CBSE Class 7 Social Science Chapter 4 Air NCERT Solutions
This chapter delves into the essential components of Earth's atmosphere, providing students with a foundational understanding of the air that surrounds us. The NCERT Solutions for Class 7 Social Science, Chapter 4, "Air," cover key concepts such as the composition of the atmosphere, the role of different gases like oxygen and carbon dioxide, and the phenomenon of the greenhouse effect. It also explains weather and climate, different types of rainfall (convectional, orographic, and cyclonic), and the concept of air pressure and its measurement. The solutions offer clear, step-by-step answers to textbook questions, including definitions, explanations, and reasoning for atmospheric phenomena. These solutions are designed to help students grasp complex ideas, prepare for exams, and build a strong base in environmental science.
Quick info
| Board | CBSE |
|---|---|
| Class | Class 7 |
| Subject | Social Science |
| Session | 2026 |
| Language | English |
| Type | NCERT Solutions |
| Chapter | Chapter 4 – Air |
Chapter summary
Chapter 4, "Air," of the Class 7 Social Science NCERT Solutions focuses on the Earth's atmosphere. It explains what the atmosphere is, the gases that constitute it (primarily nitrogen and oxygen), and the significance of gases like carbon dioxide in the greenhouse effect. The chapter also clarifies the difference between weather and climate, details the three main types of rainfall, and defines air pressure. The provided solutions offer concise answers and explanations for all questions, aiding students in understanding these fundamental atmospheric concepts.
Learning outcomes
- Understand the composition and importance of the Earth's atmosphere.
- Identify the gases responsible for the greenhouse effect.
- Differentiate between weather and climate.
- Explain the different types of rainfall: convectional, orographic, and cyclonic.
- Define air pressure and its relation to altitude.
- Identify the main layers of the atmosphere and their characteristics.
Topics covered
Paper topics
- Atmosphere
- Composition of Atmosphere
- Greenhouse Effect
- Weather
- Climate
- Types of Rainfall
- Air Pressure
- Layers of Atmosphere
- Insolation
- Wind
- Ozone Layer
- Evaporation
Important topics
- Composition of the Atmosphere
- Greenhouse Effect
- Weather vs. Climate
- Types of Rainfall
- Air Pressure and Altitude
- Ozone Layer Protection
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Questions and Solutions
Question 1
(i) What is atmosphere?
(ii) Which two gases make the bulk of the atmosphere?
(iii) Which gas creates greenhouse effect in the atmosphere?
(iv) What is weather?
(v) Name three types of rainfall.
(vi) What is air pressure?
(i) The atmosphere is defined as the thin layer of gases that envelops the Earth. It plays a crucial role in protecting life by shielding us from the sun's harmful ultraviolet rays and regulating temperature. It is composed of several gases, with nitrogen and oxygen being the most abundant.
(ii) The two primary gases that constitute the vast majority of the Earth's atmosphere are nitrogen, making up about 78%, and oxygen, comprising approximately 21%.
(iii) Carbon dioxide is the principal gas responsible for creating the greenhouse effect in the atmosphere. It traps heat, helping to keep the planet warm.
(iv) Weather describes the atmospheric conditions at a specific place and time, encompassing elements like temperature, humidity, precipitation, and wind, observed on an hour-to-hour or day-to-day basis.
(v) The three main types of rainfall are:
Convectional rainfall
Orographic rainfall
Cyclonic rainfall
(vi) Air pressure is the force exerted by the weight of the column of air above a particular point on the Earth's surface.
Question 2
(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) Trosphere
(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.
(i) The correct answer is (c) Ozone. The ozone layer absorbs most of the harmful ultraviolet radiation from the sun.
(ii) The correct answer is (a) Troposphere. This is the lowest layer where most weather phenomena occur and it is vital for life.
(iii) The correct answer is (b) Stratosphere. This layer is generally cloud-free, which is why jet aircraft often fly here.
(iv) The correct answer is (b) Decreases. As altitude increases, the density of air decreases, leading to lower air pressure.
(v) The correct answer is (b) Rain. Rain is precipitation in its liquid form.
Question 3
(i) Trade winds
(ii) Loo
(iii) Monsoon
(iv) Wind
(a) Incoming solar energy
(b) Seasonal wind
(c) Horizontal movement of air
(d) Layer of ozone gas
(e) Permanent wind
(f) Local wind
The correct matches are:
- (i) Trade winds - (e) Permanent wind. These are winds that blow constantly in the same direction throughout the year.
- (ii) Loo - (f) Local wind. The Loo is a strong, hot, and dry wind that blows in the northern plains of India during the summer.
- (iii) Monsoon - (b) Seasonal wind. Monsoon winds change their direction according to the seasons, bringing rain in summer and dry conditions in winter.
