Cambridge IGCSE Physics 0625 — 2022 Oct/Nov Paper 5 · Variant 2

1 In this experiment, you will investigate temperature changes when mixing hot and cold water. Carry out the following instructions, referring to Fig. 1.1. thermometer beaker bench Fig. 1.1 (a) Use the thermometer to measure room temperature θR. θR = ...................................°C [1] (b) • Pour 100 cm3 of cold water into beaker A. • Record the temperature θC of the cold water. θC = .......................................°C • Pour 100 cm3 of the hot water provided into beaker B. • Record the temperature θH of the hot water. θH = .......................................°C • Immediately pour the cold water into the hot water in beaker B. Stir the mixture and record the highest temperature θM of the mixture. θM = .......................................°C [2] (c) (i) Calculate the decrease in temperature Δθ1 of the hot water using the equation Δθ1 = (θH – θM). Include the unit. Δθ1 = ......................................................... [1] (ii) Calculate the increase in temperature Δθ2 of the cold water using the equation Δθ2 = (θM – θC). Include the unit. Δθ2 = ......................................................... [1] (d) Calculate the average θA of the temperatures θH and θC. Show your working. θA = ...........................................................°C [2] (e) State whether θA and θM can be considered to be equal within the limits of experimental accuracy. Justify your answer by reference to your results. statement .................................................................................................................................. ................................................................................................................................................... justification ................................................................................................................................ ................................................................................................................................................... [2] (f) State two requirements when reading the volume of water in a measuring cylinder to obtain an accurate result. 1. ............................................................................................................................................... 2. ............................................................................................................................................... [2] [Total: 11]

Mark scheme: Question Answer Marks 1(a) realistic room temperature value R 1 1(b) realistic values of C and H 1 H > M > C 1 1(c)(i) Δ1 and 2 correct 1 1(c)(ii) unit °C 1 1(d) correct method 1 A > M 1 1(e) statement to match results – expect NO 1 explanation of idea of beyond limits of experimental accuracy (e.g., values not close (enough) / too far apart / > 10% 1 difference 1(f) any two from: 2 perpendicular viewing of scale / view at eye level / eye level with the surface of the water take the reading at the bottom of the meniscus place the measuring cylinder on a (horizontal) flat surface / ensure that measuring cylinder is vertical

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2 In this experiment, you will investigate the position of the image in a plane mirror. Carry out the following instructions. Use the ray-trace sheet supplied, referring to Fig. 2.1 for guidance. hole N M R B α A L eye Fig. 2.1 (a) Draw a line 10 cm long near the middle of the ray-trace sheet. Label the line MR. Draw a normal to this line that passes through its centre. Label the normal NL. Label the point at which NL crosses MR with the letter B. [1] (b) Draw a line 7.0 cm long from B at an angle of incidence α = 30° to the normal below MR and to the left of the normal. Label the end of this line A. [1] (c) • Place the reflecting face of the mirror vertically on the line MR. • Place two pins, P1 and P2, on line AB at a suitable distance apart for this type of ray-trace experiment. Label the positions of P1 and P2. • View the images of pins P1 and P2 from the direction indicated by the eye in Fig. 2.1. Place two pins, P3 and P4, so that pins P3 and P4 and the images of P2 and P1 all appear exactly one behind the other. Label the positions of P3 and P4. [2] (d) Remove the pins and the mirror. Draw a line through the positions of P3 and P4. Continue the line until it meets MR. Measure, and record in Table 2.1, the acute angle β between this line and the line MR. Table 2.1 α/ ° β/ ° (α + β) / ° 30 45 [1] (e) Repeat the procedure in (b), (c) and (d) using an angle of incidence α = 45°. Record the value of β in Table 2.1. [1] (f) Calculate, and record in Table 2.1, the values of (α + β). [1] (g) Suggest a relationship, if any, between the two values of (α + β) in Table 2.1. ............................................................................................................................................. [1] (h) In order to investigate further a possible relationship between values of (α + β), more values are required. Suggest values of the angle of incidence α that you could use. You are not required to do this further investigation. ................................................................................................................................................... ............................................................................................................................................. [2] (i) A student does this experiment with care. Suggest a practical reason why the results may not be exactly those that the theory of reflection predicts. ................................................................................................................................................... ............................................................................................................................................. [1] Tie your ray-trace sheet into this booklet between pages 6 and 7. [Total: 11]

