Cambridge IGCSE Science - Combined 0653 — 2024 Feb/March Paper 5 · Variant 2

1 Penguins stand close together in a huddle, as shown in Fig. 1.1. Fig. 1.1 You will investigate the effect on heat loss of standing together in a huddle. You will use test-tubes to represent the penguins. The apparatus is assembled as shown in Fig. 1.2. middle clamp test-tube beaker elastic band single huddle Fig. 1.2 Procedure Step 1 Fill all the test-tubes with hot water. Step 2 Put a thermometer in the single test-tube. Step 3 Put another thermometer in the middle test-tube of the huddle. Step 4 Record in Table 1.1 the temperature of the water in these two test-tubes for time = 0 minutes. Step 5 Start the stop-clock. Step 6 Measure the temperature in each of these two test-tubes every minute for a total of 5 minutes. (a) (i) Record in Table 1.1 the temperature readings. Table 1.1 temperature / °C time / minutes single test-tube middle test-tube 0 1 2 3 4 5 [3] (ii) Calculate the overall change in temperature for each of the two test-tubes after 5 minutes. single test-tube = .......................................................... °C middle test-tube = .......................................................... °C [1] (iii) State a conclusion for your results in (a)(ii). ........................................................................................................................................... ..................................................................................................................................... [1] (b) Suggest why it is better to use the change in temperature to compare the heat loss rather than the final temperature. ................................................................................................................................................... ............................................................................................................................................. [1] (c) In this procedure you investigated the effect on heat loss of standing in a huddle. Suggest one other variable that affects heat loss in penguins. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 7]

Mark scheme: Question Answer Marks 1(a)(i) results for 0 minute recorded ; 3 all results recorded to same number of decimal places ; temperature decreases continuously for every value and smaller decrease for middle tube in huddle ; 1(a)(ii) correct calculation of temperature changes ; 1 1(a)(iii) heat loss is reduced / is less, in a huddle / slower heat loss in huddle / greater / faster heat loss, in single test tube ; 1 1(b) starting temperatures were not the same ; 1 1(c) surface area of penguins / surface area of huddle / external temperature / wind speed / volume of penguin / thickness of 1 feathers ;

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2 When a person exercises, their pulse rate changes. Plan an investigation to determine the relationship between the intensity of exercise a person does and the change in their pulse rate. You may use any common laboratory apparatus. You are not required to do this investigation. In your plan, include: • the apparatus needed • a brief description of the method and an explanation of any safety precautions you will take • what you will measure • which variables you will keep constant • how you will process your results to draw a conclusion. You may include a table that can be used to record the results if you wish. You do not need to include any results in your table. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 2 One marking point from each section and any two others (if one section is missing max 6 etc.). 7 1 Apparatus stop-clock / pulse meter / heart rate monitor (to measure pulse / exercise duration) ; exercise apparatus, e.g. treadmill / measuring apparatus for distance / height, e.g. tape measure ; 2 Method and safety describes a method to vary intensity ; measure pulse rate before and after three intensities of exercise ; wait until pulse rate returns to initial / resting, pulse rate between repeats ; check for health concerns / specific safety linked to apparatus used ; 3 What you will measure counts number of pulses in a fixed time, e.g. 15 s / measures pulse in bpm ; gives units for measurement, e.g. distance m / time s or min / height cm / speed in km / h ; 4 Which variables you will keep constant the same person each time / same characteristics of more than one person, e.g. same age / sex ; controls intensity of exercise, e.g. same duration of exercise (different intensity / speed) / same distance (different speeds) / same speed (different duration) / same exercise (different number of repetitions) ; 5 Processing results subtract initial pulse rate from final pulse rate / find change from initial and final pulse rate ; plot distance / duration / height, of exercise against pulse rate (dependent on candidate’s method) ; repeat measurements of pulse rates for the same intensity AND identify anomalies / take average AW ;

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3 You are going to investigate some properties of solution H. (a) Procedure Step 1 Measure 10.0 cm3 of solution H using a 10 cm3 measuring cylinder. Step 2 Pour this volume of solution H into a boiling tube. Step 3 Measure the temperature of solution H to the nearest 0.5 °C. (i) Record your result in Table 3.1. Table 3.1 temperature of solution H in step 3 / °C highest temperature of mixture at end of step 5 / °C temperature increase / °C [1] Step 4 Add all the aluminium foil provided to the boiling tube. Step 5 Stir the mixture in the boiling tube and measure the highest temperature reached to the nearest 0.5 °C. (ii) Record your result in Table 3.1. [1] Step 6 Filter the mixture from the boiling tube into a test-tube. (iii) Describe the appearance of the residue in the filter paper and the filtrate in the test-tube. residue .............................................................................................................................. filtrate ................................................................................................................................ [2] (iv) Calculate the temperature increase between step 3 and step 5. Record your answer in Table 3.1. [1] (v) Calculate the amount of thermal (heat) energy released q. Use the equation shown. q = 10.0 × 3.96 × temperature increase Give your answer to three significant figures. thermal energy released q = ...................................................... J [2] (vi) Explain why the reaction mixture is stirred in step 5. ........................................................................................................................................... ..................................................................................................................................... [1] (vii) The temperature increase is not as large as expected because thermal (heat) energy is transferred to the surroundings. Suggest one improvement to the apparatus that will give a more accurate value for the thermal energy released. ........................................................................................................................................... ..................................................................................................................................... [1] (b) Procedure • Add approximately 1 cm depth of solution H to a test-tube. • Slowly add aqueous ammonia to the test-tube until there is no further change. Record your observations. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (c) Procedure • Add approximately 2 cm depth of solution H to a test-tube. • Add approximately 1 cm depth of dilute nitric acid to the test-tube. • Add five drops of aqueous silver nitrate to the test-tube. • Leave for 3 minutes. (i) Record your observations. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) State the name of the salt dissolved in solution H. Use information from your observations in (b) and (c)(i). ..................................................................................................................................... [1] [Total: 13]

