NCERT Solutions For Class 7 Social Science Chapter 10 Air

(i)

Across:

6. An Indian tree having extraordinary quality of providing oxygen round the clock: Peepal

8. Gas present in atmosphere occupying only 0.03% by volume: Carbon dioxide

11. Outermost layer of atmosphere: Exosphere

12. Mixture of many gases: Air

14. Life giving gas: Oxygen

15. Air in motion: Wind

16. An Indian tree valued highly for medicinal properties: Neem

18. Gas protecting us from harmful sunrays: Ozone

19. Low pressure area: Cyclone

Down:

1. Amount of water vapour in air: Humidity

2. Condensation of water vapour around dust particles in atmosphere: Cloud

3. Example of local wind blowing in summer in northern India: Loo

4. Short term changes in atmosphere: Weather

5. Precipitation in liquid form: Rain

7. Blanket of air around the earth: Atmosphere

9. Instrument to measure pressure: Barometre

10. Incoming solar radiation: Insolation

13. Reduces visibility in winters: Fog 

17. It is noon time when sun is overhead.   

(ii)

(i) Water from wet clothes evaporates due to the presence of sun and wind. The rate of evaporation is much slower on a humid day than that on a dry day.This is because the air already has some amount of moisture present in it. Hence, it takes longer to dry wet clothes.

(ii) Sunlight falls almost vertically on the equator, while it falls at a slanting angle on the poles. Therefore,the amount of insolation decreases from equator towards the poles. The amount of insolation received by the equatorial regions is greater than that received by the polar regions.

(i) Trade winds           (e) Permanent wind

(ii) Loo                       (f) Local wind

(iii) Monsoon              (b) Seasonal wind

(iv) Wind                    (c) Horizontal movement of air 

(i) (c) Ozone ✓

(ii) (a) Troposphere ✓

(iii) (b) Stratosphere ✓

(iv) (b) Decreases ✓

(v) (b) Rain ✓

(i) The huge blanket of air that surrounds the earth is known as atmosphere.

(ii) The gases which make the bulk of atmosphere are nitrogen and oxygen.

(iii) Carbon dioxide creates green house effect in the atmosphere.

(iv) The state of atmosphere at a particular place and time is known as weather. It is the hour-to-hour, day to day condition of the atmosphere.

(v) Three types of rainfall are:

                      (a) The Convectional Rainfall
                      (b) The Relief or Orographic Rainfall, and
                      (c) The Cyclonic Rainfall

(vi) The pressure exerted by the weight of air on the earth’s surface is known as air pressure.