class 9 chapter 14 natural resource science solution
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Answers
Q1. How is our atmosphere different from the atmospheres on Venus and Mars?
Answer:
Earth's atmosphere is different from the atmosphere on Venus and Mars.
The major component of the atmosphere on Venus and Mars is found to be carbon dioxide constituting up to 95-97 \% of the atmosphere.
Whereas, the atmosphere of Earth is made of 79\% nitrogen and 20\% oxygen, with only a small fraction of carbon dioxide.
Q 2. How does the atmosphere act as a blanket?
Answer:
The atmosphere is the thick blanket of air that covers the whole of the Earth. The atmosphere acts as a blanket in the following ways:
(i) It prevents the harmful UV rays from reaching the Earth's surface.
(ii) It helps in maintaining the surface temperature during day and night.
(iii) It protects Earth from celestial objects like asteroids.
Q 3. What causes winds?
Answer:
The uneven heating of the atmosphere in different regions of the Earth creates some regions of low pressure and some regions of high pressure.
Air from the high-pressure region moves into the area of low pressure. This movement of air from one region to the other creates winds.
Q 4. How are clouds formed?
Answer:
The heating of the water bodies during the day leads to the evaporation of a large amount of water which then rises up with the hot air.
As the air rises, it expands and cools. This cooling causes the water vapour in the air to condense in the form of tiny droplets around dust particles.
These tiny droplets cluster themselves to form clouds. When these water-drops become heavy, they precipitate and fall down as rain.
In a nutshell, evaporation and condensation are the two main processes involved in the formation of clouds.
Q5. List any three human activities that you think would lead to air pollution.
Answer:
Three human activities that would lead to air pollution are:
i) Emission of harmful gases and dust particles from vehicles.
ii) Combustion of fossil fuels like coal, petroleum releasing oxides of nitrogen and sulphur.
iii) The smoke released from industries containing harmful gases like sulphur dioxide, oxides of nitrogen.