Introduction


INTRODUCTION


•           All living organisms on the Earth need air to survive.

•           A thick blanket of air, called the atmosphere, surrounds our Earth.

•           The Earth’s atmosphere has a portion that contains high levels of ozone gas.

•           This layer, called the ozone layer, protects us from the harmful ultraviolet rays of the sun, thus preventing many eye problems and skin cancer in human beings.

•           Air cannot be seen but it can be felt when it moves.

•           Air, when moves, help light-weight things move. For example, the leaves of the trees rustling or clothes on the clothesline swaying.

•           Moving air is called wind.

•           Moving air helps us in many ways. For example, wind helps paper boat, aeroplane, and pinwheel move.

•           It also helps big ships, sailboats, windmills, and hot-air balloons move.

•           Air is present all around us.

•           Air is also present in things which seem to be empty.