Crude Oil


  • Hydrocarbons are compunds of carbon and hydrogen atoms only.
  • Carbon atoms can form four covalent bonds
  • In a hydrocarbon molecule, these can be
    • carbon-carbon bonds
    • carbon hydrogen bonds
  • Hydrocarbon molecules can consist of
    • chains or rings of carbon atoms


Crude oil is

  • a complex mixture of hydrocarbons, with their carbon atoms in chains or rings
  • an important source of useful substances 
  • a finite resource
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Fractional Distillation


Crude oil can be separated by fractional distillation because its differerent hydrocarbons have different boiling points. During fractional distillation

  • oil is heated to evaporate it
  • vapours rise in the fractioning column
  • the column has a temperature gradient
  • each fraction condenses where it becomes cool enough, and is piped out of the column
    • The gases fraction does not condense and leaves at the top
    • The bitumen fraction does not evaporate and leaves at the bottom

Gases - domestic heating and cooking

Petrol - fuel for cars

Kersone - fuel for aircraft

Diesel Oil - fuel for some cars and trains

Fuel Oil - fuel for large ships

Bitumen - Surfacing roads

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Making fractionns more useful 

    • the porous pot catalyst is heated strongly
    • the liquid paraffin is heated and evaporates
    • the paraffin vapour passes over the hot porous pot and the hydrocarbon molecules break down
    • one of the products is ethene which is a gas and collects in the other tube
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