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12 Air, Water and Weather

Learning Objectives  Purification of Water
 Weather
 Air
 Water

Let’s Start Learning

We know that air and water are the basic needs of life. Besides they also have an
influence on us in many ways. Let us learn more about them.

Air

Air is the mixture of several gases and water vapours. The layer of air around the earth
is known as atmosphere. Air contains 78% nitrogen, 21% oxygen and smaller amount
of carbon dioxide, hydrogen and other gages.
We cannot see air but feel when it blows. The moving air is called wind. Gently
blowing air is called breeze whereas strongly moving air is known a gale. When the
wind moves very strongly, it is called strom.
Breezes are of two types:
 Sea breeze
 Land breeze

Sea Breeze

During the day time, land gets
heated faster than sea. So air above
the land also gets heated quickly. As
the hot air is light, it rises up. So cool
air from the sea flows in to take the
space of warm air. This is known as
Sea Breeze.

Sea breeze

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