NCERT Solutions Class 7 Social Science Chapter 4 Air

NCERT Solutions for Class 7 Social Science Geography Chapter 4 Air

1. Answer the following questions: 

(i) What is atmosphere? 

Ans. The huge blanket of air that surrounds the earth is known as atmosphere. 

(ii) Which two gases make the bulk of the atmosphere? 

Ans. The gases which make the bulk of atmosphere are nitrogen and oxygen. 

(iii) Which gas creates green house effect in the atmosphere? 

Ans. Carbon dioxide creates green house effect in the atmosphere. 

(iv) What is weather? 

Ans. 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) Name three types of rainfall. 

Ans. The three types of rainfall are: 

(a) The Convectional Rainfall 

(b) The Relief or Orographic Rainfall, and 

(c) The Cyclonic Rainfall 

(vi) What is air pressure? 

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

2. Tick/ underline the correct answer. 

(i) Which of the following gases protect us from harmful sun rays? 

(a) Carbon dioxide          (b) Nitrogen           (c) Ozone . 

(ii) The most important layer of the atmosphere is: 

(a) Troposphere .    (b) Thermosphere    (c) Mesosphere 

(iii) Which of the following layers of the atmosphere is free from clouds? 

(a) Troposphere       (b) Stratosphere .   (c) Mesosphere 

(iv) As we go up the layers of the atmosphere, the pressure: 

(a) Increases     (b) Decreases .    (c) Remains the same  

(v) When precipitation comes down to the earth in the liquid form, it is called: 

(a) Cloud                   (b) Rain .                (c) Snow 

3. Match the following. 

(i) Trade winds         (a) Incoming solar energy 

(ii) Loo                    (b) Seasonal wind 

(iii) Monsoon            (c) Horizontal movement of air 

(iv) Wind                 (d) Layer of ozone gas 

                               (e) Permanent wind 

                               (f) Local wind 

Ans. 

(i) Trade winds           (e) Permanent wind 

(ii) Loo                       (f) Local wind 

(iii) Monsoon              (b) Seasonal wind 

(iv) Wind                    (c) Horizontal movement of air   

4. Give reasons. 

(i) Wet clothes take longer time to dry on a humid day. 

Ans. Water from wet clothes evaporates under the action of sun and wind. The rate of evaporation is much slower on a humid day than on a dry day, as the air has already some amount of moisture present in it. Hence, it takes longer to dry wet clothes. 

(ii) Amount of insolation decreases from equator towards poles. 

Ans. Sunlight falls almost vertically on the equator, while it falls at slanting angle on the poles. So, the amount of insolation decreases from equator towards poles. The amount of insolation received by the equatorial regions is greater than insolation received by the polar regions. 

5. For fun. 

(i) Solve this crossword puzzle with the help of given clues. 

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) Make a weather calendar for one week. Use pictures or symbols to show different types of weather. You can use more than one symbol in a day, if the weather changes.