1. Chapter at a Glance
Hold your breath for a few seconds — you soon feel the need for air. We cannot live without air, water, sunlight, soil and many other gifts of nature. These gifts are natural resources — nature’s treasures. Some are renewed by nature quickly; others took millions of years to form and will run out if we waste them. This chapter introduces these resources and why we must use them wisely.
- Air — its composition and uses; wind.
- Water — how little fresh water we have and why we must save it.
- Energy from the Sun, forests, soil, rocks and minerals.
- Fossil fuels — coal, petroleum and natural gas.
- Renewable and non-renewable resources; natural and human-made resources.
2. Air
Air is a mixture of gases. It contains about 78% nitrogen, 21% oxygen and about 1% argon, carbon dioxide and other gases, along with water vapour and dust.
Chart — composition of air (by volume):
- Living beings use oxygen for respiration; burning also needs oxygen.
- Plants use carbon dioxide to make their food.
- Moving air is called wind. Wind turns windmills, sails boats, disperses seeds, dries clothes and spins a paper firki (pinwheel).
Smoke from vehicles and factories, burning of waste and dust pollute the air. We can reduce air pollution by using public transport, cycling or walking, planting trees and not burning garbage.
3. Water
Water covers about two-thirds of the Earth’s surface, yet most of it is salty seawater. Only a small fraction is fresh water, and much of that is frozen as ice or lies deep underground. So the fresh water we can actually use is very limited.
We use water for drinking, cooking, bathing, washing, farming and industries. Turning off taps while brushing, fixing leaks, reusing water for plants and harvesting rainwater all help save it.
4. Energy from the Sun
The Sun is the main source of energy on Earth. It gives heat and light. Plants use sunlight to make food, and all animals depend on plants directly or indirectly. Sunlight drives the water cycle and causes winds. We use solar energy for drying grains and clothes, in solar cookers and in solar panels that make electricity.
5. Forests
A forest is a large area with a dense growth of many kinds of plants. Forests give us wood, fruits, medicines, gum and honey; give food and shelter to wild animals; prevent soil erosion; help bring rain and keep the air clean. Once cut, forests take a very long time to regrow, and the animals living there lose their homes.
6. Soil, Rocks and Minerals
Soil is formed very slowly by the breaking down of rocks over thousands of years, mixed with decaying plant and animal matter. It supports plant growth and is home to many organisms like earthworms. Soils from different places differ in colour, texture and the amount of water they hold.
Rocks are made of minerals. Minerals are used to extract metals like iron, copper and aluminium and to make cement, glass, fertilisers and many other goods.
7. Fossil Fuels
Coal, petroleum and natural gas are fossil fuels. They formed over millions of years from the remains of plants and tiny organisms buried deep under the Earth. They run vehicles and machines, cook food and produce electricity. Their stocks are limited, and burning them pollutes the air. A survey of vehicles in the neighbourhood shows how much we depend on petrol, diesel and CNG.
8. Renewable and Non-renewable Resources
| Type | Meaning | Examples |
|---|---|---|
| Renewable | Replenished by nature within a reasonable time | Sunlight, air, water, forests (if not overused) |
| Non-renewable | Limited; take millions of years to form; will run out | Coal, petroleum, natural gas, minerals |
Yes, if we use it faster than nature can replace it. Forests cut faster than they regrow, or groundwater pumped faster than rain refills it, can be lost. So even renewable resources must be used carefully.
Human-made resources are things people make for convenience using natural resources — buildings, roads, vehicles, plastics, paper. Making them uses up natural resources too.
9. Resources We Use — Using Them Wisely
Almost every activity uses natural resources: cooking (LPG, firewood, water), travelling (petrol, diesel), studying (paper from trees, electricity from coal or sunlight). We should follow the 3 Rs — Reduce, Reuse, Recycle, switch off lights and fans when not needed, prefer solar and wind energy, plant trees and save water.
10. Master Table: Key Terms
| Term | Meaning |
|---|---|
| Natural resource | Anything obtained from nature that is useful to us |
| Composition of air | N₂ ≈ 78%, O₂ ≈ 21%, others ≈ 1% |
| Wind | Moving air |
| Forest | Large area with dense growth of plants |
| Minerals | Substances making up rocks; source of metals |
| Fossil fuels | Coal, petroleum, natural gas from ancient remains |
| Renewable / Non-renewable | Replenished quickly / limited and exhaustible |
| Human-made resources | Things made by humans from natural resources |
11. Master Summary Table
| Resource | Main use | Type | How to conserve |
|---|---|---|---|
| Air | Breathing, burning, wind energy | Renewable | Reduce pollution |
| Water | Drinking, farming | Renewable (limited fresh water) | Fix leaks, harvest rain |
| Sunlight | Food making, solar energy | Renewable | Use more solar devices |
| Forests | Wood, habitat, rain | Renewable if not overused | Plant and protect trees |
| Coal, petroleum | Fuel, electricity | Non-renewable | Use public transport |
| Minerals | Metals, cement | Non-renewable | Recycle metals |
12. Mind Map
- 78% N₂, 21% O₂
- Little fresh water
- Main energy source
- Habitat, rain, soil
- Soil, rocks, minerals
- Fossil fuels
- Renewable / non-renewable
- 3 Rs
13. Tips and Tricks
- Fossil fuels = “C-P-N”: Coal, Petroleum, Natural gas — all non-renewable.
