Extraction and Uses of Metals

• Metals are extracted from their ores using a method dependent on the position of the metal in the reactivity series. More reactive metals are extracted using electrolysis while less reactive metals can be heated with carbon. Other elements can be mixed with metals to produce alloys with different properties.
• Unreactive metals, such as silver and gold, can be found in the Earth’s crust in a pure form, uncombined to other elements. However, more reactive metals, such as aluminium and magnesium, will usually be found combined to another element in a compound. An ore is a rock that contains enough of the metal to make it economically worth extracting.
• The method of extracting a metal depends on its position in the reactivity series.

  
• If a metal is less reactive than carbon, it can be extracted by reacting it with carbon in a displacement reaction.
• In a displacement reaction, the more reactive metal is able to take the place of a less reactive metal in a compound, since the more reactive metal forms stronger bonds. Carbon replaces the less reactive metal in a redox reaction, where the carbon is oxidised and the metal is reduced. We therefore refer to this method as reduction using carbon.
• For example, copper is below carbon in the reactivity series so it is extracted from copper oxide by reacting it with carbon, to form pure copper and carbon dioxide. The copper loses oxygen so it is reduced while the carbon gains oxygen so it is oxidised. That’s why we call this method reduction with carbon – because the element that we are purifying is reduced.

  
• Elements which are more reactive than carbon will be extracted using electrolysis. Aluminium is more reactive than carbon so it must be extracted from ores containing aluminium oxide using this method. Electrolysis uses electricity to separate the metal from the other elements in the compound.
• Aluminium: aluminium is a very lightweight metal so it is used as a material for aeroplanes and bicycles. It also has a protective outer layer of aluminium oxide, preventing it from corrosion. These properties make aluminium particularly useful for things like wrapping food and for drinks cans.
• Copper: copper is a good conductor of heat and electricity so it is used in electrical wiring and heating systems.
• Iron: pure iron is too soft and reactive to be a useful material so it is alloyed with carbon to make steel.
• Different amounts of carbon can be added to produce different properties:

  • Low carbon steel: this is malleable and can be easily shaped so is used as a material for cars
  • High carbon steel: this is very strong and inflexible - it is used as a material for bridges
  • Stainless steel: this is hard and resistant to corrosion so it used for things like cutlery and washing machines.