Polymers and Their Properties — AQA GCSE Chemistry
Polymers are very large molecules made of many repeating units. Their structure explains their properties.
What is a polymer?
A polymer is a large molecule made when many small molecules (monomers) join together by covalent bonds. The bonds within a polymer molecule are strong covalent bonds.
Why polymers are solid
Although the covalent bonds within the chains are strong, the polymer's properties depend largely on the intermolecular forces between the long chains:
- The chains are large, so the intermolecular forces between them are relatively strong (much stronger than between small molecules).
- This means polymers are usually solids at room temperature, with higher melting points than small molecules — but lower than ionic or giant covalent substances.
Representing polymers
Polymers are drawn using a repeating unit in brackets with the letter n (showing it repeats many times). The displayed formula of the monomer can be turned into the repeating unit of the polymer.
Thermosoftening polymers
Many polymers soften when heated (thermosoftening) because heat only needs to overcome the weak intermolecular forces between chains, not the strong covalent bonds within them, so they can be remoulded.
Exam tips
- A polymer = many monomers joined by covalent bonds.
- Polymers are solids because of strong intermolecular forces between long chains.
- Draw a polymer using the repeating unit with brackets and n.
- Melting points are higher than small molecules but lower than giant structures.