Cambridge IGCSE Physics 0625 — 2017 Feb/March Paper 5 · Variant 2

1 In this experiment, you will investigate how the surrounding temperature affects the rate at which water cools. Carry out the following instructions, referring to Fig. 1.1. thermometer boiling tube beaker Fig. 1.1 (a) (i) • Pour 200 cm3 of cold water into the beaker. • Record the temperature θ1 of the water in the beaker. θ1 = ...........................................................[1] (ii) • Pour hot water into the boiling tube until it is about half full. Gently place the thermometer into the boiling tube. Place the boiling tube into the beaker of water. • Record, in the first row of Table 1.1, the temperature θ of the water in the boiling tube and immediately start the stopclock. • Record, in the table, the temperature θ of the water in the boiling tube at times t = 30 s, 60 s, 90 s, 120 s, 150 s and 180 s. Use the first and second columns. [1] (b) (i) • Carefully empty the boiling tube and the beaker. • Pour 150 cm3 of cold water and 50 cm3 of hot water into the beaker. • Record the temperature θ2 of the warm water in the beaker. θ2 = ............................................................... • Repeat the steps in (a)(ii), recording the temperature θ of the water in the boiling tube in the third column of the table. [1] (ii) Complete the heading and the time column in the table. [2] Table 1.1 tube in beaker with tube in beaker cold water with warm water t / θ / θ / (first row) 0 (c) Describe two precautions that you took to ensure that the temperature readings were as accurate as possible in the experiment. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ................................................................................................................................................... [2] (d) Write a conclusion stating how increasing the temperature of the surrounding water affects the rate of cooling of the water in the boiling tube. Justify your answer by reference to your results. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[2] (e) Suggest one change to the apparatus or procedure to ensure that the comparison of the effect of surrounding temperature on cooling is a fair test. Explain why the change is an improvement. change ...................................................................................................................................... ................................................................................................................................................... explanation ............................................................................................................................... ................................................................................................................................................... [2] [Total: 11] Question 2 begins on the next page.

Mark scheme: 1(a)(i) 1 1(a)(ii) θ decreasing and to at least 1 °C 1 1(b)(i) θ 2 > θ 1, θ for beaker B decreasing, more slowly than in (a) 1 1(b)(ii) units all correct (symbols or words) 1 t values all present (30, 60, 90, 120, 150 & 180) 1 1(c) any 2 appropriate precautions: stir before reading, keep thermometer at same level, set eye to same level as / perpendicular / right angles to scale, wait until reading stops rising (at start ), position clock so that thermometer and clock can be easily seen 2 1(d) conclusion matching results 1 correct mention of comparative temperature change over 180 s 1 1(e) any suitable improvement to apparatus or procedure relating to comparison, e.g.: • measure water into test-tube / beaker, • use same volume of water in test-tube / beaker, • use same starting temperatures in tubes, • ensure all water in tube below level of water in beaker, • use insulation / lid on beaker 1 matching explanation, e.g.: • ensure same amount of water being used each time, • cooling rates different / owtte at different volumes / temps, • all water in tube has same surrounding temperature, • keeps water in beaker at (more) constant temperature 1 Total: 11

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2 In this experiment, you will investigate the resistance of three wires X, Y and Z. The circuit has been set up for you. Carry out the following instructions, referring to Fig. 2.1. power supply A V crocodile clip X Y Z resistance wires Fig. 2.1 (a) (i) • Measure and record, in Table 2.1, the length l of resistance wire X. • Switch on. • Record, in the table, the potential difference V and the current I for wire X. • Switch off. • Disconnect both crocodile clips from X and connect them to the ends of wire Y. Record your measurements for l, V and I. • Take and record measurements for wire Z. Table 2.1 wire l / m V / V I / A R / Ω X Y Z [3] (ii) On Fig. 2.2, draw an arrow ( ) to indicate precisely between which two points you measured l . connecting lead resistance wire crocodile clip Fig. 2.2 [1] (b) Calculate, and record in the table, the resistance R of each wire. V Use the equation R = . I [2] R(c) (i) Calculate the resistance per unit length r of each wire using the equation r = . l r for wire X = ............................................................... r for wire Y = ............................................................... r for wire Z = ............................................................... [2] (ii) A student suggests that r should be the same for each wire. State whether your results support this suggestion. Justify your statement with reference to your results. statement .......................................................................................................................... justification ........................................................................................................................ ........................................................................................................................................... ........................................................................................................................................... [2] (d) One possible problem with this type of experiment is heating of the resistance wires. Suggest a precaution that could be taken to reduce this. ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[1] [Total: 11]

