Describe the differences between addition polymerisation and condensation polymerisation, including the types of monomers involved and any small molecules produced.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Polymers are large molecules made by joining many smaller monomer units together. There are two main types of polymerisation reaction studied in chemistry.
Model answer (5 marks)
Addition polymerisation:
1. Monomers contain a C=C double bond (alkenes/unsaturated monomers).
2. Polymerisation proceeds by opening the double bond; no small molecules are released – only the polymer is formed.
3. Usually a single monomer type is used, giving a homopolymer.
Condensation polymerisation:
4. Each monomer has two different functional groups (e.g. –OH and –COOH, –NH2 and –COOH).
5. When monomers join, a small molecule such as water or methanol is lost, producing a polymer and a small molecule.
Condensation often involves two different monomers, giving a copolymer.
1. Monomers contain a C=C double bond (alkenes/unsaturated monomers).
2. Polymerisation proceeds by opening the double bond; no small molecules are released – only the polymer is formed.
3. Usually a single monomer type is used, giving a homopolymer.
Condensation polymerisation:
4. Each monomer has two different functional groups (e.g. –OH and –COOH, –NH2 and –COOH).
5. When monomers join, a small molecule such as water or methanol is lost, producing a polymer and a small molecule.
Condensation often involves two different monomers, giving a copolymer.
Examiner tips
- Use the word ‘monomers’ and specify C=C for addition, two functional groups for condensation.
- State that addition gives no small molecules, condensation gives a small molecule (e.g. water).
- Mention single vs. two‑monomer systems to hit all points.
Common mistakes
- Confusing the type of monomer (e.g. saying alkanes for addition).
- Forgetting that condensation releases a small molecule.
- Mixing up which polymerisation uses a single monomer type.
Mark scheme (5 marks)
- Addition polymerisation uses monomers with a carbon–carbon double bond (alkenes / unsaturated monomers)
- In addition polymerisation no small molecules are produced / only the polymer is formed
- Condensation polymerisation uses monomers that each have two functional groups
- In condensation polymerisation a small molecule (such as water) is lost / released when monomers join
- Addition polymerisation forms a polymer from a single type of monomer whereas condensation polymerisation often involves two different types of monomer
Key terms in this question
addition polymerisation · condensation polymerisation · monomer · polymer
Related
- All OCR A-Level Chemistry A (H432) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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