Poly(ethene) is made from ethene by a process called addition polymerisation. Describe what happens to ethene molecules during addition polymerisation and explain why the product, poly(ethene), cannot undergo addition reactions in the same way that ethene can.

Edexcel GCSE Chemistry (1CH0) — 10.2 Alkenes (Chem only) · Describe and Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

During addition polymerisation, many ethene monomers join together to form a long‑chain polymer. The C=C double bond in each ethene opens or breaks during the reaction, allowing the carbon atoms to link via single bonds. The resulting poly(ethene) contains only single C–C bonds – it has no C=C double bonds. Addition reactions require a C=C double bond, so poly(ethene) cannot undergo addition reactions in the same way that ethene can.

Examiner tips

  • Use the term "addition polymerisation" and mention the opening of the double bond.
  • Explain that the polymer is saturated (only single bonds).
  • Show the link between lack of double bonds and inability to add reagents.

Common mistakes

  • Saying the polymer still has double bonds or can react by addition.
  • Forgetting to mention that the double bond opens during polymerisation.
  • Using vague terms like "chain growth" without specifying the breaking of C=C.

Mark scheme (4 marks)

  1. Many ethene monomers join together (to form a long-chain polymer)
  2. The double bond in ethene opens/breaks during polymerisation
  3. Poly(ethene) contains only single carbon-carbon bonds (no C=C double bonds)
  4. Addition reactions require a C=C double bond (so poly(ethene) cannot react in this way / is saturated)

Key terms in this question

addition polymerisation · polymer

Related

More Alkenes (Chem only) questions

▶ Try answering this question with AI marking (free) →