Cambridge IGCSE Physics 0625 — 2013 Oct/Nov Paper 5 · Variant 3

1 In this experiment, you will measure the capacity of a drinks cup by three methods. The For capacity of a cup is the maximum volume of liquid that it will hold in normal use. Examiner’s Use You have been supplied with a cup on which the maximum level MAX is marked both inside and out, as shown in Fig. 1.1. Do not fill the cup beyond this level. MAX Fig. 1.1 (a) Method 1 In Method 1, the capacity V1 is determined from the mass of water in the cup. (i) Fill the cup to the marked level with water. (ii) Place the cup, containing the water, on the balance. Read and record its mass m. m = ...............................................g [1] (iii) Leave the water in the cup for the next experiment. (iv) Calculate a value for the capacity V1, using your reading from (a)(ii) and the m equation V1 = , where ρ = 1.00 g / cm3. ρ V1 = ..................................................[2] (b) Method 2 In Method 2, the capacity V2 is measured directly from the volume of water in the cup. (i) Carefully tip the water into the measuring cylinder. (ii) Read and record the volume V2 of the water in the measuring cylinder. V2 = ..................................................[1] (c) Method 3 For Examiner’s In Method 3, the capacity V3 is estimated using the average diameter of the cup and considering the cup as an approximate cylinder. Use d1 MAX h d2 Fig. 1.2 (i) Measure and record the diameter d1 of the top of the cup, as shown in Fig. 1.2. d1 = ................................................ cm (ii) Measure and record the diameter d2 of the base of the cup. d2 = ................................................ cm (iii) Measure and record the height h from the base to the marked level MAX. h = ................................................ cm [1] (iv) Calculate the average diameter D using your readings from (c)(i) and (c)(ii), and (d1 + d2) the equation D = . 2 D = ...................................................... (v) Calculate an approximate value for the capacity V3, using your results from (c)(iii) πD 2h and (c)(iv) and the equation V3 = . 4 V3 = ...................................................... [2] (d) State a possible practical source of inaccuracy in Method 2 and a possible practical For source of inaccuracy in Method 3. Examiner’s Use Method 2 .......................................................................................................................... .......................................................................................................................................... Method 3 .......................................................................................................................... .......................................................................................................................................... [2] (e) State an additional measurement which could be taken to give a more accurate result in Method 1. .......................................................................................................................................... ......................................................................................................................................[1] [Total: 10]

Mark scheme: 1 (a) m < 250 [1] V1 value = m [1] unit cm3 [1] (b) V2 within 10% of V1 [1] (c) d1, d2, h all present and d1>d2 [1] D calculation correct to at least 1 d.p. [1] V3 calculated correctly and > V1 and V2 and 2 or 3 significant figures only [1] (d) method 2 – any one from: some water left in cup/spilt measuring cylinder not read at eye level/perpendicularly/bottom of meniscus parallax explained [1] method 3 – any one from: d1 not at liquid level d1 and d2 not inside diameters difficult to measure h (because of sloping side) h not measured at eye level/perpendicularly/parallax explained [1] (e) mass of cup / zero reading on balance [1] [Total: 10]

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2 In this experiment, you will investigate methods of preventing loss of thermal energy. For Examiner’s You are provided with two beakers labelled A and B. Beaker A has a layer of insulation. Use Do not remove this insulation. Beaker B has a lid but no insulation. You are also provided with a supply of hot water. Carry out the following instructions, referring to Fig. 2.1. clamp clamp thermometer lid insulation water water beaker A beaker B Fig. 2.1 (a) (i) Pour approximately 200 cm3 of hot water into beaker A. (ii) Place the thermometer into the water. When the reading has stopped rising, measure the initial temperature of the hot water in the beaker and, at the same time, start the stopclock. Record this temperature at time t = 0 s in the first row of Table 2.1. (iii) Measure, and record in the table, the temperature of the hot water at times t = 30 s, 60 s, 90 s, 120 s, 150 s and 180 s. (iv) Remove the lid from beaker B and pour approximately 200 cm3 of hot water into the beaker. Replace the lid. (v) Repeat steps (a)(ii) and (a)(iii) for beaker B. (vi) Complete the column headings and enter the values of t in the table. For Examiner’s Table 2.1 Use beaker A beaker B t / θ/ θ/ [5] (b) State from which beaker, if any, the rate of loss of thermal energy is the greater. Justify your answer by referring to your results. beaker .................................... justification ....................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... [2] (c) State one condition that should be controlled to ensure that the comparison between beaker A and beaker B is a fair one. .......................................................................................................................................... ......................................................................................................................................[1] (d) A student points out that the experiment does not test the effectiveness of insulation in reducing thermal energy loss. Suggest a change to this experiment which could be made so that the effect of insulation could be investigated. Explain why this change would help. suggestion ....................................................................................................................... .......................................................................................................................................... explanation ...................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... [2] [Total: 10]

