Who this is for: Cambridge IGCSE Chemistry (0620) students who want polymers — addition and condensation polymerisation, monomers and repeat units — to become structure–property answers instead of vague “plastic” descriptions.
What query it owns: how to understand and revise polymers in Cambridge IGCSE Chemistry.
Why this is safe: this page owns the polymers revision-guide angle, while Tutopiya’s Polymers subtopic page owns the learning resource and the free Polymers quiz owns the practice.

Polymers are long-chain molecules built from repeating monomer units. Cambridge IGCSE Chemistry (0620) tests addition polymerisation (alkene monomers such as ethene → poly(ethene)) and condensation polymerisation (monomers with two functional groups, releasing a small molecule such as water). You must draw repeat units, identify monomers from polymers, and link plastics to environmental issues. This guide covers both polymerisation types and typical exam stems.

Key takeaways

• Monomer = small molecule that joins to form a polymer; repeat unit = section shown in brackets with subscript n.
• Addition polymerisation: C=C bond opens; no small molecule lost — e.g. ethene → poly(ethene).
• Condensation polymerisation: two different monomers join; water (or HCl) is released.
• Poly(ethene), poly(propene), PVC (from chloroethene) are addition polymers.
• Nylon and PET are condensation polymers on the syllabus.

What are polymers in Cambridge IGCSE Chemistry?

Polymers are macromolecules made by joining many monomers. Plastics are everyday examples. The syllabus requires you to draw the repeat unit from a given monomer, deduce the monomer from a polymer structure, and distinguish addition from condensation polymerisation.

Read the full notes on Tutopiya’s Polymers subtopic page before attempting questions.

The core ideas you must master

Polymer type	Monomer(s)	Repeat unit / polymer	Small molecule lost
Addition — poly(ethene)	Ethene (C₂H₄)	–(CH₂–CH₂)ₙ–	None
Addition — poly(propene)	Propene (C₃H₆)	–(CH(CH₃)–CH₂)ₙ–	None
Addition — PVC	Chloroethene (C₂H₃Cl)	–(CHCl–CH₂)ₙ–	None
Condensation — nylon	Diamine + dicarboxylic acid	Amide link (–CONH–)	H₂O
Condensation — PET	Diol + dicarboxylic acid	Ester link (–COO–)	H₂O

Addition vs condensation polymerisation

Feature	Addition	Condensation
Monomer type	Alkene (C=C)	Two functional groups (–OH, –COOH, –NH₂)
Bond formed	C–C chain	Amide or ester link
Small molecule lost	None	Usually H₂O
Examples	Poly(ethene), PVC	Nylon, PET
Requires unsaturation	Yes (C=C)	No

Polymers in past-paper wording: command words that matter

Command word	What the question wants	Typical polymers stem
Draw	Repeat unit or monomer	”Draw the repeat unit of poly(ethene).”
State	Monomer or polymer type	”State the monomer used to make PVC.”
Identify	Type of polymerisation	”Identify the type of polymerisation used to make nylon.”
Explain	Why ethene polymerises	”Explain why ethene can form an addition polymer.”
Complete	Polymerisation equation	”Complete the equation for the polymerisation of ethene.”

Worked exam-style stems (how to answer the wording)

1. “Draw the repeat unit of poly(ethene).” Show –[CH₂–CH₂]ₙ– with the two carbons bonded and two H atoms on each carbon, brackets with subscript n. Reward: correct repeat unit with brackets.
2. “State the monomer used to make PVC.” Chloroethene (CH₂=CHCl). Reward: correct name or formula.
3. “Explain the difference between addition and condensation polymerisation.” Addition joins alkene monomers with no small molecule lost; the C=C bond opens. Condensation joins monomers with two functional groups and releases a small molecule (usually water). Reward: both types + small molecule difference.

Test yourself with the Polymers quiz once you have worked through a few examples.

How polymers connect to the rest of Organic Chemistry

Polymers link directly to Alkenes (ethene monomer), Fuels (cracking produces ethene) and Carboxylic Acids (dicarboxylic acid monomers). The Cambridge IGCSE Chemistry resource hub links all units.

Common mistakes students make

• Drawing repeat units without brackets or subscript n.
• Calling PVC’s monomer “chlorine ethene” instead of chloroethene.
• Saying condensation polymerisation produces no small molecule — water is released.
• Trying to polymerise ethane (no C=C bond) by addition.
• Confusing addition (alkene) with condensation (amide/ester link).

When you need more support

If repeat-unit drawing and polymerisation-type questions keep costing marks, work through the Polymers quiz to find the gap, then get focused help from a Cambridge IGCSE Chemistry tutor.

Frequently asked questions

What is the monomer of poly(ethene)? Ethene (C₂H₄).

What is the difference between addition and condensation polymerisation? Addition uses alkene monomers with no small molecule lost; condensation joins bifunctional monomers and releases water.

What is the repeat unit? The section of the polymer chain shown in brackets that repeats — e.g. –[CH₂–CH₂]ₙ– for poly(ethene).

How do I revise polymers effectively? Learn both polymerisation types with examples, practise drawing repeat units, then take the Polymers quiz.

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