Cambridge IGCSE Sciences - Co-ordinated (Double) 0654 — 2017 Oct/Nov Paper 5 · Variant 2

1 You are provided with a seedling from a seed that has germinated and started to grow. (a) In the box, make a large pencil drawing of the seedling. Label the root and the stem. [3] (b) (i) Measure the length of the seed provided, excluding the root and the stem. Record this length in millimetres. length of seed .....................................................mm [1] (ii) Use a straight line to show this length on your drawing. Record the length of this line in millimetres. length of line on drawing .....................................................mm [1] (iii) Use your measurements from (b)(i) and (b)(ii) to calculate the magnification of your drawing. magnification ...........................................................[1] (c) A student wants to carry out an experiment on some germinated seeds. Describe how the student can germinate the seeds. ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[2] (d) You are provided with some seeds that have been liquidised into a paste. You are going to use the tests shown in Table 1.1 to find out the nutrient content of these seeds. (i) State which test in Table 1.1 requires heat. .......................................................................................................................................[1] (ii) Complete the second row of Table 1.1 to show which nutrient each test is used to identify. [1] (iii) Carry out the tests using the three solutions supplied and complete Table 1.1 to show your observations. • Use 1 cm depth of seed paste in each of the tests. • Add 2 cm depth of test solution for the Benedict’s test and the biuret test. • Add a few drops of iodine solution for the iodine test. Table 1.1 Benedict’s test biuret test iodine test nutrient tested for observation with seed paste [3] (iv) State the nutrients present in the seeds. .......................................................................................................................................[2]

Mark scheme: 1(a) quality of drawing using at least half the box ; root correctly labelled ; stem correctly labelled ; 3 1(b)(i) correct measurement in mm ; 1 1(b)(ii) correct measurement (in mm) ; 1 1(b)(iii) magnification correctly calculated ; 1 1(c) placed in a suitable container with water ; kept in a warm place ; 2 1(d)(i) Benedict’s ; 1 1(d)(ii) Benedict’s test biuret test iodine test nutrient tested for Reducing sugar protein starch observations correct; 1 1(d)(iii) Benedict’s biuret iodine yellow / green / orange / red ; purple ; blue-black ; 3 1(d)(iv) reducing sugar, protein and starch all three = 2 marks one or two named = 1 mark 2

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2 Notes for use in Qualitative Analysis for this question are printed on page 12. A good reagent in qualitative analysis gives positive results and different results with different ions. H is a sodium compound. You are going to investigate the reactions of H and assess whether H could be used as a reagent to identify cations. You have been given a solution of H for the reactions and a sample of solid H for (c). (a) You are provided with the following solutions. ammonium sulfate copper sulfate iron(III) sulfate zinc sulfate (i) • For each of these solutions, place about 1 cm3 of the solution into a clean test‑tube. • Add solution H to each test‑tube until there is no further change. • If no change is observed in a test‑tube, keep it for use in (a)(ii). Construct a suitable table with labelled columns in the space provided and record your observations in it. [5] (ii) If no change is observed in a test‑tube in (a)(i), stir the mixture. If necessary, pour away some of the mixture to leave a half‑filled test‑tube. Then heat the test‑tube gently and carefully bring to the boil. Test for the presence of ammonia gas. Record your observations. test ..................................................................................................................................... observations ....................................................................................................................... [1] (b) (i) Use your observations in (a) to explain whether H could be used as a reagent to identify the cations in the four solutions. You should make comparisons with the usual reagents for the analysis of cations. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... .......................................................................................................................................[3] (ii) Using the Notes for use in Qualitative Analysis, suggest another reaction to test the effectiveness of H for identifying cations. ........................................................................................................................................... .......................................................................................................................................[1] (c) A student adds barium nitrate solution to solution H and a white precipitate (ppt.) is produced. The student concludes that H is sodium sulfate. You are going to check the student’s conclusion. (i) Remove the bung from the test‑tube containing solid H and add dilute hydrochloric acid. Use a delivery tube to bubble the gas produced through 2 cm depth of limewater in another test‑tube. Record your observations. ........................................................................................................................................... .......................................................................................................................................[1] (ii) Use your observations in (c)(i) to explain why H is not sodium sulfate and identify H. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... H is ..................................................................................................................................... [2] (iii) Identify the white ppt. formed when H reacts with barium nitrate solution. white ppt. is ....................................................................................................................[1] (iv) State the mistake made by the student when testing H with barium nitrate solution, which led the student to conclude that sulfate ions are present. ........................................................................................................................................... .......................................................................................................................................[1] Please turn over for Question 3.