Mark scheme: 3(a)(i) temperature of H measured to nearest 0.5 °C ; 1 3(a)(ii) highest temperature recorded to nearest 0.5 °C and greater than starting temperature ; 1 3(a)(iii) (residue) silver / grey / pink / (red-)brown / orange (solid) ; 2 (filtrate) colourless (solution) ; 3(a)(iv) correct calculated temperature increase ; 1 3(a)(v) correct calculation of thermal energy released ; 2 answer to three significant figures ; 3(a)(vi) to get even distribution of temperature / to ensure complete reaction ; 1 3(a)(vii) insulate boiling tube / lid on boiling tube / use a, plastic beaker / plastic boiling tube ; 1 3(b) (light) blue precipitate ; 2 (in excess) changes to a dark blue solution ; 3(c)(i) white precipitate / white solid (at bottom of test-tube) ; 1 3(c)(ii) copper chloride ; 1

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4 You will investigate how the resistance R of a resistance wire varies with its length l. The circuit is assembled as shown in Fig. 4.1. V A crocodile clip 0 cm metre rule resistance wire length l Fig. 4.1 (a) Procedure • Close the switch. • Place the crocodile clip on the resistance wire at a length l = 15.0 cm from the 0 cm end of the metre rule. • Measure the current I in the circuit and the potential difference V across the resistance wire. • Open the switch. (i) Record your results in Table 4.1. Table 4.1 length l of current I potential difference V resistance R resistance wire / A / V / Ω / cm 15.0 30.0 45.0 60.0 75.0 [2] Repeat the procedure in (a) for the values of length l shown in Table 4.1. (ii) Record your results in Table 4.1. [2] (b) Calculate the resistance R of the wire for each length l. Use the equation shown. V R = I Record your values of R in Table 4.1. [2] (c) (i) On the grid, plot a graph of the resistance R on the vertical axis against length l. R / Ω 0 0 l / cm [2] (ii) Draw the straight line of best fit. [1] (iii) Calculate the gradient of the line. Show on your graph the triangle you use to calculate the gradient. gradient = .......................................................... [2] (iv) The gradient of the line is a measure of the resistance per unit length of the wire. State the unit for the resistance per unit length of the wire. unit = ......................................................... [1] (d) Another student repeats the same procedure carefully. Suggest one practical source of error to explain why the other student may get measurements that are different to yours. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 13] NOTES FOR USE IN QUALITATIVE ANALYSIS Tests for anions anion test test result carbonate (CO32–) add dilute acid effervescence, carbon dioxide produced chloride (Cl –) acidify with dilute nitric acid, then white ppt. [in solution] add aqueous silver nitrate nitrate (NO3–) add aqueous sodium hydroxide, ammonia produced [in solution] then aluminium foil; warm carefully sulfate (SO42–) acidify, then add aqueous barium white ppt. [in solution] nitrate Tests for aqueous cations cation effect of aqueous sodium hydroxide effect of aqueous ammonia ammonium (NH4+) ammonia produced on warming – calcium (Ca2+) white ppt., insoluble in excess no ppt. or very slight white ppt. copper(II) (Cu2+) light blue ppt., insoluble in excess light blue ppt., soluble in excess, giving a dark blue solution iron(II) (Fe2+) green ppt., insoluble in excess green ppt., insoluble in excess iron(III) (Fe3+) red-brown ppt., insoluble in excess red-brown ppt., insoluble in excess zinc (Zn2+) white ppt., soluble in excess, giving white ppt., soluble in excess, a colourless solution giving a colourless solution Tests for gases Flame tests for metal ions gas test and test result metal ion flame colour ammonia (NH3) turns damp red litmus paper blue lithium (Li+) red carbon dioxide (CO2) turns limewater milky sodium (Na+) yellow chlorine (Cl 2) bleaches damp litmus paper potassium (K+) lilac hydrogen (H2) ‘pops’ with a lighted splint copper(II) (Cu2+) blue-green oxygen (O2) relights a glowing splint

Mark scheme: 4(a)(i) first I value recorded to at least 2 decimal places ; 2 first V value recorded to at least 1 decimal place ; 4(a)(ii) all V and I values recorded ; 2 I values decreasing and V values increasing down the table ; 4(b) all R values recorded ; 2 all values correct ; 4(c)(i) appropriate scales (plots occupying at least ½ grid) ; 2 plots all correct to ½ small square and precise plots ; 4(c)(ii) thin straight line of best fit drawn with even distribution of points ; 1 4(c)(iii) triangle method seen on graph and triangle at least half the length of line of best fit between first and last point ; 2 correct calculation of gradient ; 4(c)(iv)  / cm ; 1 (4)(d) difficult to position crocodile clip exactly / wire may not be uniform diameter / wire not perfectly straight / wire has kinks in it ; 1

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