Describe the process of addition polymerisation, including the type of monomer required and the type of bond involved in joining the monomers together.

AQA GCSE Chemistry (8462) — 4.7.3 Synthetic and naturally occurring polymers (Chem only) · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Many small molecules called monomers join together to form a polymer.
The monomers must be alkenes, i.e. they contain a carbon–carbon double bond and are unsaturated.
During the reaction the carbon–carbon double bond in the monomer opens (breaks) to allow the monomers to join.
The monomers are joined by covalent bonds to form the polymer chain; no other products are formed.

Examiner tips

  • Use the phrase "many small molecules called monomers" to show you understand the starting point.
  • Mention that the monomers must be alkenes and contain a C=C double bond.
  • Explain that the double bond opens during the reaction.
  • State that covalent bonds link the monomers and no other products are formed.

Common mistakes

  • Writing that the monomers are any hydrocarbons instead of specifying alkenes.
  • Claiming that the double bond is formed rather than broken.
  • Saying that other products are formed, e.g. small molecules or gases.

Mark scheme (4 marks)

  1. Many small molecules called monomers join together to form a polymer
  2. The monomers must be alkenes / must contain a carbon–carbon double bond / must be unsaturated
  3. The carbon–carbon double bond in the monomer opens / breaks to allow monomers to join
  4. The monomers are joined by covalent bonds (to form the polymer chain) / no other products are formed

Key terms in this question

addition polymerisation · monomers

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