2025-Sec-4E-G3-Pure-Biology-Prelim-Practical-KiasuExamPaper-6s-Copy

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[Turn over For Examiner’s Use 1 2 Total / 40 Shift Laboratory Full Name Index No. Class Anglo-Chinese School (Barker Road) PRELIMINARY EXAMINATION 2025 SECONDARY 4 EXPRESS BIOLOGY 6093/03 TIME: 1 HOUR 50 MIN INSTRUCTIONS TO CANDIDATES: Write your name and index number in the spaces provided. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is given in [ ] at the end of each question or part question. ______________________________________________________________________________ c www.KiasuExamPaper.com 3

2 4EXP/6093/03/PRELIM/2025 This question paper consists of 10 printed and 2 blank pages. www.KiasuExamPaper.com 4

3 4EXP/6093/03/PRELIM/2025 [Turn over BLANK PAGE www.KiasuExamPaper.com 5

4 4EXP/6093/03/PRELIM/2025 1 You are advised to read the whole question before you start. Living organisms are made up of essential biological molecules that play critical roles in sustaining life and supporting cellular functions. These molecules vary in structure and function, contributing to processes such as energy provision, growth, and maintenance. In this question, you are going to investigate the energy content in 1.0 g of unknown food samples S1 and S2. thermometer burning food sample (1.0 g) on a mounting needle water (20 cm3) clamp to hold boiling tube clamp to hold thermometer retort stand mounting needle attached to a test tube holder white tile Fig. 1.1 Step 1 Set up the experiment as shown in Fig. 1.1. Step 2 Measure 20 cm 3 of water and pour into a boiling tube. Step 3 Measure and record the initial temperature of the water. Step 4 Carefully stick the mounting needle into S1. DO NOT remove the attached test tube holder. Step 5 Use the mounted needle (attached to a test tube holder), to hold S1 in a flame until it starts to burn. Ensure that you place your exam script away from the setup. Step 6 Place S1 under the boiling tube while it is still burning. Step 7 Keep S1 under the boiling tube until the flame goes out. www.KiasuExamPaper.com 6

5 4EXP/6093/03/PRELIM/2025 [Turn over Repeat steps 5 and 6 until it no longer relights. Step 8 Measure and record the highest temperature of the water. Step 9 Discard the burnt sample S1 into the waste container. Step 10 Repeat steps 1 to 9 for a new sample of S1. Step 11 Calculate the average rise in temperature for S1. Step 12 Repeat the experiment for S2. (a) State two variables that are kept the same during this investigation 1 2 [2] (b) (i) Present your results in a table in the space provided. [5] www.KiasuExamPaper.com 7

6 4EXP/6093/03/PRELIM/2025 (ii) The energy contained in S1 can be calculated using the formula below. Energy (J g-1) = volume of water (cm3) x average rise in temperature (oC) x 4.2 mass of S1 (g) Use the formula to calculate the energy content (in joules per gram) of S1. Show your working in the space provided. Present your answer in kilojoules per gram and to one decimal place. Energy content of S1 kJ g-1 [2] (c) (i) This is not a very accurate way of finding out the energy content of a piece of food. Describe one key source of error and how it will affect the results of the experiment. [2] (ii) Suggest a modification to the procedure to reduce the effect of the error described in (c)(i). [2] (d) Table 1.1 shows the energy content per gram of different biological molecules. www.KiasuExamPaper.com 8

7 4EXP/6093/03/PRELIM/2025 [Turn over Table 1.1 biological molecule energy content / kJg -1 carbohydrate 16.0 fat 38.0 protein 17.0 Using information from Table 1.1, suggest whether it is possible to deduce the specific biological molecule present in S1 and S2. Explain why. [2] www.KiasuExamPaper.com 9

8 4EXP/6093/03/PRELIM/2025 (e) Plants undergo photosynthesis in the presence of light to produce glucose, which is subsequently stored as starch in leaves. Plants grown in different light intensities are reported to have different amounts of starch in their leaves. Plan an experiment to investigate if there is a relationship on the effect of light intensity on the production of starch in leaves. [6] [Total: 21] End of Question 1 Turn over to Page 8 for Question 2 2 Fig. 2.1 shows a photograph of the surface of a mammalian organ. www.KiasuExamPaper.com 10