Page 208 - Chemistry ICSE Class IX

196 ICSE Chemistry – 9

How can global warming be reduced
The global warming can be reduced by taking the following steps:
ƒ Minimise (or cut down) the use of fossil fuels. This can be achieved
by using bicycle for short distances and public transport, metrorail or
a car pool for going long distances.
ƒ Encourage the use of alternative renewable sources of energy, such
as Wind, Hydel, Solar, and Biomass
ƒ Increase vegetation cover by planting more trees
ƒ Minimise the use of nitrogenous fertilisers
ƒ Do not burn dry agricultural waste, dry leaves, wood etc.
ƒ Use chlorine-free substitutes of chloro uorohydrocarbons in
refrigeration and in chemical industry. Such substitutes which
are available in market are hydro uorocarbons (HFCs) and
methylcyclohexane (MCH).
ƒ Avoid smoking.
ƒ Spread awareness regarding the harmful effects of global warming.

ASSIGNMENT 5

Global warming, Sources of the greenhouse gases, The greenhouses effect, Adverse effects of global warming.

ϭ͘ tŚĂƚ ŝƐ ŵĞĂŶƚ ďLJ ŐůŽďĂů ǁĂƌŵŝŶŐ͍
Ϯ͘ tŚĂƚ ĂƌĞ ƚŚĞ ŐƌĞĞŶŚŽƵƐĞ ŐĂƐĞƐ͍ 'ŝǀĞ ƚǁŽ ĞdžĂŵƉůĞƐ ŽĨ ƚŚĞ ŐƌĞĞŶŚŽƵƐĞ ŐĂƐĞƐ͘
ϯ͘ tŚŝĐŚ ŽĨ ƚŚĞ ŐƌĞĞŶŚŽƵƐĞ ŐĂƐĞƐ ĐŽŶƚƌŝďƵƚĞƐ ƚŚĞ ŵŽƐƚ ƚŽǁĂƌĚƐ ŐůŽďĂů ǁĂƌŵŝŶŐ͍
ϰ͘ EĂŵĞ ƚŚĞ ƌĂĚŝĂƟŽŶ ǁŚŝĐŚ ĂƌĞ ƚƌĂƉƉĞĚ ďLJ ĐĂƌďŽŶ ĚŝŽdžŝĚĞ ŝŶ ƚŚĞ ůŽǁĞƌ ůĂLJĞƌ ŽĨ ƚŚĞ ĂƚŵŽƐƉŚĞƌĞ͘
ϱ͘ EĂŵĞ ƚŚĞ ƉŽƐƐŝďůĞ ĂĚǀĞƌƐĞ ĞīĞĐƚƐ ŽĨ ŐůŽďĂů ǁĂƌŵŝŶŐ͘
ϲ͘ ,Žǁ ĐĂŶ ǁĞ ƌĞĚƵĐĞ ƚŚĞ ŐůŽďĂů ǁĂƌŵŝŶŐ͍
Ozone Depletion

The most important gas present in the stratosphere is ozone (O ). Starting
3
at a height of about 16 km, the concentration of ozone becomes maximum
at a height of about 23 km. Its concentration in the atmosphere at a height
of about 23 km is nearly 10 parts per million (10 ppm).
How is ozone formed in the atmosphere

Ozone (O ) is formed in the atmosphere (in stratosphere) from oxygen (O )
3
2
by the action of far ultraviolet rays present in the sunlight.
O (g) + hv (O = 242 nm) o O(g) + O(g)
2
Oxygen far ultraviolet rays
O (g) + O(g) o O (g)
2
3
ozone
The blanket of ozone (16 – 23 km) around the earth is called ozone
layer. Ozone layer is one of the most important life-support systems.

What is the function (or role) of ozone layer
The radiation coming from the sun consists of ultraviolet radiation. The
ultraviolet radiation can penetrate deep into our body and cause diseases
such as cataract, skin cancer, etc. Ozone layer absorbs the harmful
ultraviolet radiation (in the region: O = 220–330 nm) coming from the sun.
Thus, the ozone layer protects animal and plant life on the earth from the
harmful effects of the ultraviolet radiation.