Getting metals from rocks

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Finding metals

  • Metals are found in ores, and ores are usually oxides of the metal. Eg. aluminium ore is called bauxite.
  • The metal ores that are used to extract metals contain enough metal to make metal extraction worthwhile.
  • Metals are separated from their ores using chemical reactions.
  • The profitability of metal extraction changes over time. Eg:
    • If the selling price of the metal decreases, it may no longer be worthwhile to extract the metal.
    • If the price and demand increases for a metal it may be worth extracting more of it.
    • Technology is advancing so much that its becoming possible to extract more metals that weren't previously worth extracting.
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Reduction with carbon

  • The position of a metal in the reactivity series determines whether its extracted by reduction with carbon or electrolysis.
  • Only metals that are below carbon in the reactivity series can be extracted using reduction with carbon. This is because carbon can only take the oxygen away from metals that are less reactive than itself.
  • So metals like Iron and Tin are extracted using reduction.
  • When an ore is reduced, oxygen is removed from it .
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Electrolysis

  • Metals that are more reactive than carbon need to be extracted using electrolysis.
  • Electrolysis is when a substance is broken down using electricity.
  • A liquid is used to conduct the electricity (electrolyte), and this is usually a metal salt solution made from the ore.
  • The electrolyte has free ions, which conduct the electricity.
  • Electrons are taken away by the positive electrode, and given away by the negative electrode. When the ions lose or gain electrons, they become atoms or molecules and are released.
  • Electrolysis is more expensive than reduction with carbon because it uses a lot of energy.
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More electrolysis

  • Copper is extracted by reduction with carbon, however, the copper that's produced this way tends to be impure , and impure copper isn't useful to use because it doesn't conduct electricity well.
  • Electrolysis can be used to purify it, even though it can be rather expensive.
  • This produces pure and useful copper, which is a much better conductor.
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Displacement reactions

  • A more reactive metal will displace a less reactive metal in a dissolved metal compound. This is because the more reactive metal will react more vigerously and bond more strongly to the non-metal part of the compound, and "pushes out" the less reactive metal.
  • Scrap iron can be used to displace copper from a solution. Scrap iron is more reactive than the copper, and so will displace the copper from the solution. This is useful because scrap iron is fairly cheap.
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