AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
The intermolecular forces between polymer molecules are relatively strong…
Full specification wording
Polymers: The intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature.
Polymer molecules are long chains.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 3 of 4
- 2 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Polymer molecules are long chains. Between one polymer molecule and its neighbours there are intermolecular forces. These forces are relatively strong compared with those between small molecules such as methane, although they are weaker than the covalent bonds inside each polymer molecule. Because the chains are long, many intermolecular forces act along each chain, so a large amount of energy is needed to separate the molecules. As a result, polymers are usually solids at room temperature. For example, poly(ethene) is a solid at room temperature, while ethene is a gas. The intermolecular forces also help explain why polymers are flexible and can be moulded when heated: heating weakens the forces between chains so the chains can slide, but the covalent bonds within the chains remain intact.
What earns the marks
- Intermolecular forces act between separate polymer molecules.
- The intermolecular forces are weaker than the covalent bonds within each polymer molecule.
- The relatively strong intermolecular forces mean polymers are solids at room temperature.
- Long polymer chains have many intermolecular forces along their length, so more energy is needed to separate them.
Common mistakes and how to put them right
Stating that polymers are solids because of strong covalent bonds between molecules.
Put it right by saying that the intermolecular forces between polymer molecules are relatively strong, while covalent bonds are within each molecule.
Saying that polymers have no intermolecular forces.
Put it right by stating that intermolecular forces exist between polymer molecules and are relatively strong.
Confusing the strength of intermolecular forces with the strength of covalent bonds.
Put it right by explaining that intermolecular forces are weaker than covalent bonds but strong enough to keep polymers solid at room temperature.
Exam tips
- Use the term 'intermolecular forces' specifically for forces between molecules, not for bonds within a molecule.
- When comparing a polymer with a small molecule, refer to the length of the polymer chain and the total effect of many intermolecular forces.
- Link the solid state at room temperature to the energy needed to overcome the intermolecular forces between chains.
Try the lesson
The start of the Polymers: 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
Why are polymers such as poly(ethene) solids at room temperature?
Listen
Polymer molecules are long chains. Between one polymer molecule and its neighbours there are intermolecular forces. These forces are relatively strong compared with those between small molecules such as methane, although they are weaker than the covalent bonds inside each polymer molecule. Because the chains are long, many intermolecular forces act along each chain, so a large amount of energy is needed to separate the molecules. As a result, polymers are usually solids at room temperature. For example, poly(ethene) is a solid at room temperature, while ethene is a gas. The intermolecular forces also help explain why polymers are flexible and can be moulded when heated: heating weakens the forces between chains so the chains can slide, but the covalent bonds within the chains remain intact. A strong answer earns marks for these points. Intermolecular forces act between separate polymer molecules. The intermolecular forces are weaker than the covalent bonds within each polymer molecule. The relatively strong intermolecular forces mean polymers are solids at room temperature. Long polymer chains have many intermolecular forces along their length, so more energy is needed to separate them. A common slip: Stating that polymers are solids because of strong covalent bonds between molecules. Instead, saying that the intermolecular forces between polymer molecules are relatively strong, while covalent bonds are within each molecule. Exam tip: Use the term 'intermolecular forces' specifically for forces between molecules, not for bonds within a molecule.
See it
Key words
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Intermolecular forces
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Polymer structure
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See every definition
- Intermolecular forces
- Forces acting between one polymer molecule and its neighbours, which are relatively strong compared with those between small molecules but weaker than the covalent bonds inside each polymer molecule.
- Polymer structure
- Polymer molecules are long chains, so many intermolecular forces act along each chain, and heating weakens the forces between chains so the chains can slide while the covalent bonds within the chains remain intact.
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3Box 3
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