Science

Useful chemicals from crude oil

Materials obtained or made from living things are sometimes called natural materials, whereas synthetic materials are made from chemicals. Today, synthetic materials offer us more durability at a lower cost than the natural materials we used to use.

Synthetic and natural materials

The materials we use are chemicals or mixtures of chemicals. For example, sugar is a chemical, but chocolate is a mixture of chemicals, one of which is sugar.

Materials can be obtained or made from living things. Examples include cotton, paper, silk and wool. These are sometimes called natural materials.

Materials can also be made from chemicals. Examples of these include plastics such as polythene. These are called synthetic materials.

Refining crude oil

Crude oil 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.

Three different hydrocarbon molecules

Crude oil is refined by the petrochemical industry. The hydrocarbons are separated into fractions of similar size. These fractions include fuels, such as petrol and diesel, lubricants and raw materials for chemical synthesis.

Most of the fractions from crude oil are burned as fuels. Only a small percentage of crude oil is used for chemical synthesis.

Polymerisation

Some small molecules can join together to make very long molecules called polymers. This process is called polymerisation.

Many polymers are made from chemicals that are obtained from crude oil. For example, molecules of ethene join together to make poly(ethene), commonly known as polythene.

Ethene makes polyethene

By polymerising other small molecules, a wide variety of different polymers can be made. These synthetic materials have many uses.

Rearrangement of atoms

In a chemical reaction, the substances that react together are called the reactants, while the substances that are formed are called the products.

reactants → products

The products have different properties from the reactants.

As a chemical reaction takes place, atoms in the reactants are rearranged to make the products. The number of atoms of each element in the reactants is the same in the products. No atoms are added or taken away. This is called the conservation of atoms.

When polythene is made from ethene, the polymer has the same number of carbon and hydrogen atoms as the ethene molecules it is made from.

Ethene makes polyethene

New synthetic materials

A window frame made from uPVC

A window frame made from uPVC

New synthetic materials are often used to make articles that at one time were made from natural materials. The new material often has better properties, and may be cheaper to make.

Window frames used to be made from wood. This has to be painted regularly, and in time may rot. Many new window frames are made from uPVC, a synthetic polymer. This can be made in a variety of colours, never needs to be painted, and does not rot.

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