Cambridge IGCSE Sciences - Co-ordinated (Double) 0654 — 2024 Feb/March Paper 5 · Variant 2

1 You are going to investigate the effect of catalase on the breakdown of hydrogen peroxide. Catalase is an enzyme found in living cells such as potato cells. Catalase speeds up the breakdown of hydrogen peroxide into oxygen gas and water. hydrogen peroxide oxygen + water You are provided with some potato puree and some hydrogen peroxide solution. (a) (i) Fig. 1.1 shows the assembled apparatus. delivery tube measuring cylinder stopper water boiling tube Fig. 1.1 Procedure • Use the stirring rod to mix the potato puree. • Remove the stopper from the boiling tube and add about 2 cm depth of potato puree. • Use the syringe to add 2 cm3 of hydrogen peroxide solution to the boiling tube and quickly replace the stopper. • Immediately start the stop-watch. • Record in Table 1.1 the total volume of gas collected in the measuring cylinder every minute for 6 minutes. Record your values to the nearest 0.5 cm3. Table 1.1 total volume of gas volume of gas collected in each time / min collected / cm3 interval of 1 minute / cm3 0 0 0 1 2 3 4 5 6 [4] (ii) Calculate the volume of gas collected in each interval of 1 minute. Use the equations shown. The value for 1 minute = total volume at 1 minute – the total volume at 0 minutes. The value for 2 minutes = total volume at 2 minutes – the total volume at 1 minute. The remaining values are calculated similarly. Record your values in Table 1.1. [2] (b) A student suggests that the volume of gas collected in the final interval of 1 minute is less than the volume of gas collected in the first interval of 1 minute. (i) Explain why the student expects the volume of gas collected in each 1 minute interval to decrease during the experiment. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) State if your results support the student’s suggestion. Use values from Table 1.1 to explain your answer. statement .................................................................................... explanation ........................................................................................................................ ........................................................................................................................................... [1] (c) Explain why repeating the procedure increases confidence in the results. ................................................................................................................................................... ............................................................................................................................................. [1] (d) Suggest one source of error in the procedure. State how to overcome this error. error .......................................................................................................................................... statement .................................................................................................................................. ................................................................................................................................................... [2] (e) Put about 1 cm depth of hydrogen peroxide solution into a clean test-tube. Add a few drops of universal indicator solution to this test-tube. State the colour observed. Determine the pH of the hydrogen peroxide solution using the colour chart. Use the pH to describe the nature of the hydrogen peroxide solution. colour ...................................................................... pH ........................................................................... description ................................................................................................................................ [2] [Total: 13]

Mark scheme: Question Answer Marks 1(a)(i) value for 1 minute; 4 full set of results; volume increases with time; all results recorded to 0.5 cm3 ; 1(a)(ii) calculation for 1 minute correct; 2 all calculations correct; 1(b)(i) hydrogen peroxide gets used up AW; 1 1(b)(ii) Statement and explanation matches their results and using 2 lots of data from table ; 1 1(c) identify / exclude anomalies; 1 1(d) gas escapes before stopper replaced ; 2 use divided flask / boiling tube / use of ignition tube / tube on string 1(e) expect yellow orange and 2 pH 4 / 5 / 6 ; weakly acidic ;

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2 Fertilisers contain nutrients that are added to crops to help them grow. A farmer has a choice of three fertilisers, A, B and C for use on his rice crop. Plan an investigation to find out which fertiliser produces the highest rate of growth of the rice plants. You are provided with: • rice plant seedlings • fertilisers A, B and C. You may also use any common laboratory apparatus. You are not required to do this investigation. Include in your plan: • the apparatus needed • a brief description of the method • the measurements you will make • the variables you will control • how you will process your results to draw a conclusion. You may include a results table if you wish, you are not required to enter any readings in the table. You may include a labelled diagram if you wish. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 2 one mark from each section and any two others 7 Apparatus measuring cylinder / syringe or balance and its use ; ruler and its use; method growing medium, rice and administering the fertiliser over fixed time for 3 fertilisers ; measurements mass / volume of fertiliser; height of plants ; lots of seedlings / at least 3 seedlings ; variables constant same volume / concentration / mass of fertiliser; same height of seedling at the start; same pH / light / temperature / humidity ; stated time left to grow; same amount of soil ; same amount of water ; processing and conclusion repeat / many seedlings and calculate average to identify / eliminate anomalies; calculate growth rate: amount grown / time / change in height / time bar chart of fertiliser against height of crop in same time / 3 graphs of time against height and gradients compared greatest height after fixed time (specified here or controlled time in the method) / highest bar on chart is best fertiliser ;

