- Crude oil is formed over millions of years, from the remains of living organisms.
- Crude oil is made up of a very large number of compounds.
- It is mainly made up of hydrocarbons (only hydrogen and carbon molecules).
- Most of the hydrocarbons are alkanes which have single bonds and the formula CnH2n+2.
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- The four smallest forms of alkanes are methane, ethane, propane and butane.
- The different lengths of hydrocarbons in crude oil can be split into fractions by fractional distillation where different fractions have different properties.
- First, all the hydrocarbons are heated and the vapours are sent up a fractionating column. The fractions with the highest boiling points (also the condensing points) collect at the bottom and are flowed out of the column. The rest of the vapours continue to rise, and, as they do so, they begin to cool.
- Once the vapours reach their condensing point, they will condense in the section that they are in and will flow out.
- Therefore, the hydrocarbons are split into groups based on their boiling points.
- Hydrocarbons with lower boiling points are more flammable, and, more viscous (flows easily).
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- Most fuels such as coal contain carbon and/or hydrogen.
- When we burn them they can release many gases as they mix with oxygen in the air.
- Solid particles can also be released, known as particulates.
- The oxidisation of fuels when they burn is combustion. For example, if carbon mixes with oxygen it can form carbon dioxide gas.
- The gases released from combustion such as carbon dioxide and sulphur dioxide can cause problems such as global warming and acid rain.
- Sulphur can be removed from the fuel before it is burned or removed from the waste gases.
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