4.5.2Organic Chemistry
Disposal of Addition Polymers — Edexcel International GCSE Science Double Award 4SD0 - Chemistry Revision Notes & Topical Questions
5 min read 7 parts Lesson 15 of 24
Part 1 of 5Why addition polymers cause a problem
Strong bonds
- Strong bonds An addition polymer is a very long chain of carbon atoms joined by strong covalent C–C bonds, formed when many small alkene monomers join together.
- These bonds make the polymer chemically unreactive, so acids, water, air and most chemicals hardly affect it.
Non-biodegradable
- Non-biodegradable Microorganisms such as bacteria and fungi cannot break the chains down, so the material is described as non-biodegradable.
- Discarded plastic therefore stays in the environment for decades or centuries.
Widespread use
- Widespread use Poly(ethene), poly(propene), PVC and poly(styrene) are used in huge quantities for packaging, pipes and containers,
- so very large amounts become waste.
Part 2 of 5Landfill
1Waste is buried
- Waste is buried Used polymer items are collected and buried in landfill sites with other rubbish.
2No breakdown
- No breakdown Decomposers cannot digest the plastic, so it does not rot like food or paper.
3Space is used up
- Space is used up The plastic stays in the ground and keeps taking up volume, so each site fills quickly.
4Land runs short
- Land runs short New sites are needed, which uses valuable land that could be used for housing, farming or wildlife.
Part 3 of 5Incineration
Burning waste polymers
Useful energy
- Useful energy Polymers release a lot of heat energy when they burn, and this energy can be used to generate electricity or heat buildings.
- Burning also greatly reduces the volume of waste going to landfill.
Carbon dioxide
- Carbon dioxide Complete combustion of a polymer makes carbon dioxide, a greenhouse gas that contributes to climate change.
Carbon monoxide
- Carbon monoxide If the supply of oxygen is limited, incomplete combustion makes carbon monoxide.
- Carbon monoxide is toxic because it reduces the ability of the blood to carry oxygen around the body.
Toxic gases from some polymers
- Toxic gases from some polymers Polymers that contain chlorine, such as PVC, release poisonous hydrogen chloride gas when they burn.
- This must be removed from the waste gases before they leave the chimney.
Part 4 of 5Comparing the two methods
| Method | Advantages | Disadvantages |
|---|---|---|
| Landfill | Simple and cheap; no harmful gases released from burning | Uses up land; polymer never breaks down; sites fill quickly |
| Incineration | Energy can be recovered; waste volume is greatly reduced | Releases CO2; risk of CO and HCl; needs expensive gas cleaning |
Part 5 of 5Reducing the problem
1
Reduce: use less plastic by avoiding unnecessary packaging and choosing reusable items.
2
Reuse: use items such as bags and bottles several times before throwing them away.
3
Recycle: collect and sort polymers by type, then melt and remould them into new products, which saves crude oil and lowers waste.
4
Develop alternatives: use biodegradable polymers that microorganisms can break down.
Key terms
| Term | Meaning |
|---|---|
| Addition polymer | A long-chain molecule formed when many small unsaturated monomers join together without losing any atoms. |
| Biodegradable | Able to be broken down by microorganisms into harmless substances. |
| Landfill | A site where waste is buried in the ground. |
| Incineration | Disposal of waste by burning it. |
| Incomplete combustion | Burning in a limited supply of oxygen, which produces carbon monoxide. |
Avoid these mistakes
1
Saying that plastics are non-biodegradable because they are 'strong'. The reason is that microorganisms cannot break the strong C–C bonds, so decomposers cannot digest them.
2
Stating that burning polymers makes only carbon dioxide. Incomplete combustion makes carbon monoxide, and PVC also gives hydrogen chloride.
3
Forgetting an advantage of incineration. Heat energy can be used, and the waste volume is reduced.
4
Claiming that plastics 'rot away slowly' in landfill. They remain for a very long time and effectively do not decompose.
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