How Can Crude Oil Be Separated?

• Hydrocarbon fractions


  • Crude oil can be separated into different fractions by fractional distillation
  • Fractions of crude oil are miscible and have different boiling points
  • Fractions are mixtures, not pure compounds, therefore range of boiling points
  • Simple covalent compounds, boiling point increases as molecular size increase because of stronger intermolecular forces of attraction
• Fractional distillation of crude oil (pg 204 revision guide)


  1. Crude oil heated to 400 degree Celsius and changes into vapour
  2. Hot vapour rises up fractionating column
  3. Different hydrocarbon fractions condense and are collected at different levels of the column
  4. Smaller hydrocarbon fractions have lower boiling points and are collected at higher levels of column. Less viscous (flow less easily) and more flammable
  5. Larger hydrocarbon fractions have higher boiling points and are collected at lower levels of column. More viscous and less flammable
• Hydrocarbon Fractions


  P - Petroleum gas

  P - Petrol

  N - Naphtha

  K - Kerosene

  D - Diesel Oil

  L - Lubricating

  B - Bitumen

  Left to right - smallest to largest