Polymer – IGCSE Chemistry Definition
IGCSE Chemistry definition of polymer: a long-chain molecule made from many monomers. Covers types, properties, disposal issues, and exam tips for Cambridge 0620.
Published by IGCSEChemistry.com.my
Chemistry teaching team: K. S. Tan (15+ years teaching IGCSE Chemistry) and Ms Yash (10+ years teaching IGCSE Chemistry) and Ms Kartini (15+ years teaching IGCSE Chemistry).
Mapped to Cambridge IGCSE Chemistry 0620 (2026–2028). Last updated 2026-08-19.
Polymers appear in two exam contexts: the chemistry of polymerisation (how they are made) and the environmental issue of plastic waste (how they are disposed of). Both carry significant marks on Paper 2 and Paper 4.
The 0620 definition
A polymer is a large, long-chain molecule made by joining together many small molecules called monomers. The process of making a polymer is called polymerisation.
The word comes from Greek: poly = many, mer = part.
Types of polymer
| Type | How formed | Example | Monomer |
|---|---|---|---|
| Addition polymer | Unsaturated monomers join; no by-product | Poly(ethene) | Ethene |
| Condensation polymer | Monomers join; small molecule lost | Nylon, polyester | Diamine + diacid |
Common polymers and their uses
| Polymer | Made from | Properties | Uses |
|---|---|---|---|
| Poly(ethene) | Ethene | Flexible, waterproof | Bags, bottles, cling film |
| Poly(propene) | Propene | Strong, flexible | Rope, crates, carpets |
| PVC | Chloroethene | Rigid or flexible, durable | Pipes, window frames |
| Polystyrene | Styrene | Lightweight, insulating | Packaging, cups |
| Nylon | Diamine + diacid | Strong, flexible, high melting point | Clothing, rope, gears |
| Polyester (PET) | Diol + diacid | Strong, crease-resistant | Bottles, clothing |
Environmental concerns
Most addition polymers are non-biodegradable — they are not broken down by microorganisms in the environment. This causes:
- Landfill problems: polymers take up space and persist for centuries
- Litter and wildlife harm: animals can ingest or become entangled in plastic waste
- Burning issues: incinerating plastics produces toxic gases (e.g. HCl from PVC, CO from incomplete combustion)
Solutions include:
- Recycling (melting and reshaping)
- Developing biodegradable polymers
- Reducing plastic use
Worked exam question
Poly(ethene) is used for plastic bags. (a) Name the monomer used to make poly(ethene). [1] (b) State one environmental problem caused by disposing of poly(ethene). [1] (c) Suggest one way to reduce this problem. [1]
Mark scheme
(a) Ethene [1]
(b) Non-biodegradable / takes up landfill space / persists in environment / harms wildlife [1]
(c) Recycle / reuse / develop biodegradable alternatives / reduce use [1]
Common exam mistakes
- Writing the monomer of poly(ethene) as “polyethene” — the monomer is ethene, not the polymer itself.
- Saying “just burn the plastic” without acknowledging the toxic gases produced.
- Confusing the repeating unit with the monomer — the repeating unit has single bonds and extending bonds; the monomer has the C=C double bond.
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