This definitions covers Key Definitions within Polymers for GCSE Chemistry. Revise Polymers in Bonding & Structure for GCSE Chemistry with 22 exam-style questions and 21 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 6 of 12 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 6 of 12
Practice
22 questions
Recall
21 flashcards
📖 Key Definitions
Polymer: A large molecule formed by joining together many small repeating units (monomers) — the backbone is held together by covalent bonds.
Monomer: A small molecule that can join together with many other monomers to form a polymer chain (must have a C=C double bond for addition polymerisation).
Addition polymerisation: The process by which many monomer molecules (containing C=C double bonds) join together to form a long chain polymer, with no atoms lost.
Repeat unit: The smallest section of the polymer chain that represents the pattern which repeats throughout — derived from the monomer structure with the double bond converted to a single bond.
Intermolecular forces: The weak attractions between separate polymer chains — these determine the physical properties like flexibility and melting point.
Thermosoftening polymer: A polymer with no cross-links between chains — held only by weak intermolecular forces. Softens and melts on heating; can be remoulded and recycled. Examples: poly(ethene), PVC, polystyrene.
Thermosetting polymer: A polymer with strong covalent cross-links between chains, formed during curing. Cannot be melted or remoulded once set — decomposes on strong heating. Examples: Bakelite, melamine, epoxy resin.
Cross-links: Covalent bonds that join adjacent polymer chains together in a thermosetting polymer, preventing them from sliding apart when heated.
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Practice Questions for Polymers
In addition polymerisation, what feature of monomer molecules allows them to join together?
Explain why thermosetting polymers are rigid and do not melt when heated.
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