RBSE Class 7 Social Science Notes Geography Chapter 4 Air

These comprehensive RBSE Class 7 Social Science Notes Geography Chapter 4 Air will give a brief overview of all the concepts.

RBSE Class 7 Social Science Notes Geography Chapter 4 Air

→ Atmosphere: Our earth is surrounded by a huge blanket of air called atmosphere. All living beings on this earth depend on the atmosphere for their survival.

→ Composition of the Atmosphere

• Air is actually a mixture of many gases. Nitrogen, oxygen, carbon dioxide, helium, ozone, argon and hydrogen are found in air in which Nitrogen 78%, Oxygen 21% and the remaining 1% is the amount of other gases.
• Apart from these gases, tiny dust particles are also present in the air.
• Plants need nitrogen and carbon dioxide for their survival. Humans and animals take oxygen from the air as they breathe. Green plants produce oxygen and take carbon dioxide during photosynthesis. Humans or animals release carbon dioxide. It makes a perfect balance.

→ Structure of the Atmosphere
Our atmosphere is divided into five layers starting from the earth’s surface. These are :

1. Troposphere,
2. Stratosphere,
3. Mesosphere,
4. Thermosphere and
5. Exosphere.

→ Weather and Climate

• → Weather is this hour-to-hour, day to day condition of the atmosphere.
• → The average weather condition of a place for a longer period of time represents the climate of a place.

→ Temperature: The degree of hotness and coldness of the air is known as temperature. The temperature of the atmosphere changes not only between day and night but also from season to season.

→ Insolation:

• Insolation is the incoming solar energy intercepted by the earth. It influences the distribution of temperature.
• The amount of insolation decreases from the equator towards the poles.
• Temperature in cities is much higher than that of villages.

→ Air Pressure

• Air pressure is defined as the pressure exerted by the weight of air on the earth’s surface.
• The air pressure is highest at sea level and decreases with height.
• Horizontally the distribution of air pressure is influenced by temperature of air at a given place. High temperature creates a low-pressure area, tow temperature creates a high pressure area.

→ Wind

• The movement of air from high pressure area to .low pressure area is called wind. Sometimes it runs fast and sometimes slow.
• Winds can be broadly divided into three types
  1. Permanent winds,
  2. Seasonal winds,
  3. Local winds.

→ Moisture: Moisture in the air at any time, is known as humidity.

→ Rainfall:

• The water vapour condenses causing formation of droplets of water. Clouds are just masses of such water droplets. When these droplets of water become too heavy to float in air, then they come down as precipitation.
• There are three types of rainfall:
  1. Convectionalrainfall,
  2. Orographic rainfall, and
  3. Cyclonic rainfall.