3.4.6Physical Chemistry
Solution to Plastic Pollution — AQA AS Chemistry Revision Notes & Topical Questions
5 min read 5 parts Lesson 81 of 102
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 5Why Plastic Waste Persists
Why Plastic Waste Persists
Unreactive
- Unreactive Poly(alkenes) contain only strong, non-polar C–C and C–H bonds, so most reagents cannot attack them.
Not biodegradable
- Not biodegradable Enzymes in microorganisms cannot break the saturated carbon chain, so plastics last for hundreds of years in landfill.
Landfill
- Landfill Dumping uses valuable land, and plastic that escapes can pollute rivers, oceans and wildlife habitats.
Burning
- Burning Incineration can release carbon dioxide and toxic gases, for example hydrogen chloride from PVC.
Part 2 of 5Ways to Deal with Plastic
Reduce and reuse
- Reduce and reuse Using less plastic, or reusing items several times, avoids creating waste in the first place.
Mechanical recycling
- Mechanical recycling Plastics are sorted, washed, ground to small pellets, melted and remoulded into new products.
Feedstock recycling
- Feedstock recycling Heating the polymer strongly breaks it down to small molecules which can be used as raw materials for new plastics.
Energy recovery
- Energy recovery Burning waste plastic releases heat which can generate electricity, though it still produces carbon dioxide.
Part 3 of 5Mechanical Recycling Process
1
Waste plastic is collected and separated by type, since mixed plastics cannot be reprocessed together.
2
The sorted plastic is washed thoroughly to remove labels, food residue and other contaminants.
3
It is ground into small pieces and then melted down into pellets.
4
The pellets are melted again and moulded into new objects.
5
Each cycle shortens some polymer chains, so the quality falls and the plastic can only be recycled a limited number of times.
Part 4 of 5Evaluating the Options
Evaluating the Options
Mechanical advantage
- Mechanical advantage It is a simpler process that needs less energy than making new plastic from crude oil.
Mechanical drawback
- Mechanical drawback Careful sorting is needed, and the recycled plastic is often of lower quality than new material.
Feedstock advantage
- Feedstock advantage It can treat mixed or contaminated plastics and reduces the use of crude oil for new monomers.
Feedstock drawback
- Feedstock drawback It needs high temperatures, so it uses a lot of energy and is more expensive.
| Method | Main advantage | Main disadvantage |
|---|---|---|
| Landfill | Cheap and simple | Plastic remains for centuries |
| Incineration | Energy recovered | Produces CO₂ and toxic gases |
| Mechanical recycling | Saves crude oil and energy | Quality falls each cycle |
| Feedstock recycling | Works on mixed plastics | High energy cost |
Part 5 of 5Exam Checklist & Tips
3.4.6 – Key Points for the Exam
- Biodegradable Able to be broken down by living organisms, such as microorganisms, into simpler substances.
- Mechanical recycling Sorting, washing, melting and remoulding of plastics without changing the polymer chemically.
- Feedstock recycling Breaking polymers down into small molecules that serve as raw materials for new plastics.
- Landfill Disposal of waste by burying it in the ground.
Common Mistakes
- Saying plastics are not biodegradable because they are strong;
- the reason is their unreactive, saturated carbon chains.
- Stating that recycling is always better without giving one drawback, such as sorting difficulty or energy use.
- Forgetting that burning PVC releases toxic hydrogen chloride as well as carbon dioxide.
- Mixing up mechanical recycling, which keeps the polymer, with feedstock recycling, which breaks it down.
Last updated:
\n