This document consists of 17 printed pages and 3 blank pages. IB08 11_0653_06/5RP © UCLES 2008 [Turn over *6554451667* For Examiner's Use 1 2 3 4 5 6 Total UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education COMBINED SCIENCE 0653/06 CO-ORDINATED SCIENCES 0654/06 Paper 6 Alternative to Practical October/November 2008 1 hour Candidates answer on the Question paper No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs, tables or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. 2 © UCLES 2008 0653/06/O/N/08 For Examiner's Use 1 A student set up an experiment to investigate the effect of light on the growth of seedlings. The seeds were set up for germination as shown in Fig. 1.1. and left for a few days. box A completely closed box B open at the top box C open at one side light light Fig. 1.1 The dishes of seedlings from each box are shown in the photographs in Fig. 1.2. seedlings from box A seedlings from box B seedlings from box C Fig. 1.2 3 © UCLES 2008 0653/06/O/N/08 [Turn over For Examiner's Use (a) (i) Construct a table to display the observations. The observations are the shape, and the vertical height of the seedlings from each box. Do not fill in the table yet. [2] (ii) Study Fig. 1.2. and write a description of the shapes of the seedlings in the table. [3] (iii) Choose one of the tallest seedlings from box A. Measure its vertical height. Take the measurement from the base of the photograph to the top of the seedling. Label this seedling on Fig. 1.2 with the letter a. Write the vertical height of this seedling in the table in (a)(i). [1] (iv) Repeat part (iii) for seedlings from boxes B and C, labelling them b and c. [2] (b) Explain why the seedlings in box C grew differently from the seedlings in box B. [1] 4 © UCLES 2008 0653/06/O/N/08 For Examiner's Use 2 A student is doing an experiment with a spring to which a weight hanger is attached. This is shown in Fig. 2.1. spring weight hanger Fig. 2.1 A 200 g mass is attached to the weight hanger. When the mass is pulled down and then released, it oscillates (bounces up and down). This is shown in Fig. 2.2. weight hanger 200 g mass mass bounces up and down Fig. 2.2 • Using a stopclock, the student finds the time in seconds taken for 20 oscillations. • He records the results in Fig. 2.3. • He increases the mass to 300 g and finds the new time. • The student repeats the experiment using 400 g and 500 g masses. mass on weight hanger /g time for 20 oscillations /s time T, for one oscillation /s T2 /s2 200 13.0 0.65 0.42 300 400 500 19.0 0.95 0.90 Fig. 2.3 5 © UCLES 2008 0653/06/O/N/08 [Turn over For Examiner's Use (a) Fig. 2.4 shows the missing times for 20 oscillations of the 300 g and 400 g masses. 0 30 45 15 mass = 300 g 0 30 45 15 mass = 400 g Fig. 2.4 (i) Read the times and record them in column 2 of Fig. 2.3. [2] (ii) Complete column 3 of Fig. 2.3 by calculating T, the time for one oscillation. [1] (iii) Find the values of T2 for the 300 g and 400 g masses and complete column 4. [1] (b) On the graph grid, Fig. 2.5, plot T2 (vertical axis) against the mass. Draw the best straight line. It will not pass through the point (0, 0). [2] 0 100 200 300 mass /g 400 500 600 1.0 0.8 0.6 0.4 0.20 T2 /s2 Fig. 2.5 6 © UCLES 2008 0653/06/O/N/08 For Examiner's Use (c) Find f , the gradient of the line, showing on the graph how you did this. f = s2 /g [2] (d) A mass of 200 g extended the spring by 75 mm. Use the gradient, f, from (c) and the equation below to calculate a value for g, the acceleration of free fall. (The extension of 75 mm produced by the 200 g mass has been included in the equation.) g = 75 x 0.0002 f [1] (e) Suggest a reason why the straight line of the graph does not pass through the point (0,0). [1] 7 © UCLES 2008 0653/06/O/N/08 [Turn over For Examiner's Use 3 The science class is making magnesium carbonate by