Page 92 - Science - 5

ATMOSPHERE
The Earth is wrapped in a layer of air. This blanket of air surrounding the Earth

is called the Earth's atmosphere. It is held by the earth's gravity and provides
the right support which helps life to survive.

w It saves the Earth from becoming very hot by screening a large part of
the Sun's heat from reaching the Earth.
w At night, it prevents the heat of the Earth to escape. If there was no

atmosphere, the Earth would have been a cold freezing place at night.
w The ozone layer in the atmosphere prevents the harmful ultraviolet rays

of the Sun to reach the Earth.
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Tyres filled with air are called pneumatic tyres. Dunlop was the first
person to make pneumatic tyres.

Layers Exosphere
Layers
Layers of the Atmosphereof the Atmosphereof the Atmosphere
Exosphere
Exosphere
Scientists have divided the atmosphere
Thermosphere
Thermosphere
into five layers. Thermosphere
Troposphere : It is the first layer of the Mesosphere
Mesosphere
Mesosphere
Earth's surface. The wind and most clouds Stratosphere
Stratosphere
Stratosphere
exist in this region. Troposphere
Troposphere
Troposphere
Stratosphere : Many aircrafts fly in this
layer. Here, the ozone layer absorbs
harmful rays from the Sun.

Mesosphere : Meteors or rock fragments are burnt up in the mesosphere.
Thermosphere : The space shuttle orbits in the thermosphere.

Exosphere : The exosphere is the uppermost limit of our atmosphere. It
is the highest and thinnest portion of the Earth’s atmosphere.

PROPERTIES OF AIR

Air has three main properties :

w It occupies space.
w It carries pressure.

w It exerts pressure.

Air contains oxygen which is consumed by living beings for respiration.
Oxygen is also essential for burning.

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