Air Composition and Importance - UNSOLVED PRACTICE SET
Chapter: Natural Resources | Topic: Air Composition and Importance
AIR COMPOSITION AND IMPORTANCE - UNSOLVED PRACTICE SET
Topic: Air Composition and Importance
Multiple Choice Questions
Q1. The most abundant gas in the Earth's atmosphere is:
- Oxygen
- Carbon dioxide
- Nitrogen
- Argon
Q2. Which gas in the atmosphere is essential for the process of respiration in humans and animals?
- Nitrogen
- Oxygen
- Carbon dioxide
- Water vapour
Q3. The small amount of carbon dioxide in the atmosphere (about 0.04%) is crucial because it:
- Helps us breathe directly
- Traps heat and is used by plants for photosynthesis
- Makes the sky blue
- Prevents air pollution
Q4. Water vapour in the atmosphere is important because it:
- Provides oxygen for breathing
- Helps in the formation of clouds and rain
- Protects us from UV rays
- Is used by animals for respiration
Q5. During a science experiment in your school lab, a burning candle is covered with a jar. The candle flame flickers and goes out after some time. This happens because:
- The candle runs out of wax
- The oxygen inside the jar gets used up
- The nitrogen becomes poisonous
- The carbon dioxide catches fire
Short Answer Questions
Q6. List the main gases present in air along with their approximate percentages. Why is nitrogen the most abundant gas even though oxygen is what we need for breathing?
Q7. What role does oxygen play in the survival of living organisms? Name two processes in nature where oxygen is essential.
Q8. Why is carbon dioxide called a "greenhouse gas" even though it is present in such a small quantity in the atmosphere? Explain its dual role - one helpful, one potentially harmful.
Q9. Your grandmother keeps freshly cut fruits from turning brown by squeezing lemon juice on them. How does this simple kitchen trick relate to the role of a gas present in air?
Long Answer Questions
Q10. Describe the composition of air in detail. Explain why each major component - nitrogen, oxygen, carbon dioxide, and water vapour - is important for life on Earth. Why is the balance of these gases crucial for maintaining life as we know it?
Q11. "Air is a mixture, not a compound." Explain this statement by describing how the components of air can be separated and how they maintain their individual properties. Why is this distinction important for understanding how living organisms use air differently?
APPLICATION / ANALYSIS
Q12. Case Study - Air Quality in Two Cities:
A study measured air composition in two Indian cities:
| Component | City A (Coastal, Kerala) | City B (Industrial, Gujarat) |
|---|---|---|
| Nitrogen | 78% | 78% |
| Oxygen | 21% | 20% |
| Carbon dioxide | 0.04% | 0.08% |
| Water vapour | Higher | Lower |
| Dust and pollutants | Low | Very high |
Answer the following:
(a) Why is the percentage of oxygen slightly lower in City B despite both cities having the same nitrogen level?
(b) How does higher water vapour in City A affect its climate and rainfall compared to City B?
(c) If you were a city planner, what is the first change you would recommend for City B to improve its air quality? Justify your answer.
Q13. Real-Life Application - School Science Fair:
Your class is preparing a model showing "Why We Cannot Live Without Air." You have four balloons to fill with different gases:
Balloon 1: Pure oxygen
Balloon 2: Pure nitrogen
Balloon 3: Normal air
Balloon 4: Air with high carbon dioxide
You also have a small mouse in a closed container (under teacher supervision) and a burning candle.
Answer the following:
(a) In which container would the candle burn the longest, and in which would the mouse survive? Explain using your knowledge of air composition.
(b) Why would the mouse die faster in pure nitrogen than in normal air, even though nitrogen is harmless?
(c) A firefighter enters a smoke-filled building. Why does he carry an oxygen cylinder instead of an air cylinder? What does this tell you about the difference between air and oxygen?