Polymers (A-Level) — A-Level Chemistry Revision

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What is Polymers (A-Level)?

A-Level polymer chemistry builds on GCSE by distinguishing between two main types of polymerisation: addition and condensation. Addition polymerisation involves the joining of monomers (usually alkenes) without the loss of any atoms. Condensation polymerisation involves the reaction between two different functional groups on monomers, with the elimination of a small molecule, usually water. The properties of polymers, such as biodegradability and the effect of plasticisers, are also explored.

Board notes: All boards require students to be able to draw the repeating units for both addition and condensation polymers. AQA often asks about the environmental issues associated with polymer disposal and the advantages of recycling and biodegradable polymers. Edexcel places emphasis on the different types of condensation polymers, including polyesters and polyamides. OCR frequently tests the hydrolysis of polymers and the identification of the constituent monomers.

Worked example

Common mistakes

• 1Confusing addition and condensation polymerisation. Addition polymers are formed from one type of monomer with a C=C bond, while condensation polymers are typically formed from two different monomers, each with two functional groups.
• 2Incorrectly drawing the repeating unit of a polymer. For an addition polymer, the double bond breaks and the repeating unit is the monomer unit with single bonds extending out. For a condensation polymer, the repeating unit consists of the monomer units joined by a new link (e.g., an ester or amide link) with the small molecule removed.
• 3Assuming all polymers are non-biodegradable. While many synthetic polymers like poly(ethene) are non-biodegradable, polyesters and polyamides can be broken down by hydrolysis, making them susceptible to degradation, especially by acids or alkalis.

Polymers (A-Level) exam questions

Exam-style questions for Polymers (A-Level) with mark-scheme style solutions and timing practice. Aligned to AQA, Edexcel and OCR specifications.

Frequently asked questions

• What is the difference between a thermoplastic and a thermosetting polymer?

  Thermoplastics consist of long polymer chains with weak intermolecular forces between them, which can be easily overcome by heating, allowing the polymer to be melted and reshaped. Thermosetting polymers have strong covalent cross-links between the chains, creating a rigid 3D structure that does not melt on heating but will char at high temperatures.

• How do plasticisers work?

  Plasticisers are small molecules that are added to a polymer. They get between the polymer chains and push them further apart, which weakens the intermolecular forces. This makes the polymer more flexible and easier to bend.