Air around us
·
Air:
the invisible gaseous substance surrounding the earth, a mixture mainly of
oxygen and nitrogen.
·
The blanket of air that surrounds 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 vapors 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.
·
Constituent
of air:
i.
Nitrogen:
plants need nitrogen to grow.
ii.
Oxygen:
used by all living things to respire and help to burn things.
iii.
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.
iv.
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.
v.
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:
i.
Air aids burning.
ii.
Air is needed for breathing.
iii.
Plants need air to make food.
iv.
Birds fly in air. Aero planes also go up in the
air because of air pressure.
v.
Moving air is called wind. The wind makes the
windmill rotate.
vi.
Air help in quick evaporation of seat that helps
in keeping us cool.
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