Cambridge IGCSE Physics 0625 — 2024 May/June Paper 5 · Variant 3

1 In this experiment, you will determine the density of modelling clay by two methods. Refer to Fig. 1.1. Method 1 l w h block A Fig. 1.1 (a) (i) Measure the length l, width w and height h of block A. Record your values in centimetres to the nearest millimetre. l = ......................................................... cm w = ......................................................... cm h = ......................................................... cm [1] (ii) Calculate the volume VA of block A. Use your measurements from (a)(i) and the equation VA = l × w × h. VA = .................................................. cm3 [1] (b) Suggest a possible source of inaccuracy in measuring the dimensions of the block. Describe how the accuracy of these measurements can be improved. You are not required to do this improved investigation. suggestion ................................................................................................................................ ................................................................................................................................................... improvement ............................................................................................................................. ................................................................................................................................................... [2] (c) Measure the mass mA of block A. Use the top-pan balance. mA = ...................................................... g [1] (d) Calculate a value ρA for the density of the modelling clay. Use your results from (a)(ii) and (c) mA and the equation ρA = . Include the unit for the density. VA ρA = ......................................................... [2] Method 2 (e) Measure the weight WB of block B, as shown in Fig. 1.2. WB = ...................................................... N [1] force meter loop of thread block B Fig. 1.2 (f) (i) Pour approximately 60 cm3 of water into the measuring cylinder. Measure and record the actual volume V1 of the water in the measuring cylinder. V1 = ........................................................ cm3 Remove the loop of thread from the force meter and lower block B carefully into the water in the measuring cylinder, as shown in Fig. 1.3. measuring cylinder Fig. 1.3 Measure and record the new reading V2 of the measuring cylinder. V2 = ........................................................ cm3 [1] (ii) Draw an arrow on Fig. 1.4 to show the correct line of sight to obtain the value for the volume of water in the measuring cylinder. bench Fig. 1.4 [1] (g) Calculate another value ρB for the density of modelling clay. Use your readings from (e) and WB × k (f) and the equation ρB = where k = 100 g / N. (V2 – V1), ρB = ......................................................... [1] [Total: 11]

Mark scheme: 1(a)(i) 1 1(a)(ii) correct calculation of VA from candidate’s values 1 1(b) difficult to measure irregular dimensions / owtte 1 repeat in several places (for each dimension) and take averages 1 1(c) mA in range 60 g to 100 g 1 1(d) A in range 1.0 to 2.0 1 unit g / cm3 seen in (d) or (g) and not contradicted 1 1(e) sensible value for WB ( 1.0 N) 1 1(f)(i) V2  V1 1 1(f)(ii) line of sight perpendicular and to bottom of meniscus 1 1(g) B within 10% of A 1

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2 In this experiment, you will investigate how the volume of water affects the rate at which hot water in a beaker cools. Refer to Fig. 2.1. clamp thermometer beaker bench Fig. 2.1 (a) Pour 200 cm3 of hot water into the beaker. Use the graduations on the beaker as a guide. Place the thermometer in the water. In the first row of Table 2.1, record the temperature θ of the water at time t = 0 and immediately start the stop-watch. Record the temperature θ of the water at times t = 30 s, 60 s, 90 s, 120 s, 150 s and 180 s. Remove the thermometer from the beaker and pour out the water. [1] (b) (i) Repeat (a), using only 75 cm3 of hot water. [2] (ii) Add units to the column headings in Table 2.1. Table 2.1 beaker beaker with 200 cm3 of hot water with 75 cm3 of hot water t / θ / θ / 0 30 60 90 120 150 180 [1] (c) Write a conclusion stating how the volume of hot water affects the rate of cooling of the water. Justify your answer by reference to your results. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (d) (i) Using your values for 75 cm3 of water, calculate the average cooling rate x1 for the first 90 s of the experiment. Use your readings from Table 2.1 and the equation θ0 – θ90 x1 = T where T = 90 s and θ0 and θ90 are the temperatures at t = 0 and t = 90 s. Include the unit for the cooling rate. x1 = ......................................................... [2] (ii) Using your values for 75 cm3 of water, calculate the average cooling rate x2 for the last 90 s of the experiment. Use your readings from Table 2.1 and the equation θ90 – θ180 x2 = T where T = 90 s and θ90 and θ180 are the temperatures at t = 90 s and t = 180 s. x2 = ......................................................... [1] (iii) A student states that it is important to start the two experiments in (a) and (b) with water at the same initial temperature. Explain whether your values for x1 and x2 support this statement. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] (e) Another student repeats the experiment. State one variable, other than initial water temperature, that she should control to obtain readings that are as close as possible to those in Table 2.1. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 11]

