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

1 You are going to investigate the glucose concentration of solution S. You are provided with solution S and four different concentrations of glucose solution. (a) Procedure step 1 Label five test-tubes A, B, C, D and S. step 2 Use a syringe to add 2 cm3 of Benedict’s solution to each of the five test-tubes. step 3 Use clean syringes to prepare the five test-tubes as shown in Table 1.1. Table 1.1 test-tube solution added A 1 cm3 of 0.0% glucose B 1 cm3 of 0.5% glucose C 1 cm3 of 1.0% glucose D 1 cm3 of 2.0% glucose S 1 cm3 of S step 4 Place the test-tubes in a hot water-bath and start the stop-clock. step 5 Leave the test-tubes in the hot water-bath for 3 minutes. You may continue with (b) and (c) while you are waiting. step 6 After 3 minutes, remove the test-tubes from the water-bath. (i) Record in Table 1.2 the final colour observed in each test-tube. Table 1.2 percentage glucose test-tube final colour observed concentration of solution A 0.0 B 0.5 C 1.0 D 2.0 S unknown [5] (ii) Suggest the percentage glucose concentration of solution S. Explain your answer. percentage = .......................................... explanation ........................................................................................................................ ........................................................................................................................................... [1] (b) (i) State and explain one safety precaution you take while doing this investigation. precaution ......................................................................................................................... explanation ........................................................................................................................ ........................................................................................................................................... [1] (ii) Suggest why a clean syringe is used to add each solution. ..................................................................................................................................... [1] (iii) Suggest how you improve this procedure to get a more accurate estimate of the percentage glucose concentration of solution S. ........................................................................................................................................... ..................................................................................................................................... [1] (c) A student uses a piece of apparatus called a colorimeter to determine the percentage glucose concentration. The higher the colorimeter reading, the lower the percentage glucose concentration. The colorimeter reading has no units. The student’s results are shown in Table 1.3. Table 1.3 percentage glucose concentration colorimeter reading 0.0 0.94 0.5 0.67 1.0 0.53 1.5 0.44 2.0 0.38 (i) On the grid, plot a graph of colorimeter reading (vertical axis) against percentage glucose concentration. [3] (ii) Draw the best-fit curve. [1] (iii) The student tests a sample of solution S. The colorimeter reading is 0.72. Use your graph to estimate the percentage glucose concentration in solution S. Show your working on the graph. percentage = ......................................................... [2] (iv) The colorimeter gives a more accurate value than Benedict’s solution for the percentage glucose concentration of solution S. Suggest why the value is more accurate. ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 16] Remember to go back and complete 1(a).

Mark scheme: 1(a)(i) blue recorded for 0.0 ; rest of the results ; yellow / green recorded for 0.5 ; red / orange recorded for 2.0 ; colour recorded for S in line with supervisor ; 1(a)(ii) concentration and explanation to match their results ; 1 1(b)(i) any one from: goggles and to protect eyes and burns / hot water / Benedict’s ; tongs / test-tube holder to protect hands / skin from burns / hot water ; gloves to protect hands / skin from Benedict’s / burns / hot water ; 1 1(b)(ii) prevent contamination / mixing and between the glucose / solutions / concentrations / test-tubes OWTTE ; 1 1(b)(iii) more intermediate glucose concentrations / glucose concentrations between 0 and 5% / examples close to colour observed ; 1 1(c)(i) axes correct orientation and labelled with quantity and unit ; sensible linear scale and plotted points cover at least half the grid and all the points can be plotted ; plots correct  ½ half small square ; 3 1(c)(ii) curve of best fit ; 1 1(c)(iii) correct reading from graph ; graph marked with 2 lines to indicate value ; 2 Question Answer Marks 1(c)(iv) quantitative / colorimeter gives value to more dp / AVP ; 1

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2 You are going to test solution T for the presence of two different nutrients. Procedure step 1 Add approximately 1 cm depth of solution T into each of two clean test-tubes. step 2 Add the same depth of biuret solution to one test-tube containing solution T. step 3 Add a few drops of iodine solution to the other test-tube containing solution T. (a) Record in Table 2.1 the final colours observed in each test-tube. Table 2.1 testing solution final colour observed conclusion biuret iodine [2] (b) Complete Table 2.1 by stating a conclusion for each observation. [2] [Total: 4]

