Cambridge IGCSE Physics 0625 — 2024 Oct/Nov Paper 6 · Variant 3

1 A student investigates the cooling of water in different sized beakers. He uses the apparatus shown in Fig. 1.1. Beaker A and beaker B have graduations as shown in Fig. 1.1. thermometer 300 cm3 beaker B beaker A 100 cm3 200 cm3 50 cm3 bench 100 cm3 30 20 10 Fig. 1.1 (a) (i) Record room temperature θR shown on the thermometer in Fig. 1.1. θR = .................................................... °C [1] (ii) Describe one technique to use so that the temperature reading is as accurate as possible in this experiment. ........................................................................................................................................... ..................................................................................................................................... [1] (b) The student pours an estimated volume of 75 cm3 of hot water into beaker A. He uses the scale on the beaker as a guide. He puts the thermometer into the water in beaker A and records, in Table 1.1, the temperature θ at time t = 0. He records, in Table 1.1, the temperature of the water in beaker A every 30 s. The student repeats the procedure for beaker B. His readings are shown in Table 1.1. Suggest one possible source of inaccuracy in the procedure, even if it is carried out carefully. ................................................................................................................................................... ............................................................................................................................................. [1] Table 1.1 beaker A beaker B t / s θ/ °C θ/ °C 0 82.5 80.0 30 80.0 75.0 60 78.0 72.0 90 76.5 69.5 120 75.0 67.0 150 74.0 65.0 180 73.0 63.5 (c) Write a conclusion describing the effect of changing the size of the beaker on the rate of cooling of the hot water. Justify your answer by reference to values from the results. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (d) Students in other schools do the same experiment using identical apparatus. State one variable that they need to control in order to obtain readings as close as possible to the readings in Table 1.1. ................................................................................................................................................... ............................................................................................................................................. [1] (e) Calculate the average cooling rate x for beaker B. Use the readings for beaker B in Table 1.1 and the equation θ0 – θ180 x = T where T = 180 s and θ0 and θ180 are the temperatures of the water in beaker B at t = 0 and t = 180 s. Include the unit for the cooling rate. x = ......................................................... [2] (f) (i) Another student thinks that more thermal energy is lost from the surface of the water in beaker B than from the sides of beaker B. Suggest an additional experiment that she can do with beaker B to test her idea. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Suggest how the cooling rate of the water in beaker B in this additional experiment compares with the value of x in (e) if her idea is correct. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] [Total: 11]

Mark scheme: Question Answer Marks 1(a)(i) θR = 22(°C ) 1 1(a)(ii) view temperature scale perpendicularly 1 1(b) source of inaccuracy e.g: 1 75 cm3 difficult to estimate with large graduations on beakers 1(c) statement matching readings in table 1 justification with comparison of temperature changes over 180 s, matching statement 1 1(d) one suitable variable not referencing apparatus e.g.: 1 volume of water, initial temperature, room / air / surrounding / environmental temperature 1(e) x = 0.0917 1 with unit °C / s 1 1(f)(i) appropriate additional experiment: 1 e.g. repeat for beaker B with lid / cover on top or with insulation on sides 1(f)(ii) cooling rate  x 1 with lid – cooling rate  x/2 1 OR with sides insulated – cooling rate  x/2 (but < x)

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2 A student determines the resistance of a resistor. She uses the apparatus shown in Fig. 2.1. l metre ruler resistance wire 100.0 cm mark A resistor crocodile clip Fig. 2.1 (a) On Fig. 2.1, draw a voltmeter connected to measure the potential difference (p.d.) across the resistor. [1] (b) The student connects the crocodile clip to the resistance wire at the 100.0 cm mark on the metre ruler and measures the potential difference V0 across the resistor. The voltmeter is shown in Fig. 2.2. 2 3 1 4 0 5 V Fig. 2.2 Read and record the value of V0 shown on the voltmeter in Fig. 2.2. V0 = .......................................................V [1] (c) The student moves the crocodile clip to a length of resistance wire l = 20.0 cm. Read and record in Table 2.1, the current for l = 20.0 cm, shown on the ammeter in Fig. 2.3. [1] 0.4 0.6 0.2 0.8 0 1.0 A Fig. 2.3 (d) The student measures the current I for lengths of resistance wire l = 30.0 cm, l = 40.0 cm, l = 50.0 cm and l = 60.0 cm. Her readings are shown in Table 2.1. Table 2.1 l / cm I / A 20.0 30.0 0.22 40.0 0.30 50.0 0.39 60.0 0.42 Plot a graph of l / cm (y-axis) against I / A (x-axis). Draw a best-fit straight line. You do not need to start the axes at the origin (0,0). [4] (e) (i) Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information. G = ......................................................... [1] (ii) Calculate the resistance R of the resistor. Use your value of V0 from (b) and the equation: G × V0 R = where k = 1.0 A 100k R = ...................................................... Ω [1] (f) Suggest one practical reason why other students might not obtain the same result as this student, even if they do the experiment carefully. ................................................................................................................................................... ............................................................................................................................................. [1] (g) The resistance wire can become very hot during this type of experiment. Suggest one change to the apparatus that prevents this. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 11]

