2025 TKGS Sec 4 Sci (Chem) Prelim Paper 1 - Answers

This document consists of 10 printed pages. TANJONG KATONG GIRLS’ SCHOOL PRELIMINARY EXAMINATION SECONDARY FOUR EXPRESS CANDIDATE NAME CLASS INDEX NUMBER SCIENCE (CHEMISTRY) 5086/01 & 5088/01 Paper 1 Multiple Choice 22 August 2025 1 hour Additional Materials: Multiple Choice Answer Sheet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Write your name, index number on the Answer Sheet. There are forty questions in this paper. Answer all questions. For each question, there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet. Read the instructions on the Answer Sheet very carefully. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. A copy of the Data Sheet is printed on page 9. A copy of the Periodic Table is printed on page 10. The use of an approved scientific calculator is expected, where appropriate.

Tanjong Katong Girls’ School 2 Sec 4 Preliminary Examination 2025 1 A student intends to measure the rate of reaction between a volume of hydrochloric acid and a lump of zinc carbonate. ZnCO3(s) + 2HCl(aq) → ZnCl2(aq) + H2O(l) + CO2(g) Which piece of apparatus is required to perform the experiment? A distillation flask B gas syringe C test-tube D thermometer 2 Which statement explains why carbon dioxide and oxygen can be separated from air by fractional distillation? A Carbon dioxide has a larger molecular mass than oxygen. B Carbon dioxide is a triatomic molecule while oxygen is a diatomic molecule. C Carbon dioxide and oxygen have different boiling points. D Carbon dioxide is less soluble in water than oxygen. 3 An element G forms a compound with nitrogen with a chemical formula of GN. Given that G has 56 particles in the nucleus, which row shows the correct composition of an ion of G? number of protons number of neutrons number of electrons A 26 30 23 B 26 30 26 C 30 26 26 D 30 26 23 4 Which element burns in excess oxygen to form a neutral oxide? A carbon B hydrogen C magnesium D sulfur

Tanjong Katong Girls’ School 3 Sec 4 Preliminary Examination 2025 5 Helium is represented by Ne10 20 . What can be deduced about neon? A It exists as diatomic molecules. B It forms a positive ion. C It has 10 protons and 10 neutrons. D It has a nucleon mass of 30. 6 Which substance has the typical properties of a covalent compound? melting point / °C boiling point / oC electrical conductivity at room temperature A -39 361 conductor B -21 105 non-conductor C 636 1300 conductor D 3727 4829 non-conductor 7 Steel is widely used in construction because of its strength and hardness as compared to pure iron. Which statement explains why steel is used over pure iron? A Carbon atoms form covalent bonds with iron atoms. B Carbon atoms disrupt the regular arrangement of iron atoms. C Steel has lower density than iron. D Carbon anions form strong electrostatic forces of attraction with iron cations.

Tanjong Katong Girls’ School 4 Sec 4 Preliminary Examination 2025 8 A metallic element, M, has the following properties: • less dense than water • easily cut by a knife • melts below 100 °C • M reacts with water to form a soluble hydroxide. What is M? A barium B copper C magnesium D potassium 9 Excess aqueous sodium hydroxide is added to salt P and the solution is heated. A gas is given off which turns red litmus blue. When this reaction is complete, aluminium foil is added to the solution. A gas is again given off which also turns red litmus blue. What is salt P? A ammonium nitrate B ammonium sulfate C zinc nitrate D zinc sulfate 10 40 cm3 of oxygen was reacted with 20 cm3 of sulfur dioxide to form sulfur trioxide. O2(g) + 2SO2(g) → 2SO3(g) What are the volume of gases remaining at the end of reaction at room temperature and pressure? Volume of oxygen / cm3 Volume of sulfur dioxide / cm3 Volume of sulfur trioxide / cm3 A 10 0 20 B 10 0 40 C 30 0 20 D 30 0 40

Tanjong Katong Girls’ School 5 Sec 4 Preliminary Examination 2025 11 Which substance contains the same number of atoms as 18 g of H2O? A 1 g of H2 gas B 12 g of Mg C 44 g of CO2 D 28 g of N2 12 The table gives information about the reactivity of three metals S, T and U. metal reaction with Fe2+(aq) reaction with Cu2+(aq) S solution remains green solution turns colourless T solution remains green solution remains blue U solution turns colourless solution turns colourless What is the order of reactivity of the metals? most reactive least reactive A S Fe T Cu U B T Fe S Cu U C U Fe S T Cu D U Fe S Cu T 13 In an endothermic reaction, what happens to the bonds in the reactants compared to the products? A Energy is released when stronger bonds form in the products. B Energy is absorbed when weaker bonds form in the products. C Energy is absorbed to break bonds in the reactants. D Energy is released to break bonds in the reactants.

Tanjong Katong Girls’ School 6 Sec 4 Preliminary Examination 2025 14 An element R reacts in the following ways. 2R(s) + O2(g) → 2RO(s) R(s) + 2HCl(aq) → RCl2(aq) + H2(g) 2R + H2O(l) → no reaction Which one of the following could be R? A calcium B copper C sodium D zinc 15 The diagram below shows the fractional distillation of petroleum. Which statement about fractions V and W is correct? A Fraction V combusts less easily than fraction W. B Fraction V has a higher density than fraction W. C Fraction V has a lower boiling point than fraction W. D Fraction V is more viscous than fraction W. heated petroleum fraction W fraction V

Tanjong Katong Girls’ School 7 Sec 4 Preliminary Examination 2025 16 How can margarine be made from vegetable oils? A addition of hydrogen to a saturated oil in the presence of nickel catalyst B addition of hydrogen to an unsaturated oil in the presence of nickel catalyst C addition of steam to a saturated oil in the presence of nickel catalyst D addition of steam to an unsaturated oil in the presence of nickel catalyst 17 The following are three reactions of hydrocarbons. Reaction 1: CH4 + Cl2 → CH3Cl + HCl Reaction 2: C10H22 → C3H8 + C7H14 Reaction 3: C2H4 + 3O2 → 2CO2 + 2H2O Which row describes the three reactions correctly? Reaction 1 Reaction 2 Reaction 3 A combustion addition cracking B substitution cracking combustion C addition combustion cracking D reduction addition combustion 18 Which environmental problem is associated with non-biodegradable plastics? A increased soil fertility B ocean acidification C pollution in landfills and marine environments D depletion of mineral resources

Tanjong Katong Girls’ School 8 Sec 4 Preliminary Examination 2025 19 The structure of an organic compound is shown. Which statement about the above compound is correct? 1 It decolourises aqueous bromine. 2 It can undergo addition polymerisation. 3 It can undergo oxidation with acidified potassium manganate(VII). 4 It can react with metal carbonates. A 1 and 2 only B 1 and 3 only C 2, 3 and 4 only D All of the above 20 A forested region was cleared, and the trees were burned to make way for development. Which combination of effects on the carbon cycle is most likely to occur as a long-term consequence? A increase in photosynthesis and decrease in ocean uptake B decrease in photosynthesis and increase in atmospheric carbon dioxide C increase in combustion and increase in photosynthesis D decrease in combustion and increase in oxygen producti