Poly(chloroethene), also known as PVC, is an addition polymer made from chloroethene monomers. State two structural features of chloroethene that allow it to undergo addition polymerisation, and for each feature, explain its role in the polymerisation process.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Chloroethene has the molecular formula C₂H₃Cl. It is the monomer used to produce poly(chloroethene), a widely used synthetic polymer.
Model answer (4 marks)
1. Chloroethene contains a carbon–carbon double bond (C=C).
The double bond is the reactive site; during addition polymerisation it opens, allowing the carbon atoms to form new single bonds with adjacent monomers, linking them into a chain.
2. Chloroethene is a small monomer with only one reactive functional group.
Because the monomer is small and contains a single double bond, all of its atoms are incorporated into the polymer; no other small molecules are released, so the chain grows by successive addition of whole monomer units.
The double bond is the reactive site; during addition polymerisation it opens, allowing the carbon atoms to form new single bonds with adjacent monomers, linking them into a chain.
2. Chloroethene is a small monomer with only one reactive functional group.
Because the monomer is small and contains a single double bond, all of its atoms are incorporated into the polymer; no other small molecules are released, so the chain grows by successive addition of whole monomer units.
Examiner tips
- Mention the C=C double bond and its opening; link to chain growth. State that the monomer is small and has only one reactive site, ensuring all atoms enter the polymer. Keep each point brief but complete. Use the exact wording from the mark scheme.
- Use the word "addition polymerisation" and explain that no by‑products are formed.
Mark scheme (4 marks)
- Chloroethene contains a carbon–carbon double bond (C=C)
- The double bond opens / breaks during polymerisation, allowing monomers to join together to form a long chain polymer
- Chloroethene is a small molecule / monomer (with reactive functionality to repeat)
- No other molecule / small molecule is produced during addition polymerisation, so all atoms of the monomer are incorporated into the polymer chain
Key terms in this question
addition polymerisation · monomer · polymer
Related
- All Pearson Edexcel International GCSE Chemistry (4CH1) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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