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Fuels from crude oil

  • Crude oil contains many different compounds that boil at different temperatures.
  • These burn under differen conditiions and so crude oil needs to be separated to make useful fuels.
  • Distillation can be used to separate mixtures of liquids.
  • Fractional distillation works because the different fractions boil (vaporise) at different temperatures.
  • Most of the compounds in crude oil are hydrocarbons - they only conatin hydrogen & carbon.
  • Alkanes are saturated hydrocarbons. They contain as many hydrogen atoms as possible in their molecules. 
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Fractional distillation

  • Crude oil is separated into fractions using fractional distillation.
  • Each fraction contains compounds with similar boiling points.
  • The larger the molecule, the higher the boiling point of the hydrocarbon.
  • Fractions with lower boiling points are less viscous (sticky/thick) and burn more easily, e.g. petrol.
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Burning fuels

  • Burning hydrocarbons in plenty of air produces carbon dioxide and water.
  • Burning hydrocarbons in a limited supply of air may produce carbon monoxide and solid particles.
  • Any sulfur compounds in the fuel burn to produce sulfur dioxide.
  • Sulfur dioxide causes acid rain.
  • Oxides of nitrogen can be formed when fuels burn under extreme conditions.
  • Nitrogen oxides also cause acid rain.
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