AQA · A-Level · Chemistry
Course version: 7405 · Version from Sept 2016
The advantages and disadvantages of different methods of disposal of…
Full specification wording
Biodegradability and disposal of polymers (A-level only): The advantages and disadvantages of different methods of disposal of polymers, including recycling.
Landfill is cheap and needs no sorting, but it takes up land, polyalkenes stay there for centuries and decomposing waste releases methane and leachate.
Checked against the AQA 7405 specification (opens in a new tab) on .
- Point 3 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Landfill is cheap and needs no sorting, but it takes up land, polyalkenes stay there for centuries and decomposing waste releases methane and leachate. Incineration destroys the polymer, cuts the volume sharply and the heat released can generate electricity, but carbon dioxide is produced, and burning PVC releases hydrogen chloride, which must be removed by passing the flue gases through a base; too low a combustion temperature also produces toxic dioxins. Recycling conserves crude oil and uses less energy than making new polymer, but the waste has to be collected, sorted by type and cleaned, and each reprocessing shortens the chains so the quality falls. Feedstock recycling instead cracks the waste back into useful small molecules.
What earns the marks
- An advantage and a matching disadvantage given for the same disposal method.
- Hydrogen chloride from burning PVC being removed by reaction with a base.
- Recycling conserving finite crude oil or saving energy.
- A practical difficulty of recycling, such as sorting mixed polymers or falling quality.
Common mistakes and how to put them right
Writing 'it harms the environment' without naming a substance or an effect.
Claiming incineration produces no carbon dioxide because the energy is recovered.
Assuming all polymers can be recycled together without separation.
Forgetting that collecting, sorting and reprocessing polymers themselves use energy.
Exam tips
- Give balanced answers in pairs; a question worth four marks usually wants two methods with one point each way.
- Name the gas and name the remedy: hydrogen chloride, removed by a base such as calcium oxide.
Try the lesson
The start of the Biodegradability and disposal of polymers (A-level only): The advantages and disadvantages of different methods of disposal of polymers, including recycling. lesson, made from checked teaching notes for this specification point.
Have a go first
What is a major environmental disadvantage of disposing of halogenated plastics, such as PVC, by incineration?
Listen
Landfill is cheap and needs no sorting, but it takes up land, polyalkenes stay there for centuries and decomposing waste releases methane and leachate. Incineration destroys the polymer, cuts the volume sharply and the heat released can generate electricity, but carbon dioxide is produced, and burning PVC releases hydrogen chloride, which must be removed by passing the flue gases through a base; too low a combustion temperature also produces toxic dioxins. Recycling conserves crude oil and uses less energy than making new polymer, but the waste has to be collected, sorted by type and cleaned, and each reprocessing shortens the chains so the quality falls. Feedstock recycling instead cracks the waste back into useful small molecules. A strong answer earns marks for these points. an advantage and a matching disadvantage given for the same disposal method. hydrogen chloride from burning PVC being removed by reaction with a base. recycling conserving finite crude oil or saving energy. a practical difficulty of recycling, such as sorting mixed polymers or falling quality. Exam tip: Give balanced answers in pairs; a question worth four marks usually wants two methods with one point each way.
See it
Key words
Say what each word means before you turn the card.
landfill
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incineration and energy recovery
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toxic combustion products
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recycling
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See every definition
- landfill
- Cheap and needs no sorting, but takes up land, polyalkenes stay there for centuries and decomposing waste releases methane and leachate.
- incineration and energy recovery
- Destroys the polymer, cuts the volume sharply and the heat released can generate electricity, but carbon dioxide is produced.
- toxic combustion products
- Burning PVC releases hydrogen chloride, which must be removed by passing the flue gases through a base, and too low a combustion temperature produces toxic dioxins.
- recycling
- Conserves crude oil and uses less energy than making new polymer, but the waste has to be collected, sorted by type and cleaned, and each reprocessing shortens the chains so the quality falls.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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