Obtaining and using metals

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Ores

  • metals are extracted from ores in the earth's crust
  • Unreactive metals are found in the earth as uncombined elements
  • Most metals are extracted from there ores by:
    • heating with carbon
    • electrolysis
  • The method used to extract a metal is related to its position on the reactivity series and cost of the extraction process
  • Electrolysis word equation example:
    • Water à hydrogen + oxygen
  • Heating with carbon word equation example:
    • Iron oxide + carbon à iron + carbon dioxide
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Re-activity series

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Oxidation and reduction

  • Oxidation is the gain of oxygen
  • Reduction is the loss of oxygen
  • Extraction of metal involves reduction of ores
  • Oxidation of metals results in corrosion
  • A metals resistance to oxidation is related to its position on the reactivity series
  • Oxidation word equation example:
    • iron + oxygen -> iron oxide
  • Reduction word equation example:
    • aluminium oxide -> aluminium + oxygen                                                             
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Recycling

  • Advantages of recycling:
    • Natural reserves of metal ores will last long
    • For most metals, less energy is needed to recycle them than is needed to extract them.
    • Recycling reduces the need to mine ores.  Mining can damage the landscape and create noise and dust pollution
    • Recycling produces less pollution
    • More recycling means that less waste metals are disposed of in landfills
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Properties of metals

  • Most metals are:
    • good conductors of heat
    • good conductors of electricity
    • Ductile (can be drawn into wires)
    • Malleable (can be hammered into shape)
    • shiny
    • have high boiling and melting points
    • Some are magnetic
  •  Aluminium:
    •  Has low density
    • Does not corrode
    • Used in making aeroplanes and cars
  •  Copper:
    •  Good electrical conductor
    • low reactivity
    • does not react with water
    • used in water pipes and electrical cables

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Properties of metals

  • Gold:
    • Very unreactive
    • Does not corrode
    • Very attractive
    • One of the best electrical conductors
    • Used inside most electrical devices and for jewellery
  • Steel:
    • Mixture of iron with carbon and other metals.
    • Stronger and harder than Iron
    • Used to make bridges, cars, electrical goods, frames for buildings and machinery
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Alloys

  • An alloy is a mixture of metals to improve their properties.
  • Alloys have different size atoms in them which stop each layer from sliding over each other
  • Shape memory alloys return to their original state with a change in condition e.g. heated
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