Mark scheme: 2(a) blue ; blue-black ; 2 2(b) no protein ; contains starch ; 2

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3 You are going to find the percentage by mass of magnesium in a mixture of magnesium and copper using two different calculations. When the mixture of magnesium and copper is added to dilute hydrochloric acid, only the magnesium reacts. Hydrogen gas is made which is collected and measured. The copper in the mixture does not react and is separated from the reaction mixture at the end of the reaction by filtration. The mass of the copper is measured. (a) (i) Procedure • Remove the conical flask from the assembled apparatus. • Record in Table 3.1 the mass of the empty conical flask. • Add the mixture of magnesium and copper to the conical flask. • Record in Table 3.1 the mass of the conical flask with this mixture. Table 3.1 mass of empty conical flask / g mass of conical flask with mixture of magnesium and copper / g mass of mixture of magnesium and copper / g [2] (ii) • Use a measuring cylinder to measure 50 cm3 of dilute hydrochloric acid. • Add the dilute hydrochloric acid to the conical flask. • Quickly replace the flask into the apparatus as shown in Fig. 3.1. delivery tube measuring cylinder water conical flask hydrochloric acid water mixture of magnesium and copper Fig. 3.1 • Wait until the reaction has finished. • Record in Table 3.2 the volume of hydrogen gas in the upturned measuring cylinder. Table 3.2 volume of hydrogen gas / cm3 [2] (iii) • Measure the mass of a filter paper and record it in Table 3.3. • Filter the contents of the conical flask using this filter paper. • Rinse the conical flask with water to get as much copper into the filter paper as possible. Continue with (b) and Q4 while you wait for the filtration to end. • Remove the filter paper containing the copper. • Place the filter paper with the copper onto a piece of plastic film. • Use a balance to find the mass of the filter paper with the copper and plastic film. • Record this mass in Table 3.3. Table 3.3 mass of filter paper / g mass of filter paper, copper and plastic film / g mass of copper / g [2] (b) (i) Even though you replace the conical flask quickly, some hydrogen gas is still lost to the air and not collected. Suggest how the procedure is changed to give a more accurate value for the volume of hydrogen formed. Do not include repeating the experiment. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Using the values in Table 3.1, calculate the mass of the mixture of magnesium and copper added to the conical flask. Record your value in Table 3.1. [1] (iii) Calculate the mass of magnesium in the mixture. Use the equation shown. volume of hydrogen gas × 24 mass of magnesium = 24 000 mass of magnesium = ...................................................... g [1] (iv) Calculate the percentage of magnesium in the mixture of magnesium and copper. Use the equation shown. mass of magnesium from (b)(iii)percentage of magnesium = × 100 mass of mixture of magnesium and copper from Table 3.1 percentage of magnesium = ......................................................... [1] If the filtering in (a)(iii) is not finished, complete Question 4. (c) (i) Suggest how the procedure is changed to give a more accurate value for the mass of copper on the filter paper. Do not include repeating the experiment or subtracting the mass of the plastic film. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Use the values in Table 3.3 to calculate the mass of copper. Assume the plastic film has no mass. Record your value in Table 3.3. [1] (iii) Calculate the percentage of magnesium in the mixture. Use the equation shown, Table 3.1 and Table 3.3. mass of copper percentage of magnesium = 100 – × 100 mass of mixture of magnesium and copper percentage of magnesium = ......................................................... [1] [Total: 13]

Mark scheme: 3(a)(i) mass of empty conical flask recorded ; mass of conical flask and mix recorded AND larger than mass of flask AND to same number of dp ; 2 3(a)(ii) volume of gas recorded ; value within 10% of the supervisors value ; 2 3(a)(iii) mass of filter paper recorded ; mass of filter paper and copper recorded AND larger than mass of filter paper ; 2 3(b)(i) have a divided flask / have the Mg in a tube in the flask / add the acid via a tap / thistle funnel ; 1 3(b)(ii) mass of mixture from student’s results ; 1 3(b)(iii) mass of magnesium calculated ; 1 3(b)(iv) percentage of Mg calculated ; 1 Question Answer Marks 3(c)(i) dry the copper ; 1 3(c)(ii) mass of copper calculated ; 1 3(c)(iii) percentage of Mg calculated ; 1

