Lesson focus: How can we use resources while reducing waste?
Evaluate reduction, reuseUsing something again instead of throwing it away, like refilling a water bottle. and recycling using material and energy flows.
Build on earlier learning
How does recycling work?Revisit recycling, now tracking recovery across repeated cycles.
You will be successful when you can…
- Distinguish reduce, reuse and recycle.
- Calculate repeated percentage recovery.
- Account for material losses.
- Compare equal services and system inputs.
Words that carry the science
- reduce
- Use less material or avoid demand for a product.
- reuse
- Use an item again for the same or another service.
- recycle
- Process discarded material into feedstock for new products.
- recovery rate
- Fraction or percentage entering a process that is recovered for the stated output.
- material flow
- Tracked movement of matter through a system.
Track recovered material and compare waste-reduction strategies fairly
01Prevention comes before processing
Reduction can avoid extraction and manufacture. reuseUsing something again instead of throwing it away, like refilling a water bottle. extends service from an existing item, though washing, transport and breakage may matter.
02Recycling retains some material value
Collection and processing can recover feedstock, but contamination, degradation and separation create losses. Local systems determine what is actually recovered.
03Loss from one stream is not disappearance
Matter rejected from recycling remains in residues, other products, landfill, emissions or dispersed waste. Conservation does not guarantee easy recovery.
Recycling makes resources last
Metal ores are finite: once dug up and used, they are gone. Recycling means less new ore is needed each year, so the reserve lasts longer. Demand here grows by 2% a year.
Controls
Numbers are illustrative. Recycling also saves energy and reduces mining waste and landfill, but collecting and sorting have costs too.
Apply repeated recovery
Each cycle recovers 80% of material. Begin with 100 kg.
- Cycle 1: 100 × 0.80 = 80 kg recovered.
- Cycle 1 diverts 20 kg elsewhere.
- Cycle 2: 80 × 0.80 = 64 kg recovered.
- Cycle 2 diverts 16 kg from its input; 36 kg total is outside the target stream.
How to make the reasoning visible: After two cycles, 64 kg remains available in the target stream.
Strategy comparison
Compare the same service and state the system boundary.
| Strategy | Avoided input | Required input | Evidence needed |
|---|---|---|---|
| Reduce packaging | Material/manufacture | Product protection redesign | Damage + mass data |
| Reuse jar | New jars | Washing/return transport | Uses + wash energy |
| Recycle jar | Some raw material | Collection/reprocessing | Recovery rate |
| Discard | Little recovery | Replacement production | Waste destination |
Where is the 36 kg not recovered after two cycles?
Why compare per delivered service?
Use the table. Why does reusing a jar still need some energy?
Check your understanding
Answer from memory, then check against the suggested answer.
What is reduce?
What is reuse?
What is recycle?
Put these in order from best to worst for resources: recycle, reduce, reuse.
Give one example of reusing.
At 75% recovery, how much of 200 kg remains after two cycles?
What evidence decides between washing/reusing a jar and recycling it each time?
Why is recycling usually better than throwing an item away?
Exam Question Practice
Exam Question Practice
Mark points shown after marking
A recycling process recovers 80% of the material in each cycle. It starts with 100 kg of material.
Calculate the mass recovered after two cycles. Show your working.
(3)Explain what has happened to the material that is not recovered.
(2)Total for this question: 5 marks
Command word: Show each percentage step and distinguish process loss from disappearance.