Plastics & their Disposal
Section: 11. Organic Chemistry | Syllabus: Cambridge IGCSE Chemistry (0620)
Plastics and Their Properties
Plastics are materials made from polymers. The same properties that make plastics useful - they are strong, lightweight, and chemically unreactive (they resist being broken down) - also mean most plastics do not decompose naturally once thrown away. This has serious implications for how plastic waste must be disposed of.
Environmental Challenges Caused by Plastics
- Disposal in landfill sites: most plastics do not decompose, so they take up space in landfill permanently rather than breaking down
- Accumulation in oceans: plastic waste that reaches rivers and seas persists for a very long time, harming wildlife (e.g. through entanglement or ingestion)
- Formation of toxic gases from burning: burning some plastics (e.g. those containing chlorine, such as PVC) can release toxic gases, such as hydrogen chloride
Because plastics resist natural breakdown, recycling - melting and reshaping plastics, or (for polyesters like PET) converting them back into monomers to re-polymerise - is an important way to reduce these problems.
Worked Example
- Question (based on a real exam question): which statements explain why plastics should be recycled - (1) most do not decompose in landfill; (2) they pollute rivers and oceans, harming wildlife; (3) they can produce toxic gases when burned?
- Answer: all three (1, 2 and 3) are correct reasons to recycle plastics.
Common Mistakes
- ❌ Thinking landfill safely gets rid of plastic waste
- ✓ because most plastics are not broken down by natural processes, they simply persist in landfill sites rather than disappearing - landfill does not solve the problem, it just stores it
Interactive revision notes, videos and practice questions load below.