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3 You are going to investigate which metal ions catalyse a reaction. When aqueous sodium thiosulfate reacts with aqueous iron(III) nitrate the reaction mixture immediately turns a dark brown-purple colour. The colour of this mixture slowly fades. A catalyst will make the brown-purple colour fade more quickly. Fig. 3.1 shows the experiment. aqueous sodium thiosulfate and aqueous iron(III) nitrate cross on a piece of white paper Fig. 3.1 When the brown-purple colour fades it is possible to see the cross through the reaction mixture. The time for the cross to become visible is measured. (a) (i) Procedure Step 1 Using the measuring cylinder labelled S, add 20 cm3 of aqueous sodium thiosulfate into a clean conical flask. Step 2 Place the conical flask over the cross on the piece of paper. Step 3 Using a clean dropping pipette add only 1 drop of distilled water to the conical flask. Step 4 Using the measuring cylinder labelled I measure 20 cm3 of aqueous iron(III) nitrate. Step 5 Add the aqueous iron(III) nitrate to the conical flask, immediately swirl the flask and start the stop-watch. Step 6 Look through the mixture and when the cross becomes visible stop the stop-watch. Step 7 Record in Table 3.1 the time taken to the nearest second. [1] Table 3.1 aqueous solution time taken for the cross rate of reaction added in Step 3 to become visible / s per 100 s distilled water copper(II) ions iron(II) ions sodium ions zinc ions (ii) Repeat the procedure in (a)(i) four times. Each repeat has one drop of a different solution added in Step 3 as shown in Table 3.1. [4] (b) (i) Calculate the rate of each reaction. Use the equation shown. 100 rate of reaction = time taken Record in Table 3.1 your values to two significant figures. [2] (ii) Distilled water is not a catalyst for this reaction. The experiment with distilled water is a control for the investigation. Explain why a control is used. ........................................................................................................................................... ..................................................................................................................................... [1] (iii) Use the values in Table 3.1 to place the aqueous copper(II) ions, aqueous iron(II) ions, aqueous sodium ions and aqueous zinc ions in order of the rates of reaction. highest rate (best catalyst) ....................................................... ....................................................... ....................................................... lowest rate ....................................................... [1] (c) (i) Repeat the procedure in (a)(i) but in Step 3 add 5 drops of aqueous copper(II) ions instead of one drop of distilled water. Record the time taken for the cross to become visible. time = ...................................................... s [1] (ii) Suggest why 5 drops of each solution are not used in the procedure in (a)(i). ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 11]

Mark scheme: 3(a)(i) time for distilled water recorded ; 1 3(a)(ii) all times recorded ; 4 times to the nearest second ; iron(II) ions shortest time ; distilled water / sodium ions / zinc ions longest ; 3(b)(i) correct calculations ; 2 all calculations to 2sf ; 3(b)(ii) to get time without a catalyst so can compare the others to it ; 1 3(b)(iii) order matches results ; 1 3(c)(i) 0 s / half or less the value for Cu2+ in 3(a)(ii) ; 1 3(c)(ii) too fast to measure / instantaneous ; 1

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4 You are going to identify two aqueous solutions, J and K. (a) Procedure • Add approximately 1 cm depth of aqueous J into each of three test-tubes. • Complete the tests detailed in Table 4.1. • Record your observations in Table 4.1. • Repeat the tests using aqueous K instead of aqueous J. • Record your observations in Table 4.1. Table 4.1 observations test aqueous J aqueous K add a few drops of aqueous ammonia add excess aqueous ammonia add 1 cm depth of dilute nitric acid followed by a few drops of aqueous silver nitrate add 1 cm depth of dilute nitric acid followed by 1 cm depth of aqueous barium nitrate [7] (b) State the identity of aqueous J and aqueous K. aqueous J ................................................................................................................................................ aqueous K ................................................................................................................................ [2] [Total: 9]

