Cambridge IGCSE Physics 0625 — 2025 Feb/March Paper 5 · Variant 2

1 In this experiment, you will investigate the behaviour of a spring and use it to determine the mass of an object. A stand and spring have been set up for you. Refer to Fig. 1.1. (a) Suspend a mass m = 100 g from the spring as shown in Fig. 1.1. clamp spring l mass m Fig. 1.1 Measure, and record in Table 1.1, the stretched length l of the spring, as indicated in Fig. 1.1. Repeat this step for values of m = 200 g, m = 300 g, m = 400 g and m = 500 g. Remove the mass m from the spring. Table 1.1 m / g l / cm 100 200 300 400 500 [2] (b) Describe a technique you used when measuring the length of the spring, to ensure an accurate reading. You may draw a diagram. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1] (c) Plot a graph of l / cm (y-axis) against m / g (x-axis). Start the axes from the origin (0, 0). Draw a best-fit straight line. The line might not go through the origin. 0 0 [4] (d) Use the graph to determine the length l of the spring with no load on it. 0 l = .................................................... cm [1] 0 (e) Suspend object X from the spring and measure the stretched length l of the spring. X l = .......................................................... cm X Use the graph and your value of l , to determine the mass of object X. X mX Show clearly on the graph how you obtained your answer. mX = ............................................................ g [2] (f) Two students measure the mass of another object using the same method and apparatus. One student records the mass as 132.6 g. The other student records the mass as 130 g. State and explain which answer has the more suitable number of significant figures for this experiment. statement .................................................................................................................................. explanation ............................................................................................................................... ................................................................................................................................................... [1] [Total: 11]

Mark scheme: Question Answer Marks 1(a) 5 readings of l, values increasing 1 all to nearest mm 1 1(b) One technique from: 1 reading viewed perpendicularly; ruler close to spring; use of set-square described; use of horizontal marker 1(c) graph: 1 • axes correct way round and labelled with quantity and unit • appropriate scales (plots occupying at least ½ grid) 1 • plots all correct to ½ small square and precise plots 1 • well-judged line and thin line 1 1(d) correct reading of intercept with length axis 1 1(e) lX present and lines / mark on graph to show how value used to find mX 1 mX in range 295 g to 365 g 1 1(f) 130 is more suitable 1 AND data values in table to less significant figures than other answer / reference to precision of apparatus

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2 In this experiment, you will investigate the effect of insulation on the cooling of water. Refer to Fig. 2.1. Beaker A is covered with material that is a thermal insulator. Beaker B is identical to beaker A but has no insulation. clamp thermometer beaker A beaker B bench insulation Fig. 2.1 (a) • Pour 200 cm3 of hot water into beaker A. • Place the thermometer in the water. • In the first row of Table 2.1, record the temperature θ of the water at time t = 0 and immediately start the stop-watch. • Record, in Table 2.1, the temperature θ of the water at times t = 30 s, t = 60 s, t = 90 s, t = 120 s, t = 150 s and t = 180 s. [1] Remove the thermometer from the beaker. (b) Repeat the procedure in (a) for beaker B. [2] Table 2.1 beaker A with insulation beaker B without insulation t / s θ / °C θ / °C 0 30 60 90 120 150 180 (c) Write a conclusion stating whether the insulation affects the rate of cooling of the water. Justify your answer by referring to values from your results. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (d) (i) Calculate the average cooling rate x1 during the first half of the experiment for the water in beaker B. Use your readings for beaker B from Table 2.1 and the equation: θ0 – θ90 x1 = T , where T = 90 s and θ0 and θ90 are the temperatures of the water in beaker B at times t = 0 and t = 90 s. Include the unit. x1 = .......................................................... [1] (ii) Calculate the average cooling rate x2 during the second half of the experiment for the water in beaker B. Use your readings for beaker B from Table 2.1 and the equation: θ90 – θ180 x2 = T where T = 90 s and θ90 and θ180 are the temperatures of the water in beaker B at times t = 90 s and t = 180 s. Include the unit. x2 = .......................................................... [1] (e) A student suggests that, for this type of experiment, the temperature of the water in each beaker at time t = 0 must be the same for the comparison to be fair. Use your answers from (d)(i) and (d)(ii) to explain whether this is necessary. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (f) (i) A student wants to eliminate, from the comparison, any thermal energy lost from the surface of the water. Suggest a change to the equipment which will do that. You are not required to carry out this additional experiment. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Suggest what effect this change will have on the cooling rates of the water in beaker A and beaker B. ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 11]