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4 Pure water boils at a temperature of 100 °C. When salt is dissolved in the water, the boiling temperature increases. Plan an experiment to find the relationship between the mass of salt added to water and the increase in boiling temperature. You are provided with: • pure water • salt. You may use any common laboratory apparatus. You are not required to do this experiment. Include in your plan: • the apparatus you will use • a brief description of the method and explain any safety precautions you will take • what you will measure and how you will make these as accurate as possible • which variables you will control • how you will process your results and use them to draw a conclusion. You may include a labelled diagram if you wish. You may also include a table that can be used to record results. You are not required to include any results. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7] Remember to go back and complete Question 3.

Mark scheme: 4 One mark from each section and any two others apparatus balance and use ; thermometer and use ; Bunsen burner and use ; goggles protect eyes from boiling water OR gloves / test-tube holders to protect hands / skin from hot apparatus / boiling water ; method add salt to water, boil and measure a temperature for at least two masses of salt ; measure mass of salt ; boiling temperature ; repeat each mass and exclude / identify anomalies ; at least 5 masses of salt ; control volume of water ; one with no salt and one with salt added ; process and conclusion plot graph of boiling temperature against mass of salt ; IF mass is increased is the increase in bpt increased / or shape of graph explanation ;

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5 You are going to determine the mass of a piece of modelling clay by two different methods. You are provided with a metre rule, a pivot and a piece of modelling clay. (a) Procedure • Mould the piece of modelling clay into the approximate shape of a cube. • Place the modelling clay on the metre rule so that its centre is at a distance of 10.0 cm from the zero end of the rule. • Place the rule on the pivot. • Adjust the position of the pivot so that the rule is as close to balance as possible. Fig. 5.1 shows the arrangement of the apparatus. modelling clay metre rule x y bench 0 10 50 100 pivot Fig. 5.1 (i) Record to the nearest 0.1 cm the distance x from the centre of the modelling clay to the pivot. x = .................................................... cm [1] (ii) Record to the nearest 0.1 cm the distance y from the pivot to the 50.0 cm mark. y = .................................................... cm [1] (b) Remove the modelling clay from the metre rule and remove the metre rule from the pivot. Use the balance provided to measure the mass M of the metre rule. Record your reading to the nearest gram. M = ...................................................... g [1] (c) Calculate the mass m1 of the piece of modelling clay. Use your answers to (a)(i), (a)(ii) and (b) and the equation shown. M × y m1 = x Record your answer to two significant figures. m1 = ...................................................... g [2] (d) (i) Procedure • Pour approximately 50 cm3 of water into the measuring cylinder. • Record the volume V1 of water in the measuring cylinder. V1 = ........................................................ cm3 • Use the thread to lower the modelling clay into the measuring cylinder until it is completely immersed. You will need to re-mould your modelling clay into any shape that fits into the measuring cylinder. • Record the new volume V2. V2 = ........................................................ cm3 [1] (ii) Calculate the volume V of the piece of modelling clay. Use the equation shown. V = V2 – V1 V = .................................................. cm3 [1] (iii) Describe how you avoid a line-of-sight (parallax) error when reading the scale of the measuring cylinder. ........................................................................................................................................... ..................................................................................................................................... [1] (e) The density ρ of the modelling clay is 1.9 g / cm3. Calculate the mass m2 of the modelling clay. Use your answer from (d)(ii) and the equation shown. m2 = V × ρ m2 = ...................................................... g [1] (f) Two values are considered to be equal within the limits of experimental accuracy if they are within 10% of each other. Compare your value m1 from (c) with your value m2 from (e). State if your values for the mass of the modelling clay are equal, within the limits of experimental accuracy. Justify your statement with a calculation. statement .................................................................................................................................. justification ................................................................................................................................ ................................................................................................................................................... ................................................................................................................................................... [2] [Total: 11]

Mark scheme: 5(a)(i) x recorded to the nearest 0.1 cm ; 1 5(a)(ii) y recorded to the nearest 0.1 cm and x > y ; 1 5(b) M recorded to the nearest gram ; 1 Question Answer Marks 5(c) m1 calculation correct ; answer to 2 significant figures ; 2 5(d)(i) V1 and V2 present and V2 > V1 ; 1 5(d)(ii) V correct ; 1 5(d)(iii) view scale at right angles (to the reading) / view scale perpendicular (to the reading) ; 1 5(e) m2 calculation correct ; 1 5(f) 10% of one of the values calculated ; either + or – the 10% and other value shown to be either within the 10% or not ; OR using difference calculate difference ; calculate percentage ; 2

