Cambridge IGCSE Science - Combined 0653 — 2022 Oct/Nov Paper 5 · Variant 1

1 You are going to investigate the effect of temperature on the rate of respiration in yeast cells. When yeast cells respire, they produce carbon dioxide gas. (a) You are provided with a suspension of respiring yeast cells in a beaker labelled yeast. Procedure step 1 Half-fill the empty beaker labelled warm water with warm water. (i) Record the temperature of the warm water in the beaker. temperature of warm water = .......................... °C [1] step 2 Stir the yeast suspension. step 3 Use a syringe to add 10 cm3 of yeast suspension to a clean boiling tube (large test-tube). step 4 Place the boiling tube of yeast suspension in the beaker of warm water. step 5 Fig. 1.1 shows the apparatus. Make sure the syringe barrel contains water and is fully submerged in the container of water. delivery tube bung boiling tube beaker of warm water 10 cm3 syringe barrel yeast suspension container of water Fig. 1.1 step 6 Keep the syringe barrel fully submerged in the container of water and place the bung in the boiling tube of yeast suspension. step 7 Measure the initial volume of gas in the syringe barrel. (ii) Record in Table 1.1 this value to the nearest 0.5 cm3. [1] step 8 Start the stop-clock and wait for 5 minutes. Continue with (b) while you are waiting. step 9 After 5 minutes, measure the final volume of gas in the syringe barrel. (iii) Record in Table 1.1 this value to the nearest 0.5 cm3. [1] Table 1.1 initial volume of gas final volume of gas volume of gas collected beaker / cm3 / cm3 / cm3 warm water cold water step 10 Remove the bung from the boiling tube of yeast suspension. step 11 Repeat step 2 to step 9 using the beaker of cold water. (iv) Record in Table 1.1 the initial and final volumes of gas for cold water. [1] (v) Calculate the volume of gas collected in each experiment. Use the equation shown. volume of gas collected = final volume of gas – initial volume of gas Record these values in Table 1.1. [1] (vi) State the effect of temperature on the rate of respiration in yeast cells. ........................................................................................................................................... ..................................................................................................................................... [1] (vii) The yeast suspension is stirred in step 2 to mix it. Suggest why this is important. ........................................................................................................................................... ..................................................................................................................................... [1] (b) A student repeats the procedure in (a) at five different temperatures. The student’s results are shown in Table 1.2. Table 1.2 temperature volume of gas collected / °C / cm3 5 2.0 10 4.5 15 8.5 20 10.0 25 10.0 (i) On the grid, plot a graph of volume of gas collected (vertical axis) against temperature. [3] (ii) Draw the best-fit curve. [1] (iii) State and explain whether the student’s results in Table 1.2 support your answer in (a)(vi). Place a tick (3) in the appropriate box. support do not support explanation ........................................................................................................................ ........................................................................................................................................... ........................................................................................................................................... [1] (iv) Suggest why the volume of gas collected by the student does not go above 10 cm3. ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 13] Check that you have completed 1(a).

Mark scheme: Question Answer Marks 1(a)(i) temperature recorded ; 1 1(a)(ii) initial volume for warm water recorded to nearest 0.5 cm3 ; 1 1(a)(iii) final volume for warm water recorded that is greater than 1(a)(ii) ; 1 1(a)(iv) both volumes recorded for cold water ; 1 1(a)(v) correct calculations ; 1 1(a)(vi) as temperature increases, the rate of respiration increases / ORA ; 1 1(a)(vii) even distribution of yeast / AW ; 1 1(b)(i) axes correct way round and labelled with units ; 3 suitable linear scales such that plots cover at least half of grid ; plots correct ; 1(b)(ii) best-fit curve suitable for plots ; 1 1(b)(iii) support higher temperature gives higher volume of gas / graph has a positive gradient ; 1 OR do not support graph levels off / no increase, after 20 °C / at higher temperature / after 10 cm3 of gas collected ; 1(b)(iv) reaction has finished / no more respiration / sugar used up / not enough sugar / syringe only holds 10 cm3 / gas syringe is 1 full ;

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2 You are going to investigate the reaction of dilute hydrochloric acid with three solids, K, L and M. You are provided with the three solids, K, L and M. (a) Procedure for solid K • Put a spatula of K into a clean test-tube. • Add approximately 3 cm depth of dilute hydrochloric acid to the test-tube. • Gently swirl the test-tube and its contents. • Leave the test-tube for about four minutes while you do parts (b) and (c). Record your observations of the contents of the test-tube after four minutes. ................................................................................................................................................... ............................................................................................................................................. [1] (b) Procedure for solid L • Put a spatula of L into a clean test-tube. • Add approximately 3 cm depth of dilute hydrochloric acid to the test-tube. (i) Record your observations. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (ii) Explain how your observations in (b)(i) show that solid L contains carbonate ions. ........................................................................................................................................... ..................................................................................................................................... [1] (c) Procedure for solid M • Put a piece of M into a clean test-tube. • Add approximately 3 cm depth of dilute hydrochloric acid to the test-tube. • Test the gas made with a glowing splint. (i) One observation is that the mixture fizzes. Describe one other observation of the reaction in the test-tube. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Describe the result of the gas test. ........................................................................................................................................... ..................................................................................................................................... [1] (iii) Explain why it is not possible to use this gas test to identify the gas made in this reaction. ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 7] Check that you have completed 2(a).

