STD 8 Social Science: Chapter 10 The Blanket of The Earth - Questions and Answers
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Social Science Chapter 10: The Blanket of The Earth - Questions and Answers
1. What is the atmosphere?
• Atmosphere is the blanket of air surrounding the earth.
2. Name the atmospheric gases which play a major role in maintaining the earth as a life-supporting planet.
• Oxygen and carbon dioxide
3. Plants are significant in regulating the amount of oxygen and carbon dioxide in the atmosphere. Justify
• Through the process of photosynthesis the plants gather energy for
their growth.
• In this process plants intake carbon dioxide and give out oxygen.
4. What are the major constituents of the atmosphere?
• Gases, moisture and dust particles
5. List out the major gases in the atmosphere. Name the most abundant gas among them.
• Nitrogen, Oxygen, Argon, Carbon dioxide, Ozone, Neon, Helium, Krypton, Hydrogen, Xenon
• Nitrogen
6. Rearrange the gases in the descending order of their proportion in the atmosphere.
• Argon - oxygen-carbon dioxide - nitrogen
Answer:
• nitrogen - oxygen-Argon -carbon dioxide
7. Oxygen, carbon dioxide and nitrogen are equally important in sustaining life on Earth. Substantiate.
• Plants utilize carbon dioxide for photosynthesis
• Organisms including humans, use oxygen to breathe.
• Plants use nitrogen gas for their growth through nitrogen fixation.
8. What is the importance of oxygen, carbon dioxide and nitrogen in the
existence of life forms.
• Plants make use of Carbon dioxide for photosynthesis.
• Man and other organisms make use of oxygen for respiration.
• Plants make use of nitrogen for their growth through nitrogen fixation.
9. Point out the factors that influence the amount of water in the atmosphere.
• Rate of evaporation will be high at places experiencing higher
temperatures. So the water content in such places will be high.
• The amount of water will be high in the atmosphere close to the surface
water sources such as oceans, rivers and other water bodies.
10. What are the main sources of dust particles in the atmosphere?
• Dust particles brought to the atmosphere by wind.
• Dust particles erupted through volcanoes.
• Ash formed by burning of meteors
11. Why dust particles are called condensation nuclei?
OR
The fine dust particles in the atmosphere are very significant in climate. Elucidate.
• Water vapour condenses around fine dust particles in the atmosphere to form clouds.
12. What is the significance of dust particles in the atmosphere?
• Frequent condensation concentrating around the fine dust particles in the atmosphere help in cloud formation.
13. Which of the following places is most likely to have the highest amount of atmospheric humidity? Why?
(a)Thiruvananthapuram
(b)Bangalore
(c)Delhi
(d)Hyderabad
Answer:
• Thiruvananthapuram
• Thiruvananthapuram is near the sea
14. Give reasons for the following circumstances.
i) The atmospheric humidity is high in equatorial regions but low in the polar regions.
ii) Humidity is less inland than in coastal areas.
Answer:
i) In tropical areas, evaporation is high. So high humidity.
ii) Evaporation is more likely to occur near terrestrial water bodies (ocean, lake, rivers)
15.Why the mountaineers climbing Mount Everest take oxygen cylinders with them?
• The gases (oxygen) get rarefied with increasing altitude.
16.Why glass is largely used in the construction of buildings in cold countries?
• Glass panes have the capacity to allow insolation to pass through them
and check the terrestrial radiation.
• Thus temperature is maintained within the buildings without fall. So feel
hot.
17.How the property of glass is made use of in the agricultural sector in cold countries?
• By preventing the terrestrial radiations the temperature required for the
growth of plants is retained inside such constructions
18.What are Greenhouses?
• Greenhouses are glass buildings designed for the protection of plants
against excessive cold or heat
19.Write a short note on the Greenhouse effect.
• Carbon dioxide, methane, ozone etc present in the atmosphere can
permit insolation and prevents terrestrial radiation. These gases and water vapour present in the atmosphere absorb terrestrial radiation and retain the temperature of the atmosphere. This phenomenon is called the Greenhouse effect.
