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Topic 5 Alkenes, taught by a specialist chemistry teacher.

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Lesson 4 of 4

Polymerisation of Alkenes and Polymer Waste

This virtual lesson covers addition polymerisation of alkenes, the formation of poly(alkenes), and the significant environmental challenges posed by polymer waste.

The lesson opens by explaining how alkenes undergo addition polymerisation, where many small monomer molecules join together through their pi bonds to form a long-chain polymer. The repeating unit of a polymer is identified from the monomer structure, and the displayed formula of a poly(alkene) is drawn and interpreted.

Common examples are then worked through, including poly(ethene), poly(propene), and poly(chloroethene) (PVC), examining how the identity of the monomer determines the properties of the resulting polymer. The lesson also covers working backwards from a polymer structure to identify the monomer from which it was formed.

The second part of the lesson addresses the environmental impact of polymer waste. Because addition polymers are non-biodegradable, they persist in the environment for hundreds of years. Methods used to manage polymer waste are evaluated, including recycling, combustion for energy recovery, and the development of biodegradable and photodegradable polymers as more sustainable alternatives.

This lesson connects organic chemistry to real-world materials science and environmental science, rounding off the alkenes topic and illustrating how alkenes are used beyond the laboratory.

Specification points for Topic 5

5.1know the general formula of alkenes and understand that alkenes and cycloalkenes are hydrocarbons which are unsaturated (have a carbon-carbon double bond which consists of a σ bond and a π bond)
5.2be able to explain geometric isomerism in terms of restricted rotation around a C=C double bond and the nature of the substituents on the carbon atoms
5.3understand the E-Z naming system for geometric isomers and why it is necessary to use this when the cis- and trans- naming system breaks down
5.4be able to describe the reactions of alkenes, limited to:
5.5know the qualitative test for a C=C double bond using bromine or bromine water
5.6be able to describe the mechanism (including diagrams), giving evidence where possible, of:
5.7be able to describe the addition polymerisation of alkenes and draw the repeat unit given the monomer, and vice versa
5.8understand how chemists limit the problems caused by polymer disposal by:

Polymerisation of Alkenes and Polymer Waste

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