Exercise Solutions Available
Step-by-step answers for all textbook questions in this chapter
Where Does Our Garbage Go?
Garbage from homes is collected by sanitation workers, transported to a landfill or waste treatment facility.
Problems with large landfills:
- Occupy huge land areas.
- Produce foul smells.
- Harmful chemicals from garbage seep into groundwater.
- Non-biodegradable waste remains for hundreds of years.
Types of Waste
1. Biodegradable Waste
Waste that can be broken down by bacteria and other microorganisms into harmless substances.
Examples: Vegetable and fruit peels, food scraps, leaves, paper, cotton cloth, leather, wood.
2. Non-Biodegradable Waste
Waste that cannot be broken down by microorganisms naturally.
Examples: Plastic, polythene bags, glass, metal cans, synthetic fibres (polyester, nylon), rubber.
| Type | Breaks Down? | Examples |
|---|---|---|
| Biodegradable | Yes | Vegetable peels, food, paper |
| Non-biodegradable | No | Plastic, glass, metal |
Composting
- A method of converting biodegradable waste into natural fertiliser called compost.
- Done in a compost pit dug in the ground.
How to Make a Compost Pit
1. Dig a pit about 1 metre deep. 2. Add kitchen waste (vegetable peels, food scraps), garden waste (leaves, grass), paper. 3. Do not add plastic, glass, or metal. 4. Cover lightly with soil. 5. Add water occasionally to keep moist. 6. After 3–4 months, compost is ready.
Compost is better than chemical fertilisers because:
- It improves soil texture and water retention.
- It is cheap — made from waste.
- Does not cause chemical pollution.
Vermicomposting
- Composting using earthworms.
- Earthworms eat organic waste → excrete vermicompost (dark, crumbly material).
- Vermicompost is richer in nutrients than regular compost.
- Process is faster.
How it works:
- Earthworms are added to a box with organic waste.
- They eat and digest the waste.
- Their castings become vermicompost.
The 3R Principle — Reduce, Reuse, Recycle
| Action | Meaning | Example |
|---|---|---|
| Reduce | Use less material | Buy only what you need, avoid excess packaging |
| Reuse | Use the same item again | Use glass bottles again, use both sides of paper |
| Recycle | Convert waste into new products | Melt plastic bottles to make new products, paper recycling |
Problems with Plastics
- Plastic bags are non-biodegradable — they stay in soil for hundreds of years.
- Animals eat plastic bags and die.
- Blocking drains causes flooding.
- Burning plastic releases toxic gases (dioxins) — harmful to health.
Alternatives to plastic:
- Cloth bags (cotton or jute)
- Paper bags
- Newspaper wrapping
Waste at School
- Paper waste can be reduced: use both sides, avoid tearing out pages, recycle.
- Old newspapers, magazines → donate or recycle.
- Avoid one-time-use plastic items — bring water in reusable bottles, use cloth napkins.
Key Vocabulary
| Term | Meaning |
|---|---|
| Garbage / Waste | Materials that are no longer needed |
| Biodegradable | Can be broken down by microorganisms |
| Non-biodegradable | Cannot be broken down naturally |
| Compost | Decomposed organic matter used as fertiliser |
| Composting | Making compost from biodegradable waste |
| Vermicomposting | Composting using earthworms |
| Landfill | Large area where garbage is dumped |
| Recycling | Converting waste into reusable material |
Exam Tips
- Biodegradable vs non-biodegradable — give 3 examples of each.
- Composting vs vermicomposting difference — earthworms are used in vermicomposting.
- Why plastic is harmful — non-biodegradable, chokes animals, blocks drains.
- 3R — Reduce, Reuse, Recycle — definition + one example each is a common 3-mark question.
- Why burning garbage is bad — releases toxic gases, causes air pollution.