AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Alkenes can be used to make polymers such as poly(ethene) and…
Full specification wording
Addition polymerisation: Alkenes can be used to make polymers such as poly(ethene) and poly(propene) by addition polymerisation.
Addition polymerisation is the process in which many small unsaturated alkene molecules, called monomers, join together to form a large saturated molecule called a polymer.
Checked against the AQA 8462 specification (opens in a new tab) on .
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Study notes
From the checked teaching notes for this specification point.
The idea
Addition polymerisation is the process in which many small unsaturated alkene molecules, called monomers, join together to form a large saturated molecule called a polymer. The monomers contain a carbon-carbon double bond, which opens up during the reaction. For example, ethene monomers join to form poly(ethene), and propene monomers join to form poly(propene). The polymer is the only product, so no other small molecule is eliminated. You should be able to recognise the repeat unit in a polymer structure, draw the repeat unit from a given monomer, and identify the monomer from a given polymer. The general equation can be represented as n monomer → polymer, where n is a large number. The double bond becomes a single bond in the polymer chain.
What earns the marks
- Define addition polymerisation as the joining of many unsaturated monomer molecules to form a polymer.
- Identify ethene and propene as monomers used to make poly(ethene) and poly(propene).
- Recognise the carbon-carbon double bond in an alkene monomer and explain that it opens during polymerisation.
- Draw or identify the repeat unit of a polymer from a given monomer structure.
- Identify the monomer from a given polymer structure by locating the two-carbon repeat unit and restoring the double bond.
Common mistakes and how to put them right
Drawing the repeat unit with a double bond still present.
Put it right by showing a single bond between the carbon atoms in the polymer backbone.
Omitting the 'n' or placing it inside the brackets.
Put it right by placing the repeat unit in brackets with a subscript 'n' outside to show many units join.
Confusing addition polymerisation with condensation polymerisation.
Put it right by noting that addition polymerisation produces only the polymer, whereas condensation polymerisation produces a small molecule such as water as well.
Exam tips
- When drawing a repeat unit, show the two carbon atoms of the original double bond with single bonds and extend the bonds through the brackets.
- Check that the polymer repeat unit has the same atoms as the monomer, with no atoms added or removed.
- Use the name of the monomer to derive the polymer name, for example ethene gives poly(ethene).
Try the lesson
The start of the Addition polymerisation: Alkenes can be used to make polymers such as poly(ethene) and poly(propene) by addition polymerisation. lesson, made from checked teaching notes for this specification point.
Have a go first
Which type of polymerisation uses alkenes to make polymers such as poly(ethene)?
Listen
Addition polymerisation is the process in which many small unsaturated alkene molecules, called monomers, join together to form a large saturated molecule called a polymer. The monomers contain a carbon-carbon double bond, which opens up during the reaction. For example, ethene monomers join to form poly(ethene), and propene monomers join to form poly(propene). The polymer is the only product, so no other small molecule is eliminated. You should be able to recognise the repeat unit in a polymer structure, draw the repeat unit from a given monomer, and identify the monomer from a given polymer. The general equation can be represented as n monomer → polymer, where n is a large number. The double bond becomes a single bond in the polymer chain. A strong answer earns marks for these points. Define addition polymerisation as the joining of many unsaturated monomer molecules to form a polymer. Identify ethene and propene as monomers used to make poly(ethene) and poly(propene). Recognise the carbon-carbon double bond in an alkene monomer and explain that it opens during polymerisation. Draw or identify the repeat unit of a polymer from a given monomer structure. A common slip: Drawing the repeat unit with a double bond still present. Instead, showing a single bond between the carbon atoms in the polymer backbone. Exam tip: When drawing a repeat unit, show the two carbon atoms of the original double bond with single bonds and extend the bonds through the brackets.
See it
Label the diagram
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