Cambridge IGCSE Physics 0625 — 2016 Feb/March Paper 5 · Variant 2

1 In this experiment, you will determine the density of glass. Carry out the following instructions, referring to Fig. 1.1. boiling tube d l Fig. 1.1 (a) (i) • Measure the length l of the boiling tube provided. l = ..........................................................cm • Measure the external diameter d of the boiling tube. Use the wooden blocks to help you. d = ..........................................................cm [1] (ii) Describe how you measured the external diameter d of the boiling tube. You may draw a diagram. Include one precaution you took to ensure that the value of d is as reliable as possible. ........................................................................................................................................... ........................................................................................................................................... .......................................................................................................................................[2] (iii) Assuming that the boiling tube is an approximate cylinder, calculate a value for its πd 2l external volume V1 using the equation V1 = . 4 V1 = ................................................... cm3 [1] (b) (i) • Completely fill the boiling tube with water. • Pour the water from the boiling tube into the measuring cylinder. • Read and record the volume V2 of the water. V2 = .................................................. cm3 [1] (ii) Describe briefly how you read the measuring cylinder to obtain a reliable value for the volume of water. You may draw a diagram. ........................................................................................................................................... ........................................................................................................................................... .......................................................................................................................................[1] (iii) Calculate the volume V3 of the glass, using the equation V3 = V1 – V2. V3 = .................................................. cm3 [1] (c) • Use the balance to measure the mass m of the boiling tube. m = .............................................................g m • Calculate the density ρ of the glass, using the equation ρ = . V3 ρ = ............................................................... [2] (d) State one possible source of inaccuracy in the experiment. Explain what effect this inaccuracy would have on the value obtained for ρ. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[2] [Total: 11]

Mark scheme: 1 (a) (i) l and d sensible values clearly in cm [1] (ii) boiling tube between blocks, ruler spanning gap [1] suitable precaution: [1] e.g. measure in (at least) 2 places (and take average), avoid lip, ensure blocks smooth, no dirt between tube and block (iii) V1 correctly calculated [1] (b) (i) V2 present and < V1 [1] (ii) line of sight perpendicular to reading [1] OR read bottom of meniscus (iii) V3 calculation correct [1] (c) m present and ρ in range 1 to 3 [1] unit g / cm3 [1] (d) suitable source of inaccuracy [1] e.g. • any reference to why tube is not a cylinder, • tube may contain some water when mass taken, • difficult to fill to brim and then pour out appropriate effect on value of ρ explained [1] [Total: 11]

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2 In this experiment, you will investigate the relationship between potential difference and current for a resistor. The circuit has been set up for you. Carry out the following instructions, referring to Fig. 2.1. power supply slide wire resistor crocodile clip A V Fig. 2.1 (a) • Switch on. • Adjust the position of the crocodile clip on the slide wire until the potential difference V across the resistor is 0.4 V. • Record, in Table 2.1, the value of the current I shown on the ammeter. • Move the crocodile clip and record values of I for V = 0.8 V, 1.2 V, 1.6 V and 2.0 V. • Switch off. Table 2.1 V / V I / A 0.4 0.8 1.2 1.6 2.0 [1] (b) Plot a graph of V / V (y-axis) against I / A (x-axis). Start both axes at the origin (0,0). 0 0 [4] (c) (i) Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information. G = ...........................................................[1] (ii) The resistance R of the resistor is numerically equal to G. Give a value for R, to a suitable number of significant figures for this experiment. Include the unit. R = ...........................................................[2] (d) A student suggests that potential difference and current for this resistor should be proportional. State whether your graph supports this suggestion. Justify your statement by reference to your graph. statement .................................................................................................................................. ................................................................................................................................................... justification ................................................................................................................................ ................................................................................................................................................... ................................................................................................................................................... [2] (e) The student notices that her slide wire becomes very hot during the experiment. Suggest a change to the apparatus or procedure that might prevent this. ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[1] [Total: 11]

Mark scheme: 2 (a) 5 I values, all < 1.00 A and all increasing [1] (b) graph: • axes labelled with quantity and unit [1] • appropriate scales (plots occupying at least ½ grid) [1] • plots all correct [1] • well-judged line and thin line, neat plots [1] (c) (i) G present AND triangle method seen using at least ½ line [1] (ii) R in range 4 Ω to 6 Ω [1] to 2 / 3 significant figures and with correct unit [1] (d) statement matching graph with reference to straight line [1] reference to passing through origin (within limits of experimental accuracy / owtte) [1] (e) suitable change: [1] e.g. reduce supply voltage / current, use thinner / longer wire, material with greater resistivity [Total: 11]

