SKSS 4NA Sci Chem Prelim P4

12 Name and Index Number: ( ) Class: SENG KANG SECONDARY SCHOOL 2025 PRELIMINARY EXAMINATION SCIENCE (CHEMISTRY) 5105/04 5107/04 Secondary 4 Normal (Academic) 4 August 2025 Paper 4 Paper 3 and 4: 1 hour 15 minutes READ THESE INSTRUCTIONS FIRST Write your index number and name on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, 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 12. 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. For Examiner’s use Section A / 22 Section B / 8 Total Marks / 30 This document consists of 12 printed pages. Do not turn over the page until you are told to do so.

2 [Turn over Section A [22 marks] Answer all questions. 1 Choose from the substances listed to answer the questions. brass calcium hydroxide carbon dioxide carbon monoxide chlorine oxygen hydrogen zinc chloride Each substance may be used once, more than once or not at all. Identify the element or compound that: (a) relights a glowing splint, …………………………………………………………………………………………… (b) contains a halide ion, …………………………………………………………………………………………… (c) is a gas formed from the reaction between calcium and water, …………………………………………………………………………………………… (d) is a mixture of zinc and another element, …………………………………………………………………………………………… (e) has a mass of 14.8 g for every 0.2 mol of the substance. …………………………………………………………………………………………… [5] [Total: 5]

3 [Turn over 2 A piece of phosphorous is fastened to a copper wire and left for a few days in the apparatus shown in Fig. 2.1. Phosphorous reacts with oxygen in the air to form phosphorous oxide, causing the water to slowly rise in the test-tube. The reaction is allowed to proceed, until all of the oxygen has been reacted. Fig. 2.1 (a) Name two gases that are left in the test-tube after a few days. …………………………………………………………………………………………… [2] (b) State the vertical distance travelled by the water in the test-tube. vertical distance travelled ……………………… mm [1] (c) The phosphorous oxide that was formed is added to a beaker, as shown in Fig. 2.2. The beaker contains distilled water and a few drops of Universal Indicator. Fig. 2.2 Describe the colour change of Universal Indicator when phosphorous oxide dissolves in distilled water. colour changes from ……………………….. to ………………………… [1] [Total: 4] test-tube copper wire dry air 100 mm phosphorous glass trough water phosphorous oxide water and a few drops of universal indicator 100 mm

4 [Turn over 3 Table 3.1 shows the boiling points of some organic compounds that can be found in crude oil. Table 3.1 compounds boiling point / °C hexane 69 heptane 99 octane 125 (a) State the name of the homologous series to which the organic compounds belong to. …………………………………………………………………………………………… [1] (b) Name a separation technique that could be used to separate a mixture of the compounds found in Table 3.1. …………………………………………………………………………………………… [1] (c) Crude oil, when burnt, releases carbon dioxide into the atmosphere. Describe a positive test for carbon dioxide gas. …………………………………………………………………………………………… [1] (d) Biofuels are known to be an alternative energy source that could replace crude oil. (i) Name one example of a biofuel. ……………………………………………………………………………………. [1] (ii) Explain why biofuels are considered more environmentally sustainable compared to crude oil. ………………………………………………..…………………………………………. ……………………………………………………………………………………. [1] [Total: 5]

5 [Turn over 4 A student uses the apparatus shown in Fig. 4.1 to study the reaction between sodium hydroxide and ammonium nitrate. Ammonia gas is one of the products of the reaction. Fig. 4.1 (a) Identify liquid X. …………….……………………………………………………………………………... [1] (b) A teacher commented that the set-up in Fig. 4.1 is not suitable for collecting ammonia gas. Explain why the set -up in Fig. 4.1 is not suitable for collecting ammonia gas and suggest how this should be corrected. explanation …………………………………………………………………………………… ……………………………………………….………………………………………………… correction …………………………...………………………………………………………… ……………………………………………….………………………………………………… …………………………………………………………………………………………… [2] sodium hydroxide and ammonium nitrate liquid X clamp inverted 100 cm3 measuring cylinder trough water heat

6 [Turn over (c) The student learnt that ammonia gas can be toxic. He decides to modify the set-up from Fig. 4.1 to convert ammonia gas to nitrogen gas. The modified set-up is shown in Fig. 4.2. Fig. 4.2 (i) When ammonia gas is passed over hot copper(II) oxide, the reaction produces copper, water and nitrogen. Balance the chemical equation for this reaction. …….. CuO + …….. NH3 → …….. Cu + …….. H2O + …….. N2 [1] (ii) The volume of nitrogen gas produced can be determined by reading the inverted measuring cylinder. State the volume of nitrogen gas shown in the inverted measuring cylinder. volume of nitrogen gas = ………………… cm3 [1] (iii) The volume of nitrogen gas is measured and recorded at one-minute intervals. The results obtained by the student are shown in Table 4.3. Table 4.3 time / min 0 1 2 3 4 5 6 volume of gas / cm3 0 28 46 55 59 60 60 Using Table 4.3, plot a graph of volume of gas against time, marking each point with a cross (x). Draw a curved line of best fit taking into account all your plotted points. [2] clamp inverted 100 cm3 measuring cylinder trough water copper(II) oxide sodium hydroxide and ammonium nitrate heat liquid X heat 40 50

7 [Turn over (iv) Use your graph to estimate the time at which the reaction is completed. estimated time = ………………… min [1] [Total: 8] 0 10 20 30 40 50 60 70 0 1 2 3 4 5 6 volume of gas / cm3 time / min

8 [Turn over Section B [8 marks] Answer one question from this section. 5 Table 5.1 shows information about four non-metallic elements. All four non-metals are in the same group of the Periodic Table. Table 5.1 element melting point / °C boiling point / °C density / g / cm3 V −307 −188 0.00155 W −102 −34 ? X −7 78 3.10 Y 114 184 4.93 The following is known about the non-metals: • they exist as diatomic molecules; • they all have 7 valence electrons. (a) Define the term diatomic. …………………………………………………………………………………………………. ……………………………………………………………………..……………………. [1] (b) State which group of the Periodic Table these elements can be found in. Group ……………………. [1] (c) Pre