the process of precipitation. The teacher gives them this equation for the reaction. MgCl2 (aq) + K 2CO3(aq) → MgCO3(s) + 2KCl(aq) (a) State the meaning of the symbols (i) (aq) [1] (ii) (s) [1] The teacher gives a student 50 cm3 of magnesium chloride solution and a beaker of potassium carbonate solution. The teacher says that the potassium carbonate solution is more concentrated than the magnesium chloride solution. (b) What volume of potassium carbonate solution will the student need to react with all the 50 cm3 of the magnesium chloride solution? Tick the correct answer. less than 50 cm3 exactly 50 cm3 more than 50 cm3 [1] The student begins to add potassium carbonate solution, a few drops at a time, to the magnesium chloride solution. She stirs the mixture. This is shown in Fig. 3.1. magnesium chloride solution potassium carbonate solution Fig. 3.1 8 © UCLES 2008 0653/06/O/N/08 For Examiner's Use The student decides that she has added enough potassium carbonate to react with all of the magnesium chloride. She wants to filter the mixture to remove the magnesium carbonate. This is shown in Fig. 3.2. filtrate mixture of solutions filter paper Fig. 3.2 (c) Here is her filter paper circle. Show by completing the diagram, or by describing, how to fold the filter paper to fit it into the filter funnel. Fig. 3.3 [2] The student collects the magnesium carbonate in the filter paper. The filtrate is collected in the beaker. (d) The student wants a pure sample of magnesium carbonate. She does not take the magnesium carbonate out of the filter paper. What does she do next? [1] 9 © UCLES 2008 0653/06/O/N/08 [Turn over For Examiner's Use (e) The student wants to find out if, in Fig. 3.1, enough potassium carbonate was added to the magnesium chloride solution. Explain how she can do this, using the filtrate from (c) and a few more drops of potassium carbonate solution. [2] (f) Suggest a way of getting a pure sample of potassium chloride crystals from the filtrate. [2] 10 © UCLES 2008 0653/06/O/N/08 For Examiner's Use 4 (a) This question is about reaction time which involves the nervous system. The reaction time is the time taken from a stimulus to the response produced. In the experiment the stimulus is a falling ruler and the response is its capture by the person’s hand. A student did an experiment to find the reaction time of several different people, A, B, C and D. He did this by holding a ruler just above the thumb of the person and letting it fall. The person then caught the falling ruler between finger and thumb as quickly as possible (see Fig. 4.1). The vertical distance, d, travelled by the ruler is noted. The greater the distance the slower the reaction time. Each reading was taken twice. 0 cm 50 cm 0 cm 50 cm d start line ruler falls ruler after being caught ruler at start Fig. 4.1 The readings were recorded in Fig. 4.2. values for d /cm person first reading second reading average reaction time /sec A 25.2 26.6 25.9 0.23 B 35.1 35.7 35.4 C 21.7 D 21.7 Fig. 4.2 11 © UCLES 2008 0653/06/O/N/08 [Turn over For Examiner's Use (i) Read the rulers, shown in Fig. 4.3 to complete the readings, d, for persons C and D in Fig. 4.2. The pointers indicate the position of the top edge of the person’s thumb. [2] 25.0 24.0 23.0 22.0 21.0 20.0 C 23.0 22.0 21.0 20.0 19.0 18.0 D ruler graduated in centimetres and millimetres Fig. 4.3 (ii) Calculate the average values of d for persons C and D and write them in Fig. 4.2. [2] (iii) Use the average values of d to the nearest centimetre, and the information in Fig. 4.4 to complete the column for reaction time in Fig. 4.2. d /cm reaction time /s 20 0.20 21 0.21 22 0.21 23 0.22 24 0.22 25 0.23 26 0.23 27 0.24 28 0.24 29 0.24 30 0.25 31 0.25 32 0.26 33 0.26 34 0.26 35 0.27 36 0.27 Fig. 4.4 [3] 12 © UCLES 2008 0653/06/O/N/08 For Examiner's Use (b) Briefly describe how the impulse (message) travels from the brain to the hand. [1] (c) From the results suggest which person, A, B, C or D would be the least safe driver of a car and explain why. person explanation [3] 13 0653/06/O/N/08 [Turn over BLANK PAGE Please turn over for Question 5. 