Polymers can be divided into two main types based on how they are formed: addition polymers and condensation polymers. Explain the differences between addition polymerisation and condensation polymerisation, including reference to the types of monomers used and any by-products formed.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
Addition polymerisation uses monomers with C=C double bonds (e.g. alkenes). The double bond opens and monomers link directly, giving a long chain with no other products.
Condensation polymerisation uses monomers bearing two different functional groups (e.g. –OH and –COOH, or –NH2 and –COOH). Each time two monomers join a small molecule by‑product (water or methanol) is released, and the polymer contains a repeat linkage such as an ester or amide.
Condensation polymerisation uses monomers bearing two different functional groups (e.g. –OH and –COOH, or –NH2 and –COOH). Each time two monomers join a small molecule by‑product (water or methanol) is released, and the polymer contains a repeat linkage such as an ester or amide.
Examiner tips
- State the type of monomer for each process
- Explain the bond change and by‑product for condensation
- Mention the repeat linkage in condensation polymers
Common mistakes
- Confusing the presence of a double bond with the need for a catalyst
- Saying condensation gives no by‑product
- Forgetting to mention the repeat linkage (ester/amide)
Mark scheme (5 marks)
- Addition polymerisation involves monomers that contain a C=C double bond (alkenes/unsaturated monomers)
- In addition polymerisation, the double bond opens/breaks and monomers join together to form a long chain with no other products
- Condensation polymerisation involves monomers with two functional groups (e.g. –OH and –COOH, or diamine and dicarboxylic acid)
- In condensation polymerisation, a small molecule by-product is released each time monomers join
- Condensation polymers contain a repeat linkage group such as an ester linkage (in polyesters) or an amide linkage (in polyamides/nylon)
Key terms in this question
addition polymerisation · condensation polymerisation · monomer · by-product
Related
- All Edexcel A-Level Chemistry (9CH0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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