Mark scheme: 2(a) normal correct 1 2(b) line AB 7.0  0.2 cm long at 30° to the normal ( 2°) 1 2(c) P1 P2 distance at least 5.0 cm 1 P3 and P4 in correct area and straight line drawn through them 1 2(d) angle correct to  2° 1 2(e) values recorded with realistic lines on ray-trace 1 2(f) correct values of (+ ) 1 2(g) values are identical (within the limits of experimental accuracy) / almost equal / really close / not too far apart 1 2(h) at least 1 value < 30(°) and 1 value > 45(°) 1 all recorded values less than 90° 1 2(i) difficulty in lining up pins / pins too thick / lines too thick / thickness of mirror (glass) / precision of protractor 1

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3 In this experiment, you will investigate the balancing of a metre rule. Carry out the following instructions, referring to Fig. 3.1. 90.0 cm S metre rule 0 100 pivot bench Fig. 3.1 (a) Place the metre rule on the pivot, with its scale facing upwards, so that the metre rule is as near as possible to being balanced. Record the scale reading S on the metre rule at the point where the rule balances on the pivot. S = ................................................... cm [1] (b) • Place object Q with its centre on the metre rule at the 90.0 cm mark. • Place a load P of weight P = 1.0 N on the metre rule. (i) Adjust the position of the load P so that the metre rule is as near as possible to being balanced. The pivot must remain directly below the scale reading S. Measure, and record in Table 3.1, the distance a from the centre of load P to the centre of load Q, as shown in Fig. 3.2. [1] a metre rule P Q S 0 100 90.0 cm pivot bench Fig. 3.2 (ii) Repeat the steps above, using loads of weight P = 2.0 N, 3.0 N, 4.0 N and 5.0 N. Record all the values of a in Table 3.1. Table 3.1 1 1 P / N a / cm P N / 1.0 1.00 2.0 0.50 3.0 0.33 4.0 0.25 5.0 0.20 [3] 1 1(c) Plot a graph of a / cm (y-axis) against (x-axis). Start the y-axis at a / cm = 30. Start the P N x-axis at 0. / [4] 1(d) Record the value of a when = 0. Show clearly on the graph how you obtained the necessary P information. a = ......................................................... [2] [Total: 11]

Mark scheme: 3(a) S in range 50.0  2.0 (cm) recorded to the nearest mm 1 3(b)(i) first a value recorded in cm 1 3(b)(ii) a values decreasing 1 a values all to the nearest mm 1 a values all > 45.0 cm 1 3(c) axes correctly labelled with quantity and unit and correct way round 1 suitable scales with a axis starting from 30 1 all plots correct to ½ small square 1 good line judgement, thin, continuous line 1 3(d) method clearly shown on graph 1 value correct to  ½ small square 1

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4 A student investigates the effect on the resistance of a wire when the tension in the wire is increased. The apparatus is shown in Fig. 4.1. The tension in the wire is increased by adding loads to the hook attached to the wire. The student measures the current I in the wire and the potential difference (p.d.) V across the wire. She determines the resistance R of the wire using the V equation R = . I You are not required to carry out this investigation. The student takes all the necessary safety precautions. You are not required to write about safety precautions. The following apparatus is available: • resistance wire • power source, connecting wires and crocodile clips • ammeter • voltmeter • selection of loads and a hanger. A resistance wire crocodile clip pulley clamp hook bench load hanger load floor Fig. 4.1 Plan an experiment to investigate the effect on the resistance of a wire when the tension in the wire is increased. You should: • complete the circuit diagram in Fig. 4.1 to show a voltmeter connected to measure the potential difference across the resistance wire • explain briefly how you would carry out the investigation • state the key variables that you would keep constant • draw a table, or tables, with column headings, to show how you would display your readings (you are not required to enter any readings in the table) • explain how you would use your readings to reach a conclusion. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 4 MP1 circuit diagram 1 voltmeter correctly positioned with correct circuit symbol MP2 method 1 attach a load, record / note / check V and I (and the value of the load) MP3 calculate / measure / record the resistance of the wire 1 MP4 repeat with at least two other loads 1 MP5 control variable 1 distance / length of wire between crocodile clips MP6 table 1 columns for load / tension / mass / number of loads, V, I and R with units at the head of each column MP7 conclusion 1 compare load with resistance to see if there is an effect / plot graph of load against resistance. Additional graph notes: NOTE: The principle to apply here is ‘could I draw a significantly better line, using these points, under examination conditions?’ If the answer is definitely ‘yes’, do not award the mark. NOTE: – If candidate’s scale consists of actual readings at equal intervals this will produce a perfect straight line! The only mark available in this case is the first (axes right way round and labelled) So maximum 1. – If axes are wrong way round, the other 3 marks are still available.

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