

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7 (a) Fig. 7.1 shows cross-sections through a root and a stem of a flowering plant. A B Fig. 7.1 (i) State which diagram, A or B, represents the root. Give two reasons for your answer. The root is diagram ................................... reason 1 ............................................................................................................................ ........................................................................................................................................... reason 2 ............................................................................................................................ ........................................................................................................................................... [2] (ii) On diagram B, in Fig. 7.1, shade in one area where the xylem is found. [1] (b) Use the words or phrases to complete the sentences about transpiration. Each word may be used once, more than once or not at all. cuticle diffuses dissolves guard cells higher lower mesophyll cells stomata similar xylem Water evaporates from the surfaces of ........................................... inside the leaf. This gives the air inside the leaf a ........................................... concentration of water vapour than the atmosphere. As a result the water vapour ........................................... out of the leaves through tiny holes called the ........................................... . [4] (c) Water is one of the raw materials for photosynthesis. Complete the word equation for photosynthesis. water + + [2]

Mark scheme: 7(a)(i) A no mark presence of root hairs ; xylem / phloem / vascular tissue (stele) found in the central area ; 2 7(a)(ii) one area of xylem correctly shaded in B ; 1 7(b) mesophyll cells ; higher ; diffuses ; stomata ; 4 7(c) carbon dioxide ; sugar / glucose + oxygen ; 2

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8 (a) A teacher uses the apparatus shown in Fig. 8.1 to demonstrate the electrolysis of lead(II) bromide. low voltage d.c. supply solid lead(II) bromide Fig. 8.1 Predict whether this electrolysis works. Explain your answer. prediction .................................................................................................................................. explanation ............................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... [1] (b) A student electrolyses aqueous copper chloride using the apparatus shown in Fig. 8.2. low voltage d.c. supply aqueous copper chloride Fig. 8.2 Copper forms on the negative electrode. A gas forms at the positive electrode. The student tests this gas with damp litmus paper. Name the gas and predict its effect on the colour of the litmus paper. name ......................................................................................................................................... effect ......................................................................................................................................... [2] (c) Copper can be extracted by heating copper oxide with carbon. The equation for this reaction is: copper oxide + carbon carbon dioxide + copper Identify one substance which is oxidised and one substance which is reduced during this reaction. oxidised .................................................................................................................................... reduced ..................................................................................................................................... [2] (d) Carbon dioxide is present in clean air in small quantities. (i) Name one other gas which is present in clean air in small quantities. .......................................................................................................................................[1] (ii) Name two substances present in clean air which cause rusting. 1. ....................................................................................................................................... 2. ....................................................................................................................................... [1]

Mark scheme: 8(a) (prediction) no reaction AND (explanation) lead bromide is solid / needs to be molten / liquid ; 1 8(b) (name) chlorine ; (effect) bleaches / (turns) white / decolourises ; 2 8(c) (oxidised) carbon ; (reduced) copper oxide ; 2 8(d)(i) water (vapour) / noble gas / named noble gas ; 1 8(d)(ii) oxygen / O2 AND water (vapour) / H2O ; 1

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9 Fig. 9.1 shows a circuit diagram for an investigation of how the resistance of a lamp changes with the current in the lamp. V A Fig. 9.1 (a) Name the circuit component with the symbol ...............................................................................................................................................[1] (b) Table 9.1 shows some results from the investigation. Table 9.1 experiment voltmeter ammeter resistance of number reading / V reading / A lamp / Ω 1 6.0 0.54 11 2 4.0 0.46 8.7 3 3.0 0.40 4 2.0 0.32 6.3 (i) Complete Table 9.1 by calculating the missing resistance value. State the formula you use and show your working. formula working [2] (ii) Suggest what happens to the lamp as the experiments are carried out in turn from experiment 1 to experiment 4. .......................................................................................................................................[1] (c) (i) On Fig. 9.1 add a second identical lamp in parallel with the first lamp. [1] (ii) Experiment 1 is now repeated with the second lamp in the circuit in parallel with the first lamp. Suggest how the ammeter reading will compare with the reading in the original experiment 1. Give a reason for your answer. effect on ammeter reading ................................................................................................ reason ............................................................................................................................... ........................................................................................................................................... [2]

Mark scheme: 9(a) variable resistor ; 9(b)(i) R = V / I = 3.0 / 0.40 ; = 7.5 (Ω) ; 2 9(b)(ii) Brightness changes / resistance decreases ; 1 9(c)(i) lamp in parallel ; 1 9(c)(ii) higher (current) reading ; combined resistance of two resistances in parallel is less than either of the two resistances ; 2

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