Cambridge IGCSE Physical Science 0652 — 2023 Oct/Nov Paper 5 · Variant 1

1 You are going to investigate the amount of precipitate formed when aqueous sodium carbonate reacts with aqueous barium nitrate. The word equation for the reaction is shown. sodium carbonate(aq) + barium nitrate(aq) barium carbonate(s) + sodium nitrate(aq) (a) Procedure • Label 6 test-tubes 1, 2, 3, 5, 6 and 7 (there is no test-tube 4). • Using a measuring cylinder, add 5 cm3 of aqueous barium nitrate into each test-tube. • Using a clean measuring cylinder, add 1 cm3 of aqueous sodium carbonate to test-tube 1 and stir with a glass rod. • Using the measuring cylinder used for adding aqueous sodium carbonate to test-tube 1, add the volumes of aqueous sodium carbonate shown in Table 1.1 to the other test-tubes, stirring each with a glass rod. • Leave the test-tubes to stand for at least 10 minutes to allow the precipitate to settle. Complete Question 2 while you wait. • After at least 10 minutes measure the height of precipitate in each test-tube. Record, in Table 1.1, these heights in millimetres to the nearest millimetre. Table 1.1 volume of test-tube height of precipitate aqueous sodium carbonate number / mm added / cm3 1 1 ...................... 2 2 ...................... 3 3 ...................... 5 5 ...................... 6 6 ...................... 7 7 ...................... [3] (b) (i) Suggest a piece of apparatus suitable for measuring the 5 cm3 of aqueous barium nitrate more accurately than the measuring cylinder. ..................................................................................................................................... [1] (ii) Explain why it is difficult to get an accurate value for the height of the precipitate. ........................................................................................................................................... ..................................................................................................................................... [1] (c) (i) On the grid, plot a graph of the height of precipitate (vertical axis) against volume of aqueous sodium carbonate added. [3] (ii) Draw the best-fit line. [1] (iii) Describe the relationship between the height of precipitate and the volume of aqueous sodium carbonate added. ........................................................................................................................................... ..................................................................................................................................... [1] (iv) Use your graph to estimate the height of the precipitate formed when 4.0 cm3 of aqueous sodium carbonate is added to 5 cm3 of aqueous barium nitrate. Show clearly on your graph how you arrived at your answer. ................................................... mm [2] (d) Suggest how the procedure can be adapted to increase confidence in the results. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 13]

Mark scheme: Question Answer Marks 1(a) height for 1 cm3 ; 3 height for all tubes ; height increases down the table ; 1(b)(i) burette ; 1 1(b)(ii) bottom of test-tube is curved ; 1 1(c)(i) axes correct orientation and labelled with quantity and unit ; 3 sensible linear scales with plotted points ⩾ ½ grid ; points plotted correctly  ½ small square ; 1(c)(ii) best-fit straight line ; 1 1(c)(iii) as volume (of barium nitrate) increases so the height (of the precipitate) increases ; 1 1(c)(iv) value from graph  ½ small square ; 2 working shown on the graph ; 1(d) repeat and average ; 1

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2 You are going to investigate further the reaction in Question 1. (a) (i) In the experiment in Question 1, when aqueous sodium carbonate reacts with aqueous barium nitrate, a white precipitate forms. The precipitate is separated from the mixture by filtration. Draw a labelled diagram of the assembled filtration apparatus. [1] (ii) Label the residue and the filtrate on your drawing in (a)(i). [1] (b) Procedure Read the whole of (b) before doing the experiment. • Put approximately 1 cm depth of aqueous sodium carbonate into a test-tube. • Add approximately 1 cm depth of aqueous barium nitrate to the test-tube. • Add approximately 3 cm3 of dilute nitric acid to the test-tube. • Identify the gas given off. Keep the test-tube and contents for (b)(iii). (i) Describe what you see in the test-tube when the dilute nitric acid is added. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (ii) Describe the test which identifies the gas given off. Give the observation for the positive result. test .................................................................................................................................... observation .................................................................................................................. [1] (iii) Use the test-tube from the end of the procedure in 2(b) for this test. • add a few drops of aqueous barium nitrate to the test-tube. Record your observations. ........................................................................................................................................... ..................................................................................................................................... [1] (c) Barium nitrate is used to identify sulfate ions. When aqueous barium nitrate is added to a solution of sulfate ions, a white precipitate is formed. Explain why nitric acid is also added in the test for sulfate ions. ................................................................................................................................................... ............................................................................................................................................. [1] Remember to go back and complete Question 1. [Total: 7]

Mark scheme: 2(a)(i) filter funnel and filter paper inside (and a V at bottom of filter paper) and either funnel of filter paper labelled ; 1 (filter) funnel filter paper residue / barium carbonate filtrate / sodium nitrate 2(a)(ii) residue / barium carbonate and filtrate / sodium nitrate labelled ; 1 2(b)(i) bubbles ; 2 precipitate / solid dissolves / (colourless) solution formed ; 2(b)(ii) (bubble into) limewater and goes milky ; 1 2(b)(iii) no reaction / no precipitate / colourless solution / stays clear ; 1 2(c) to remove carbonate ions ; 1

