Fractional Distillation

  • Crude oil is a mixture of different hydrocarbons, must be separated before we can use it

  • Use fractional distillation because the different substances have similar boiling points

  • Fractional distillation

    • Crude oil is heated to make a vapour (evaporate it)

    • Vapour rises up the column, cools down to condense

    • Column is hot at the bottom and cool at the top

    • Hydrocarbons condense at different temperatures depending on their boiling point

    • Longer chains condense at the bottom as they have a higher boiling point and it’s hotter at the top, short chains condense at the top as they have lower boiling points and it’s cooler at the top

  • Short chains

    • Low BP

    • Higher volatility (tendency to turn into gas)

    • Lower viscosity (very runny)

    • Higher flammability

  • Long chains

    • High BP

    • Lower volatility

    • Higher viscosity (thick)

    • Lower flammability