Mark scheme: 2(a)(i) 1 V all < 4.00 V and to 1dp at least 1 I all < 1.00 A and to 2dp at least 1 2(a)(ii) arrow on wire between the inside edge of each crocodile clip 1 2(b) correct calculations of R 1 consistent 2 or consistent 3 sig. figs. 1 2(c)(i) correct calculations of r 1 all within 10% 1 2(c)(ii) statement matching results 1 justification matching statement and results (‘within limits of experimental accuracy’ / owtte) 1 2(d) any suitable precaution: reduce current / voltage, use longer / thinner resistance wires, 1 Total: 11

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3 In this experiment, you will investigate the magnification produced by a converging lens. Carry out the following instructions, referring to Fig. 3.1. illuminated u triangle screen lens ho Fig. 3.1 (a) Measure the height ho of the illuminated triangle, as indicated in Fig. 3.1. ho = ...........................................................[1] (b) Arrange the apparatus as shown in Fig. 3.1. • Set the distance u between the illuminated triangle and the lens to 20.0 cm. • Place the screen near the lens. Move the screen until a sharp image of the triangle is formed on the screen. • Measure and record, in Table 3.1, the height hI of the image formed on the screen. • Repeat the procedure for values of u = 25.0 cm, 35.0 cm, 45.0 cm and 55.0 cm. Table 3.1 u / cm hI / cm M 20.0 25.0 35.0 45.0 55.0 [1] (c) Calculate and record, in Table 3.1, a value for the magnification M at each distance of u. Use your result from (a) and the equation hI M = . ho [1] (d) Plot a graph of M (y-axis) against u / cm (x-axis). [4] (e) From your graph, determine the value of u when M = 1.0. Show clearly on your graph how you obtained the information. u = ...........................................................[2] (f) Describe one difficulty that might be experienced when measuring the height of the image. Suggest one improvement to the apparatus to overcome this. difficulty ..................................................................................................................................... ................................................................................................................................................... improvement ............................................................................................................................. ................................................................................................................................................... [2] [Total: 11]

Mark scheme: 3(a) sensible value for hO (1.0 to 2.5 cm) 1 3(b) hI values all decreasing 1 3(c) M calculations correct 1 3(d) graph: axes labelled with quantity and unit 1 appropriate scales (plots occupying at least ½ grid) 1 plots all correct to within ½ small square 1 well judged line and single, continuous thin line 1 3(e) construction line(s) clearly seen on graph 1 u in range 25.0 to 35.0 (cm) 1 3(f) any appropriate difficulty: e.g. hand / ruler in way of image 1 matching improvement: e.g. use translucent screen and view from behind, fix ruler / grid to screen 1 Total: 11

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4 A student is investigating how the material of a spring affects its behaviour when stretched. The following apparatus is available to the student: wires of different thickness, length and material a set of 10 g masses and a set of 100 g masses, both with hangers a wooden rod approximately 1 cm in diameter other standard laboratory equipment. Plan an experiment which would enable you to test the stretch of springs made from different materials. You are not required to carry out the experiment. In your plan, you should include: • instructions for making a spring from the wire that is provided, • what you would measure, • instructions for carrying out the experiment, • the variables you would keep the same to ensure the comparison is a fair test, • any precaution which should be taken or difficulty which might occur, • how you would present your results. You may draw a diagram if it helps to explain your plan. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ......................................................................................................................................................[7] [Total: 7]

Mark scheme: 4 apparatus: MP1 springs made by winding wire around rod (or similar) 1 method: MP2 apply load, measure length / extension of spring 1 MP3 repeat for spring(s) of different material 1 MP4 record results in suitable annotated table / bar chart / graph 1 control variables: MP5 mark gained for any two of: unstretched length of spring, diameter of wire, coil spacing, load / range of loads used diameter of spring 1 MP6 precautions / difficulties / additional points: MP7 any two from: clamp retort stand / might topple, use small loads / spring might overstretch / spring too weak / use loads which don’t overstretch spring to support loads need to apply force smoothly / slowly, suggested range of loads, workable arrangement for applying load to spring (e.g. small loop at end of spring) trial experiment to find (range of) loads to use how to determine extension of spring, repeat each reading and take average, at least 5 loads for each sample if producing graph 2 Total: 7

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