Polymers — AQA GCSE Combined Science
Test yourself on Polymers with AQA GCSE practice questions.
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Polymers explained
Polymers are macromolecules formed when many small monomer units join together, so each polymer molecule contains thousands of atoms held by strong covalent bonds.
Read the full explanation
Within a polymer chain, atoms are linked by strong covalent bonds, but the chains themselves are attracted to neighbouring chains by intermolecular forces. Because polymer molecules are very large, these intermolecular forces are relatively strong overall, so a large amount of energy is needed to separate the chains. This is why polymers such as poly(ethene) and nylon are solids at room temperature. On heating, the intermolecular forces between chains are overcome first, allowing chains to slide over one another; the strong covalent bonds within each chain usually remain intact unless the polymer is strongly heated or burned.
Students should be able to recognise polymers from diagrams showing their bonding and structure.
Polymers are large molecules built from many small monomer units joined by covalent bonds. In diagrams, look for a long chain of atoms connected by single lines representing covalent bonds, often with a repeating unit shown in brackets and a subscript n. The chain backbone is usually carbon atoms, and each carbon may also bond to hydrogen or other atoms. Recognising a polymer means identifying this repeating pattern. For example, poly(ethene) is drawn as a chain of –CH₂–CH₂– units; the brackets and n show that the unit repeats many times. The intermolecular forces between polymer molecules are relatively strong, so these substances are solid at room temperature. However, they still have lower melting points than giant covalent structures, while the covalent bonds within each chain remain strong.
Your focus
- Describe polymers as very large molecules in which atoms are linked by strong covalent bonds.
- Explain why relatively strong intermolecular forces between polymer molecules make polymers solids at room temperature.
- Distinguish between covalent bonds within polymer chains and intermolecular forces between polymer chains when explaining melting behaviour.
Show all 6 objectives
- Identify a polymer from a diagram showing a repeating unit or long chain.
- Describe the strong covalent bonding within polymer chains and the relatively strong intermolecular forces between them.
- Distinguish polymers from small molecules and giant covalent structures using diagrams.
Polymers exam tips
Marking Points
- State that polymers are very large molecules made from many repeating monomer units.
- Identify that atoms within a polymer molecule are joined by strong covalent bonds.
- Explain that intermolecular forces between polymer molecules are relatively strong.
- Link the relatively strong intermolecular forces to the solid state of polymers at room temperature.
- Explain that heating overcomes intermolecular forces between chains before covalent bonds within chains break.
- Compare polymers with small molecules, noting that larger molecules have stronger overall intermolecular forces.
- Identify a polymer diagram as a long chain of many atoms joined by covalent bonds, often with a repeating unit.
- Recognise the repeating unit shown in brackets with a subscript n, indicating many identical units joined together.
- Distinguish polymers from small molecules by the large number of atoms and the chain structure.
- State that atoms within a polymer chain are held by strong covalent bonds, while separate chains are held by relatively strong intermolecular forces.
- Use the displayed formula to identify the monomer repeat unit, for example –CH₂–CH₂– in poly(ethene).
Examiner Tips
- 💡Refer to the size of polymer molecules when explaining why their intermolecular forces are relatively strong.
- 💡Distinguish clearly between covalent bonds within a chain and intermolecular forces between chains.
- 💡Use a named polymer such as poly(ethene) to support an explanation of solid state at room temperature.
- 💡When shown a diagram, first look for brackets and a subscript n; these are strong clues that the structure is a polymer.
- 💡If asked to name the polymer, identify the repeating unit and relate it to the monomer, for example ethene forms poly(ethene).
- 💡Use the terms 'monomer', 'repeating unit' and 'polymer chain' accurately in your answers, and remember that intermolecular forces between chains are relatively strong.
Common Mistakes
- Saying that polymers melt because covalent bonds break: correct this by explaining that heating first overcomes intermolecular forces between chains, while covalent bonds within chains remain intact.
- Describing intermolecular forces as weak in all molecular substances: correct this by noting that in polymers the forces between the very large molecules are relatively strong.
- Confusing monomers with polymers: correct this by stating that monomers are small repeating units and polymers are very large molecules built from many monomers.
- Mistaking a polymer diagram for a small molecule: correct by checking for a repeating unit and a subscript n, which show many units joined.
- Thinking intermolecular forces between polymer chains are weak: correct by stating that because polymer molecules are large, the intermolecular forces between them are relatively strong, making them solid at room temperature.
- Confusing a polymer with a giant covalent structure: correct by noting that a polymer is made of many separate chains, not one continuous giant lattice.