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Dear students,
Science is activity based. Its method is the unprejudiced investigation
of truth, based on scientific evidence. If what is generally considered
right today is scientifically proved wrong tomorrow, it would be
accepted. This is how science works. This rational method has to be
employed in learning science. Continuous observation,
experimentations and analyses lead the scientific perspectives to new
dimensions. Hence, you have to make use of every possible
opportunity to observe and experiment.
The student's role is pivotal in the process of construction of
knowledge. This science textbook is only a resource in the learning
process. Your teachers and supplementary materials will help you in
the creation of knowledge. ’Samagra’, the education portal and
technology enabled Q R code printed textbooks would definitely make
your learning activity in classrooms easy and joyful. I.C.T has also been
considered in the textbook.
This book includes lessons which spread light on greenhouse gases,
Greenhouse effect, ozone depletion, and Global warming. This also
provides an idea about the drastic effects of these phenomenon’s on
the natural existence of the earth and the living world.
The method of presentation is more conducive to the learner to
achieve knowledge and delight. We expect the textbook to be helpful
in the further learning of science.
Love and Regards,
Text Book Development Team.
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TEXT BOOK DEVLOPMENT TEAM
Dr. Saphia L
(Assistant Professor Natural Science Department,
CSI College of Education, Parassala)
Ganga J S
(Teacher Trainee, CSI College of Education Parassala)
Gopika G S
(Teacher Trainee, CSI College of Education Parassala)
Blessy S S
(Teacher Trainee, CSI College of Education Parassala)
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CONTENT
GREENHOUSE EFFECT:
• Greenhouse gases
• Sources
OZONE DEPLETION:
• Causes
• World ozone day
GLOBAL WARMING:
• Global warming
• Cause
• Impact
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Icons used in the textbook for convenience:
For further reading
Let us assess
Extended activities
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EARTH FOR TOMORROW
Ramu saw a poster exhibited in a competition conducted at school on the topic
“save earth from global warming”.
Do you hearded about Global warming?
Do you think about how this phenomenon occurs?
What do you understand from this picture?
What happens to the radiations entered into the glass house?
Is all radiations escape from the glass house? What do you mean by this
phenomenon?
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Greenhouse effect
The greenhouse effect describes how natural gases in the earth’s atmosphere
reduce the amount of heat escaping from the earth into the atmosphere. The
more of these gases there are, the more the earth heats up.
The gases which cause greenhouse effect are called greenhouse gases. Major
greenhouse gases are;
• Carbon dioxide
• Nitrous oxide
• Chloro Fluro carbon
•
•
•
Find more greenhouses gases and note it in your science diary.
This picture
indicate global
warming?
Why the picture of
earth is depicted
like this?
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Carbon dioxide
Carbon dioxide is one of the primary greenhouse gasses comprising of 85% of all
the greenhouse gases. It absorbs long wave length infrared rays and re-radiate it
to the earth itself.
Where all these co2
gases do comes from?
Sources
• Industrialization
• Human respiration
• Burning of fossil fuels
• Volcanic eruption and wild fires
•
•
•
Nitrous oxide
It is the major gas capturing infrared radiation from the earth’s surface and
subsequently warming the troposphere.
carbondioxide
nitruos oxide
methane
CFCs
green house gases
carbondioxide nitruos oxide methane CFCs
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Sources
• Microbial activity
• Industrial production of nitric acid
• Biomass burning
•
•
•
Chlorofluro carbon (CFCs)
CFCs is a harmful gas that depletes the ozone layer and cause green house
effect. Each CFC molecule can trap as much as heat as 100000 CO2 molecule
can. They remain in the atmosphere for a long time.
Sources
• Aerosol sprays
• Coolant in refrigerator and air conditioner
• Cleaning solvents
•
•
Methane
Second most important greenhouse gas. It is 80 times potent than CO2 and it
remains in the atmosphere for over 10-20 years.
Sources
• Oil and natural gas system
• Sanitary landfills
• Waste water treatment
•
•
•
•
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Indicators
❖ What is greenhouse effect?
❖ Which one is the primary greenhouse gas?
❖ Name some anthropogenic activities which responsible for
greenhouse effect?
Observe these pictures given below. Compare the pictures and write your
inferences in science diary.
Ozone depletion
The ozone layer is a region in the earth’s
stratosphere which protect the earth from the
harmful ultraviolet radiations from the sun. It
absorbs about 97-99% of ultraviolet rays which
affect the existence of life on earth.
It was entered into Force on
1st
January 1985. It is an
International treaty to
protect Ozone layer.
Do you know?
Montreal Protocol
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A poster related to ozone day
is given below. What is the
need of protecting the ozone
layer? Discuss and prepare
notes in your science diary.
Indicators
❖ Which day we celebrate world ozone day?
❖ Effect of greenhouse gases in ozone depletion?
❖ What is the need of protecting ozone layer?
Do you observe the picture shown in the beginning of the chapter? It is a poster
shows global warming. You already learned about global warming.
Global warming
Global warming is a gradual increase in the earth’s temperature generally due to
the greenhouse effect caused by increased levels of greenhouse gases.
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There are many causes for global warming;
Causes of global warming
Global warming is caused by natural and anthropogenic activities.
Natural causes of global warming
➢ Change in the earth’s orbit and rotation
➢ Variations in solar activity
➢ Change in the earth’s reflectivity
➢ Volcanic activity
➢ Changes in naturally occurring CO2 concentration
➢ Microbial activity
➢
➢
➢
➢
Anthropogenic (manmade) causes of global warming
➢ Deforestation
➢ Fossil fuels
➢ Landfills
➢ Over population
➢ Mining
➢ Use of fertilizers
➢
➢
➢
➢
Global warming has severe impact on the existence of life on earth. Discuss
with your friends and add some adverse effect of global warming.
Impact of global warming
➢ Increased drought
➢ Melting of ice in polar region
➢ Loss of species
➢ More health risks
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➢ Flood
➢ Migration
➢
➢
➢
➢
It is not when climate changes happen that one should think about nature
conservation. Nature conservation should become part and parcel of everyone’s
life. Nature should be used wisely and preserved for the generations to come.
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Let as assess
1. Which one of the following is not a greenhouse gas?
a) Carbon monoxide
b) Methane
c) CFCs
d) Carbon dioxide
2. Prepare a poster based on world ozone day?
3. Complete the chart by filling the effect of global warming?
4. What is the need of preventing the formation of greenhouse gases for the
protection of earth?
flood
--------
--------
--------
health
risk
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Extended activity
1. Analyze the illustration given below. How this picture relate with global
warming? Collect information regarding the reasons for global warming,
its consequences and remedial measures?
2. Why does more ozone hole see over Antarctica?
