5.21 understand that condensation polymerisation produces a small molecule, such as water, as well as the polymer.

Condensation reactions takes two molecules and reacts them together to form a larger molecule and the elimination of a smaller molecule like water.
e.g.
Reacting a carboxylic acid and alcohol together forms an Ester with the elimination of a water molecule.

5.20 understand that some polymers, such as nylon, form by a different process called condensation polymerisation

Nylon is a product of a process called condensation polymerisation.

5.18 describe some uses for poly(chloroethene)

• Poly(chloroethene) or PVC for short is tougher than poly(ethene), very hard wearing and more stable to heat
• It's used for plastic sheets, drainpipes and gutters, insulation for wires and casing for electrical plugs

5.16 draw the repeat unit of poly(chloroethene)

This is the monomer of poly(chloroethene) and is called chloroethene.

This is the repeat unit of poly(chloroethene).