I/GCSE Chemistry: Crude oil 

In I/GCSE Chemistry, we will learn about crude oil.

The materials that we use are chemicals or mixtures of chemicals and include metal and include metals, polymers and ceramics. Materials can be obtained or made from living things e.g. cotton, paper, silk and wool – these are called NATURAL MATERIALS. An alternative to these are SYNTHETIC MATERIALS that are made from chemicals e.g. plastics such as polythene.

Raw materials from the Earth’s crust can be used to make synthetic materials. For instance CRUDE OIL is a raw material obtained from the Earth’s crust. It is a mixture of many different chemicals, most of which are HYDROCARBONS. These are chain molecules of varying length that are made from hydrogen and carbon atoms only.

When it comes to I/GCSE Chemistry,  different hydrocarbons have different boiling points because their molecular chains are different lengths. The strength of the forces between the hydrocarbon molecules increases as the length of the molecule increases.

When extracted CRUDE OIL is a thick, black sticky liquid however is not very useful until it has been processed at an oil refinery. The process of refining involves separating the hydrocarbons into fractions or batches using a technique called FRACTIONAL DISTILLATION. Each fraction separates as they have different boiling points. The crude oil is heated in a furnace to around 400˚C. This allows all of the hydrocarbons in the crude oil to move into the bottom of the fractionating tower.

• The smallest molecules contained in the crude oil have lower boiling points and so move to the top of the tower. This is because the forces between these molecules are weak, so little energy is required to vaporise them.
• Larger molecules will remain lower down the tower as they have higher boiling points. This is because forces between the molecules are stronger.

Refer to I/GCSE Chemistry, the PETROCHEMICAL INDUSTRY refines naturally occurring crude oil to produce fuels, lubricants and raw materials for chemical synthesis. Only a small proportion of crude oil is used in chemical synthesis, most of it is used for fuels.

As a chemical reaction takes place, atoms in the reactants are rearranges to make the products. The number of atoms of each element in the reactants is the same in the products (CONSERVATION OF MASS).

Some small molecules called MONOMERS can join together to make very long molecules called POLYMERS. Polymerisation can be used to create a wide range of different materials that have different properties and therefore can be used for different purposes. Many traditional (natural) materials have been replaced by polymers because of their superior properties.

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