Mark scheme: 2 (a) units correct (symbols or words) [1] times correct (0, 30, 60, 90,120,150,180) [1] θ beaker A and θ beaker B decreasing [1] θ to at least 1oC [1] smaller/same change in 180 s in beaker B compared to A [1] (b) statement matching temperature changes (accept ‘no significant difference’ if justified) and justification matching statement (comparison of temperature changes) [1] including specific mention of temperature change in same time [1] (c) appropriate condition relating to comparison, any one from: same size/thickness of beaker same volume of water same initial temperature same room temperature / appropriate environmental condition same time for cooling [1] IGCSE – October/November 2013 0625 53 (d) any sensible alteration e.g.: put lid on/cover top of A extra experiment without insulation or lid / take lid off B [1] matching explanation e.g.: most thermal energy loss by convection o.w.t.t.e. have only changed one factor o.w.t.t.e. [1] [Total: 10]

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3 In this experiment, you will investigate the current and potential difference in an electrical For circuit. Examiner’s Use The circuit has been set up for you. Carry out the following instructions, referring to Fig. 3.1. power supply V crocodile clip A resistance wire F E D C B A Fig. 3.1 (a) (i) Connect the crocodile clip to the resistance wire at the position labelled A. (ii) Switch on. Read and record in Table 3.1, the potential difference V and the current I. Switch off. (iii) Repeat step (a)(ii) with the crocodile clip at positions B, C, D, E and F. Table 3.1 position V / V I / A A B C D E F [2] (b) Plot a graph of V / V (y-axis) against I / A (x-axis). For Examiner’s Use [4] (c) (i) Determine the gradient M of the graph. Show clearly on the graph how you obtained the necessary information. M = ..................................................[2] (ii) The gradient M is numerically equal to the resistance R of the power supply. Write down the resistance R to a suitable number of significant figures for this experiment. R = ..................................................[2] [Total: 10]

Mark scheme: 3 (a) potential differences all < 2.5 V and to at least 1 d.p. [1] currents all < 1.50 A and to at least 2 d.p. [1] (b) axes labelled, with units [1] appropriate scales (plots occupying at least ½ grid) [1] plots correct to ½ square [1] best-fit line and thin, neat line, neat plots [1] (c) (i) triangle method seen on graph [1] large triangle (at least 1/2 candidate’s line) [1] (ii) R = M and < 2.0 [1] 2 or 3 significant figures and unit Ω (symbol or word) [1] [Total: 10]

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4 In this experiment, you will investigate the reflection of light by a plane mirror. For Examiner’s Carry out the following instructions, referring to Fig. 4.1. Use ray-trace sheet O L eye C _ A B N D Fig. 4.1 (a) Draw a line about 8 cm from the bottom of your ray-trace sheet. Label this line AB. For Mark a point N, near the centre of AB. Examiner’s Draw a normal to AB at point N. Label the other end of this normal L. Use (b) Draw a line CD passing through N and at an angle α to AB where α = 20°. (c) Place two pins P1 and P2 some distance apart on line LN. Label the positions of P1 and P2. (d) Place the mirror on line CD and view the images of P1 and P2 from the direction indicated by the eye in Fig. 4.1. Place two pins P3 and P4 some distance apart so that the images of P1 and P2, and the pins P3 and P4, all appear exactly one behind the other. Label the positions of P3 and P4. (e) Remove the mirror and the pins. Repeat steps (b), (c) and (d) for an angle α = 30°, replacing pins P1 and P2 in their original positions in step (c). (f) Remove the mirror and the pins. (g) Draw a line passing through the first P3 and P4 positions and reaching AB. (h) Measure, and record in Table 4.1, the angle θ between this line and the normal NL. (i) Repeat steps (g) and (h) for the second set of P3 and P4 positions. Table 4.1 α/ ° θ/ ° 20 30 [1] (j) A student suggests that θ should always be equal to 2α. State whether your experimental results support this idea. Justify your answer with reference to the results. statement ......................................................................................................................... .......................................................................................................................................... justification ....................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... [2] (k) Suggest two precautions that could be taken to ensure accurate results from this For experiment. Examiner’s Use 1. ...................................................................................................................................... .......................................................................................................................................... 2. ...................................................................................................................................... .......................................................................................................................................... [2] Tie your ray-trace sheet between pages 10 and 11. [5] [Total: 10]

Mark scheme: 4 (a) (i) ray trace: normal correct [1] CD at 20o within1o and equivalent reflected line in correct place [1] CD at 30o within 1o and equivalent reflected line in correct place [1] all lines thin and neat [1] P1 – P2 pin separation at least 5 cm [1] table: θ = 40o and 60o within 2o (e.c.f. from candidate’s α ) [1] (j) definite statement matching results (expect YES but allow e.c.f. if difference >10%) and justification matching statement (expect ‘within the range of experimental accuracy’ o.w.t.t.e.) [1] values from results shown/used (correctly w.r.t. statement) [1] (k) any two suitable precautions: thin lines / fine pencil view protractor perpendicularly / parallax explained lines through centre of pin holes pins well separated pins vertical/not bent/viewed at base place mirror so that reflecting surface is on line o.w.t.t.e. [2] [Total: 10]

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