Mark scheme: 2(a)(i) (pale) blue (solution) (above a black solid) ; 1 2(b)(i) fizzes / effervescence / bubbles ; 2 blue (solution) (formed) ; 2(b)(ii) carbonates, fizz / give off gas, with acid ; 1 2(c)(i) test-tube gets warmer / solid disappears / solid gets smaller ; 1 2(c)(ii) glowing splint does not relight / splint goes out / splint still glows ; 1 2(c)(iii) idea that, there is no positive result for a gas ; 1

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3 Aqueous hydrogen peroxide is a colourless solution that decomposes to make water and oxygen gas. Fig. 3.1 shows the word equation for the decomposition of hydrogen peroxide. hydrogen water + oxygen peroxide Fig. 3.1 Manganese(IV) oxide powder is added to aqueous hydrogen peroxide to allow the decomposition to happen at room temperature. Plan an investigation to determine the relationship between the mass of manganese(IV) oxide powder added and the volume of oxygen gas made. You are provided with: • aqueous hydrogen peroxide • manganese(IV) oxide powder. You may use any common laboratory apparatus in your plan. You are not required to do this investigation. Include in your plan: • the apparatus you will use • 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: 3 one marking point from each section and then any two others 7 1 apparatus balance / measuring cylinder, used to measure hydrogen peroxide ; gas syringe / measuring cylinder in water, used for collecting gas ; 2 brief description of method and safety precautions idea of adding manganese(IV) oxide to hydrogen peroxide AND waiting for, complete reaction / volume of gas to stop increasing / bubbles to stop ; detail given about, sealing apparatus / putting in bung immediately after adding, manganese(IV) oxide / hydrogen peroxide ; repeat the (same) procedure using different masses of manganese(IV) oxide ; use at least 4 different masses of manganese(IV) oxide ; wearing, safety glasses / goggles, to keep, hydrogen peroxide / manganese(IV) oxide powder, out of eyes ; 3 measurements measure mass of manganese(IV) oxide used / stated mass of manganese(IV) oxide used / units of mass of manganese(IV) oxide stated as grams ; measure the volume of hydrogen peroxide used / stated volume of hydrogen peroxide used / states units of volume for hydrogen peroxide as cm3 ; measure volume of gas / states units for volume of gas as cm3 ; 4 constant variables volume of hydrogen peroxide ; concentration of hydrogen peroxide ; temperature ; 5 processing plot graph of volume against mass / calculate ratio of volume of gas to mass, of manganese(IV) oxide added ; take averages from repeated experiments / repeat and exclude anomalous results ;

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4 You are going to use a balancing method to determine the mass of a metre rule. (a) Place the centre of the 30 g mass on the metre rule at the 15.0 cm mark. Use the tape to fix the mass in place. The mass hides the markings on the metre rule. Explain how you make sure that the centre of the 30 g mass is directly over the 15.0 cm mark. You may include a diagram in your answer. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (b) Place the metre rule on the pivot. Carefully slide the metre rule backwards and forwards on the pivot until the metre rule is balanced (or as close to balance as possible). Fig. 4.1 shows the metre rule at balance. u v 30 g mass centre of metre rule metre rule 0 cm 15.0 cm 50.0 cm 100.0 cm pivot Fig. 4.1 (not to scale) (i) Record the position of the pivot to the nearest 0.1 cm. position of pivot = ................................................... cm [2] (ii) Calculate the distance u between the centre of the 30 g mass and the position of the pivot. Use the equation shown. u = position of pivot – 15.0 u = ................................................... cm [1] (iii) Use your answer to (b)(i) to calculate the distance v between the pivot and the 50.0 cm mark, the centre of the metre rule. Use the equation shown. v = 50.0 – position of pivot v = ................................................... cm [1] (c) Calculate the mass m of the metre rule. Use your answers to (b)(ii) and (b)(iii) and the equation shown. 30 u m = v Record your answer to two significant figures. m = ...................................................... g [2] (d) Suggest one practical reason why it is difficult to get an accurate result using this balancing method. ................................................................................................................................................... ............................................................................................................................................. [1] (e) Remove the 30 g mass and tape from the metre rule. (i) Measure the weight W of the metre rule using the newton meter. W = ..................................................... N [1] (ii) Calculate the mass m of the metre rule. Use your answer to (e)(i) and the equation shown. m = W × 100 m = ...................................................... g [1]

Mark scheme: 4(a) words and / or a diagram to explain: 2 recording the position of each edge of the mass ; idea that centre (at 15) is halfway between the two reference points recorded ; 4(b)(i) sensible value for pivot ; 2 to nearest 0.1 cm ; 4(b)(ii) correct calculation for u ; 1 4(b)(iii) correct calculation for v ; 1 4(c) correct calculation ; 2 recorded to two sig. figs. ; 4(d) difficulty with, achieving perfect balance / finding exact position of centre of mass / ruler sliding off pivot very easily ; 1 4(e)(i) sensible value for weight ; 1 4(e)(ii) correct calculation ; 1 4(f) calculates difference between higher and lower value ; calculates percentage difference AND states appropriate conclusion ; OR calculates 10% increase of lower value / 10% decrease of higher value ; compares higher value to 10% range of lower value AND states appropriate conclusion / compares lower value to 10% range of higher value AND states appropriate conclusion ;

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