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3 In this experiment, you will investigate the refraction of light by a transparent block. You will determine a quantity known as the refractive index for the material of the 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 M e A B N D C L eye Fig. 3.1 (a) • Place the block approximately in the centre of the ray-trace sheet. Carefully draw around the block and label the corners ABCD as indicated by Fig. 3.1. • Remove the block from the ray-trace sheet. • Draw a normal to line AB at its centre. Extend the normal so that it crosses line CD. Label the point at which the normal crosses AB with the letter N and the point at which it crosses CD with the letter L. [1] (b) Draw a line NM, as indicated by Fig. 3.1, approximately 8 cm long and at an angle θ = 20°. [1] (c) • Replace the block in exactly the same position as in (a). • Place two pins P1 and P2 on line NM, a suitable distance apart. • Label the positions of P1 and P2. • View the images of 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 P1 and P2, all appear exactly one behind the other. • Label the positions of P3 and P4. • Remove the block and pins from the ray-trace sheet. [1] (d) (i) • Draw a line joining P3 and P4. Extend this line until it meets NL. • Label the point at which this line crosses CD with the letter E, and the point at which it meets NL with the letter F. • Draw a line joining points N and E. [1] (ii) • Measure the length a of line NE. a = ............................................................... • Measure the length b of line FE. b = ............................................................... a • Calculate a value n1 for the refractive index, using the equation n1 = . b n1 = ............................................................... [3] (e) (i) • Repeat steps (b) and (c) for a new angle θ = 40°. • Draw a line joining the new positions of P3 and P4. Extend this line until it meets NL. • Label the point at which this line crosses CD with the letter G and the point at which it meets NL with the letter H. • Draw a line joining points N and G. [1] (ii) • Measure the length c of line NG. c = ............................................................... • Measure the length d of line HG. d = ............................................................... c • Calculate a second value n2 for the refractive index, using the equation n2 = . d n2 = ............................................................... [1] (f) Describe two precautions you took in order to obtain reliable results in this experiment. 1. ............................................................................................................................................... ................................................................................................................................................... 2. ............................................................................................................................................... ................................................................................................................................................... [2] Tie your ray-trace sheet into this Booklet between pages 10 and 11. [Total: 11]

Mark scheme: 3 (a) normal correct [1] (b) incident line at θ = 20° [1] (c) pin separations > 5.0 cm [1] (d) (i) first set of lines all in correct place [1] (ii) correct values for a and b from ray trace [1] correct calculation of n1 and in range 1.3 to 1.8 [1] no unit for n1 or n2 [1] (e) (i) all lines thin and second set of lines in correct place with θ = 40° [1] (ii) c and d present and n2 within 10% of n1 [1] (f) any two suitable precautions: [2] e.g. • view pins from base / ensure pins upright, • large pin separations • use of thin pencil lines / sharp pencil / thin pins • repeat with different angles [Total: 11]

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4 A student suggests that the area of the water surface will affect the rate of cooling of hot water in a container. Plan an experiment to investigate the relationship between surface area and rate of cooling. Write a plan for the experiment, including: • the apparatus needed • how you will obtain a range of surface areas • instructions for carrying out the experiment • the measurements you will take • the precautions you will take to ensure that the results are as reliable as possible • the graph you will plot from your results – you should sketch the axes, with appropriate labels. A diagram is not required but you may draw one if it helps to explain your plan. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... 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Mark scheme: 4 apparatus: (set of) different sized beakers / containers, thermometer and stop clock / watch [1] method: pour hot water into container (and allow to cool) [1] and measure temperature and time repeat for a second container with a different surface area [1] precautions: any two from: [2] same volume of hot water same initial hot water temperature same room temperature or other environmental condition graph: temperature change / rate of cooling against surface area, [1] temperature against time, time to cool between fixed temperatures against surface area additional point: any one from: [1] • at least 5 different surface areas, • sensible range of container sizes given, • sensible amount of water stated, • use of lagging / insulating material for container walls, • same type of container • how surface area may be calculated [Total: 7]

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