Nylon is a condensation polymer made from two different types of monomer. Explain how condensation polymerisation differs from addition polymerisation in terms of the monomers used and the products formed.

Pearson Edexcel International GCSE Chemistry (4CH1) — 4.8 Synthetic polymers · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Condensation polymerisation uses monomers that each have two reactive functional groups, so that when two monomers join a small molecule (for example H₂O or CH₃OH) is released. Addition polymerisation uses monomers that contain only one reactive group, usually a carbon–carbon double bond (C=C) in an alkene. In condensation polymerisation the joining of monomers produces a small molecule as a by‑product, whereas in addition polymerisation the only product is the polymer chain – no small molecule is lost.

Examiner tips

  • State the key difference in monomer functionality – two groups vs one double bond.
  • Mention the small molecule produced in condensation but not in addition.
  • Use the terms ‘condensation polymerisation’ and ‘addition polymerisation’ exactly as in the mark scheme.
  • Keep the answer concise – 4 marks only.

Common mistakes

  • Confusing the type of functional groups (e.g., saying addition uses two groups).
  • Forgetting to mention the small molecule produced in condensation.
  • Using vague terms like ‘reactive groups’ without specifying double bonds or functional groups.

Mark scheme (4 marks)

  1. Condensation polymerisation uses monomers with two functional groups (whereas addition polymerisation uses monomers with one functional group / a double bond)
  2. Addition polymerisation uses monomers that contain a carbon–carbon double bond (C=C / are unsaturated / are alkenes)
  3. In condensation polymerisation a small molecule (such as water) is also produced / lost when monomers join
  4. In addition polymerisation the only product is the polymer itself / no small molecule is lost

Key terms in this question

condensation polymerisation · addition polymerisation · monomer

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