- (iv) Wind - (c) Horizontal movement of air. Wind is defined as the movement of air from an area of high pressure to an area of low pressure.
Question 4
(i) Wet clothes take longer time to dry on a humid day.
(ii) Amount of insolation decreases from equator towards poles?
(i) On a humid day, the air already contains a high amount of water vapour. Evaporation is the process by which water changes into vapour. When the air is already saturated with moisture, it cannot readily accept more water vapour, thus slowing down the rate of evaporation from the wet clothes. This leads to them taking longer to dry.
(ii) Insolation, which is the incoming solar radiation, decreases from the equator towards the poles because of the Earth's spherical shape and its tilt. At the equator, the sun's rays strike the Earth's surface more directly (almost vertically), concentrating the energy over a smaller area and resulting in higher temperatures. As you move towards the poles, the sun's rays become more slanted. These slanting rays travel through a greater thickness of the atmosphere, and their energy is spread over a larger area, leading to less intense heating and a decrease in the amount of insolation received.
Question 5
Across
1. Amount of water vapour in air
3. Example of local wind blowing in summer in northern India
4. Short term changes in atmosphere
5. Precipitation in liquid form
7. Blanket of air around the earth
9. Instrument to measure pressure
10. Incoming solar radiation
13. Reduces visibility in winters
17. It is ..... time when sun is overhead
19. Low pressure area
Down
2. Condensation of water vapour around dust particles in atmosphere
6. An Indian tree having extraordinary quality of providing oxygen round the clock
8. Gas present in atmosphere occupying only 0.03% by volume
11. Outermost layer of atmosphere
12. Mixture of many gases
14. Life giving gas
15. Air in motion
16. An Indian tree valued highly for medicinal properties
18. Gas protecting us from harmful sunrays
Here is the solution to the crossword puzzle: Across 1. HUMIDITY 3. LOO 4. WEATHER 5. RAIN 7. ATMOSPHERE 9. BAROMETER 10. INSOLATION 13. FOG 17. NOON 19. DEPRESSION Down 2. CLOUD 6. PEEPAL 8. CARBON DIOXIDE 11. EXOSPHERE 12. AIR 14. OXYGEN 15. WIND 16. NEEM 18. OZONE
Common mistakes
- Confusing weather with climate.
- Misunderstanding the role of different gases in the atmosphere.
- Incorrectly associating insolation with altitude instead of latitude.
- Difficulty in explaining the reasons behind varying drying times for clothes.
Revision tips
- Focus on understanding the definitions of key terms like atmosphere, weather, and air pressure.
- Memorize the percentages of major gases in the atmosphere.
- Visualize the different types of rainfall and where they occur.
- Review the reasons given for phenomena like slow drying of clothes on humid days and insolation variation with latitude.
Practice MCQs
Q1. Which gas in the atmosphere is crucial for protecting us from harmful ultraviolet (UV) rays from the sun?
Explanation: The ozone gas layer in the stratosphere absorbs most of the harmful ultraviolet radiation from the sun, protecting life on Earth.
Q2. What is the primary reason why wet clothes dry slower on a humid day?
Explanation: Humidity means the air already holds a lot of water vapour, which slows down the rate of evaporation from the wet clothes.
Q3. Which of the following is NOT a type of rainfall?
Explanation: Monsoon refers to seasonal winds, not a specific type of rainfall mechanism like convectional, orographic, or cyclonic.
Q4. As altitude increases in the atmosphere, what generally happens to air pressure?
Explanation: With increasing altitude, there is less air above, meaning less weight pressing down, hence air pressure decreases.
Q5. The 'greenhouse effect' in the atmosphere is primarily caused by which gas?
Explanation: Carbon dioxide is a significant greenhouse gas that traps heat in the atmosphere, contributing to the greenhouse effect.
Frequently asked questions
What is the atmosphere?
The atmosphere is a thin blanket of air that surrounds the Earth. It is composed of various gases, primarily nitrogen and oxygen, and it protects us from the sun's harmful rays.
Which gases make up the largest portion of the Earth's atmosphere?
Nitrogen, at approximately 78%, and oxygen, at about 21%, together make up the bulk of the Earth's atmosphere.
What is the difference between weather and climate?
Weather refers to the short-term, hour-to-hour or day-to-day condition of the atmosphere, while climate describes the long-term average weather patterns of a region.
What are the three main types of rainfall?
The three main types of rainfall are convectional rainfall, orographic rainfall (caused by mountains), and cyclonic rainfall (associated with low-pressure systems).
How does air pressure change with altitude?
As you go higher in the atmosphere (increase in altitude), the air pressure decreases because there is less air above to exert pressure.
Why do wet clothes take longer to dry on a humid day?
On a humid day, the air is already saturated with water vapour. This high humidity slows down the process of evaporation, making clothes take longer to dry.
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