This guide covers IGCSE Chemistry topic 14 (part 3): organic chemistry – polymers. You will revise addition polymerisation (many small molecules join; no other product), monomer and polymer (e.g. ethene → poly(ethene)), drawing repeat unit, and uses and disposal of plastics.

Key concepts to revise

• Addition polymerisation – Many monomers (alkenes) join; double bond opens; no other product (only the polymer). Ethene → poly(ethene); propene → poly(propene); chloroethene → poly(chloroethene) (PVC).
• Repeat unit – The repeating part of the polymer chain; draw in brackets with n outside (e.g. -(-CH2-CH2-)n- for poly(ethene)).
• Uses – Poly(ethene): bags, bottles; PVC: pipes, cling film; poly(propene): ropes, crates. Link to properties (flexible; waterproof; durable).
• Disposal – Non-biodegradable; landfill; incineration (energy but CO2/pollution); recycling (reduce waste; save raw materials).

Exam tips and command words

• State – The monomer of a given polymer (e.g. poly(ethene) from ethene); the type of polymerisation (addition).
• Draw – The repeat unit of a polymer from the monomer (open double bond; extend bonds to next repeat).
• Write – Equation for polymerisation (n monomer → polymer; show repeat unit with n).
• Describe – One advantage and one disadvantage of plastic disposal (e.g. recycling: saves materials; but collection/sorting cost).

Common mistakes

• Drawing the monomer with a double bond inside the repeat unit (the double bond opens; repeat unit has single bonds only).
• Forgetting n in the equation (many monomers → one polymer molecule; use n).
• Saying addition polymerisation produces “water” or another small molecule (only polymer; no other product).

Revision checklist

• State the monomer for poly(ethene), poly(propene) and PVC; state that they are made by addition polymerisation.
• Draw the repeat unit of poly(ethene) from ethene.
• Write the equation for the formation of poly(ethene) from ethene (n C2H4 → (-C2H4-)n or repeat unit form).
• State one use of a given polymer and one problem with plastic disposal.

Next steps

Book a free trial with an IGCSE Chemistry tutor to practise polymer questions, or explore Tutopiya’s learning portal for more revision resources.

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