Disposal of addition polymers
5 marks · HardA city is searching for ways to manage its addition polymer waste. Answer the following questions about the disposal of addition polymers.
State what is meant by the term 'biodegradable'.
Explain, using the structure of addition polymers, why most of them are not biodegradable.
Describe two environmental problems caused by the build-up of non-biodegradable addition polymers.
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(a) Able to be broken down by living organisms (such as bacteria) in the environment.
(b) Addition polymers have strong, non-reactive covalent bonds and a backbone that most bacteria and enzymes cannot break. Therefore, they do not decompose in natural conditions.
(c) Problems could include: 1) Build-up in landfill sites, taking up space, and remaining for years. 2) Harm to wildlife, e.g. animals may ingest plastics or get entangled, or plastics entering food chains.
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Marking points
B1 (a) · 1 mark · Defines 'biodegradable' as able to be decomposed by microorganisms (bacteria, fungi) or natural processes.
M2 (b) · 1 mark · Identifies the structure of addition polymers: long chains with strong covalent bonds (C–C backbone), lack of reactive groups.
A2 (b) · 1 mark · Explains that this structure makes them resistant to breakdown/enzymatic attack so microorganisms cannot decompose them.
B3 (c) · 1 mark · Describes one valid environmental problem (e.g., landfill build-up, space taken up, pollution of land/water).
B4 (c) · 1 mark · Describes a second valid environmental problem (e.g., harm to animals, entering food chain, blocking drains).
Worked solution
a) Biodegradable means able to be broken down by living organisms, such as bacteria or fungi.
b) Most addition polymers have long chains of carbon atoms joined by strong covalent bonds and very few functional groups. This makes them chemically inert so enzymes or bacteria cannot break these bonds. As a result, they are not biodegradable.
c) One environmental problem is that addition polymers accumulate in landfill sites and take up space for very long periods. Another is that animals may be harmed if they ingest pieces of plastic, and the plastics can enter food chains.