Explain why poly(ethene) cannot be used as a fuel, and describe how ethene monomers join together to form poly(ethene). Include in your answer the type of polymerisation involved and the conditions required for the reaction.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Poly(ethene) is one of the most widely produced plastics in the world. It is made from ethene, which is obtained from the cracking of crude oil fractions.
Model answer (5 marks)
Poly(ethene) cannot be used as a fuel because it does not burn – the C=C bonds are already saturated in the polymer and it is difficult to ignite.
In the polymerisation of ethene the C=C double bond opens up. Many ethene monomers link together to form a long chain, giving poly(ethene).
The polymerisation is an addition polymerisation. It requires high pressure and/or a catalyst to proceed.
In the polymerisation of ethene the C=C double bond opens up. Many ethene monomers link together to form a long chain, giving poly(ethene).
The polymerisation is an addition polymerisation. It requires high pressure and/or a catalyst to proceed.
Examiner tips
- Use the phrase ‘does not burn’ to hit the key point on fuel use.
- Show the double bond opening and chain growth in a clear sequence.
- Mention ‘addition polymerisation’ and the need for high pressure or catalyst to meet the marks for conditions.
Common mistakes
- Confusing poly(ethene) with ethene as a fuel – writing that it can burn.
- Failing to state that the reaction is an addition polymerisation.
- Omitting the requirement for high pressure or a catalyst.
Mark scheme (5 marks)
- Poly(ethene) cannot be used as a fuel because it does not burn / is difficult to ignite / does not combust easily
- The C=C double bond in ethene opens up / breaks
- Many ethene monomers join together / link to form a long chain (polymer)
- The type of polymerisation is addition polymerisation
- The reaction requires high pressure and/or a catalyst
Key terms in this question
monomer · polymer · poly(ethene)
Related
- All Edexcel A-Level Chemistry (9CH0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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