Fractional distillation separates crude oil into fractions of similar hydrocarbons

1. Crude oil is a mixture of many different hydrocarbons.
2. Fractional distillation is a physical process that separates these hydrocarbons into groups called fractions.
3. A fraction is a mixture of hydrocarbons whose molecules contain a similar number of carbon atoms.
4. The separation is possible because hydrocarbons of different sizes have different boiling points.

A hot-to-cool column makes hydrocarbons condense at different heights

1. Crude oil is heated so that most of it evaporates into a gas.
2. The hot vapours enter the bottom of a tall fractionating column.
3. The column has a temperature gradient: it is hot at the bottom and cooler towards the top.
4. As the vapours rise through the column, they cool down.
5. Each hydrocarbon condenses back to a liquid once the temperature drops below its boiling point.
6. Hydrocarbons with high boiling points, which have long chains, condense low down where it is hot.
7. Hydrocarbons with low boiling points, which have short chains, rise higher and condense near the cooler top.
8. Each fraction is drawn off the column at the height where it condenses.

Crude-oil fractions become fuels and chemical feedstock

1. Fuels from crude oil
   1. A fuel is a substance that releases energy when it burns.
   2. Fractions are processed into fuels such as petrol, diesel oil, kerosene, heavy fuel oil and liquefied petroleum gases (LPG).
   3. You are not expected to name any other specific fractions or fuels.
2. Feedstock for the petrochemical industry
   1. A feedstock is a raw material used to make other useful substances.
   2. The petrochemical industry processes substances from crude oil into fuels and other carbon-based materials.
3. Useful materials made from petrochemicals
   1. Solvents dissolve other substances.
   2. Lubricants reduce friction between moving surfaces.
   3. Polymers are used to make plastics and synthetic fibres.
   4. Detergents help water lift away grease and dirt.

Carbon forms huge families of natural and synthetic compounds

1. Carbon atoms can bond to each other and to hydrogen in many different arrangements.
2. This lets related carbon compounds be grouped into families that are built in similar ways.
3. Natural carbon compounds occur in nature, such as the hydrocarbons in crude oil.
4. Synthetic carbon compounds are made by chemical processes, such as many polymers and detergents.
5. Carbon's ability to form families of similar compounds is why there is such a vast array of natural and synthetic carbon compounds.