AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
In addition polymerisation reactions, many small molecules (monomers) join…
Full specification wording
Addition polymerisation: In addition polymerisation reactions, many small molecules (monomers) join together to form very large molecules (polymers).
Addition polymerisation is a type of reaction in which many small unsaturated molecules, called monomers, join together to form one very large saturated molecule, called a polymer.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 2 of 4
Study notes
From the checked teaching notes for this specification point.
The idea
Addition polymerisation is a type of reaction in which many small unsaturated molecules, called monomers, join together to form one very large saturated molecule, called a polymer. The monomers must contain a carbon–carbon double bond, C=C. During the reaction, this double bond opens up and each monomer forms new single bonds to two neighbouring monomers, creating a long chain. For example, ethene, CH₂=CH₂, polymerises to form poly(ethene), a long chain of –CH₂–CH₂– units. No other product is formed, so all the atoms of the monomers end up in the polymer. The reaction is represented by showing the monomer and the repeating unit, with the double bond replaced by single bonds and the chain extended by bonds to other repeating units.
What earns the marks
- Addition polymerisation involves many small monomer molecules joining together.
- The monomers are unsaturated and contain a C=C double bond.
- The product is a very large molecule called a polymer.
- The reaction opens the C=C double bond, allowing each monomer to bond to two others.
- No other molecule is formed; all atoms of the monomers become part of the polymer chain.
- The polymer is a saturated long-chain molecule made of repeating units derived from the monomer.
Common mistakes and how to put them right
Thinking that addition polymerisation produces a small molecule such as water.
Put it right by stating that no other molecule is formed.
Believing that any small molecule can undergo addition polymerisation.
Put it right by specifying that the monomer must contain a C=C double bond.
Writing the polymer as a collection of separate monomer molecules rather than one long chain.
Put it right by showing the repeating unit joined by single bonds.
Exam tips
- When describing addition polymerisation, always mention the C=C double bond in the monomer and that it becomes single bonds in the polymer.
- Use the term 'repeating unit' when explaining the structure of the polymer, and show it with bonds extending beyond the brackets.
- Check that your answer states that no other product is formed, as this distinguishes addition from condensation polymerisation.
Try the lesson
The start of the Addition polymerisation: In addition polymerisation reactions, many small molecules (monomers) join together to form very large molecules (polymers). lesson, made from checked teaching notes for this specification point.
Have a go first
Which term describes the very large molecule formed when many small monomer molecules join together in an addition polymerisation reaction?
Listen
Addition polymerisation is a type of reaction in which many small unsaturated molecules, called monomers, join together to form one very large saturated molecule, called a polymer. The monomers must contain a carbon–carbon double bond, C=C. During the reaction, this double bond opens up and each monomer forms new single bonds to two neighbouring monomers, creating a long chain. For example, ethene, CH₂=CH₂, polymerises to form poly(ethene), a long chain of –CH₂–CH₂– units. No other product is formed, so all the atoms of the monomers end up in the polymer. The reaction is represented by showing the monomer and the repeating unit, with the double bond replaced by single bonds and the chain extended by bonds to other repeating units. A strong answer earns marks for these points. Addition polymerisation involves many small monomer molecules joining together. The monomers are unsaturated and contain a C=C double bond. The product is a very large molecule called a polymer. The reaction opens the C=C double bond, allowing each monomer to bond to two others. A common slip: Thinking that addition polymerisation produces a small molecule such as water. Instead, stating that no other molecule is formed. Exam tip: When describing addition polymerisation, always mention the C=C double bond in the monomer and that it becomes single bonds in the polymer.
See it
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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