NCERT Solutions for Class 7 Geography Chapter 4 – Air
1. Answer the following questions.
(i) What is atmosphere?
Answer – Atmosphere is an envelope of gases which surrounds the earth. The atmosphere protects the earth from becoming either too hot or too cold and also prevents the harmful rays of the sun from entering the earth. It has different layers within it such as the troposphere, stratosphere, mesosphere and the exosphere.
(ii) Which two gases make the bulk of the atmosphere?
Answer – The atmosphere consists of a number of gases within it, most of which is contained within the troposphere. The two most important gases which makes the bulk of the atmosphere are: Nitrogen which accounts for 78% of the atmosphere and oxygen which accounts for 21%. Some other gases present in the atmosphere are argon, carbon dioxide, nitrous oxides, methane, etc.
(iii) Which gas creates green house effect in the atmosphere?
Answer – Greenhouse gases which effect the atmosphere are carbon dioxide and methane.
(iv) What is weather?
Answer – Weather is the condition of the atmosphere in a particular day at a particular place. For example, the weather may be sunny, humid or rainy or cold.
(v) Name three types of rainfall?
Answer – There are three main types of rainfall.
1.Convectional rainfall
2. Cyclonic/Frontal rainfall
3. Orographic/Relief rainfall
(vi) What is air pressure?
Answer – Air pressure is the weight of air molecules pressing down on the Earth within the atmosphere. It is measured by a barometer. The standard air pressure is 1,013.25 mbar.
NCERT Solutions for Class 7 Geography Chapter 4 – Air
2. Tick the correct answer.
(i) Which of the following gases protects 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
NCERT Solutions for Class 7 Geography Chapter 4 – Air
3. Match the following.
NCERT Solutions for Class 7 Geography Chapter 4 – Air
4.Give reasons.
(i) Wet clothes take longer time to dry on a humid day? On a humid day, the moisture in the atmosphere or simply air is quite high. This is also known as saturation level of the air. If the moisture content is already high, the air molecules will not be able to absorb more moisture from the clothes and thus will take a longer time to dry.
(ii) Amount of insolation decreases from equator towards poles? This is due to the shape of the earth. As the earth bulges near the equator, the sun’s rays are more or less vertical within the tropics, away from the tropics, the amount of insolation slowly decreases as the rays have to travel a longer distance and moreover the rays become slanting close to the poles reducing insolation amount.
NCERT Solutions for Class 7 Geography
- Chapter 1 – Environment
- Chapter 2 – Inside Our Earth
- Chapter 3 – Our Changing Earth
- Chapter 5 – Water
- Chapter 6 – Natural Vegetation and Wild Life
- Chapter 7 – Human Environment: Settlement Transport and Communication
- Chapter 8 – Human Environment Interactions
- Chapter 9 – Life in the Deserts
