Page 205 - Chemistry ICSE Class IX

Atmospheric Pollution 193

ASSIGNMENT 4

Acid rain; its causes, harmful effects and reductions of harmful effects

ϭ͘ EĂŵĞ ƚŚĞ ŐĂƐĞƐ ƌĞƐƉŽŶƐŝďůĞ ĨŽƌ ĂĐŝĚ ƌĂŝŶ͘
Ϯ͘ ,Žǁ ŝƐ ƐƵůƉŚƵƌŝĐ ĂĐŝĚ ŽĨ ĂĐŝĚ ƌĂŝŶ ĨŽƌŵĞĚ͍
ϯ͘ tŚĂƚ ŝƐ ƚŚĞ ƌĂŶŐĞ ŽĨ Ɖ, ĨŽƌ ĂĐŝĚ ƌĂŝŶ͍
ϰ͘ tŚLJ ĚŽ LJŽƵ ĞdžƉĞĐƚ ƚŚĞ ďƵŝůĚŝŶŐƐ ůŝŬĞ ƚŚĞ dĂũ DĂŚĂů ƚŽ ŐĞƚ ĚĂŵĂŐĞĚ ďLJ ĂĐŝĚ ƌĂŝŶ͍
ϱ͘ tŚĂƚ ŝƐ ƚŚĞ ŝŵƉĂĐƚ ŽĨ ĂĐŝĚ ƌĂŝŶ ŽŶ ;ĂͿ ƉůĂŶƚƐ ;ďͿ ƐŽŝů ;ĐͿ ǁĂƚĞƌ ďŽĚŝĞƐ͍
ϲ͘ 'ŝǀĞ ƚǁŽ ƐƵŐŐĞƐƟŽŶƐ ƚŽ ƌĞĚƵĐĞ ƚŚĞ ĨŽƌŵĂƟŽŶ ŽĨ ĂĐŝĚ ƌĂŝŶ͘

Global Warming

What is meant by global warming

The gradual increase in the global temperature (or temperature of the
earth) caused by the increased concentration of the greenhouse gases in the
atmosphere is called global warming. This is because the greenhouse gases
can trap the sun’s heat.
Carbon dioxide (CO ), Methane (CH ), Nitrous oxide (N O), Ozone
2
2
4
(O ), Water vapour (H O) and Chloro uorocarbons (CFCs) are called the
3
2
greenhouse gases (GHG). The greenhouse gases constitute 1–2% of the
atmosphere. dŚĞƌĞ ĂƌĞ ĚŝǀĞƌƐĞ ŽƉŝŶŝŽŶƐ ĂďŽƵƚ ƚŚĞ
ĐĂƵƐĞƐ ŽĨ ŐůŽďĂů ǁĂƌŵŝŶŐ͘
The contribution of these gases towards global warming is:
Greenhouse gas : CO CH CFCs O N O H O(v)
2
3
2
2
4
Percentage contribution : 50 19 17 8 4 2
What are the sources of greenhouse gases
The sources of the greenhouse gases are described below.
Carbon dioxide
Various sources of carbon dioxide (CO ) gas are:
2
ƒ Burning of fossil fuels, that is, of coal, petrol, diesel, natural
gas
ƒ Decaying organic matter, such as plants
ƒ Respiration by animals, humans and plants
ƒ Various chemical processes, such as manufacture of lime
from limestone, fermentation of sugars, etc.
Relative contribution of different GHGs in the
Methane temperature rise
Various sources of methane gas are:
ƒ Anaerobic decomposition of organic matter, such as animal dung
ƒ Sewage containing domestic wastes
ƒ Marshy lands

Nitrous oxide
Nitrous oxide (N O) is formed during the combustion of petrol and diesel
2
in automobiles, and coal in thermal power plants. N O is also produced
2
during wild res.