Cambridge IGCSE Physics 0625 — 2022 Feb/March Paper 5 · Variant 2

1 In this experiment, you will investigate the extension of a spring and use it to determine the weight of a metre rule. The spring has been set up for you. Carry out the following instructions. clamp l0 spring lS 1.0 N load Fig. 1.1 Fig. 1.2 (a) Measure and record the unstretched length l 0 of the spring, as shown in Fig. 1.1. l 0 = .......................................................... cm Suspend the 1.0 N load from the spring, as shown in Fig. 1.2. Measure and record the stretched length l S of the spring. l S = .......................................................... cm [1] (b) Suspend the metre rule from the spring using the hook fixed at the 95.0 cm mark, as shown in Fig. 1.3. Place the other end of the metre rule so that the 5.0 cm mark of the rule rests on the pivot. The metre rule must rest on the pivot at the 5.0 cm mark throughout the experiment. Place the load W on the metre rule with its centre at a distance d = 20.0 cm from the pivot. Ensure that the metre rule is horizontal by adjusting the clamp that holds the spring. clamp metre rule d l 5.0 cm mark load W 95.0 cm mark pivot bench Fig. 1.3 Measure, and record in Table 1.1, the stretched length l of the spring, as shown in Fig. 1.3. Repeat this procedure for distances d = 30.0 cm, d = 40.0 cm, d = 50.0 cm and d = 60.0 cm from the pivot. Table 1.1 d / cm l / cm 20.0 30.0 40.0 50.0 60.0 [2] (c) Plot a graph of l / cm (y-axis) against d / cm (x-axis). Start the axes at the origin (0,0). 0 0 [4] (d) (i) From your graph, determine L, the value of l when d = 0.0 cm. L = ......................................................... [1] (ii) Calculate WR, the weight of the metre rule, using your value of L from (d)(i), the values of l 0 and l S from (a) and the equation 2(L – l0) WR = × k (lS – l0) where k = 1.0 N. WR = ......................................................... [1] (e) (i) It is sometimes difficult to position the load W on the scale of the metre rule at the correct distance d from the pivot. Suggest one change to the apparatus to overcome this difficulty. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Suggest one possible source of inaccuracy other than the difficulty described in (e)(i). Assume that the experiment is carried out carefully. ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 11]

Mark scheme: 1(a) and lS > l0 1 1(b) 5 × l values increasing 1 all to the nearest mm. 1 1(c) graph: • axes labelled with quantity and unit 1 • appropriate scales (occupying at least ½ grid) 1 • plots all correct to ½ small square and precise plots 1 • line well-judged and thin and extended to axis 1 1(d)(i) L read correctly from graph 1 1(d)(ii) WR in range 0.9 to 2.1 and with unit of N 1 1(e)(i) suspend load from loop of thread / any other suitable method to avoid standing load over marks on rule 1 1(e)(ii) valid source of uncertainty e.g. test load not exactly 1.0 N / spring extension not linear / metre rule not uniform 1

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2 In this experiment, you will investigate the thermal insulation properties of air. Carry out the following instructions, referring to Fig. 2.1 and Fig. 2.2. Beaker A is covered in thin black card. Beaker A is used on its own for the first part of the investigation and is placed inside beaker B for the second part of the investigation. clamp thermometer lid beaker A bench Fig. 2.1 (a) Remove the lid from beaker A. Pour 150 cm3 of hot water into beaker A and replace the lid. Place the thermometer in the water. In the first row of Table 2.1, record the temperature θ of the water at t = 0 and immediately start the stop-clock. Record 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] (b) Remove the thermometer and lid from beaker A and pour away the water. Place beaker A inside beaker B, as shown in Fig. 2.2, so that there is an air gap between the sides of the two beakers. beaker B air gap beaker A bench Fig. 2.2 (i) Repeat (a) for this arrangement, ensuring that the lid fits inside beaker B after pouring water into beaker A. [2] (ii) Add units to the column headings in Table 2.1. [1] Table 2.1 beaker A beaker A inside beaker B t / θ/ θ/ 0 30 60 90 120 150 180 (c) Write a conclusion stating whether the air gap affects the rate of cooling of the water. Justify your answer by reference to values from your results. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (d) A student suggests that glass is a thermal insulator and the experiment does not just test the effect of the air gap. Suggest one change to the apparatus that would test the air gap more effectively. ................................................................................................................................................... ............................................................................................................................................. [1] (e) Another student repeats the experiment using the apparatus you used for your investigation. State two variables that this student should control to obtain readings as close as possible to your readings. 1. ............................................................................................................................................... ................................................................................................................................................... 2. ............................................................................................................................................... ................................................................................................................................................... [2] (f) Calculate the average cooling rate R for beaker A cooling on its own. Use your readings for beaker A in Table 2.1 and the equation θ0 – θ180 R = T where T = 180 s and θ0 and θ180 are the temperatures of the water in beaker A at t = 0 and t = 180 s. Include the unit for the cooling rate. R = ......................................................... [2] [Total: 11]

