Cambridge IGCSE Physics 0625 — 2023 May/June Paper 5 · Variant 2

1 In this experiment, you will investigate the stretching of a spring. Carry out the following instructions, referring to Fig. 1.1. spring metre ruler clamp stand bench Fig. 1.1 (a) The metre ruler is clamped in position near to the spring. Do not change the position of the metre ruler. (i) The value l0 is the length of the spring when the load L is 0.0 N. Measure the unstretched length l0 of the spring. Do not include the loops at the ends of the spring in your measurement. Record l0 in cm to the nearest mm in Table 1.1. [1] (ii) Draw a diagram of the spring to show clearly the length l0 of the spring. [1] (b) • Suspend a load L = 1.0 N from the spring. • Record the new length l of the spring in Table 1.1. • Calculate the extension e of the spring using the equation e = (l – l0). • Record the value of e in Table 1.1. • Repeat the procedure using loads L = 2.0 N, 3.0 N, 4.0 N and 5.0 N. • Record all the readings and results in Table 1.1. Table 1.1 L / N l / cm e / cm 0.0 0 1.0 2.0 3.0 4.0 5.0 [3] (c) Plot a graph of L / N (y-axis) against e / cm (x-axis). Draw the best-fit line. [4] (d) Use the graph to determine eA, the extension produced by a load of 2.5 N. Show clearly on the graph how you obtained the necessary information. eA = ......................................................... [2] [Total: 11]

Mark scheme: 1(a)(i) 1 1(a)(ii) diagram clearly showing the distance l0 1 1(b) increasing values of l for loads from 1 N to 5 N 1 all greater than l0 1 correct e values 1 1(c) graph:  axes correctly labelled with quantity and unit and the right way round 1  suitable scales filling  ½ the grid between the extreme plotted points 1  six plots correct to ½ small square – origin must be included 1  good line judgement, thin, continuous line 1 1(d) method shown clearly on graph 1 value correct to ½ small square – unit needed 1

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2 In this experiment, you will investigate the cooling of water. Carry out the following instructions, referring to Fig. 2.1. thermometer lid bench beaker Fig. 2.1 (a) Use the thermometer to measure the room temperature θR. θR = ......................................................... [1] (b) (i) Pour 200 cm3 of hot water into the beaker. Place the lid on the beaker. Place the thermometer in the hot water in the beaker. Record, in Table 2.1, the temperature θ of the hot water at time t = 0. Immediately start the stop-watch. Continue recording the temperature in Table 2.1 at 30 s intervals until you have seven sets of readings. [2] (ii) Complete the column headings in Table 2.1. Table 2.1 t / θ/ 0 30 60 90 120 150 180 [1] (c) (i) Calculate the decrease in temperature Δθ between t = 0 and t = 180 s. Δθ = ......................................................... [1] Δθ (ii) Calculate the average rate of cooling R of the water using the equation R = , Δt where Δt = 180 s. Include the unit. R = ......................................................... [2] (d) A student states that the water cools slowly. Suggest two changes to the experiment that you could make to increase the rate of cooling of the hot water without changing the starting temperature of the hot water. Room temperature remains constant. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ............................................................................................................................................. [2] (e) State one precaution that you take to obtain accurate temperature readings. Explain briefly the reason for this precaution. statement .................................................................................................................................. explanation ............................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] [Total: 11]

Mark scheme: 2(a) realistic room temperature 1 2(b)(i) temperatures decreasing 1 all to at least 0.5 °C or 1 °C 1 2(b)(ii) s, °C 1 2(c)(i)  correct 1 R correct 1 2(c)(ii) unit °C / s 1 2(d) any two from:  remove lid  thinner lid  paint the beaker black  stir the water  change beaker to container that is a better conductor / named metal  increase surface (area of water / beaker)  use a wider beaker  blow air over water surface / use a fan  use a smaller volume of water 2 Question Answer Marks 2(e) statement: view thermometer / scale / reading at right angles / eye level explanation: to avoid parallax error OR statement: stir (before taking reading) explanation: to distribute water evenly / to ensure that all the water is at the same temperature OR statement: ensure thermometer does not touch the side / base of beaker explanation: temperature different to that of the bulk of the liquid OR statement: wait until the thermometer (reading) stops rising at the start explanation: so that the maximum temperature of the liquid is recorded 2

