AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Polymers have very large molecules. The atoms in the polymer molecules are…
Full specification wording
Polymers: Polymers have very large molecules. The atoms in the polymer molecules are linked to other atoms by strong covalent bonds. The intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature.
Polymers are macromolecules formed when many small monomer units join together, so each polymer molecule contains thousands of atoms held by strong covalent bonds.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 1 of 2
Study notes
From the checked teaching notes for this specification point.
The idea
Polymers are macromolecules formed when many small monomer units join together, so each polymer molecule contains thousands of atoms held by strong covalent bonds. 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.
What earns the marks
- 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.
Common mistakes and how to put them right
Saying that polymers melt because covalent bonds break.
Put it right 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.
Put it right by noting that in polymers the forces between the very large molecules are relatively strong.
Confusing monomers with polymers.
Put it right by stating that monomers are small repeating units and polymers are very large molecules built from many monomers.
Exam 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.
Try the lesson
The start of the Polymers: Polymers have very large molecules. The atoms in the polymer molecules are linked to other atoms by strong covalent bonds. The intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature. lesson, made from checked teaching notes for this specification point.
Have a go first
Which statement describes the size of the molecules in a polymer?
Listen
Polymers are macromolecules formed when many small monomer units join together, so each polymer molecule contains thousands of atoms held by strong covalent bonds. 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. A strong answer earns marks for these 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. A common slip: Saying that polymers melt because covalent bonds break. Instead, explaining that heating first overcomes intermolecular forces between chains, while covalent bonds within chains remain intact. Exam tip: Refer to the size of polymer molecules when explaining why their intermolecular forces are relatively strong.
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