20. What are greenhouses? Explain the greenhouse effect.
• Glass roofed homes are being built to protect plants from harsh winter conditions. This helps the plants retain the heat they need, as it injects solar radiation and prevents radiation. Such structures are greenhouses.
• Gases such as Carbon dioxide, methane, ozone etc. and water vapour present in the atmosphere absorb the terrestrial radiation and retain the temperature of the atmosphere. This phenomenon is called the Greenhouse effect and the gases causing the phenomena are called Greenhouse gases.
21. Give three examples of greenhouse gases.
• Carbon dioxide, methane, ozone
22.Cloudy days are warmer than days with a clear sky. Why?
• Water vapour and clouds contribute to the greenhouse effect. It blocks the terrestrial radiation and absorbs more heat. Thus the lower atmosphere remains warm.
23.Write different sources of greenhouse gases.
• Volcanic eruptions, decay of biological matter (natural means)
• Deforestation, burning of fossil fuels etc.(human activities)
24.How deforestation leads to an increase in the amount of carbon dioxide in the atmosphere?
• Trees remove some of the carbon dioxides from the atmosphere through
photosynthesis and store that carbon in their tissues and in the soil.
• Deforestation reduces the removal component of this cycle, further
increasing the carbon dioxide in the air.
25.What is Global warming?
• The increase in temperature in the atmosphere due to greenhouse gases
referred to as Global warming.
26. Explain how 'forestry combat global warming '.
• Photosynthesis increases with forestry. Thus more carbon dioxide will be absorbed. - thereby the greenhouse effect is reduced and atmospheric heat falls.
27. ‘The air temperature rises with the increase in greenhouse gases'
i) Name the phenomenon.
ii) How does this process threaten the survival of life?
Answer:
i) Global Warming
ii) (a) Sea level rises through polar ice melting-
(b) Destruction of coastal ecosystems create food shortages and migration
(c) Endanger of Species
28.How Global warming becomes a threat to the life forms of the earth?
• Sea level may rise as a result of the melting of polar ice.
• Destruction in the coastal ecosystem may lead to the problems such as
food crisis, large scale migration etc
• Leads to the depletion of many species of plants and animals in the
ecosystem.
29.Suggest a few alternatives to resist global warming.
• Drive fuel-efficient vehicles
• Protect trees and forests
30. Deforestation causes the accumulation of carbon dioxide in the atmosphere. How?
• Deforestation increases the process of photosynthesis. This causes an increase in carbon dioxide in the atmosphere.
31. Write anyone reason for the increase of carbon dioxide in the atmosphere.
• Deforestation increases the process of photosynthesis. This causes an increase in carbon dioxide in the atmosphere.
32. Although the greenhouse effect is essential to the survival of life, it also has adverse effects. Elucidate. What are the sources of greenhouse gases?
• Excessive increases in greenhouse gases cause the air temperature to rise.
• Human activities that generate greenhouse gases - industrial fumes, deforestation, vehicle smoke/fossil fuel burning
• Natural processes that create greenhouses
• Bio-degradation, volcanic eruption etc.
33.What is the Ozone layer? Write its significance
• As the ozone gas is concentrated in the upper atmosphere as a layer, it is
called the Ozone layer.
• It protects the life forms of the earth by absorbing the harmful ultraviolet
rays from the sun.
34.What is Ozonisation?
• The single-atom oxygen molecules react with ordinary oxygen molecules
to form tri atomic ozone gas. This process is called Ozonisation.
35.List out the negative impacts of ultraviolet rays.
• Climate change
• Blindness
• Skin cancer
• Premature ageing
• Stunted growth of plants
• Crop failure
• Destruction in the food chain
36. How harmful are UV rays to the earth? What causes UV rays to reach Earth?
• Gases such as Chloro Fluro carbons and halogen decompose ozone.
• Refrigerators, air conditioners, different types of sprays, fire
extinguishers, Combustion Gases, paints, etc.
37.What are the sources of gases such as chlorofluorocarbons, halon etc.?
