Propene is a product of cracking. Propene can undergo addition polymerisation to form poly(propene). Explain how addition polymerisation produces poly(propene) from propene monomers, and state one use of poly(propene) as a polymer.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Propene (C₃H₆) is an alkene produced by cracking long-chain hydrocarbons. It contains a carbon–carbon double bond.
Model answer (5 marks)
Propene molecules act as monomers and many join together during the polymerisation process.
The carbon–carbon double bond in each propene opens (breaks) when the reaction is initiated.
The open bonds allow the monomers to link, forming a very long chain – a large polymer molecule.
No other small molecules are produced; the reaction is an addition polymerisation.
Poly(propene) is used to make plastic containers, packaging and other everyday plastic items.
The carbon–carbon double bond in each propene opens (breaks) when the reaction is initiated.
The open bonds allow the monomers to link, forming a very long chain – a large polymer molecule.
No other small molecules are produced; the reaction is an addition polymerisation.
Poly(propene) is used to make plastic containers, packaging and other everyday plastic items.
Examiner tips
- Use the term ‘monomer’ and ‘polymer’ explicitly. Mention the opening of the double bond. State that no small molecules are lost. Give a specific, correct use of the polymer.
Common mistakes
- Confusing addition with substitution polymerisation. Failing to mention that no small molecules are lost. Giving a non‑polymer use or a vague use such as ‘plastic’ without specifying a product.
Mark scheme (5 marks)
- Propene molecules are monomers / many propene monomers join together
- The carbon–carbon double bond in propene opens / breaks during polymerisation
- The monomers join to form a very long chain / large molecule (polymer)
- No other product / no small molecule is lost during addition polymerisation
- One correct use of poly(propene) stated, e.g. plastic containers / ropes / crates / clothing fibres / packaging
Key terms in this question
addition polymerisation · monomer · polymer
Related
- All AQA A-Level Chemistry (7405) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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