14 © UCLES 2008 0653/06/O/N/08 For Examiner's Use 5 The science class is doing an experiment to compare the expansion of liquids. They are comparing the expansion of water, ethanol and methanol. The apparatus is shown in Fig. 5.1. stirrer ethanol water bath initial level water methanol gentle heat expansion tubes Fig. 5.1 • Each test-tube is filled with liquid and the expansion tube is inserted so that there is no air in the tube. • The initial level of the liquid in the expansion tube is marked. • The water-bath is gently heated and stirred. • After a few minutes, the new levels of the liquids in the expansion tubes are noted. 15 © UCLES 2008 0653/06/O/N/08 [Turn over For Examiner's Use Fig. 5.2 shows the levels of the liquids in the expansion tubes before and after heating. water initial level new level ethanol initial level new level methanol initial level new level Fig. 5.2 (a) (i) Use a ruler to measure, to the nearest millimetre, the increase in height of the liquid in each tube. Record your results in Fig. 5.3. liquid water methanol ethanol increase in height /millimetres Fig. 5.3 [3] (ii) Explain the importance of placing all three tubes in the same water bath. [1] (iii) Explain the importance of stirring the water in the water-bath during heating. [1] 16 © UCLES 2008 0653/06/O/N/08 For Examiner's Use (b) A student obtained an unexpected result from one of his tubes. The teacher saw that there was air in the tube, shown in Fig. 5.4. air space water Fig. 5.4 Explain why this would give a different result. [2] (c) (i) The teacher told the class that the glass of the test-tubes also expands when heated. Did the glass expand more than, the same as or less than the liquids? Explain your answer. [2] (ii) Use the results of the experiment to suggest how the forces of attraction between molecules in water compare with the forces between molecules in ethanol. [1] 17 0653/06/O/N/08 [Turn over BLANK PAGE Please turn over for Question 6. 18 © UCLES 2008 0653/06/O/N/08 For Examiner's Use 6 The class is given a sample of solid A. They are also given solution B and solution C. They carry out the experiments described below. Complete Figs. 6.1, 6.2 and 6.3 to show the tests, observations and conclusions. (a) experiments on solid A test observation conclusion Dissolve solid A in water and divide the solution into three parts. (i) To the solution of solid A, add aqueous barium chloride and dilute hydrochloric acid. A precipitate is formed that has a colour [1] Solid A contains ions [1] (ii) To the solution of solid A, add a piece of magnesium ribbon. [1] The solution is acid. Test the gas given off with a lighted spill. [1] The gas is hydrogen. (iii) To the solution of solid A, add solid sodium carbonate. Test the gas given off with 1. a lighted spill [1] 2. lime water. [1] The gas is carbon dioxide. Fig. 6.1 19 © UCLES 2008 0653/06/O/N/08 For Examiner's Use (b) experiments on solution B test observation conclusion (i) To solution B, add aqueous sodium hydroxide. [1] Solution B contains iron(III) ions. (ii) To solution B, add dilute nitric acid and aqueous [1] [1] Solution B contains chloride ions. Fig. 6.2 (c) experiments on solution C test observation conclusion Acidify solution C with hydrochloric acid and add to solution B in a large test-tube. Warm the mixture. After cooling, add excess aqueous sodium hydroxide. A precipitate is formed that has a colour [1] The iron(III) ions in solution B have been changed into iron(II) ions. Fig. 6.3 20 Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. 0653/06/O/N/08 BLANK PAGE