Air around Us - Revision Notes

 CBSE Class–VI Subject Science

Revision Notes
CHAPTER – 15
Air Around Us

Air: The invisible gaseous substance surrounding the earth, a mixture mainly of oxygen and nitrogen.

  • The blanket of air that surround the earth is called atmosphere.
  •  Air is found everywhere. We cannot see air, but we can feel it.
  • Air in motion is called wind.
  • Air occupies space.
  • Air is present in water and soil.
  • Air is a mixture of nitrogen, oxygen, carbon dioxide, water vapour and a few other gases. Some dust particles may also be present in it.
  • Atmosphere is essential for life on earth.
  • Aquatic animals use dissolved air in water for respiration.
  • Plants and animals depend on each other for exchange of oxygen and carbon dioxide from air.

Diffrent Layers of Atmosphere

  1. Troposhere
  2. Stratosphere
  3. Meseosphere
  4. Thermosphere

Constituent of Air 

  • Air contains mostly nitrogen and oxygen . Nitrogen  is nearly 78% of the air . Oxygen is nearly 21% of the air. Rest 1% is carbon ioxide, water vaour, dust particles and some other gases. The composition of gases in air changes from place to place.
  1. Nitrogen : Plants need nitrogen to grow.
  2. Oxygen : Used by all living things to respire and help to burn things.
  3. Carbon dioxide: Plants and animals consume oxygen and produce carbon dioxide during respiration. It is used by green plants for photosynthesis. It is released on burning.
  4. Water Vapour: Formed due to evaporation of water. Amount of water vapour present  in the air is called humidity. Varies from place to place and also in the same place during day and night.

   5. Dust and Smoke: Smoke contains a few gases and fine dust particles. It is very harmful.                Presence of dust particles in air varies from time to time and from place to place.

Importance of Air 

  • Air aids burning.
  •  Air is needed for breathing.
  •  Plants need air to make food.
  •  Birds fly in air. Aeroplanes also go up in the air because of air pressure.
  •  Moving air is called wind. The wind makes the windmill rotate.