Mark scheme: 2(a)(i) neat table with appropriate headings ; solution observation ammonium sulfate no reaction / no ppt. ; copper sulfate blue ppt ; iron(III) sulfate brown / orange ppt ; zinc sulfate white ppt ; 5 2(a)(ii) (damp) red litmus and goes blue ; 1 2(b)(i) different coloured ppts. / different results ; same coloured ppts. as NaOH or ammonia ; ammonia from ammonium (as with NaOH) / no ammonia from ammonium (unlike NaOH) ; 3 2(b)(ii) add H to iron(II) sulfate ; 1 2(c)(i) limewater turns milky ; 1 2(c)(ii) carbon dioxide produced / 2(c)(i) is the test for a carbonate / sodium sulfate would not give a gas ; H is sodium carbonate ; 2 2(c)(iii) barium carbonate 1 2(c)(iv) should have added dilute nitric acid or dilute hydrochloric acid before adding the barium nitrate ; 1

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3 You are going to investigate the cooling rates of different volumes of water. A supply of hot water, a beaker and a thermometer have been provided for you. • Pour hot water into the beaker up to the 200 cm3 mark. • Place the thermometer into the beaker. • Wait approximately 60 s. (a) (i) Start the stopclock. Record, in Table 3.1, the temperature θ of the hot water at time t = 0. [1] (ii) Record, in Table 3.1, the temperature θ of the water and the time t at 30 s intervals for 3 minutes. [3] Table 3.1 cooling of 200 cm3 of hot cooling of 100 cm3 of hot water water time t / s temperature θ / °C temperature θ / °C 0 (b) Empty the beaker. • Pour hot water into the beaker up to the 100 cm3 mark. • Place the thermometer into the beaker. • Wait approximately 60 s. Repeat (a)(i) and (a)(ii). [1] (c) Suggest why it is important to wait 60 s before measuring the initial temperature of the hot water. ................................................................................................................................................... ...............................................................................................................................................[1] (d) On the grid provided, plot a graph of θ (vertical axis) against t for only the 100 cm3 volume of water. You do not need to start both axes from (0,0). Draw the best‑fit line. [4] (e) Explain how your graph shows that the rate of cooling of the water is greater at the start of the experiment than at the end of the experiment. ................................................................................................................................................... ...............................................................................................................................................[1] (f) A student suggests that the rate of cooling is slower for the larger volume of water than for the smaller volume of water. State whether your results support this suggestion. Justify your answer by referring to your results in Table 3.1. statement ................................................................................................................................... justification ................................................................................................................................. ................................................................................................................................................... [2] (g) The experiment is repeated with the same apparatus to check the results. Suggest two variables that should be kept constant. variable 1 ................................................................................................................................... variable 2 ................................................................................................................................... [2]

Mark scheme: 3(a)(i) 1 3(a)(ii) for 200 cm3 : t values correct ; all values of temperature recorded ; θ values decreasing ; 3 3(b) larger change over 180 s for 100 cm3 beaker ; 1 3(c) to allow maximum temperature of hot water to be recorded / wtte ; 1 3(d) axes labelled with units ; suitable choice of scales (⩾ half the grid used) ; at least 5 plots correct to half a small square (penalise ‘blobs’) ; good best-fit curve judgement ; 4 3(e) gradient greater / graph steeper at start of experiment 1 3(f) statement matching temperature changes and justification referring to results ; justification referring to temperature changes in the same time ; 2 3(g) any two from: room temperature / initial water temperature / same volume(s) of water / keep thermometer the same depth ;; 2

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