BTYSS Sec 2 Science 2025 EOY (Section C)

BEATTY SECONDARY SCHOOL END-OF-YEAR EXAMINATION 2025 SECONDARY TWO G3 CANDIDATE NAME CLASS REGISTER NUMBER LOWER SECONDARY SCIENCE 6 October 2025 Setter: Ms Ain Sections A, B and C: 2 hours Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST This Lower Secondary Science Paper consists of 3 sections – Sections A, B and C. SECTION C (30 MARKS) You are advised to spend no more than 90 minutes on Sections B and C. Write your name, class and register number on all the work you hand in. You may use an HB pencil for any diagrams, graphs, tables or rough working. Write in dark blue or black pen. 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. Answer all questions in the spaces provided on the question paper. A copy of the Periodic Table is printed on page 11. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use C 30 This document consists of 11 printed pages and 1 blank page. [Turn over

2 Section C Answer all the questions in this section in the spaces provided. 9 The Central Processing Unit (CPU) supports the main processes in a modern computer. In an experiment, the relationship between the current flowing through a CPU and the temperature of the CPU is investigated. Fig. 9.1 shows how the temperature varies with current. Fig. 9.1 Table 9.1 shows the current and power used by the CPU when different applications are used in a computer for varying durations. Table 9.1 type of application current / A power / kW duration / h web browsing 0.16 0.962 1.0 playing music 0.22 1.55 0.5 gaming 0.35 2.78 2.0 Table 9.2 shows a comparison of electricity prices from different retailers in the Open Electricity Market (OEM). Table 9.2 retailer price per kWh / cents Volt & Co. 29.62 PowerFlow 29.30 SunGrid 31.10 current / A 60 80 100 40 20 temperature / C 0 0.1 0.2 0.3 0.4 0.5

3 (a) Using Fig. 9.1 and Table 9.1, state the temperature of the CPU when the computer is used for web browsing only. ……………………………………………………………………………………………. [1] (b) A family has a subscription to the electricity retailer PowerFlow. Using the information given in Table 9.1 and Table 9.2, calculate the total cost of electricity for running all three applications for their respective durations. Show all your working clearly. total cost = $…………………… [3] (c) A heat sink is usually attached on top of the CPU to help it to cool down as shown in Fig. 9.2. Fig. 9.2 The heat sink is mainly made of numerous metallic vertical fins. Using your knowledge of heat transfer, (i) explain why the fins are made of metal; ……………………………………………………………………………………….. ……………………………………………………………………………………….. ……………………………………………………………………………………. [1] CPU heat sink metallic fins

4 (ii) explain why numerous fins are used; ……………………………………………………………………………………….. ……………………………………………………………………………………….. ……………………………………………………………………………………. [1] (iii) explain why the heat sink is usually black in colour; ……………………………………………………………………………………….. ……………………………………………………………………………………….. ……………………………………………………………………………………. [1] (iv) explain why the heat sink is attached above, not below the CPU; ……………………………………………………………………………………….. ……………………………………………………………………………………….. ……………………………………………………………………………………. [1] (v) state and describe how thermal energy is transferred from the CPU to the heat sink. ……………………………………………………………………………………….. ……………………………………………………………………………………….. ……………………………………………………………………………………….. ……………………………………………………………………………………….. ……………………………………………………………………………………. [2] [Total: 10]

5 10 (a) Fig. 10.1 shows a set-up where 20 cm3 of acid and 10 drops of Universal Indicator are added to the beaker. The magnetic stirrer is switched on to ensure the mixture is thoroughly mixed throughout. Potassium hydroxide ( KOH) solution from the burette is added drop wise to the beaker. Potassium nitrate (KNO 3) salt and one other product is produced in the chemical reaction. Fig. 10.1 Fig. 10.2 shows the results of pH measurements taken by the pH sensor at regular intervals as it monitors the mixture's pH value. Fig. 10.2 burette KOH solution beaker acid with Universal Indicator magnetic stirrer pH sensor 12 11 10 9 8 7 6 5 4 3 2 1 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 pH volume of KOH added / cm3

6 (i) Identify the acid used in the set-up. ……………………………………………………………...…………………….. [1] (ii) Write a word equation for the chemical reaction. ……………………………………………………………...…………………….. [1] (iii) State the volume of KOH solution that turns the mixture in the beaker green. volume = …………………… cm3 [1] (iv) State the final colour of the mixture. ……………………………………………………………...…………………….. [1] (v) The experiment is repeated using the same concentration of acid and alkali as in the previous experiment, but this time using 30 cm3 of acid. Calculate the volume of KOH solution that turns the mixture green. Show your working clearly. volume = …………………… cm3 [1] (vi) Apart from Universal Indicator, Table 10.1 shows the colour changes of different indicators that could be used. Table 10.1 indicator pH range and colour of indicator methyl orange < pH 3.1 red pH 3.1 – 4.4 orange > pH 4.5 yellow phenolphthalein < pH 8.3 colourless pH 8.3 - 10 light pink > pH 10 pink bromothymol blue < pH 6 yellow pH 6 – 7.6 green > pH 7.6 blue Using Table 10.1, explain which indicator is best used to indicate the point of complete neutralisation between potassium hydroxide and the acid used. ……………………………………………………………………………………….. ……………………………………………………………………………………. [1]

7 (b) Ms Tan is the chief chemist at a water treatment plant. During routine maintenance, three storage containers of water treatment chemicals were accidentally damaged, and their contents spilled into separate collection trays. She needs to identify each chemical quickly to ensure water treatment operations can continue safely. The three chemicals that were stored separately are: • tray A which contains zinc powder • tray B which contains calcium carbonate • tray C which contains sodium chloride Ms Tan must test samples from each tray to confirm their identity before they can be safely disposed of or reused. Suggest and d escribe an experiment that can be carried out in a school Science laboratory to identify these chemicals. In your answer, you should include the expected observations. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ………………………………………………………………………………………….… [4] [Total: 10]

8 11 (a) A woman keeps track of her menstrual cycle using the calendar shown in Fig. 11.1. She has a regular 28-day menstrual cycle and has indicated the day on which she began menstruating in May with a circle. May M T W T F S S 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31