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3 In this experiment, you will investigate the refraction of light using a semicircular transparent block. Carry out the following instructions, using the separate ray-trace sheet provided. You may refer to Fig. 3.1 and Fig. 3.2 for guidance. eye hole N A C B P Q D L Fig. 3.1 (a) • Draw a line across the ray-trace sheet supplied, approximately in the middle. Label the line PQ. • Place the transparent block, largest face down, with the straight side on the line PQ and the curved side below the line. • Draw round the outline of the block. Label the ends of the straight side of the block A and B. • Remove the block and draw the normal NL through the centre of AB. Continue the normal so that it passes through the curved side of the block. • Label the point C where the normal NL crosses AB. [1] (b) • Draw the line DC at an angle i = 20° to the normal, as shown in Fig. 3.1. • Place the paper on the pin board. • Place two pins, P1 and P2, on line DC at a suitable distance apart for this experiment. • Replace the block and look from the position of the eye shown in Fig. 3.1 to observe the images of P1 and P2 through side AB of the block. Adjust your line of sight until the images of P1 and P2 appear one behind the other. • Place two pins, P3 and P4, between your eye and the block so that P3, P4, and the images of P1 and P2 seen through the block, appear one behind the other. • Label the positions of P1, P2, P3 and P4. • Remove the block and the pins. • Draw a line joining the positions of P3 and P4. Continue the line to AB. • Label E, the end of the line furthest from AB. [3] (c) Measure the acute angle θ between the line NL and the line EC. (An acute angle is less than 90°.) θ = ....................................................... ° [2] (d) State one precaution that you take to produce an accurate ray trace. ................................................................................................................................................... ............................................................................................................................................. [1] (e) hole N A C B P Q F eye D L Fig. 3.2 • On the ray-trace sheet, draw a line FC at an angle i = 70° to the normal NL, as shown in Fig. 3.2. • Replace the transparent block on the ray-trace sheet in the position shown in Fig. 3.2. • Place pins P1 and P2 on line FC at a suitable distance apart for this type of experiment. • Observe the images of P1 and P2 through the curved side of the block. Look from the position of the eye shown in Fig. 3.2. • Adjust your line of sight until the images of P1 and P2 appear one behind the other. • Place two pins, P5 and P6, between your eye and the block so that P5, P6, and the images of P1 and P2 seen through the block, appear one behind the other. • Label the positions of P5 and P6. • Remove the block and the pins. • Draw a line joining the positions of P5 and P6. Continue the line to AB. • Label G, the end of the line furthest from AB. [2] (f) Measure the acute angle θ between the line NL and the line GC. (An acute angle is less than 90°.) θ = ....................................................... ° [2] [Total: 11] Tie your ray-trace sheet into this question booklet between pages 8 and 9.

Mark scheme: 3(a) normal at 90° and in centre of AB 1 3(b) i = 20°  2° 1 P1 and P2 at least 5.0 cm apart 1 all lines neatly drawn in approximately correct positions 1 3(c)  correct to  2° 1  > candidate’s i 1 3(d) any one from:  view bases of pins  place pins as far apart as possible / > 5 cm apart  ensure pins are vertical / at right angles to ray-trace sheet  draw thin lines  use a sharp pencil  use thin pins 1 3(e) line (through P5 and P6) to right of normal drawn in approximately correct position, below AB 1 line meets AB at C  2 mm 1 3(f)  correct to  2° 1  = 70  2° 1

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4 A student investigates the change in current in a conducting liquid as the distance between two electrodes is changed. The circuit is shown in Fig. 4.1. A electrodes Fig. 4.1 Plan an experiment to investigate the change in current in the liquid as the distance between the electrodes is changed. You are not required to do this investigation. You should: • explain briefly how to do the investigation • state the key variables to keep constant • draw a table, or tables, with column headings, to show how to display your readings (you are not required to enter any readings in the table) • explain how to use your readings to reach a conclusion. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 4 MP1 method: measure the distance between the electrodes 1 MP2 method: measure / record / take / check / note the current or the ammeter reading 1 MP3 method: repeat with at least four other distances 1 MP4 key variables: potential difference / supply voltage / battery voltage / power supply 1 MP5 key variables: any one from:  depth of immersion of electrodes  volume / amount of liquid  mass / size / material of the electrodes  room temperature  temperature / concentration of the liquid  type of liquid / electrolyte 1 MP6 table: table with columns for distance and (change in) current with appropriate units 1 MP7 conclusion: draw a graph of (change in) current against distance OR (use results table to) compare distances with currents OR (compare results to) see if changing the distance has any effect on the current 1

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