Science · Class 6
Air Around Us
Composition of air, importance of oxygen, and air pollution basics.
4 sections15–25 min read6 MCQs · 2 examples
Chapter Overview
Air is a mixture of gases surrounding Earth. This chapter covers composition of air, importance of oxygen and nitrogen, role of air in combustion and life, and air pollution basics.
Composition of Air
- Nitrogen ≈ 78%
- Oxygen ≈ 21%
- Argon ≈ 0.9%; carbon dioxide ≈ 0.04%
- Water vapour, dust, pollen also present
Importance of Components
- Oxygen: respiration, burning (combustion)
- Nitrogen: dilutes oxygen; used in fertilisers
- CO₂: used by plants in photosynthesis
- Atmosphere protects from harmful UV rays
Experiments
- Oxygen supports burning (glowing splint relights)
- CO₂ turns lime water milky
- Air has mass and occupies space
Solved Examples
Step-by-step solutions — read each step before checking the final answer.
Oxygen use
Why do mountaineers carry oxygen cylinders at high altitude?
- 1Air pressure decreases at height
- 2Less oxygen per breath
- 3Extra oxygen helps breathing and prevents sickness
Answer
Thin air has less oxygen
CO₂ test
How do you test for carbon dioxide in air exhaled?
- 1Blow exhaled air into lime water
- 2CO₂ reacts with lime water
- 3Solution turns milky
Answer
Lime water turns milky
Key Points to Remember
- ✓ Air expands on heating, becomes lighter, rises
- ✓ Wind is moving air
- ✓ Plants balance CO₂ and O₂ in atmosphere
Exam Tips
- • State percentage composition of air
- • Explain why candle goes out in closed jar
- • List activities that need air
Practice MCQs — Air Around Us
Test your understanding with topic-wise multiple choice questions. Explanations appear after each answer.
Question 1 of 6Score: 0/0
Most abundant gas in air is: