qtss comb chem prelim 2024 p3 answer

This document consists of 9 printed pages. Name: ………………………………………………….. ( ) Class: Sec 4 SG 5 / 6 Queenstown Secondary School Preliminary Examination 2024 Secondary Four Normal (Academic) Science (Chemistry) 5105/04 30 July 2024 Time: 1015 – 1130h Tuesday Papers 3 and 4: 1 hour 15 minutes Setter: Additional Materials: 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. Section A Answer all questions. Write your answers in the spaces provided. Section B Answer one question. Write your answers in the spaces provided. The use of an approved scientific calculator is expected, where appropriate. In calculations, you should show all the steps in your working, giving your answer at each stage. You are advised to spend no longer than 30 minutes on Paper 3. You may proceed to answer Paper 4 as soon as you have completed Paper 3. A copy of the Periodic Table is printed on page 9. At the end of the examination hand in your answers to Paper 3 and Paper 4 separately. The number of marks is given in brackets [ ] at the end of each question or part question. Examiner’s Use Section A /22 Section B /8 TOTAL /30

2 Queenstown Secondary School [Turn over Section A Answer all questions. 1 Fig. 1 shows the apparatus that is used to fractionally distill petroleum into different fractions. Fig. 1 (a) (i) Name the physical property that allows the fractions to be separated. The fractions are miscible liquids with different boiling points. [1] (ii) State why the fractions condense in the condenser. The fractions have a lower boiling point than the water in the condenser. [1] (b) The petrol fraction has a boiling point range of 35oC to 70oC. (i) Explain why the petrol fraction is collected over a range of temperatures rather than at a single temperature. The petrol fraction is a mixture. [1]

3 Queenstown Secondary School [Turn over (ii) Explain what happens when a liquid boils. Your answer should explain boiling in terms of the kinetic particle theory and of the energy changes involved. When a liquid boils, it gains energy. During boiling, the particles move further apart, from being close together [liquid] to far apart [gas]. [arrangement] During boiling, the particles move faster, from sliding over each other [liquid] to moving randomly [gas]. [movement] [1] [1] [1] [Total: 6] 2 A student carries out an experiment to study the reaction between dilute hydrochloric acid, HCl, and exc