IGCSE · Practice questions · Addition polymers

Open the bond, link the chain.

Six original Cambridge-style questions on addition polymers and plastics.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Keep these straight

C=C opens, chain grows.

Polymer: large molecule made of many monomers.
Addition: alkene C=C opens; polymer is the only product.
Extended, monomer: two backbone carbons, put the C=C back.
Disposal: landfill, oceans, toxic gases on burning; recycle.

Recall

[2 marks]

Define the terms polymer and monomer.

Monomer: a small molecule that can join with many others to form a polymer. ✓
Polymer: a large molecule built up from many monomers. ✓

Recall

[2 marks]

Write an equation for the formation of poly(ethene) from ethene, showing the repeat unit.

n CH₂=CH₂ → –[CH₂–CH₂]_n– ✓
The repeat unit has single C–C bonds, in brackets with continuation bonds and subscript n. ✓

Analysis

[2 marks]

(Extended) Draw (or write) the repeat unit of the polymer made from tetrafluoroethene, CF₂=CF₂, and name the polymer.

Repeat unit: –CF₂–CF₂– (single bond between the carbons). ✓
Poly(tetrafluoroethene), PTFE. ✓

Analysis

[2 marks]

(Extended) A section of polymer is –CH₂–CH(CN)–CH₂–CH(CN)–. Deduce the structure of the monomer.

The repeat unit is –CH₂–CH(CN)–. ✓
Put the double bond back between the two carbons: CH₂=CH(CN). ✓

Explain

[3 marks]

Describe three problems caused by the disposal of plastics.

In landfill: they are non-biodegradable and take up space for hundreds of years. ✓
In oceans: they accumulate and harm animals that swallow them or are trapped. ✓
Burning: releases toxic gases (such as hydrogen chloride from PVC, carbon monoxide) and carbon dioxide. ✓

Calculation

[2 marks]

A poly(propene) molecule has M_r 126 000. Calculate the number of propene, C₃H₆, monomers in the molecule. (A_r: C 12, H 1)

M_r of propene = 3 × 12 + 6 × 1 = 42. ✓
Number of monomers = 126 000 ÷ 42 = 3000 (no atoms are lost in addition polymerisation). ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.