Lesson 9 of 9
Evaluate plastic use and recycling
Compare what happens to the molecules and to the wider system.
O-Level 6092 (2026) / SEC G3 K324 (2027)
I can explain plastic pollution.Syllabus
Syllabus K324, 11.4(g). Explain plastic pollution
I can compare recycling routes.Syllabus
Syllabus K324, 11.4(h). Compare recycling routes
I can evaluate recycling issues.Syllabus
Syllabus K324, 11.4(j). Evaluate recycling issues
Evaluate plastic use and recycling
Compare what happens to the molecules and to the wider system.
Many plastics are non-biodegradable: natural biological processes do not break them down readily. Persistent waste can harm wildlife through ingestion or entanglement, accumulate in habitats and fragment into small pieces. Burning plastics releases carbon dioxide and, depending on the plastic and conditions, other pollutants. Disposal shifts a problem unless its consequences are considered.
| Route | What happens | Trade-off |
|---|---|---|
| Physical recycling | Sort and clean plastic, cut it into pieces, then melt it into pellets; poly(ethene) is an example | Retains polymer molecules but mixed materials or contamination can reduce product quality |
| Chemical recycling by cracking | Break plastic molecules into smaller hydrocarbons that can be used as fuel | Can process molecules differently, but requires energy; burning the fuel still releases carbon dioxide |
Pure: chemical recycling can also use depolymerisation to recover chemical feedstock. Acid-catalysed polyester hydrolysis can regenerate monomers for making new material. Cracking to fuel and depolymerising to monomers have different products; neither should be described merely as melting.
| Dimension | Questions that matter |
|---|---|
| Social | Is collection accessible? Are sorting instructions understandable? Are workers and nearby communities affected? |
| Economic | What do collection, transport, sorting and processing cost? Is there a market for the recovered material? |
| Environmental | How much energy, transport and virgin resource use are avoided or added? What emissions and unrecovered waste remain? |
Worked exampleCompare two claims
One plan melts clean separated poly(ethene) locally; another ships mixed plastic far away for cracking. Is either always better?
Try it first. Then show the worked stepsHide the worked steps
- The first may use less processing but depends on clean sorted input and a useful output market.
- The second may accept different waste but adds transport and cracking energy.
- Compare actual quantities, energy sources, yields and avoided virgin production.
A justified decision uses evidence across the whole process, rather than assuming the word recycling guarantees a lower impact.
Check your understanding
Does melting used poly(ethene) into pellets turn it back into ethene?
Show the answer
No. Melting only changes its shape; the long polymer chains remain intact.
Mechanical recycling is a physical change. Getting the monomer back needs a chemical process that breaks the chain.