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A polymer is a long chain molecule made up of small, repeating units.

Poly(ethene) is a polymer made from a very large number of ethene molecules bonded together.

The reaction is called a polymerisation reaction:

• ethene is the monomer
• poly(ethene) is the polymer

The number of molecules (n) joining up is variable, but is in the region of 2000 to 20000.

The C=C double bond in ethene is involved in the polymerisation reaction. It allows ethene molecules to join, so it is an example of an addition reaction>. Poly(ethene) is an addition polymer.

The table shows the structure of ethene and its polymer.

Poly(chloroethene) is commonly known by the initials of its old name, PVC (poly vinyl chloride). Poly(chloroethene) is made by polymerising chloroethene.

Modelling addition polymerisation - Higher tier

Equations use repeating units to model addition polymerisation reactions. The letter n stands for a large number.

Disposing of polymers

Polymers are unreactive, so they are suitable for storing food and chemicals safely. Unfortunately, this also makes them difficult to dispose. They are often buried in landfill sites or incinerated.

Landfill

Waste polymers are disposed in landfill sites, but this uses valuable land and suitable sites often fill up quickly.

Incineration

Polymers release a lot of energy when they burn, which can be used to heat homes or generate electricity. But burning polymers produces carbon dioxide, adding to global warming, and – if not burnt at high temperatures – release toxic gases.