Mark scheme: 2(a) θ for beaker A decreasing 1 2(b)(i) θ for beaker A in beaker B decreasing and recorded to at least 1 °C 1 decreasing less quickly than for beaker A 1 2(b)(ii) s, °C, °C all correct 1 2(c) statement matching readings in table 1 comparison of temperature changes over 180s, matching statement (need to see values used in justification) 1 2(d) suitable change e.g. use conducting material / metal for beaker B / support beaker A in beaker B so that there is an air gap underneath too 1 2(e) 2 suitable control variables e.g. initial temperature / volume of water / room temperature or other appropriate environmental condition 2 2(f) correct calculation of R 1 unit °C / s 1

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3 In this experiment, you will investigate the refraction of light using a transparent block. Carry out the following instructions, using the separate ray-trace sheet provided. You may refer to Fig. 3.1 for guidance. hole ray-trace sheet E L eye θ N A B 2 cm D C mirror 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 ABCD, as shown in Fig. 3.1. • Remove the block from the ray-trace sheet. • Draw a normal to line AB at a point 2 cm from A. Label the normal NL, as shown in Fig. 3.1. • Draw a line NE, 8 cm long and at an angle θ1 = 15°, as indicated in Fig. 3.1. [2] (b) • Replace the block in exactly the same position as in (a). • Place the plane mirror on line CD with its face against the block, as shown in Fig. 3.1. • Place two pins, P1 and P2, on line NE a suitable distance apart for accurate ray tracing. • Label the positions of pins P1 and P2. • View the images of pins P1 and P2 through the block from the direction indicated by the eye in Fig. 3.1. Place two pins, P3 and P4, a suitable distance apart so that pins P3 and P4, and the images of pins P1 and P2, all appear exactly one behind the other. • Label the positions of pins P3 and P4. • Remove the block, mirror and pins from the ray-trace sheet. [1] (c) • Draw a line through P3 and P4 and extend this line 4 cm below CD. • Label the point at which this line meets AB with the letter G. • Label the lower end of this line with the letter H. [1] (d) (i) • Draw a new line NE, 8 cm long and at an angle θ2 = 35°, as indicated in Fig. 3.1. • Repeat the steps in (b). • Draw a line joining the new positions of pins P3 and P4 and extend this line 4 cm below CD. • Label the point at which this line meets AB with the letter R. • Label the lower end of this line with the letter S. • Label the point at which GH and RS cross with the letter T. [2] (ii) Measure the angle β, where β is the angle between lines GT and RT. β = ......................................................... [1] (iii) A student suggests that the angle β should be equal to θs, where θs is calculated using the equation θs = θ2 – θ1. State whether your results support this suggestion. Justify your answer by reference to values from your results. statement .......................................................................................................................... justification ........................................................................................................................ ........................................................................................................................................... [2] (e) Suggest one precaution to take in this type of experiment to ensure accurate results. ................................................................................................................................................... ............................................................................................................................................. [1] (f) Suggest one reason why different students, all carrying out this experiment carefully, may not obtain identical results. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 11] Tie your ray-trace sheet into this booklet between pages 8 and 9.

Mark scheme: 3(a) normal correct 1 θ1 = 15±1(°) 1 3(b) pin separation sufficiently large 1 3(c) first line present, complete and straight 1 3(d)(i) second set of lines present, complete and straight 1 in correct relation to first set 1 3(d)(ii) β = 20° ± 2° 1 3(d)(iii) statement matching results 1 justification with correct values matching statement 1 3(e) one suitable precaution e.g. thin lines OR thin pencil / view bottom of pins OR keep pins upright / ensure pins far apart 1 3(f) difficult to align pins/place pins accurately, pins (too) thick mirror (too) thick 1

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4 A student investigates the heating of water using an immersion heater. An immersion heater is an electrical heater that can be placed directly into water. Plan an experiment to investigate how one factor affects the rate at which the temperature of the water rises when heated using an immersion heater. You are not required to carry out the experiment. The apparatus available includes: • an immersion heater • equipment to connect the circuit, part of which is shown in Fig. 4.1 • a stop-clock • a beaker to contain the water. In your plan, you should: • state the one factor which you have chosen and list any additional apparatus needed to measure the factor • complete the circuit diagram in Fig. 4.1 • explain how to do the experiment, including any precautions to ensure reliable results • state the key variables to be kept 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. immersion power heater supply beaker variable resistor Fig. 4.1 .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 4 MP1 factor: valid factor which may affect rate of temperature rise 1 MP2 apparatus: thermometer and additional apparatus necessary to measure independent variable 1 MP3 method: • measure independent variable • measure temperature (change) and / or time appropriate to procedure • repeat for new value of independent variable 1 MP4 control variable: any significant variable appropriate to independent variable (e.g. volume of water if current is the independent variable) 1 MP5 table: columns, with units, for independent variable and dependent variable 1 MP6 analysis: compare readings in the table to see if change in factor produces change in (rate of) temperature rise, plot (line) graph (with axes specified) 1 MP7 additional point (one from): 2nd valid control variable stated, at least 5 sets of data taken, repeat each measurement and take average, 1

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