Poly(ethene) is made from ethene by a process called addition polymerisation. Describe what happens to ethene molecules during addition polymerisation and state one use of poly(ethene).
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
The double bond in each ethene molecule opens, allowing the carbon atoms to form new single bonds. As a result, many ethene molecules link together to give a long polymer chain. No other substance is produced – the reaction is an addition polymerisation. One use of poly(ethene) is in plastic bags.
Examiner tips
- Use the term "double bond opens" and "link together" to hit the key points
- Mention that no by‑product is formed
- Give a specific, common use such as plastic bags
Common mistakes
- Saying the double bond is *broken* instead of *opened*
- Claiming a by‑product is formed
- Giving a non‑specific or incorrect use of poly(ethene)
Mark scheme (4 marks)
- The double bond in ethene opens / breaks
- Many ethene molecules join together / link together to form a long chain
- No other substance / no by-product is produced (addition polymerisation produces only the polymer)
- A correct use of poly(ethene) e.g. plastic bags / bottles / packaging / insulation for electrical cables / containers
Key terms in this question
addition polymerisation · polymer
Related
- All Cambridge International IGCSE Chemistry (0620) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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