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6 You are going to investigate the rate of cooling of hot water. The apparatus is assembled as shown in Fig. 6.1. thermometer stand beaker Fig. 6.1 (a) Record the room temperature θ R to the nearest 0.5 °C. θ R = ..................................................... °C [1] (b) Procedure • Place the beaker on the stand under the thermometer. • Pour hot water into the beaker up to the 200 cm3 mark. • Lower the thermometer into the hot water. • Wait for 30 s. • Measure the temperature θ of the hot water. (i) Record, in Table 6.1, θ to the nearest 0.5 °C at time t = 0 and start the stop-clock. Table 6.1 time t / minutes temperature θ/ °C 0 1 2 3 4 5 6 [1] (ii) Record, in Table 6.1, the temperature of the water every minute for 6 minutes. [2] (c) Explain why you wait for 30 s before measuring the initial temperature of the hot water. ................................................................................................................................................... ............................................................................................................................................. [1] (d) (i) Calculate the temperature decrease ΔθF of the water during the first 3 minutes of cooling. Use your readings in Table 6.1. ΔθF = ..................................................... °C [1] (ii) Calculate the temperature decrease ΔθL of the water during the last 3 minutes of cooling. Use your readings in Table 6.1. ΔθL = ..................................................... °C [1] (e) Use your results to write a conclusion about the rate at which hot water in a beaker cools. ................................................................................................................................................... ............................................................................................................................................. [1] (f) Use your answers to (d) to estimate the temperature of the water after it cools for 9 minutes. You are not required to make this measurement. temperature = ..................................................... °C [1] [Total: 9] NOTES FOR USE IN QUALITATIVE ANALYSIS Tests for anions anion test test result carbonate (CO32–) add dilute acid effervescence, carbon dioxide produced chloride (Cl –) acidify with dilute nitric acid, then white ppt. [in solution] add aqueous silver nitrate bromide (Br –) acidify with dilute nitric acid, then cream ppt. [in solution] add aqueous silver nitrate nitrate (NO3–) add aqueous sodium hydroxide, then ammonia produced [in solution] aluminium foil; warm carefully sulfate (SO42–) acidify, then add aqueous barium white ppt. [in solution] nitrate Tests for aqueous cations cation effect of aqueous sodium hydroxide effect of aqueous ammonia ammonium (NH4+) ammonia produced on warming – calcium (Ca2+) white ppt., insoluble in excess no ppt., or very slight white ppt. copper(II) (Cu2+) light blue ppt., insoluble in excess light blue ppt., soluble in excess, giving a dark blue solution iron(II) (Fe2+) green ppt., insoluble in excess green ppt., insoluble in excess iron(III) (Fe3+) red-brown ppt., insoluble in excess red-brown ppt., insoluble in excess zinc (Zn2+) white ppt., soluble in excess, giving a white ppt., soluble in excess, giving a colourless solution colourless solution Tests for gases Flame tests for metal ions gas test and test result metal ion flame colour ammonia (NH3) turns damp red litmus paper blue lithium (Li+) red carbon dioxide (CO2) turns limewater milky sodium (Na+) yellow chlorine (Cl 2) bleaches damp litmus paper potassium (K+) lilac hydrogen (H2) ‘pops’ with a lighted splint copper(II) (Cu2+) blue-green oxygen (O2) relights a glowing splint

Mark scheme: 6(a) room temperature recorded to the nearest 0.5 °C ; 1 6(b)(i) temperature recorded at t = 0 (to the nearest 0.5 °C) ; 1 6(b)(ii) all other temperature values ; values decreasing ; 2 6(c) to allow the thermometer to measure the maximum temperature (of the hot water) ; 1 6(d)(i) F correct ; 1 Question Answer Marks 6(d)(ii) L correct ; 1 6(e) the rate of cooling decreases as the hot water cools ; 1 6(f) temperature difference between candidate’s answer and the temperature at 6 minutes < L (d)(ii) ; 1

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