NCERT Class 7 Geography Chapter 4 air notes.

Chapter-4: Air

These NCERT Class 7 Geography Chapter 4 notes explain the importance of air and the role of the atmosphere in supporting life on Earth. The chapter helps students understand why air is essential for breathing, plant growth, weather and climate.

Air introduces the composition of air, including nitrogen, oxygen and carbon dioxide, and explains the layers of the atmosphere such as the troposphere and stratosphere. It also discusses weather, climate, air pressure and different types of winds, with special focus on the Indian monsoon.

This chapter builds a strong foundation for understanding atmospheric processes and environmental issues.

1. Introduction

  • Air is invisible but essential for all forms of life on Earth.
  • Humans need air for breathing and survival.
  • Plants need air to make food through photosynthesis.
  • Weather and rainfall depend on the presence of air.
  • Air acts as a shield that protects Earth and a life-giver that supports living beings.

2. Atmosphere

  • The atmosphere is a blanket of air surrounding the Earth.
  • It protects Earth from harmful ultraviolet (UV) rays of the Sun.
  • The atmosphere prevents extreme heat during the day and extreme cold at night.
  • It helps in the formation of clouds, winds and rainfall.
  • Weather and climate exist because of the atmosphere.

3. Composition of air

  • Air is a mixture of gases, not a single gas.
  • Nitrogen (78%) is the most abundant gas and supports plant growth.
  • Oxygen (21%) is necessary for breathing and burning.
  • Carbon dioxide (0.03%) is used by plants and controls Earth’s temperature.
  • Other gases like argon, helium and ozone are present in small amounts.
  • Water vapour and dust particles help in cloud formation and rainfall.

4. Structure of the atmosphere

  • The atmosphere is divided into five vertical layers.
  • Each layer has different characteristics and functions.
  • The troposphere is the lowest and most important layer.
  • The stratosphere contains the ozone layer.
  • The mesosphere, thermosphere and exosphere lie above it.

5. Troposphere

  • The troposphere is the lowest layer of the atmosphere.
  • It contains the air that we breathe.
  • All clouds and rainfall occur in this layer.
  • Weather changes happen only in the troposphere.
  • Rain, fog and storms are common in this layer.

6. Stratosphere

  • The stratosphere lies above the troposphere.
  • It contains the ozone layer.
  • The ozone layer protects Earth from harmful UV rays.
  • It helps prevent skin diseases and eye damage.
  • This layer is important for maintaining life on Earth.

7. Mesosphere

  • The mesosphere lies above the stratosphere.
  • It is the coldest layer of the atmosphere.
  • Temperatures drop very low in this layer.
  • Meteors burn here before reaching the Earth’s surface.
  • This layer protects Earth from space debris.

8. Thermosphere and exosphere

  • The thermosphere is an extremely hot layer of the atmosphere.
  • It helps in radio communication.
  • Artificial satellites move in this layer.
  • The exosphere is the outermost layer of the atmosphere.
  • It gradually merges with outer space.

9. Weather and climate

  • Weather refers to the day-to-day condition of the atmosphere.
  • Weather changes quickly and can vary within a day.
  • Climate refers to the average weather condition over many years.
  • Climate changes slowly and remains stable for long periods.
  • Rajasthan has a hot and dry climate.
  • Kerala has a hot and wet climate.

10. Elements of weather and climate

  • Temperature shows how hot or cold a place is.
  • Rainfall refers to the amount of rain received.
  • Humidity is the amount of moisture present in air.
  • Wind is the movement of air from one place to another.
  • These elements together decide the weather and climate of a place.

11. Air pressure

  • Air pressure is the pressure exerted by air on the Earth’s surface.
  • Hot air becomes light and rises upward.
  • Rising hot air creates low pressure.
  • Cold air is heavy and sinks downward.
  • Air always moves from high pressure to low pressure.

12. Winds

  • Wind is moving air.
  • Permanent winds blow throughout the year.
  • Seasonal winds change direction in different seasons.
  • Local winds blow for a short time in small areas.
  • Winds play an important role in weather and climate.

13. Indian monsoon winds

  • Monsoon winds are seasonal winds in India.
  • They bring most of the rainfall to the country.
  • Indian agriculture depends heavily on monsoon rainfall.
  • The Indian economy is closely linked with monsoon performance.
  • Failure of monsoon leads to drought and crop loss.

14. Air pollution

  • Air pollution is caused by vehicle smoke and factory emissions.
  • Burning of coal and petrol increases air pollution.
  • Polluted air causes respiratory diseases.
  • It leads to acid rain and global warming.
  • Using clean energy and planting trees can reduce air pollution.

15. Important keywords

  • Atmosphere is the blanket of air around the Earth.
  • Troposphere is the lowest layer where weather occurs.
  • Stratosphere contains the ozone layer.
  • Weather and climate describe atmospheric conditions.
  • Air pressure and wind control weather patterns.
  • Air pollution harms human health and the environment.

Understanding NCERT Class 7 Geography Chapter 4 is important to learn how the atmosphere protects life and controls weather and climate on Earth. The chapter clearly explains air composition, atmospheric layers and the movement of winds.

The ideas discussed in Air help students understand environmental balance and atmospheric changes and are highly useful for school examinations and foundation-level preparation.

Continue reading NCERT Class 7 Geography Chapter 5 – Water to understand the distribution of water on Earth, the water cycle and the need for water conservation.

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FAQs

Q1. What is atmosphere according to NCERT Class 7 Geography Chapter 4?
The atmosphere is a blanket of air surrounding the Earth that supports life and controls weather.

Q2. Which gas is most abundant in the atmosphere?
Nitrogen is the most abundant gas in the atmosphere.

Q3. In which layer of the atmosphere does weather occur?
All weather changes occur in the troposphere.

Q4. What is the ozone layer?
The ozone layer protects the Earth from harmful ultraviolet rays of the Sun.

Q5. Why is this chapter important for exams?
It explains atmospheric composition, weather and winds, making it important for school exams and foundation-level preparation.

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