How are products from oil obtained and used?

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How are products from oil obtained and used?

Crude oil is a vital substance used frequently in our everyday lives. However we are all aware that oil is being used faster than it can be produced and that there are only scarce amounts left. The question is how can we make these products last as long as possible and what are the alternatives?

Crude oil is a fossil fuel, made naturally from decaying plants and animals living in ancient seas millions of years ago. It is usually found under the ground and under the sea in certain parts of the world such as the Middle East and Texas, in the USA. Although crude oil is very important substance, the oil itself has no direct use, so has to be refined.  The first step in the refinery of crude oil is fractional distillation.

Fractional distillation is used to separate fractions such as gasoline, bitumen, kerosene, petroleum, fuel oil, etc from crude oil. During fractional distillation the crude oil is split into a variety of fractions, during the process each fraction of the crude oil will evaporate and can therefore be collected by condensing it. This means that if you know the certain boiling points of each fraction you can separate the certain substance you need. 

The process begins in the oil refinery. In the oil refinery the crude oil is heated to turn the oil in to a vapour; it is then fed into the bottom of the fractionating column. Here several condensers are fitted at different heights. The column is hot at the bottom and cool at the top. The hydrocarbons with the lower boiling points turn into vapour easily compared to those with a higher boiling point. When the vapour reaches a height in the tower where the temperature of the column is equal to that substance's boiling point, it will condense to form a liquid. Substances with very high boiling points (e.g. bitumen and fuel oil) condense immediately and are tapped of at the bottom of the column.  These fractions not only have the highest boiling point, but are more difficult to burn and have the smokiest flame; they also have the largest molecules meaning they have a higher viscosity. Substances with lower boiling points condense on the way to the top, however, the fraction with the lowest boiling point called refinery gases remain as a gas and are tapped out at the top of the column. The fractions at the top of the fractionating column have a low boiling point, very volatile, low viscosity and ignite easily; these properties create the best fuels.

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Each fraction can have a number of different uses. For example most of them create mainly fuels but others can also be turned into plastics;

Very few of the substances above come out of the fractional distillation column ready for the market. Some fractions such as the residue from the distillation tower need to be transformed into new components.  Low-value fractions that aren't in great demand can be converted to petrol and other useful chemicals. The most used conversion method is called cracking because it uses heat and pressure to crack large hydrocarbon molecules into smaller ones. Catalytic ...

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Mark: 4/5 This is a very detailed and comprehensive answer. An attempt has been made to evaluate the alternatives to fossil fuels and the writer has described how fossil fuels are obtained in good detail. In order to get to 5/5, the writer must use subsections throughout in order to provide a clear structure. Also, a better description of the composition of fossil fuel is needed.