NCERT Solutions Class 7 Social Science (Geography)
The NCERT Solutions in English Language for Class 7 Social Science (Geography – Our Environment) Chapter – 4 (Air) has been provided here to help the students in solving the questions from this exercise.
Chapter – 4 (Air)
Exercises
1. Answer the following questions.
(i) What is the atmosphere?
Answer – Atmosphere is a thin blanket of air that surrounds the earth. It protects us from the harmful rays of the sun. It consists of several gases in which nitrogen and oxygen occupy the major portion.
(ii) Which two gases make the bulk of the atmosphere?
Answer – Nirtrogen (78%) and oxygen (21%) make the bulk of the atmosphere.
(iii) Which gas creates a greenhouse effect in the atmosphere?
Answer – Carbon dioxide is the gas that creates the greenhouse effect in the atmosphere.
(iv) What is the weather?
Answer – The hour to hour or the day to day condition of the atmosphere is called weather. Weather can change dramatically from day-to-day. It may be classified as hot, dry, cold or wet.
(v) Name three types of rainfall?
Answer – The three types of rainfall are as follows:-
1. Convectional rainfall
2. Orographic rainfall
3. Cyclonic rainfall
(vi) What is air pressure?
Answer – Air pressure is defined as the pressure exerted by the weight of air on the earth’s surface. The air pressure decreases as height increases and is the highest at the sea level.
2. Tick the correct answer.
(i) Which of the following gases protects us from harmful sun rays?
(a) Carbon dioxide
(b) Nitrogen
(c) Ozone
Answer – (c) Ozone
(ii) The most important layer of the atmosphere is
(a) Troposphere
(b) Thermosphere
(c) Mesosphere
Answer – (a) Troposphere
(iii) Which of the following layers of the atmosphere is free from clouds?
(a) Troposphere
(b) Stratosphere
(c) Mesosphere
Answer – (b) Stratosphere
(iv) As we go up the layers of the atmosphere, the pressure
(a) Increases
(b) Decreases
(c) Remains the same
Answer – (b) Decreases
(v) When precipitation comes down to the earth in the liquid form, it is called
(a) Cloud
(b) Rain
(c) Snow
Answer – (b) Rain
3. Match the following.
| (i) Trade Winds | (a) Incoming solar energy |
| (ii) Loo | (b) Seasonal wind |
| (iii) Monsoon | (c) The horizontal movement of Air |
| (iv) Wind | (d) A layer of ozone gas |
| (e) Permanent wind | |
| (f) Local wind |
Answer –
| (i) Trade Winds | (e) Permanent wind |
| (ii) Loo | (f) Local wind |
| (iii) Monsoon | (b) Seasonal wind |
| (iv) Wind | (c) The horizontal movement of Air |
4. Give reasons.
(i) Wet clothes take longer time to dry on a humid day?
Answer – Wet clothes take longer time to dry on a humid day because on a humid day, there is more water in the air than on a sunny day. So, air can soak less water from wet clothes, i.e. rate of evaporation decreases.
(ii) Amount of insolation decreases from the equator towards poles?
Answer – Insolation is the incoming solar energy intercepted by the earth. Amount of insolation decreases from the equator toward poles, because sun rays fall vertically on the equator and slant on the poles.