Mark scheme: 4(a) white ppt ; (pale) blue ppt ; 7 colourless solution / dark blue solution ; dissolves ; white ppt ; no change ……. ….no change ; white ppt ; 4(b) zinc chloride ; 2 copper sulfate ;

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5 You are going to measure the focal length f of a converging lens. The equipment is assembled as shown in Fig. 5.1. illuminated object screen converging lens in holder u v Fig. 5.1 (a) (i) Procedure • Switch on the lamp. • Place the lens a distance u = 20.0 cm from the illuminated object. The illuminated object is the triangular hole in the card. • Adjust the position of the screen until a sharp image of the illuminated object is formed on the screen. • Record in Table 5.1 the image distance v from the screen to the lens to the nearest 0.1 cm. Table 5.1 object distance u image distance v magnification m / cm / cm 20.0 30.0 40.0 50.0 60.0 [1] (ii) Calculate the magnification m of the image. Use the equation shown. image distance m = object distance Record m to one decimal place in Table 5.1. [1] (b) Fig. 5.2 shows the illuminated object. In the blank space on the right-hand side of the illuminated object, draw a diagram of the image seen on the screen. illuminated object Fig. 5.2 [2] (c) Repeat the procedure in (a) for values of u = 30.0 cm, 40.0 cm, 50.0 cm, and 60.0 cm. [2] (d) (i) On the grid, plot a graph of v (vertical axis) against m. [3] (ii) Draw the best-fit straight line. [1] (iii) The gradient of the line is equal to the focal length f of the lens. Calculate the gradient of your line. Show on your graph the values you choose to calculate the gradient. f = ......................................................... [2] (e) When measuring u and v, it is important to avoid line-of-sight (parallax) errors. Describe how to avoid such errors. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 13]

Mark scheme: 5(a)(i) image distance for u = 20 cm recorded to the nearest 0.1 cm 1 5(a)(ii) calculation correct and to 1 decimal place 1 5(b) image drawn inverted; 2 image drawn magnified; 5(c) full set of v and m values; 2 v and m values decreasing; 5(d)(i) axes labelled with quantity and units ; 3 suitable scales and plotted points cover ≥ ½ the grid ; 5 points plotted correctly  ½ small square ; 5(d)(ii) best-fit line 1 5(d)(iii) indication on graph of how data were obtained and ≥ ½ the line between the plotted points used and calculation; 2 15  1 (cm); 5(e) read scale at right angles / eye close to scale reading ; 1

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6 You are going to investigate the stretching of a spring. The spring and the metre ruler have been assembled for you as shown in Fig. 6.1. Do not remove the spring from the clamp. Do not adjust the height of the clamps. metre ruler clamp clamp spring stand stand bench Fig. 6.1 (a) (i) Take the reading r on the metre ruler at the bottom of the spring. Use the set-square to make this reading accurate. Record in Table 6.1 the reading r to the nearest 0.1 cm for mass m = 0 g. Table 6.1 mass m 0 100 200 400 / g reading r / cm [1] (ii) Draw a diagram to show how you use the set-square to take an accurate reading. [1] (b) Procedure • Suspend a mass m = 100 g from the spring. • Record in Table 6.1 the reading r at the bottom of the spring. Repeat this procedure for masses m = 200 g and 400 g. [2] (c) A student suggests that the reading r on the metre ruler is directly proportional to the mass m. State if your readings support this suggestion. Use values from Table 6.1 to justify your answer. statement .................................................................................................................................. justification ................................................................................................................................ ................................................................................................................................................... [1] (d) Procedure • Remove the 400 g mass from the spring. • Suspend the load L from the spring. (i) Record the reading r at the bottom of the spring to the nearest 0.1 cm. r = ................................................... cm [1] (ii) Use your answer to (d)(i) and the readings in Table 6.1 to predict the mass M of the load L. M = ...................................................... g [1] [Total: 7]

Mark scheme: 6(a)(i) r recorded to the nearest 0.1 cm 1 6(a)(ii) set-square drawn perpendicular to the bottom of the spring and lined up with the rule ; 1 6(b) full set of readings; 2 readings increasing; 6(c) No and doubling m does not double r with an example / ratio of r / m is not constant with 2 calculations ; 1 6(d)(i) r value between Table values for 100 g and 200 g 1 6(d)(ii) 150 g  20 g / relevant calculation 1

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