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Grade 10 Advanced About 15 min Version 1 Awaiting review Premium

Oxidation and reduction with copper

When a substance gains oxygen, it is oxidised. When a substance loses oxygen, it is reduced. Shiny copper heated in air combines with oxygen to form black copper oxide: copper is oxidised. Heating copper oxide with carbon does the opposite: carbon takes the oxygen away, so copper oxide is reduced back to copper, and the carbon is oxidised to carbon dioxide. Oxidation and reduction always happen together, so these are called redox reactions.

What you will learn

  • Define oxidation and reduction in terms of oxygen.
  • Describe the oxidation of copper and the reduction of copper oxide by carbon.
  • Explain why the mass of copper increases when it is oxidised.

Before you start

  • Know the difference between elements and compounds.

Materials

  • Copper foil
  • Copper(II) oxide
  • Carbon powder

Equipment

  • 2 heat-proof dishes
  • Bunsen burner (shown as a hot plate)
  • Tongs

Procedure

  1. Dish A holds 5 g of shiny copper foil. Heat it strongly and observe the colour.
  2. Dish B holds black copper oxide. Mix in carbon powder and heat it strongly.
  3. Compare what is left in each dish.

How this simulation is simplified

  • Each change is shown as soon as the dish reaches the heating temperature.
  • All the copper oxide is reduced and all the carbon is used up.