4. AIR


air pressure belt diagram

 NCERT Solutions for Class 7 Social science Chapter 4 Air

Question.1 Answer the following questions-

(a) What is atmosphere?
Answer.- The huge blanket of air surrounding the Earth is called atmosphere.

(b) Which two gases make the bulk of the atmosphere?
Answer.-   Nirtrogen (78%) and oxygen (21%)

 (c) Which gas creates greenhouse effect in the atmosphere?
Answer.- Carbon dioxide 
 
(d) What is weather?
Answer.-  Weather is the hour-to-hour, day-to-day condition of the atmosphere.
 
(e) Name three types of rainfall?
Answer.- 1. Convectional rainfall  2. Orographic rainfall 3.  Cyclonic rainfall
 
(f) What is air pressure?
Answer.- The pressure exerted by the weight of air on the earth’s surface is known as air pressure.
 
Question.2 Tick the correct answer-
 
(a) Which of the following gases protects us from harmful sun rays?
(a) Carbon dioxide
(b) Nitrogen
(c) Ozone
 
(b) The most important layer of the atmosphere is
(a) Troposphere
(b) Thermosphere
(c) Mesosphere
 
(c) Which of the following layers of the atmosphere is free from clouds?
(a) Troposphere
(b) Stratosphere
(c) Mesosphere
 
(d) As we go up the layers of the atmosphere, the pressure
(a) Increases
(b) Decreases
(c) Remains the same
 
(e) When precipitation comes down to the Earth in the liquid form, it is called
(a) Cloud
(b) Rain
(c) Snow
 
Answer.-   A. (c) Ozone  B. (a) Troposphere  
C. (b) Stratosphere      D. (b) Decreases      E. (b) Rain
 
Question.3  Match the following-
 Answer.-
 

(i) Trade Winds

(e) Permanent wind

(ii) Loo

(f) Local wind

(iii) Monsoon

(b) Seasonal wind

(iv) Wind

(c) Horizontal movement of air
 

Question.4  Give reasons-

(a) Wet clothes take longer time to dry on a humid day?
Answer.- Humidity is the amount of moisture or water vapour present in air at any moment in time.
1. On the equator, insolation comes through vertical rays.
2. It covers up less space. Hence heat is felt more.
 
(b) Amount of insolation decreases from Equator towards Poles?
Answer.- it goes on coming through slanting rays. Slanting rays come on the earth passing longer distances through the atmosphere. They heat up more space. Hence there is less heat on a point of space.