Mark scheme: 2(a) correct voltmeter symbol in parallel with resistor 1 2(b) V0 = 3.2(V) 1 2(c) I = 0.18(A) recorded in Table 2.1 1 2(d) graph: • axes labelled with quantity and unit 1 • 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 2(e)(i) G present 1 and triangle method seen on graph 2(e)(ii) R in range 4.8 () to 5.8 () 1 2(f) valid practical source of inaccuracy, e.g: 1 uncertain connection point on crocodile clip / resistance wire irregular / curved / not uniform / differing thickness along wire 2(g) suitable improvement e.g: 1 reduce e.m.f. of power supply / thinner resistance wire / use of additional series / protective resistor to reduce current

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3 A student investigates the refraction of light by a transparent block. He determines a quantity known as the refractive index of the material of the block. The student’s ray-trace sheet is shown full-size in Fig. 3.1. E P1 P2 N A B D C P4 P6 P5 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. Extend the normal downwards until it crosses line CD. Label the point at which it crosses CD with the letter F. [1] (ii) The student draws line EN as shown in Fig. 3.1. On Fig. 3.1, measure the acute angle θ1 between the lines LN and EN. (An acute angle is always less than 90°.) θ1 = ......................................................... [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 = ......................................................... [1] (ii) Suggest 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 straight line through P3 and P4. Extend this line to cross NF. Label the point at which this line meets NF with the letter G. Label the point at which this line crosses CD with the letter H. Join points H and N with a straight line. [1] (d) (i) Measure the length a of line HN. a = ......................................................... cm Measure the length b of line HG. b = ......................................................... cm [1] a (ii) Calculate a value n for the refractive index, using the equation n = . b n = ......................................................... [1] (e) The student repeats the above procedure for an angle θ2 = 40°. He places two pins P5 and P6 so that pins P5 and P6 and the images of P1 and P2 all appear exactly one behind the other. Draw a line through pins P5 and P6. Extend the line until it meets GH. Label the point at which this line meets GH with the letter K. Label the point at which this line crosses CD with the letter R. (i) Measure the angle α, where α is the acute angle between lines RK and GH. α = ......................................................... [1] (ii) Another student suggests that angle α should be equal to the difference between angle θ2 from (e)(i) and angle θ1 from (a)(ii). State whether your results support this suggestion. Justify your answer by reference to values from your results. statement .......................................................................................................................... justification ........................................................................................................................ ........................................................................................................................................... [2] (f) Suggest one technique to use in this type of experiment to ensure results are accurate. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 11]

Mark scheme: 3(a)(i) normal correct 1 3(a)(ii) θ1 = 15°±1° 1 3(b)(i) d = 3.5 (cm) 1 3(b)(ii) separation not suitable 1 and pin separation should be as large as possible / pin separation is too small / owtte 3(c) all lines present and in correct positions 1 3(d)(i) a = 6.1 (cm) and b = 4.2 (cm) 1 3(d)(ii) n = 1.5 / ecf and no unit 1 3(e)(i) α = 23° ± 2° 1 3(e)(ii) statement matching results 1 justification matching statement e.g. within limits of experimental accuracy / owtte with values to support 1 3(f) one valid technique e.g.: 1 thin lines / use sharp pencil, look at base of pins / keep pins vertical, thin pins

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4 A student investigates the speed of a small trolley moving down a sloping ramp. Plan an experiment which will enable her to compare the effect of different angles of slope on the average speed of the trolley between points on the ramp. Average speed can be calculated from the equation: distance average speed = time The apparatus available includes: • a long ramp with a support that enables it to be set at different angles of slope • a small trolley. In your plan: • list any additional apparatus needed • explain briefly how to do the experiment, including how to take the measurements so that the average speed can be determined • suggest a possible source of inaccuracy even if the method is carried out carefully • 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. You may draw a diagram if it helps to explain your plan. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 4 MP1 1 apparatus: stopwatch and metre ruler and protractor MP2 1 method: measure independent variable measure distance and time between points repeat for different angle MP3 1 source of inaccuracy (one from): difficult to time at exact point, ramp surface not regular, trolley travels at an angle across slope MP4 1 control variable (one from): distance from start to first point, distance between points MP5 1 table: columns for independent variable, time and speed, all with units MP6 1 analysis: compare readings of angle with speed or time plot line graph (with axes specified) MP7 1 additional point (one from): at least 5 sets of data taken, repeat each measurement and take average, 2nd control variable stated,

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