NCERT Solutions for Class 7 Geography Chapter 4 Air contains answers to the exercise questions given in the “Our Environment”. All the answers provided here are accurate and simple that will help you understand the concepts easily and continue your studies without a doubt. These solutions will also help you to score higher marks with the help of well-illustrated answers.
Class 7 Geography Chapter 4 Air Questions and Answers
Question 1: Answer the following questions.
(i) What is the atmosphere?
Answer: The blanket of air surrounding the earth is called the atmosphere. The atmosphere primarily comprises nitrogen and oxygen in bulk and other gases like carbon dioxide, helium, ozone, etc in lesser quantities. All living beings on earth depend on the atmosphere for their survival.
(ii) Which two gases make the bulk of the atmosphere?
Answer: The two gases that make the bulk of the atmosphere are:
- Nitrogen gas – 78%
- Oxygen gas – 21%
(iii) Which gas creates a greenhouse effect in the atmosphere?
Answer: Carbon dioxide creates a greenhouse effect in the atmosphere.
(iv) What is the weather?
Answer: Weather refers to the short-term changes in the atmosphere. It is the hour-to-hour, day-to-day condition of the atmosphere.
(v) Name three types of rainfall?
Answer: The three types of rainfall are as follows:
- Convectional rainfall
- Orographic rainfall
- 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.
Question 2: Tick the correct answer.
(i) Which of the following gases protects us from harmful sun rays?
(a) Carbon dioxide
(b) Nitrogen
(c) Ozone
Solution: (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
Question 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 |
Question 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 the amount of water in the air is more on a humid day than on a sunny day. Due to which, the rate of evaporation decreases and air soaks in less water from the clothes.
(ii) Amount of insolation decreases from the equator towards poles?
Answer: Insolation refers to the incoming solar radiations intercepted by the Earth. The amount of sunlight received by the regions close to the Equator is greater than the amount of sunlight received by the regions close to the Poles. This is because of the tilt of the Earth’s axis. As a result of this tilt, the incoming solar radiations cover a greater area at the Equator than at the Poles.