Mark scheme: 2(a) for beaker A decreasing 1 2(b) for beaker B decreasing 1 decreasing more quickly than A 1 2(c) beaker A / insulated beaker cools more slowly (owtte) 1 comparison of temperature changes over 180 s, matching statement (need to see values used in justification) 1 2(d)(i) x2 < x1 (from correct calculation) 1 2(d)(ii) units °C / s 1 2(e) comparison of their x1 and x2 1 yes / therefore beaker A and B must start at same temperature 1 AND so comparison only depends on insulation 2(f)(i) add lids to both beakers / add insulation all over both beakers / cover both beakers 1 2(f)(ii) both cooling rates decrease 1

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3 In this experiment, you will investigate the refraction of light by a transparent block. Use the separate ray-trace sheet provided. You may refer to Fig. 3.1 for guidance. hole E θ N A B 2 cm D C eye Fig. 3.1 (a) Place the transparent block approximately in the centre of the ray-trace sheet. Carefully draw round the block and label the corners A, B, C and D as indicated by Fig. 3.1. Remove the block from the ray-trace sheet. Draw a normal to line AB at a point N, 2 cm from A. Draw a line EN, as indicated by Fig. 3.1, 8 cm long and at an angle θ = 40° to the normal. [2] (b) Replace the block in exactly the same position as in (a). Place two pins P1 and P2 on line EN, a suitable distance apart for accurate ray tracing. Mark with crosses and label the positions of P1 and P2. View the images of P1 and P2 through the block, from the direction indicated by the eye in Fig. 3.1. Place two pins P3 and P4 so that pins P3 and P4 and the images of P1 and P2 all appear exactly one behind the other. Mark with crosses and label the positions of P3 and P4 . Remove the block and pins from the ray-trace sheet. Draw a line through P3 and P4 . Extend this line to meet line CD. Label the point at which this line meets CD with the letter F. Label the lower end of this line with the letter G. Extend line EN to approximately 5 cm below line CD. Label the point at which this line crosses CD with the letter H. Label the lower end of this line with the letter J. [2] (c) (i) Measure the acute angle α between lines CD and GF. An acute angle is an angle less than 90°. α = .......................................° Measure the acute angle β between lines CD and JH. β = .......................................° [1] (ii) A student suggests that angle α should be equal to angle β. State whether your results support this suggestion. Justify your answer by reference to values from your results. statement .......................................................................................................................... justification ........................................................................................................................ ........................................................................................................................................... [2] (d) Draw a new line EN, as indicated by Fig. 3.1, 8 cm long and at an angle θ = 20° to the normal. Repeat the steps in (b). [2] (e) Describe one technique to use in this type of experiment to ensure accurate results. ................................................................................................................................................... ............................................................................................................................................. [1] (f) Suggest one reason why different students, all doing this experiment carefully, may not obtain identical results. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 11] Write your name, centre number and candidate number on your ray-trace sheet. Tie your ray-trace sheet into this booklet between pages 8 and 9.

Mark scheme: 3(a) normal correct 1 = 40°1° 1 3(b) pin separation ⩾ 5.0 cm 1 1st set of lines present and in correct positions 1 3(c)(i) and = 50° 2° 1 3(c)(ii) statement matching results 1 justification matching statement (‘within limits of experimental accuracy’ / within 10% / close together owtte) 1 3(d) 2nd set of lines present and in correct positions 1 displacement between F and H less than in (b) 1 3(e) One valid technique e.g.: 1 draw thin lines / use sharp pencil; look at base of pins / keep pins vertical; use thin pins; ensure pins are as far apart as possible 3(f) difficult to align pins accurately owtte 1

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4 A student investigates the resistance of a wire. Plan an experiment which enables the student to investigate how the length of a wire affects the resistance of the wire. V Resistance R is calculated from the equation: R = I where V is the potential difference (p.d.) across the wire and I is the current in the wire. You are not required to do the experiment. The apparatus available includes: • a selection of wires • a variable power supply • an ammeter • a voltmeter. In your plan: • list any additional apparatus needed • complete Fig. 4.1 to show a voltmeter connected to measure the potential difference across the wire • explain briefly how to do the experiment, including the measurements to take so that the resistance can be determined • state the key variables to keep constant • draw a table, or tables, with column headings, to show how to display the readings (you are not required to enter any readings in the table) • explain how to use the readings to reach a conclusion. variable power supply A wire Fig. 4.1 .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. ............................................................................................................................................................ [7]

Mark scheme: 4 MP1 circuit diagram: 1 correct voltmeter circuit symbol shown in parallel with all or part of wire MP2 apparatus: 1 metre ruler MP3 method: 1 measure / record length; measure p.d. and current; specific reference to repeating with different length MP4 key / control variable: 1 constant diameter / radius / guage of wire; material of wire / same wire / same type of wire MP5 table: 1 columns, with units, for length, p.d., current, resistance MP6 analysis: 1 compare readings in the table to see if change in length produces change in resistance; plot resistance-length or length-resistance graph MP7 additional point (one from): 1 at least 5 sets of data taken; repeat for each length and take average; 2nd control variable: diameter / material / temperature of wire; use of protective resistor

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