Worksheets and lesson ideas to challenge students to think hard about addition and condensation polymers (GCSE and Key Stage 3)
We are essentially walking talking polymers. Our skin, brain and muscles are made from proteins (or polypeptides), and our energy stores are made from polysaccharides. We wear various polymers in the form of nylon, cotton or wool. All of these polymers are condensation polymers, so called because when two monomers add together a small molecule of water is lost. The other type of polymer, addition polymers, are very different. Addition polymers are formed by a different mechanism, involving the breaking of a double bond. Addition polymers have some interesting differences from condensation polymers such as when they form there is only one product they are also less reactive. The irony of course of addition polymers is that their greatest advantage i.e. their chemical inertness, is also their greatest weakness i.e. they don’t biodegrade and this is causing a variety of concerns globally.
Where to start?
Demo how to produce nylon in the lab if teaching about condensation polymers. Make sure students are aware that they are made from many different condensation polymers.
You can help students to understand polymerisation by performing the following model. Ask students to build an ethene molecule using molymods. Then ask five students to come to the front of the class – get each student to break the double bond. Then link up the monomers. Bring further students to the front of the class until you have a long molecule of poly(ethene). You can repeat this activity with propene if you have time. Question around the energetics of the reaction i.e. bond forming and bond breaking. Why are polymers so inert? Why don’t plastic bags rot?
Compare and contrast addition polymerisation with condensation polymerisation
Venn diagrams or a table work well here.
Life cycle of a plastic bag
Ask students to collect all their plastic bags up at home and bring them into school. Pile all the bags up in one giant heap at the front of the class. You can then pose some questions about where the bags came from, how long they will last and what may happen to them in the future? This can then lead to a range of activities, where students are required to consider the life cycle of a plastic bag and perhaps contrast this to other bags.
- Suggest why life evolved to use condensation polymers and non addition polymers.
- How would life be different if humans were made from addition polymers?
- Why are plastic bags inert?
- What are the disadvantages of a plastic bag tax?