NYGH Sec 2 Science 2025 Practice paper

NYGH 2025 Secondary 2 Science Practice Paper 4; Pg. 1 2025 SECONDARY 2 SCIENCE Past Year Papers Practice 4 Duration: 35 minutes Name: ( ) Class: 2/ Section A – Multiple Choice Questions (5 marks) Each question is worth 1 mark. Answer all questions in this section in the table provided below. 1. 2. 3. 4. 5. 1. Which statement about atoms is correct? A The mass of an atom is almost entirely due to its nucleus. B The protons and neutrons attract each other. C The protons and neutrons have opposite charges. D The shell furthest away from the nucleus always contain the most electrons. 2. Three elements W, X and Y are found one after another, in the same period in the Periodic Table. They have increasing proton (atomic) numbers. If element Y is a noble gas, which row about the formation of the ions of element W is correct? each atom of element W ions of element W are A gains one electron negatively charged B gains two electrons negatively charged C loses one electron positively charged D loses two electrons positively charged 3. A piece of red litmus paper was immersed in an unknown solution and removed after a minute. The red litmus paper remained red. Which is a valid conclusion about the unknown solution? A The solution cannot be alkaline. B The solution may turn Universal Indicator blue. C The pH of the solution cannot be 7. D The pH of the solution can be higher than 7. 4. The diagram shows part of the carbon cycle. Which stage releases oxygen gas into the atmosphere? 25 carbohydrates in animals carbon dioxide in the air carbon compounds in fossil fuels B C A D carbohydrates in plants

NYGH 2025 Secondary 2 Science Practice Paper 4; Pg. 2 5. Which human action is not paired correctly with its effects on the environment? human action effects on the environment A bring reusable bag to do shopping reduces the use of plastic bags B increase rate of reforestation increases the carbon dioxide in the air by reducing carbon store C take public transport or walk reduces the combustion of fossil fuels D wasting food depletes energy, water and natural resources

NYGH 2025 Secondary 2 Science Practice Paper 4; Pg. 3 Section B – Structured Questions (20 marks) Answer all of the questions in the spaces provided. 6. (a) Use the Periodic Table provided to complete the following table. [ 2 ] particle symbol number of electronic structure proton neutron electron nitrogen atom 7 7 sodium ion 𝑁𝑁𝑁𝑁11 23 + 11 2.8 (b) Two nitrogen atoms can combine chemically to form a nitrogen molecule, N2. [ 1 ] Determine the relative molecular mass of N2. ………………………………………………………………………………………………………….. ………………………………………………………………………………………………………….. (c) Element Z has two naturally occurring isotopes: • Isotope Z-63 with a relative abundance of 69.2% • Isotope Z-65 with a relative abundance of 30.8% Calculate the relative atomic mass of element Z. Show your working clearly and give your answer to 1 decimal place. [ 1 ] (d) Study the following chemical equation. Where necessary, write whole numbers in the spaces provided to balance the chemical equation. [ 1 ] .......Na + .......NH 3 → .......NaNH2 + .......H2 [Total: 5]

NYGH 2025 Secondary 2 Science Practice Paper 4; Pg. 4 7. (a) Identify the type of chemical change described in each of the following scenarios. [ 1 ] scenario type of chemical change When copper(II) carbonate is heated strongly, the solid turns from green to black and carbon dioxide gas is evolved. Rust forms at the iron legs of a table after some time. (b) Using the setup in Figure 7.1, the water is broken down to form hydrogen gas and oxygen gas by passing an electric current through it. This is known as electrolysis. Effervescence is observed around both carbon electrodes. Figure 7.1 (i) Is this a physical change or a chemical change? Explain why. [ 1 ] …………………………………………………………………………………………………………... …………………………………………………………………………………………………………... (ii) Describe a test to confirm that the gas evolved at one of the electrodes in Figure 7.1 is hydrogen. [ 2 ] …………………………………………………………………………………………………………... …………………………………………………………………………………………………………... ………………………………………………………………………………..…………………………. [Total: 4]

NYGH 2025 Secondary 2 Science Practice Paper 4; Pg. 5 8. Helen was working in her school’s Science laboratory. The following reagents were on the laboratory work bench in front of Helen. Note: All the reagents are in aqueous solution. (a) From the list of chemicals that are available to Helen in the laboratory , write the chemical names of two reagents that Helen could react together to form ammonia gas. [ 1 ] …………………………………………………………………………………………………………... (b) From the list of chemicals that are available to Helen in the laboratory , write the chemical names of two reagents that Helen could react together to form carbon dioxide gas. [ 1 ] …………………………………………………………………………………………………………... (c) Write a balanced chemical equation for the reaction that takes place when the reagents named in 15 (b) react together. Note: State symbols are not required. [ 1 ] …………………………………………………………………………………………………………... [Total: 3]

NYGH 2025 Secondary 2 Science Practice Paper 4; Pg. 6 9. Canadian pondweed is a species of aquatic plant from North America. A student grew Canadian pondweed along with another species of pondweed native to Singapore, in water tanks both separately and together. Figure 9.1 shows the results. Figure 9.1 (a) Besides light intensity and temperature, state one other physical factor that should be kept constant and explain how it affects pondweed growth. [ 1 ] …………………………………………………………………………………………………………... …………………………………………………………………………………………………………... (b) Describe the results when both species of pondweeds were grown together. [ 2 ] …………………………………………………………………………………………………………... …………………………………………………………………………………………………………... …………………………………………………………………………………………………………... (c) Suggest what would happen if the Canadian pondweed were introduced into Singapore’s local pond ecosystem. [ 1 ] …………………………………………………………………………………………………………... …………………………………………………………………………………………………………... [Total: 4]

NYGH 2025 Secondary 2 Science Practice Paper 4; Pg. 7 10. Figure 10.1 shows some lichen on the bark of trees. Lichen is made up of two types of organisms, algae and fungi growing together. Figure 10.1 Figure 10.2 shows the cross-section of a type of lichen. Figure 10.2 (a) Algae contains chloroplasts while fungi have cell wall that is made up of chitin that is relatively strong and water-proof. Suggest how algae and fungi benefit from their association with each other. [ 2 ] …………………………………………………………………………………………………………... …………………………………………………………………………………………………………... (b) State the relationship between the algae and fungi. [ 1 ] …………………………………………………………………………………………………………...

NYGH 2025 Secondary 2 Science Practice Paper 4; Pg. 8 (c) Lichens are sensitive to pollution as they can take up chemicals in the air. Figure 10.3 Using Figure 10.3, explain why bushy lichens are usually more sensitive to pollution. [ 1 ] …………………………………………………………………………………………………………... …………………………………………………………………………………………………………... [Total: 4]

NYGH 2025 Secondary 2 Science Practice Paper 4; Pg. 9