Plastics are artificial compounds manufactured in factories. There are many different kinds of plastics made from the carbon atoms of natural materials such as coal and oil. Plastics are made to imitate traditional wood, leather, metal, glass and ceramics.
Most plastics are made from crude oil that is pumped from underground. In a refinery, the oil is divided into different products called hydrocarbons. These are purified, then combined with elements such as oxygen, nitrogen, chlorine and sulphur. These elements link with the oil's carbon atoms to make small units of plastic called monomers.
The small units of plastic are linked together by more chemical reactions to make long chains of thousands of atoms called polymers. Polymers are like lots of beads strung on a long, single string. When these small units of plastic are combined in different orders, they make many kinds of plastic.
More than 90 per cent of plastics will melt when heated. They are called thermoplastics. Some of these plastics are soft and are used in milk jugs. Others are tougher and are made into washing powder jugs. The other main type of plastic that won't melt is called thermoset and is used in bathtubs, boats and glue.