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SAI International School
Subject - Chemistry
Class - VIII
Topic – COMBUSTION AND FLAME
Sub-Topic- Green House Effect; Global warming

LESSON NOTES
Green House effect
The greenhouse effect is the process by which radiations from the sun are absorbed by the
greenhouse gases and not reflect into space. This insulates the surface of the earth and prevents
it from freezing.

A greenhouse is made of glass that can be used to grow plants. The sun’s radiations warm the
plants and the air inside the greenhouse. The heat trapped inside can’t escape out and warms
the greenhouse which is essential for the growth of plants.

The same is the case in the earth’s atmosphere. During the
the sun heats the earth’s atmosphere. At night, when the earth
cools down the heat is radiated back into the atmosphere.
During this process,the heat is absorbed by the greenhouse
gases in the earth’s atmosphere. This is what makes the
surface of the earth warmer, which makes the survival of living
beings on earth possible.

However, due to the increased levels of greenhouse gases,
the temperature of the earth has increased to a very high
level due to several drastic effects. More greenhouse gases mean more heat will be
absorbed.

Greenhouse Gases
The gases that absorb infrared radiation and create a
greenhouse effect are called greenhouse gases. Some
of the major greenhouse gases are water vapour, carbon
dioxide, methane, ozone, nitrous oxide,
chlorofluorocarbons (CFC).

The major contributors to the greenhouse gases are
factories, automobiles, deforestation, etc. The increased
number of factories and automobiles increases the
amount of these gases in the atmosphere. The
greenhouse gases never let the radiation to escape from
the earth and increase the surface temperature of the
earth. This then leads to global warming.