- Air composition: “78–21–1”.
- If a resource takes millions of years to form, it is non-renewable.
- Thinking water is unlimited because it covers most of the Earth — most is salty.
- Calling forests non-renewable — they are renewable but regrow slowly and must be protected.
- Writing that oxygen is the main gas in air — nitrogen is.
14. Important One-liners
- Air is a mixture of gases; nitrogen is about 78%.
- Oxygen (about 21%) is needed for respiration and burning.
- Moving air is wind.
- Most water on Earth is salty; fresh water is limited.
- The Sun is the main source of energy on Earth.
- Soil forms slowly from the breaking of rocks.
- Rocks are made of minerals.
- Coal, petroleum and natural gas are fossil fuels.
- Fossil fuels are non-renewable.
15. Exam-pattern Questions with Detailed Answers
Which gas is present in the largest amount in air?
- Oxygen
- Carbon dioxide
- Nitrogen
- Argon
Show answer
Nitrogen is about 78% of air; oxygen about 21%.
Answer: (C) Nitrogen
Classify as renewable or non-renewable: sunlight, coal, water, natural gas.
Show answer
Renewable: sunlight, water. Non-renewable: coal, natural gas.
Answer: Renewable — sunlight, water; non-renewable — coal, natural gas
What is wind?
Show answer
Moving air is called wind.
Answer: Moving air
Why is petroleum called a non-renewable resource?
Show answer
Petroleum formed over millions of years from buried remains of tiny organisms. Its stock is limited and it cannot be replaced in a human lifetime, so it will run out if used continuously.
Answer: Takes millions of years to form; limited stock
Water covers two-thirds of the Earth. Why do we still face water shortage?
Show answer
Most water is salty seawater, and much fresh water is frozen in ice or deep underground. Only a small fraction is available for use, and pollution and wastage reduce it further.
Answer: Very little usable fresh water
What happens to soil when trees are cut on a hill slope?
Show answer
Roots of trees hold soil together. Without them, rain and wind wash or blow away the top fertile soil (soil erosion), making the land barren and causing landslides.
Answer: Soil erosion increases
Suggest three ways your school can reduce water use.
Show answer
Fix leaking taps; use rainwater harvesting; reuse water from washing for plants; put up reminders to close taps; use buckets instead of hoses for cleaning.
Answer: Fix leaks, harvest rain, reuse water
List three uses of energy from the Sun.
Show answer
Plants make food using sunlight; drying grains and clothes; solar cookers and solar panels for electricity; it also drives the water cycle.
Answer: Food making, drying, solar electricity
Can a renewable resource become scarce? Explain with an example.
Show answer
Yes. Groundwater is renewed by rain, but if it is pumped faster than it is refilled, water tables fall and wells dry up. Forests too can disappear if cut faster than they regrow.
Answer: Yes — when used faster than nature renews it
What would happen if sunlight did not reach the Earth for a long time?
Show answer
The Earth would become very cold; plants could not make food and would die; animals depending on plants would starve; the water cycle and winds would stop. Life would not survive.
Answer: No food, extreme cold — life would end
Compare cooking on an LPG stove, a firewood chulha and a solar cooker. Give one advantage and one disadvantage of each.
Show answer
LPG: quick and clean flame; but non-renewable and costly. Firewood: cheap and available in villages; but smoky and leads to cutting of trees. Solar cooker: free, renewable, no smoke; but slow and works only on sunny days.
Answer: Each has trade-offs; solar is cleanest and renewable
16. Quick Revision Summary
- Air: 78% nitrogen, 21% oxygen, 1% others; moving air is wind.
- Fresh water is a small fraction of Earth’s water — save it.
- The Sun is the main energy source; forests give habitat, rain and soil protection.
- Soil forms from rocks; rocks contain minerals; fossil fuels formed over millions of years.
- Renewable (sun, air, water, forests) vs non-renewable (coal, petroleum, natural gas, minerals); use all wisely with the 3 Rs.