Types of Chemical Reaction · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Four types of chemical reaction

Science · Matter & Materials · ages 12-13
Name ______________________   Date ____________

  1. Iron slowly turning to orange-brown rust in damp air is an example of...

    • combustion
    • oxidation
    • thermal decomposition

  2. Which of these is an example of combustion?

    • Methane burning in plenty of oxygen, with a clean blue flame
    • Iron slowly gaining oxygen in damp air
    • Limestone splitting into two substances in a hot kiln

  3. Thermal decomposition starts with two substances joining together.

    Circle one:   True   False

  4. A student drops a strip of copper into iron sulfate solution and waits. Nothing happens. Why not?

    • Copper is less reactive than iron, so it cannot push iron out of its compound
    • Copper is more reactive than iron, so the reaction finished too quickly to see
    • Displacement always needs strong heating, and the solution was cold

  5. A Bunsen burner with its air hole open burns gas with a clean blue flame. Plenty of oxygen reaches the flame. What forms?

    • Carbon monoxide and soot
    • Iron oxide
    • Carbon dioxide and water

  6. Calcium carbonate is heated and decomposes into calcium oxide and a gas. Which gas?

    • Water vapour
    • Carbon dioxide
    • Oxygen

  7. Reactivity order from most to least reactive: zinc, iron, copper, silver. Which pair will react: zinc added to iron sulfate solution, or copper added to iron sulfate solution?

    • Zinc and iron sulfate, because zinc is more reactive than iron
    • Neither, because iron sulfate can't react with a metal
    • Copper and iron sulfate, because copper is more reactive than iron

  8. Zara drops magnesium into copper sulfate solution. The blue colour fades and pink copper appears. What tells her this is displacement, not thermal decomposition?

    • Heat was used, and only one substance was present at the start
    • A gas escaped and the solution got hot
    • Two substances started the reaction, and a metal swapped places
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Four types of chemical reaction W1-mt_v0K6GRi4ZL-s1

  1. oxidation · Rusting is oxidation. Iron gains oxygen slowly, with no flame involved.
  2. Methane burning in plenty of oxygen, with a clean blue flame · Combustion is a substance burning in oxygen. Methane burning with a clean flame is combustion. Iron gaining oxygen slowly is oxidation, and limestone splitting under heat is thermal decomposition.
  3. False · Decomposition starts with just one substance, which heat breaks apart into simpler substances.
  4. Copper is less reactive than iron, so it cannot push iron out of its compound · A metal can only displace a less reactive metal. Iron is more reactive than copper, so copper cannot take iron's place in iron sulfate. Nothing happens.
  5. Carbon dioxide and water · Plenty of oxygen means complete combustion, which produces carbon dioxide and water.
  6. Carbon dioxide · The word equation is calcium carbonate → calcium oxide + carbon dioxide.
  7. Zinc and iron sulfate, because zinc is more reactive than iron · Zinc sits above iron in the reactivity order, so it can displace iron from iron sulfate. Copper sits below iron, so it can't.
  8. Two substances started the reaction, and a metal swapped places · Displacement needs two starting substances, a metal and a compound, and ends with a new metal appearing. Decomposition starts with just one substance and needs heat.
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