Lesson T4.2.1

T4.2.1 Combustion and thermal decomposition Quiz: KS3 Chemistry, Unit 4

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson T4.2.1, Combustion and thermal decomposition: 20 multiple choice questions for the KS3 Chemistry (National Curriculum), Unit 4: Chemical reactions, written with Revision Ninja.

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The 20 questions

  1. What is combustion?

    • A reaction in which a substance reacts with oxygen and releases energy
    • A reaction in which a substance splits into smaller substances using heat only
    • A change in which a solid turns into a liquid with no reaction
    • A reaction in which two substances are joined by a magnet

  2. What are the main products when a hydrocarbon fuel such as methane burns completely in air?

    • Carbon dioxide and water
    • Carbon monoxide and hydrogen
    • Iron and sulfur
    • Oxygen and nitrogen

  3. What is thermal decomposition?

    • A substance dissolves in water when it is heated to a high temperature
    • A substance breaks down into simpler substances when heated
    • A substance joins with oxygen from the air when it is heated strongly
    • A substance melts and then solidifies again when it is cooled slowly

  4. When calcium carbonate is heated strongly, what gas is produced?

    • Oxygen
    • Carbon dioxide
    • Hydrogen
    • Nitrogen

  5. Which test identifies carbon dioxide gas?

    • Adding it to universal indicator, which turns red
    • Holding a lit splint near it, which gives a squeaky pop
    • Holding a glowing splint in it, which relights
    • Bubbling it through limewater, which turns cloudy

  6. Which gas relights a glowing splint?

    • Oxygen
    • Carbon dioxide
    • Hydrogen
    • Nitrogen

  7. What is the name of the solid left after heating copper carbonate?

    • Copper carbonate
    • Copper oxide
    • Copper sulfate
    • Copper hydroxide

  8. Which of these is a combustion reaction?

    • Burning natural gas in air
    • Dissolving sugar in tea
    • Melting ice to form water
    • Heating limestone to give quicklime

  9. A student heats magnesium in air and a white powder forms. Which type of reaction is this?

    • Combustion, because magnesium reacts with oxygen
    • Dissolving, because magnesium forms a solution
    • Neutralisation, because magnesium reacts with an alkali
    • Thermal decomposition, because magnesium splits up

  10. Limestone (calcium carbonate) heated strongly gives calcium oxide and carbon dioxide. Which type of reaction is this?

    • Thermal decomposition
    • Oxidation of a metal
    • Displacement
    • Combustion

  11. Why does combustion of a fuel need oxygen?

    • Oxygen cools the fuel so it burns slower
    • Oxygen turns the fuel into a metal
    • Oxygen is a reactant that combines with the fuel
    • Oxygen dissolves the fuel in air

  12. Which product of combustion of a carbon-containing fuel turns limewater cloudy?

    • Carbon dioxide
    • Oxygen
    • Water vapour
    • Hydrogen

  13. What happens to the mass of a metal when it burns in air and forms an oxide?

    • It increases, because oxygen is added to it
    • It decreases, because the metal evaporates away
    • It disappears, because the metal becomes energy
    • It stays exactly the same, since nothing changes

  14. Which gas is produced when a metal carbonate such as copper carbonate is heated?

    • Carbon dioxide
    • Chlorine
    • Nitrogen
    • Hydrogen

  15. A green sample of copper carbonate is heated and turns black. What does this suggest?

    • A new substance such as copper oxide has formed
    • The sample has melted into a liquid that then cooled down
    • The sample has evaporated completely from the dish in the heat
    • The sample has dissolved into the air around the dish

  16. Why is the thermal decomposition of limestone used industrially?

    • It produces quicklime (calcium oxide) that is used in building and in making other chemicals
    • It produces a liquid metal that is used to make electrical wiring and cables for homes
    • It produces hydrogen gas that is stored and used as a clean fuel in many fuel cells
    • It produces pure oxygen that is supplied only for medical use in hospitals and clinics

  17. A student says combustion always produces carbon dioxide. What is wrong?

    • Combustion produces only solid products such as ash and soot in every case
    • Some fuels, such as hydrogen, produce water and no carbon dioxide
    • Combustion never produces any gas at all, only heat and light are given off
    • Combustion always produces nitrogen gas as well as water in the reaction

  18. Which statement correctly describes the energy in combustion?

    • Energy is absorbed from the surroundings, so it is endothermic
    • Energy is released to the surroundings, so it is exothermic
    • Energy is destroyed as the reaction proceeds
    • No energy is released or absorbed

  19. Which observation shows that a combustion reaction is taking place?

    • The fuel freezes into a solid block
    • The fuel is turned into a metal
    • The fuel dissolves into a clear solution
    • Heat and light are given out as the fuel burns

  20. Why does heating green copper carbonate turn it black?

    • A new compound, copper oxide, is made and it is black
    • The copper carbonate melts and turns into a black liquid
    • The copper carbonate absorbs water and turns green again
    • The copper carbonate turns into copper metal and water

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