2025 4E Dunman Sec ScChem P3 2025 QP

This document consists of 22 printed pages. DUNMAN SECONDARY SCHOOL CANDIDATE NAME CLASS INDEX NUMBER PRELIMINARY EXAMINATION 2025 SECONDARY 4 EXPRESS SCIENCE (PHYSICS, CHEMISTRY) 5086/03 SCIENCE (CHEMISTRY, BIOLOGY) 5088/03 Paper 3 Chemistry 27 August 2025 1 hour 15 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, class and index number on all the work you hand in. 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. 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. Section A Answer all questions. Write your answers in the spaces provided on the question paper. Section B Answer one question. Write your answers in the spaces provided on the question paper. A copy of the Data Sheet is printed on page 21. A copy of the Periodic Table is printed on page 22. The number of marks is given in brackets [ ] at the end of each question or part question.

2 5086/5088/03/Prelim/4Exp/2025 Section A Answer all the questions in the spaces provided. 1 Table 1.1 below shows information on seven particles. Note that the letters do not represent chemical symbols of the elements. Table 1.1 particle A B C D E F G nucleon number 4 9 12 27 29 35 80 proton number 2 4 6 13 13 17 35 number of electrons 2 2 6 13 13 17 35 (a) Use the letters, A, B, C, D, E, F and G to answer the following questions. Each letter can be used once, more than once or not at all. (i) Which particle is an ion with a charge of 2+? …………………………………………………………………………………………… [1] (ii) Which particles are different elements from the same group in the Periodic Table? …………………………………………………………………………………………… [1] (iii) Which two particles chemically combine to form a covalent compound? …………………………………………………………………………………………… [1] (iv) Which particle is chemically inert? …………………………………………………………………………………………… [1]

3 5086/5088/03/Prelim/4Exp/2025 (b) Two of the particles in Table 1.1 are isotopes. (i) Define the term isotopes. ……………………………………………………………………………………………….. …………………………………………………………………………………………… [1] (ii) Identify the isotopes in Table 1.1. …………………………………………………………………………………………… [1] [Total: 6]

4 5086/5088/03/Prelim/4Exp/2025 2 Geosmin is an organic compound with a melting and boiling point of 78°C and 270°C respectively. (a) (i) In the space provided below, draw the arrangement of particles of geosmin at 280°C. Particles of geosmin may be represented with a . 280°C [1] (ii) Describe, using the kinetic particle theory, the change in motion of particles in solid geosmin as it changes into a liquid. ………………………………………………………………..……………………………… …………………………………………………………………..………………………. [1] (b) A sample of geosmin was heated from 25°C to 100°C. Using the axes below, draw the heating curve for this sample of geosmin. [2] [Total: 4] Temperature / °C Time / min

5 5086/5088/03/Prelim/4Exp/2025 3 Sodium chloride exist s as a solid while ammonia exists as a gas at room temperature and pressure. (a) Explain, in terms of structure and bonding why solid sodium chloride cannot conduct electricity. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. …………………………………………………………………………...………………………. [2] (b) Explain why ammonia gas has a low boiling point. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. …………………………………………………………………………...………………………. [2]

6 5086/5088/03/Prelim/4Exp/2025 (c) Draw ‘dot-and-cross’ diagrams to show the bonding in sodium chloride and ammonia. Show only the outer shell electrons. (i) sodium chloride [2] (ii) ammonia gas [2] [Total: 8]

7 5086/5088/03/Prelim/4Exp/2025 4 Fig. 4.1 describes reactions involving alkaline solutions. Fig. 4.1 (a) Name the substances A, B, C and D. A ………………………………………….. B ………………………………………….. C ………………………………………….. D ………………………………………….. [4] (b) Write a balanced chemical equation, with state symbols, for colorless solution A reacting with aqueous sodium hydroxide. …………………………………………………………………………………………………….[2] [Total: 6] metallic salt A colorless solution A colorless gas C that turns damp red litmus paper blue colorless solution D white precipitate B that dissolves easily in excess aqueous ammonia dissolve in water mix with aqueous ammonia warm with aluminium powder and aqueous sodium hydroxide mix gas C with water white precipitate B that dissolves easily in excess aqueous sodium hydroxide mix with aqueous sodium hydroxide

8 5086/5088/03/Prelim/4Exp/2025 5 In an experiment, a student carried out the following procedures: • measure 25 cm3 of 1.0 mol/dm3 hydrochloric acid into a glass beaker • measure the initial temperature of the hydrochloric acid (T1) • add 30 cm3 of 1.0 mol/dm3 aqueous potassium hydroxide, in excess • record the maximum temperature the mixture reached (T2) The temperature readings of the reaction mixture are shown in the thermometers below. T1 (oC) T2 (oC) (a) Use the information provided to complete the table below. initial temperature (oC) final temperature (oC) temperature change (oC) [2] (b) Using the information in the table from (a), suggest what kind of reaction occurred. Explain your answer. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………… [2]

9 5086/5088/03/Prelim/4Exp/2025 (c) Write the ionic equation for the reaction between dilute hydrochloric acid and aqueous potassium hydroxide. ………………………………………………………………………………………………….. [1] [Total: 5] 6 Both lemongrass and citronella are used to repel mosquitoes. A student used paper chromatography to determine the pigments present in both substances, using alcohol as a solvent. Fig. 6.1 shows the chromatograms of lemongrass and citronella. Fig. 6.1 (a) How many components does lemongrass contain? …………………………………………………………………………………………...……… [1] (b) State two other conclusions about lemongrass and citronella that can be made from the chromatogram. ……………………………………………………………………..……………….…...…………... ……………………………………………………………………..……………….…...…………... ……………………………………………………………………..……………….…...…………... ……………………………………………………………………………………...…...……… [2] start line chromatography paper lemongrass citronella

10 5086/5088/03/Prelim/4Exp/2025 (c) The structure of a molecule of citronella is as shown below. Write the molecular formula of a molecule of citronella. ……………………………………………………………………………………...…...……… [1] [Total: 4] key: : carbon atom : hydrogen atom : oxygen atom