Polymerisation

Ethene molecules have a double bond betwen the two carbon atoms. Lots of ethene molecules can be made to join up to form one long molecule called poly(ethene). The poly(ethene) only has single bonds between carbon atoms.

Other small alkene molcules can be joined up to make long molecules. The small molecules are called monomers. Lots of monomers join up to make polymers.

Properties and uses
Differen polymers have different properties, so they have differrent uses.