Fractional Distillation

• Crude oil is made over millions of years
• Crude oil is a fossil fuel. It's formed from the remains of plants and animals, mainly plankton, that died millions of years ago and were burried in mud
• Over millions of years, with high temperature and pressure, the remains turn to crude oil, which can be drilled up from the rocks where it's found
• Fossil fuels like coal, oil and gas are called non-renewable fuels as they take so long to make that they're being used up much faster than they're being formed. They're finite resources
• Fractional distillation can be used to separate hydrocarbon fractions
• Crude oil is a mixture of lots of different hydrocarbons, most of which are alkanes
• The different compounds in crude oil are separated by fractional distillation
• 1. The oil is heated until most of it has turned into gas. The gases enter a fractionating column (and the liquid bit is drained off)

  
• 2. In the column there's a temperature gradient - it's hot at the bottom and get cooler as you go up

  
• 3. The longer hydrocarbons have high boiling points. They condense back into liquids and drain out of the column early on, when they're near the bottom.

  
• 4. The shorter hydrocarbons have lower boiling points. They condense and drain out much later on, near to the top of the column where it's cooler

  
• 5. You end up with the crude oil mixture separated out into different fraction. Each fraction conatins a mixture of hydrocarbons that all contain a similar number of carbon atoms, so have similar boiling points

  
• LPG (Liquefied Petroleum Gas) contains mostly propane and butane
• Heavy fuel oil can be heating oil, fuel oil or lubricating oil