Ethene (C₂H₄) can be converted into poly(ethene) by a process called addition polymerisation. Describe what happens during addition polymerisation and explain why the product, poly(ethene), has different properties to ethene.

Eduqas GCSE Chemistry — C7 Organic chemistry · Describe and Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

During addition polymerisation, many ethene monomers join together to form a polymer.
The double bond in each ethene opens (breaks) so that the carbon atoms can link to neighbouring monomers.
The resulting poly(ethene) has a very large/high molecular mass compared to ethene.
Because of the larger molecules, poly(ethene) is a solid at room temperature, has a higher melting point and stronger intermolecular forces, whereas ethene is a gas.

Examiner tips

  • Use the term "addition polymerisation" and mention the opening of the double bond.
  • Show that the polymer has a much higher molecular mass and link this to its solid state and higher melting point.

Common mistakes

  • Failing to state that the double bond opens during the reaction.
  • Confusing the properties of the polymer with those of the monomer, e.g. saying the polymer is a gas.

Mark scheme (4 marks)

  1. Many/thousands of ethene monomers join together (to form a polymer)
  2. The double bond in ethene opens/breaks to allow the monomers to join
  3. Poly(ethene) has a very large/high molecular mass compared to ethene
  4. The larger molecules in poly(ethene) mean it is a solid at room temperature / has a higher melting point / stronger intermolecular forces, whereas ethene is a gas

Key terms in this question

addition polymerisation · polymer

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