Cambridge IGCSE Science - Combined 0653 — 2021 Oct/Nov Paper 5 · Variant 2

1 (a) Fig. 1.1 shows two animals, one from a cold climate and one from a hot climate. cold climate hot climate Fig. 1.1 The animal from the cold climate is much larger than the animal from the hot climate. Identify two other visible differences which can be seen in Fig. 1.1. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ................................................................................................................................................... [2] (b) You are going to investigate heat loss in animals of different sizes. Two beakers of different sizes will represent the animals: • A large 250 cm3 beaker will represent a large animal. • A small 50 cm3 beaker will represent a small animal. (i) Procedure • Carefully clamp a thermometer in the large beaker as shown in Fig. 1.2. thermometer clamp large beaker Fig. 1.2 • Ask for hot water to be added to the large beaker. • Wait for the reading on the thermometer to stop rising. • Record this temperature in Table 1.1 at time = 0 seconds. • Start the stop-watch. • Record in Table 1.1 the temperature of the water every 60 seconds for 300 seconds. Table 1.1 temperature of water in temperature of water in time large beaker small beaker / seconds / °C / °C 0 60 120 180 240 300 [2] (ii) You are now going to use the small 50 cm3 beaker. • Remove the thermometer from the large beaker. • Replace the large beaker with the small empty beaker. • Repeat the procedure using the small beaker instead of the large beaker. Record in Table 1.1 the temperature of the water in the small beaker every 60 seconds for 300 seconds. [2] (c) Calculate the temperature decrease of the water in each beaker. Use the equation shown. temperature decrease = (temperature at 0 seconds) – (temperature at 300 seconds) temperature decrease in large beaker = .......................................................... °C temperature decrease in small beaker = .......................................................... °C [1] (d) You are going to plot a graph of temperature against time for both beakers on the same axes. • Use a scale for the temperature axis that is suitable for both beakers. You do not need to start the scale at zero. • Plot the points for the large beaker. • Draw the smooth best-fit curve. Label this curve L. • Plot the points for the small beaker. • Draw the smooth best-fit curve. Label this curve S. temperature / °C 0 60 120 180 240 300 time / seconds [4] (e) Suggest which animal, large or small, loses heat more quickly. Explain your choice using your answers to (c) and (d). animal ..................................................... explanation ............................................................................................................................... ................................................................................................................................................... [1] (f) Suggest one improvement to the procedure which gives a fairer comparison of the rate of heat loss from the beakers. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 13]

Mark scheme: 1(a) any two from: the animal from the cold climate / the bear, has: ORA thick(er) / long(er) / more, fur ; a short(er) / no, tail ; (all) legs of equal length / short relative to body size ; small(er) eyes (relative to size of animal) ; 2 1(b)(i) all temperature values recorded for large beaker ; highest temperature at t = 0 AND values decrease between 0 and 300 seconds ; 2 1(b)(ii) all temperature values recorded for small beaker ; values for small beaker decrease more than for large beaker ; 2 1(c) correct calculation of decrease for both beakers ; 1 1(d) linear temperature scale such that points cover more than 50% of grid ; points for small beaker plotted correctly ; points for large beaker plotted correctly ; smooth, lines / curves, of best-fit drawn ; 4 1(e) small animal / animal from hot climate AND temperature change in larger beaker is smaller / slope of graph is less steep ; ORA 1 1(f) use same starting temperature of water / use higher starting temperature / increase measurement time ; 1

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2 You are going to prepare a sample of copper(II) sulfate solution. You will react a sample of solid copper(II) carbonate with dilute sulfuric acid. (a) Procedure • Use a measuring cylinder to measure 20 cm3 of dilute sulfuric acid. • Pour the dilute sulfuric acid into the glass beaker. • Add a spatula of copper(II) carbonate to the dilute sulfuric acid. • Stir the mixture with a glass rod for approximately 30 seconds. Describe your observations of what happens in the beaker when the copper(II) carbonate reacts with the dilute sulfuric acid. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (b) • Add another spatula of copper(II) carbonate to the reaction mixture in the beaker and stir the mixture for approximately 30 seconds. • If all the copper(II) carbonate reacts fully, add more copper(II) carbonate and stir again. • Keep adding copper(II) carbonate until no more reacts. There will be solid copper(II) carbonate left in the beaker. • Filter some of the mixture into a test-tube. • Collect at least 3 cm depth of filtrate. Keep this for the tests in (c). • While the mixture filters, write your answers to (b)(i), (b)(ii) and (b)(iii). (i) Describe the appearance of the filtrate in the test-tube. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Describe, in detail, how to make large crystals of copper(II) sulfate from the filtrate. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [3] (iii) Describe the appearance of the residue in the filter paper. ........................................................................................................................................... ..................................................................................................................................... [1] (c) Place 2 cm depth of filtrate into a clean test-tube. (i) Add 10 drops of aqueous potassium iodide to the filtrate in the test-tube. Describe your observations. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Add 4 cm depth of aqueous sodium thiosulfate to the mixture in (c)(i). Describe your observations. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (d) A student does a flame test. The student: • cleans a flame test wire • dips the flame test wire into a sample of solid copper(II) sulfate • places the wire in the top of a blue Bunsen burner flame • observes a blue-green and yellow flame. (i) Suggest why the student cleans the flame test wire. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Explain why the student thinks the sample of copper(II) sulfate is not pure. ........................................................................................................................................... ..................................................................................................................................... [1] (iii) Suggest why it is important to use a blue Bunsen burner flame rather than a yellow Bunsen burner flame in the flame test. ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 13]

