AQA · A-Level · Chemistry
Course version: 7405 · Version from Sept 2016
Students should be able to: draw the repeating unit from monomer…
Full specification wording
Condensation polymers (A-level only): Students should be able to: draw the repeating unit from monomer structure(s) draw the repeating unit from a section of the polymer chain draw the structure(s) of the monomer(s) from a section of the polymer explain the nature of the intermolecular forces between molecules of condensation polymers.
Work in whichever direction the question asks.
Checked against the AQA 7405 specification (opens in a new tab) on .
- Point 4 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Work in whichever direction the question asks. From monomers: join them, take out a molecule of water at each new link, then bracket the result with both bonds passing through the brackets. From a chain: find where the pattern repeats and cut through two equivalent points, usually the middle of two identical links. From polymer back to monomers: break each link and put an -OH on the carbonyl carbon and an -H on the oxygen or nitrogen, which is adding the water back. For the forces, the polar C=O gives permanent dipole-dipole attractions in both families, and van der Waals forces act along the chains, but only a polyamide has an N-H, so only a polyamide hydrogen bonds between chains.
What earns the marks
- A repeating unit with the bonds drawn through the brackets.
- Adding water back across each link when the monomers are deduced from the polymer.
- Hydrogen bonding named between the N-H of one chain and the C=O of another in a polyamide.
- A polyester having no N-H, so only permanent dipole-dipole and van der Waals forces act between its chains.
Common mistakes and how to put them right
Returning monomers with the link still joined, so the two 'monomers' are really a dimer.
Drawing hydrogen bonds between polyester chains, which have no N-H or O-H to donate.
Showing the hydrogen bonds inside one chain when the question asks about forces between chains.
Saying that hydrolysis breaks the intermolecular forces, when it breaks covalent bonds in the backbone.
Exam tips
- When deducing monomers, count the links you cut: each one needs a water molecule added back, split as -OH and -H.
- A force question wants the force named and located: say which atom on which chain is attracted to which.
Try the lesson
The start of the Condensation polymers (A-level only): Students should be able to: draw the repeating unit from monomer structure(s) draw the repeating unit from a section of the polymer chain draw the structure(s) of the monomer(s) from a section of the polymer explain the nature of the intermolecular forces between molecules of condensation polymers. lesson, made from checked teaching notes for this specification point.
Have a go first
Which type of intermolecular force acts between the polymer chains in a condensation polymer such as nylon-6,6?
Listen
Work in whichever direction the question asks. From monomers: join them, take out a molecule of water at each new link, then bracket the result with both bonds passing through the brackets. From a chain: find where the pattern repeats and cut through two equivalent points, usually the middle of two identical links. From polymer back to monomers: break each link and put an -OH on the carbonyl carbon and an -H on the oxygen or nitrogen, which is adding the water back. For the forces, the polar C=O gives permanent dipole-dipole attractions in both families, and van der Waals forces act along the chains, but only a polyamide has an N-H, so only a polyamide hydrogen bonds between chains. A strong answer earns marks for these points. a repeating unit with the bonds drawn through the brackets. adding water back across each link when the monomers are deduced from the polymer. hydrogen bonding named between the N-H of one chain and the C=O of another in a polyamide. a polyester having no N-H, so only permanent dipole-dipole and van der Waals forces act between its chains. Exam tip: When deducing monomers, count the links you cut: each one needs a water molecule added back, split as -OH and -H.
Key words
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repeating unit
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deducing monomers
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hydrogen bonding between chains
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permanent dipole-dipole forces
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See every definition
- repeating unit
- The part of the polymer chain that repeats, drawn with both bonds passing through the brackets.
- deducing monomers
- Breaking each link and putting an -OH on the carbonyl carbon and an -H on the oxygen or nitrogen, which is adding the water back.
- hydrogen bonding between chains
- Occurs in a polyamide between the N-H of one chain and the C=O of another.
- permanent dipole-dipole forces
- Attractions arising from the polar C=O, present in both families of condensation polymer.
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Test your understanding of Condensation polymers (A-level only): Students should be able to: draw the repeating unit from monomer structure(s) draw the repeating unit from a section of the polymer chain draw the structure(s) of the monomer(s) from a section of the polymer explain the nature of the intermolecular forces between molecules of condensation polymers.
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