Cambridge IGCSE Physics 0625 — 2025 Feb/March Paper 6 · Variant 2

1 A student investigates the behaviour of a spring, and then uses the spring to determine the mass of an object. The apparatus is shown in Fig. 1.1. clamp spring l mass m Fig. 1.1 (a) The student suspends a mass m = 100 g from the spring. She measures, and records in Table 1.1, the stretched length l of the spring, as indicated in Fig. 1.1. Describe two techniques for measuring the length of the spring, to ensure an accurate reading. You may draw a diagram. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ................................................................................................................................................... [2] (b) She repeats step (a) for values of m = 200 g, m = 300 g, m = 400 g and m = 500 g. Her readings are shown in Table 1.1. Table 1.1 m / g l / cm 100 6.0 200 9.2 300 13.6 400 16.8 500 21.0 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] (c) Use your graph to determine the length l of the spring with no load on it. 0 l = .................................................... cm [1] 0 l X object X Fig. 1.2 (d) An object X is suspended from the spring. (i) On Fig. 1.2, measure the stretched length l of the spring. X l = ......................................................... [1] X (ii) Use the graph and your reading from (d)(i), to determine the mass mX of object X. Show clearly on the graph how you obtained your answer. mX = .......................................................g [2] (e) 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) Two techniques from: 2 reading viewed perpendicularly; ruler close to spring; use of set-square / short ruler to measure length of spring; use of set-square to check ruler is vertical; use of horizontal marker. 1(b) 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(c) correct reading of intercept 1 1(d)(i) lx = 10.0 cm 1 1(d)(ii) lines / mark on graph to show how value used 1 mX in range 180 g to 240 g 1 1(e) 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 A student investigates the effect of insulation on the cooling of water. He uses the apparatus shown in 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 30 20 10 Fig. 2.1 (a) (i) Record room temperature θR shown on the thermometer in Fig. 2.1. θR = .......................................................... [1] (ii) Describe one technique used to ensure that the room temperature reading is as accurate as possible. ........................................................................................................................................... ..................................................................................................................................... [1] (b) The student pours 200 cm3 of hot water into beaker A and records the temperature θ at time t = 0. He records, in Table 2.1, the temperature of the water in the beaker every 30 s. The student repeats the procedure for beaker B. It is important that the temperatures are recorded at exactly every 30 s. Describe a technique which will make it easier for the student to do that. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1] Table 2.1 beaker A beaker B with insulation without insulation t / s θ / °C θ / °C 0 92.5 93.0 30 90.5 90.5 60 89.0 88.5 90 87.5 87.0 120 86.0 85.5 150 85.0 84.0 180 85.5 83.0 (c) Write a conclusion stating whether the insulation affects the rate of cooling of the water. Justify your answer by referring to values from the results. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (d) (i) Calculate the average cooling rate x1 during the first half of the experiment for the water in beaker B. Use the 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 the 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 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. ........................................................................................................................................... ..................................................................................................................................... [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)(i) R = 21(°C) 1 2(a)(ii) read scale perpendicularly 1 2(b) reference to how to take reading at precise time 1 e.g. have stop-watch and thermometer near each other; e.g. set a timer for every 30 s; e.g. one student watch timer & another student read thermometer 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) x1 = 0.067 and x2 = 0.044 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) cooling rates decrease 1

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3 A student investigates the refraction of light by a transparent block. The student’s ray-trace sheet is shown full-size in Fig. 3.1. E P1 P2 N A B D C P4 P3 Fig. 3.1 (a) The student places a transparent block ABCD near the centre of the ray-trace sheet as indicated in Fig. 3.1. (i) Draw a normal to point N, extending above AB. Label the upper end of the normal with the letter L. [1] (ii) The student draws line EN as shown in Fig. 3.1. On Fig. 3.1, measure the acute angle θ between the lines LN and EN. An acute angle is an angle of less than 90°. θ = ............................... [1] (b) The student places two pins P1 and P2 on line EN as shown in Fig. 3.1. (i) Measure distance d between pins P1 and P2 . d = ............................... cm [1] (ii) State whether the two pins are a suitable distance apart for accurate ray tracing. Explain your answer. statement .......................................................................................................................... explanation ........................................................................................................................ ..................................................................................................................................... [1] (c) The student views the images of P1 and P2 through the block. He places 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. Draw a line through P3 and P4 . Extend this line to meet 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. [1] (d) (i) Measure the acute angle α between lines CD and GF. 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] (e) Describe two techniques to use in this type of experiment to ensure results are accurate. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ................................................................................................................................................... [2] (f) Suggest one reason why different students, all doing this experiment carefully, may not obtain identical results. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 11]

Mark scheme: 3(a)(i) normal correct 1 3(a)(ii) = 40°1° 1 3(b)(i) d = 4(.0 cm) 1 3(b)(ii) not a suitable distance apart / owtte 1 and pin separation should be as large as possible / pin separation is too small / owtte 3(c) set of lines present and in correct positions 1 In this context: Line FG must touch P3 and P4 Line EJ must be straight (accept EJ not shown within block) 3(d)(i) α = 53°  2° and = 50°  2° 1 3(d)(ii) statement matching results 1 justification matching statement (‘within limits of experimental accuracy’/ within 10% / close together owtte) 1 3(e) Two valid techniques from: 2 draw thin rays / 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 1

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4 A student investigates the resistance of a wire. Plan an experiment which enables him 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. 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 / gauge 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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