Mark scheme: 2(a) 1 2(b)(i)  for 75 cm3 decreasing 1 decreasing more quickly than  for 200 cm3 1 2(b)(ii) s, °C both correct 1 2(c) statement matching readings in table 1 comparison of temperature changes over 180 s, matching statement 1 2(d)(i) correct calculation of x1 1 unit °C / s 1 2(d)(ii) x2  x1 1 2(d)(iii) explanation matching values of x1 and x2 1 2(e) any one from:  volume(s) of water  same / size / material / surface area of beaker  room temperature 1

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3 In this experiment, you will determine the focal length of a converging lens. Refer to Fig. 3.1. illuminated object u screen lens hO bench Fig. 3.1 (a) Set up the apparatus as shown in Fig. 3.1. (i) Measure the height hO of the illuminated object. Fig. 3.1 shows the height to measure on the illuminated object provided. hO = ................................................... cm [1] (ii) Place the lens a distance u = 20.0 cm from the illuminated object. Place the screen near the lens. Switch on the lamp. Move the screen until a focused image of the illuminated object is seen on the screen. Measure, and record in Table 3.1, the height hI of the image on the screen. Repeat the procedure for u = 25.0 cm, 30.0 cm, 35.0 cm and 40.0 cm. Switch off the lamp. Table 3.1 u / cm hI / cm W 20.0 25.0 30.0 35.0 40.0 [1] (iii) Describe a technique for obtaining an image that is as sharp as possible. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] (b) For each distance u, calculate, and record in Table 3.1, a value W. Use your results from (a) hO and the equation W = . hI [1] (c) Plot a graph of u / cm (y-axis) against W (x-axis). You do not need to start your axes at the origin (0, 0). Draw the best-fit line. [4] (d) (i) Determine the gradient G of the line. Show clearly on the graph how you obtained the necessary information. G = ......................................................... [1] (ii) The focal length f of the lens is numerically equal to the gradient G. Record a value of f for this experiment. f = ................................................... cm [1] (e) A student decides to continue the experiment using larger values of u. Explain why this produces less accurate values for W. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1]

Mark scheme: 3(a)(i) sensible value for hO (1.5 to 2.5 (cm)) 1 3(a)(ii) hI decreasing 1 3(a)(iii) move screen slowly / back and forth 1 3(b) W calculations correct 1 3(c) graph:  axes labelled with quantity and unit 1  appropriate scales (plots occupying at least ½ grid between plotted points) 1  plots all correct to ½ small square and precise plots 1  well-judged line and thin line 1 3(d)(i) G present and triangle method seen on graph 1 3(d)(ii) f in range 12.0 (cm) to 18.0 (cm) and to 2 or 3 significant figures 1 3(e) values of hI become (very) small / difficult to measure or greater % uncertainty 1

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4 A student investigates the relationship between the diameter of a wire and the electrical resistance of the wire. Plan an experiment which enables him to investigate how the diameter 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. You are not required to do this experiment. The apparatus available includes wires of different known diameters. In your plan: • list any additional apparatus needed • complete Fig. 4.1 to show a circuit suitable for measuring the resistance of a 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. power supply resistance wire Fig. 4.1 .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 4 MP1 apparatus: ammeter and voltmeter 1 MP2 circuit diagram: correct circuit symbols shown in correct connection 1 MP3 method: record diameter measure p.d and current repeat for new diameter 1 MP4 control variable: any one from:  length of wire  material of wire  temperature of wire 1 MP5 table: columns, with units, for diameter, p.d., current, (resistance) any variable mentioned must have correct units 1 MP6 analysis: compare readings in the table to see if change in diameter produces change in resistance plot line graph (with axes specified) 1 MP7 additional point any one from:  at least 5 sets of data taken  repeat for each value of independent variable and take average  2nd appropriate control variable stated 1

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