• Refrigerators, air conditioners, different types of sprays, fire
extinguishers, Combustion Gases, paints, etc.
38.How Ozone hole is formed?
• Gases like chlorofluorocarbons, halon etc rising to the upper atmosphere
react with ultraviolet rays from the sun to form chlorine and bromine
• Chlorine and bromine are capable to decay ozone molecules.
• This depletion in the atmospheric ozone layer is called an Ozone hole.
39.Which day is celebrated as World Ozone Day? Write its importance.
• 16th September
• To create awareness on the need for conservation of ozone and to control
the use of products leading to ozone depletion
40.What is the difference between the homosphere and heterosphere?
• The composition of the atmosphere is somewhat uniform up to about 90
Kilometres from the surface of the earth. This part of the atmosphere is
called homo sphere.
• Beyond 90 Km from the earth there is no uniformity in the gaseous
composition. This part of the atmosphere is called a hetero sphere.
41. Which of the following is the extent of the 'homo sphere'
a) 0 - 8 km
b) Up to 50 km
c) 50 to 80 km
d) 0 - 90 km
Answer:
d) 0 - 90 km
42. Beyond 90 km above the Earth's surface, there is no uniformity in the composition of gases. What is the name of this atmospheric layer?
a) The homosphere
b) Troposphere
c) Mesosphere
d) heterosphere
Answer:
(d) heterosphere
43.Each layer in the atmosphere has its own indigenous characteristics. State the characteristics of each layer in a tabular format.
Troposphere
• This layer extends up to about 90 Km from the surface of the earth and lies close to the earth.
• The height of the troposphere is more in the equatorial regions because of strong convection here. (about 18 Km)
• Almost all the weather and climatic phenomena such as cloud formation, rain, snow, wind, thunder and lightning etc. take place in this layer.
• In the troposphere the temperature decreases at a uniform rate of 1°Celcius for every 165 metres of altitude. This is called Normal Lapse Rate.
• The zone of transition above the troposphere is called the tropopause.
Stratosphere
• Extends up to a height of about 50 Km from the earth and lies above the tropopause.
• In the lower parts of the stratosphere there is no change in temperature with altitude. This zone is called the isothermal zone. Beyond this, there is an increase in temperature with altitude.
• Ozone layer which forms part of this layer absorbs the harmful ultraviolet rays from the sun and prevents it from reaching the earth.
• Allows the free movement of jet aircraft through clear atmospheric conditions and the absence of air gutters.
• The zone of transition above the stratosphere is called stratopause.
Mesosphere
• Extends from about 50 to 80 Km altitude from the earth.
• Temperature decreases with altitude and the lowest temperature of the atmosphere are felt at the mesopause. (-80°C to -100°C)
• The meteors on reaching the mesosphere get burnt out due to friction.
• The zone of transition above the mesosphere is called mesopause.
Thermosphere
• Extends from about 80 to 600 Km altitude.
• There is a considerable increase in temperature with altitude.
• The lower part of the thermosphere is known as the ionosphere.
• Ionosphere helps in the transmission of radio waves.
44.What is a Normal Lapse Rate?
• In the troposphere the temperature decreases at a uniform rate of
1°Celcius for every 165 metres of altitude. This is called Normal Lapse
Rate.
45. There is a Normal Lapse rate in temperature with altitude.
i) Which layer of the atmosphere experiences a Normal Lapse rate?
ii) What is the Normal Lapse rate?
iii) Calculate the approximate temperature at an altitude of 1650 m when sea level temperature is 30o Celsius.
Answer:
i) Troposphere
ii) 10C / 165 m
iii) 1650/165 = 10
Temperature at 1650m= 30o - 10o= 20o C
46.What are Transition zones?
• Transition zones are the parts of the atmosphere separating the major
atmospheric layers.
47.What is an isothermal zone?
• In the lower parts of the stratosphere there is no change in temperature
with altitude. This zone is called the isothermal zone
48.Put a tick mark ( ✔) in the appropriate columns by identifying the
atmospheric layer to which the given statements are related.
49.Flow chart
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