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3 You are going to investigate the refraction of light by a transparent block. You will use the diagram shown in Fig. 3.1. F P1 N P2 θ A B E transparent block D C L position of eye Fig. 3.1 (a) (i) Measure and record the angle θ that line FE makes with the normal NL. θ = ....................................................... ° [1] (ii) Procedure • Arrange this paper so that page 6 lies over the pinboard provided. • Place the block inside the labelled rectangle shown in Fig. 3.1. • The longer side of the block must lie along AB with the normal NL crossing the longer side approximately in the centre. The side of the block closest to the line CD is now referred to as side CD. • Insert one pin at position P1 and another pin at position P2 on line FE. • View the images of P1 and P2 through the side CD of the block from the position indicated by the eye. Move your head slightly so that the images of P1 and P2 appear one behind the other. • Place a third pin between side CD and your eye, in line with the images of P1 and P2. This is pin P3. • Place a fourth pin a suitable distance from pin P3, in line with pin P3 and the images of P1 and P2. This is pin P4. • Label the positions of the pins P3 and P4. • Remove the block and pins from the paper. • Draw a line joining the positions of P3 and P4. • Continue the line until it meets the normal NL and label this point H. • Also label the point at which the line crosses CD with the letter G. • Join points G and E with a straight line. [2] (iii) Measure the length a of line GE. a = ......................................................... cm Measure the length b of line GH. b = ......................................................... cm Calculate a value n1 for the refractive index. Use the equation: a n1 = b Record your value of n1 to a suitable number of significant figures. n1 = ............................................................... [3] (b) You are now going to repeat the process using a different angle of incidence. You will use the diagram shown in Fig. 3.2. N A B E transparent block D C L position of eye Fig. 3.2 (i) Procedure • On Fig. 3.2, draw a line to the left of the normal NL at an angle of incidence i = 50°. Label the line FE. • Arrange this paper so that page 8 lies over the pinboard provided. • Place the block inside the labelled rectangle shown in Fig. 3.2 as in part (a)(ii). • Insert two pins a suitable distance apart on line FE. Label the positions of the pins P5 and P6. • View the images of P5 and P6 through the side CD of the block from the position indicated by the eye. Move your head slightly so that the images of P5 and P6 appear one behind the other. • Place a third pin between side CD and your eye, in line with the images of P5 and P6. This is pin P7. • Place a fourth pin a suitable distance from pin P7, in line with pin P7 and the images of P5 and P6. This is pin P8. • Label the positions of the pins P7 and P8. • Remove the block and pins from the paper. • Draw a line joining the positions of P7 and P8. • Continue the line until it meets the normal NL and label this point H. • Also label the point at which the line crosses CD with the letter G. • Join points G and E with a straight line. [1] (ii) Measure the length c of line GE. c = ......................................................... cm Measure the length d of line GH. d = ......................................................... cm Calculate a value n2 for the refractive index. Use the equation: c n2 = d Record your value of n2 to a suitable number of significant figures. n2 = ............................................................... [2] (c) (i) Two quantities are considered equal within the limits of experimental error if their values are within 10% of each other. A student suggests that the values n1 and n2 should be considered equal. State whether your results support this suggestion. Justify your answer by reference to your results. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (ii) Explain why the value n2 is likely to be a more accurate value for the refractive index than n1. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] (d) Suggest why different students, all doing this experiment carefully, may obtain slightly different results. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 13]

Mark scheme: 3(a)(i) = 30°  2° 1 3(a)(ii) P3 and P4 separation ⩾ 2 cm 1 line joining P3 and P4 drawn back to the normal 1 3(a)(iii) a and b correctly measured  1 mm 1 n1 correctly calculated 1 n1 in range 1.3 to 1.7 1 3(b)(i) line drawn at 50°  2° to NL 1 3(b)(ii) c and d present 1 both values of n have no units and n2 to 2 or 3 significant figures 1 3(c)(i) yes / no, depending on candidate’s values 1 attempt at a calculation of 10% 1 3(c)(ii) measured lines are longer / smaller (percentage) uncertainty 1 3(d) any one from: 1 • difficulty in aligning / placing pins accurately / getting the pins vertical • pins too thick

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4 Conducting putty is modelling clay that conducts electrical current. Plan an experiment to investigate the relationship between the diameter d of the conducting putty and its resistance R. Resistance is calculated using the equation V R = I where V is the potential difference across the conductor and I is the current through the conductor. The student has a battery pack, connecting leads and some conducting putty which can be moulded into a cylinder shape as shown in Fig. 4.1. d Fig. 4.1 Other apparatus normally available in a school laboratory may also be used. You will not be doing this experiment. Your plan should include: • any additional apparatus needed • a brief description of the method, including the measurements you make, a circuit diagram and the table you use to record your results (you are not required to enter any readings into the table) • the variables to control • the precautions you take to ensure the results are as accurate as possible • an explanation of how you use your results to reach a conclusion. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 4 additional apparatus 7 • voltmeter and ammeter • (metre) rule / micrometer / callipers method • circuit diagram with ammeter in series and voltmeter in parallel with the putty • measure / record / note diameter • take readings of current and potential difference • repeat with different diameter • table drawn with columns and headings for potential difference, current and diameter and correct units control variables • length of the conduction putty / conductor • type of conduction putty / conductor precautions • a minimum of three diameters • take several readings of diameter for one piece • take several readings of current and potential difference (for each diameter) and average processing • plot a graph of d against R • compare the values of R to see if / how the diameter of the putty affects the resistance

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