Mark scheme: 2(a) fizzes / bubbles ; blue solution ; 2 2(b)(i) blue solution ; 1 2(b)(ii) any three from: heat (solution) ; until crystals start to form / until saturated / to reduce the volume / to evaporate (the solution) ; idea of leaving (after heating) to cool ; filter crystals from solution / dry crystals on filter paper ; 3 2(b)(iii) green solid ; 1 2(c)(i) brown (mixture forms) ; 1 2(c)(ii) (goes) white / paler brown ; precipitate present ; 2 2(d)(i) idea of preventing contamination from the wire ; 1 2(d)(ii) (yellow indicates) it has sodium (ions) in it / the colour should just be (blue-)green / flame contains yellow / not a single colour ; 1 2(d)(iii) it is hotter / higher temperature / does not leave soot on the wire / heats faster ; 1

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3 You are going to determine the density of a cork. (a) Use the balance to measure the mass of the cork. Record the mass to the nearest 0.1 g. mass = ...................................................... g [1] (b) You are going to determine the volume of the cork using the method of displacement. Procedure Fig. 3.1 shows the three steps in the procedure. thread measuring cylinder cork water bob step 1 step 2 step 3 Fig. 3.1 step 1 • Add 70 cm3 of water to the measuring cylinder. step 2 • Holding the thread, carefully lower the bob into the water in the measuring cylinder until the bob is completely under water. (i) Record the total volume of the water and bob. volume of water and bob = .................................................. cm3 [1] step 3 • Remove the bob from the water. • Make sure that the volume of water in the measuring cylinder is 70 cm3. • Use the thread to attach and secure the cork close to the bob, as shown in Fig. 3.1. • Carefully lower the bob and cork into the water in the measuring cylinder until the bob and cork are completely under water. (ii) Record the total volume of the water, bob and cork. volume of water, bob and cork = .................................................. cm3 [1] (iii) Use your answers to (b)(i) and (b)(ii) to calculate the volume of the cork. Use the equation shown. volume of cork = (volume of water, bob and cork) – (volume of water and bob) volume of cork = .................................................. cm3 [1] (c) Calculate the density of the cork. Use the equation shown. mass density = volume Give your answer to two significant figures. density of cork = .............................................. g / cm3 [2] (d) Cork floats on water. Suggest why the bob is needed in this experiment. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 7]

Mark scheme: 3(a) mass recorded to 0.1 g ; 1 3(b)(i) volume recorded > 70 (cm3) ; 1 3(b)(ii) volume recorded > (b)(i) (cm3) ; 1 3(b)(iii) correct volume of cork (cm3) ; 1 3(c) correct calculation ; answer to 2 sig. figs. ; 2 3(d) to immerse the cork / to make it sink completely under the water / AW ; 1

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4 A student has clothes made of three different materials: cotton, polyester and wool. After washing the clothes, the student observes the wet clothes becoming dry as the water evaporates. The student wants to know if the material of the clothes affects the rate at which the water evaporates. Plan an investigation to determine how the material of the clothes affects the rate of evaporation of water from the clothes. You are provided with: • samples of cotton, polyester and wool • water You may use any common laboratory apparatus in your plan. You are not required to do this investigation. Include in your plan: • the apparatus needed • a brief description of the method, explaining 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 labelled diagram. You may include a results table (you are not required to enter any readings in the table). .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 4 one from each section and then any other two marks 1. apparatus stop-watch / timer / (stop-)clock / chronometer ; balance ; 2. method wet sample(s) of material(s) / dip into water ; spread flat / hang up ; use a fan / put in warm place / put in oven / place in specified outdoor conditions, e.g. sun, wind ; safety precaution specific to, heating apparatus / use of fan / cutting ; 3. measurements measure mass of wet sample at start ; measure mass of sample after a specified amount of time / measure time taken for a specific mass to evaporate ; 4. variables to be controlled fabric surface area / (specified) size of fabric ; temperature OR stated drying, environment / place / conditions ; 5. processing and use of results (repeat each experiment and) calculate average ; the one with shortest drying time or most mass lost has the fastest rate of evaporation ORA ; 7

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