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Year 10 Science — Chemical reactions and equations

Balance a skeletal equation by counting atoms, name the five kinds of reaction the chapter sets out, and say which substance has been oxidised and which reduced.

Name: ________________________

  1. 1.Sort each reaction by the kind of reaction it is.

    Groups: Combination · Decomposition · Displacement · Double displacement

    • Carbon burning in oxygen to give carbon dioxide
    • An iron nail left in copper sulphate solution
    • Ferrous sulphate crystals heated in a boiling tube
    • Limestone heated in a kiln
    • Sodium sulphate solution mixed with barium chloride solution
    • Calcium oxide and water make slaked lime

  2. 2.Hydrogen is passed over heated copper(II) oxide: CuO + H₂ → Cu + H₂O. Which substance has been reduced?

    • a) Hydrogen
    • b) Copper
    • c) Water
    • d) Copper(II) oxide

  3. 3.Limestone is heated strongly in a kiln and gives quick lime and carbon dioxide. What kind of reaction is that?

    • a) Thermal decomposition
    • b) A displacement reaction
    • c) A combination reaction
    • d) A precipitation reaction

  4. 4.Sort each of these by whether energy comes out of the reaction or goes into it.

    Groups: Heat given out · Energy taken in

    • Green crystals heated until they give off a sharp smell
    • Respiration in our cells
    • Silver chloride left in sunlight
    • Natural gas burning
    • Water split by an electric current
    • Quick lime added to water

  5. 5.Bags of crisps are flushed with nitrogen before they are sealed. What is that for?

    • a) It keeps the fat in them from being oxidised
    • b) It stops the bag from being crushed
    • c) It cools the crisps down
    • d) It keeps the crisps dry

  6. 6.Match each everyday sight to what it is called.

    • An iron gate turning reddish brown
    • A silver spoon going black
    • Butter left out until it smells off
    • A white solid appearing as two clear solutions meet
    • Corrosion
    • Precipitation
    • Rusting
    • Rancidity

  7. 7.Zinc granules are dropped into dilute sulphuric acid. Bubbles rise round them and the tube grows warm. Which two of the chapter's signs of a reaction is that?

    • a) The colour changes, and a gas is given off
    • b) A gas is given off, and the temperature changes
    • c) The temperature changes, and the colour changes
    • d) The state changes, and the colour changes

  8. 8.Butter kept too long smells and tastes different, because the fat in it has been oxidised. What is this change called? Answer with one word.

Answer key — Year 10 Science — Chemical reactions and equations

  1. 1. Calcium oxide and water make slaked lime → Combination; Carbon burning in oxygen to give carbon dioxide → Combination; Ferrous sulphate crystals heated in a boiling tube → Decomposition; Limestone heated in a kiln → Decomposition; An iron nail left in copper sulphate solution → Displacement; Sodium sulphate solution mixed with barium chloride solution → Double displacement
  2. 2. d) Copper(II) oxide
  3. 3. a) Thermal decomposition
  4. 4. Quick lime added to water → Heat given out; Respiration in our cells → Heat given out; Natural gas burning → Heat given out; Silver chloride left in sunlight → Energy taken in; Water split by an electric current → Energy taken in; Green crystals heated until they give off a sharp smell → Energy taken in
  5. 5. a) It keeps the fat in them from being oxidised
  6. 6. An iron gate turning reddish brown → Rusting; A silver spoon going black → Corrosion; Butter left out until it smells off → Rancidity; A white solid appearing as two clear solutions meet → Precipitation
  7. 7. b) A gas is given off, and the temperature changes
  8. 8. rancidity