Atmosphere
1. Choose the right option:
a) Melting of polar ice caps is taking place due to
i) Global warming.[√]
ii) Rise in salinity of the sea.[ ]
iii) Drying up of rivers.[ ]
b) Global warming would lead to
i) Increase in the density of air.[ ]
ii) Change in the ions of the ionosphere.[ ]
iii) Cyclones and hurricaness in coastal areas.[√]
c) The main objective of the Montreal Protocol was
i) To increase global forest cover.[ ]
ii) To reduce pollution of water bodies.[ ]
iii) To lower the production of Ozone Depleting Substances.[√]
d) The ozone layer helps in
i) Preventing the ultraviolet rays from reaching the earth.[√]
ii) Preserving the optimum temperature of the earth.[ ]
iii) Absorbing the polluting gases released by the earth.[ ]
2. Give one term for each of the following:
a) The gas that occupies the maximum volume of the atmosphere. [ Nitrogen ]
b) The upper limit of the troposphere that separates it from the stratosphere. [ Tropopause ]
c) The coldest layer of the atmosphere. [ Mesosphere ]
d) A fossil fuel that contributes to global warming. [Coal ]
e) The hottest layer of the atmosphere. [ Thermosphere ]
f) The continent over which a large ozone hole has developed. [ Antarctica ]
g) Harmful rays that lead to cataract and skin cancer in human beings. [ Ultra Violet ]
3. Give one reason to explain each of the following:
a) All changes in weather conditions occur in the troposphere.
= All changes in the weather conditions involving clouds, rain, snow, fog and storm, occur in the troposphere due to the presence of water vapour.
b) The stratosphere protects the earth from extremes of temperature.
= This layer of the atmosphere acts as a blanket protecting the earth from extreme heat during the day. It also traps terrestrial heat, therefore keeping the earth warm during the night.
c) Stratosphere provides ideal flying conditions for aircraft.
= This is because of absence of water vapour makes this free from weather disturbances. Hence, no turbulence can be felt.
d) Meteors slow down and burn up when they enter the mesosphere.
= This layer is of vital importance as meteors slow down and burn up due to friction and frictional heat when they enter the mesosphere.
e) Deforestation contributes to global warming.
= Forests are a major carbon sink and in their absence the carbon dioxide level in the atmosphere increases, which traps heat in the atmosphere leading to global warming.
f) Incandescent light bulbs should be replaced by CFL bulbs.
= Because they consume less energy as compared to incandescent bulbs.
4. Answer the following questions in brief:
a) Define atmosphere. Why is it denser in its lower layers?
= The atmosphere is made up of a mixture of gases that form a layer surrounding the earth.
Though, the atmosphere extends beyond 1500 km above the earth's surface, 99 per cent of its mass lies within a height of 32 km from the ground. This is because the density of the atmosphere is greater in the lower layers.
b) What are ions? Why is their presence in the atmosphere significant?
= The temperature increases with height as this layer absorbs various types of solar radiations. This result in the breaking up to the molecules of atmosphere gases into electrically charged particles called ions.
These ions reflect radio waves back to the earth and enable. Radio broadcast and wireless communication.
c) Discuss how an ozone hole is created.
= Certain human activities release chlorofluorocarbon and other harmful chemicals that destroy the beneficial ozone and splits it apart. Thus, they are a major cause behind the thinning of the ozone layer and an ozone hole is created.
d) Why do polar bears face extinction in near future?
= Polar ice caps are becoming thinner and melting at an alarming rate due to global warming. The loss of sea ice habitats due to climate change is biggest threat to the survival of polar bears and they face extinction in near future.
5. Answer the following questions in detail.
a) Discuss the composition of the atmosphere.
= Nitrogen is the one most abundant gas in the atmosphere. It comprises about 78 percent of the total volume of the atmosphere. Oxygen forms 21 per cent of the atmosphere. The remaining 1 per cent consists of minute quantities of various gases such as carbon dioxide, hydrogen, helium, ozone, argon and others. In its lower layers, the atmosphere contains varying amounts of water vapour and also suspended solid particles such as dust, salt and pollen.
b) Discuss the importance and significance of the three Rs in bringing about sustainable development.
= By following the three Rs - Reduce, Recycle and Reuse - strategy, we can use natural resources for our growth as well as save them for the need of our growth as well as save them for the need of the future generations. This is called sustainable development.
We must reduce the use of natural resources so that they do not get depleted.
We must reuse resources instead of throwing them away after each use. 'Reuse' conserves new resources and prevent old resources from entering the waste stream.
We must 'Recycle' or convert waste materials into new products changing them from their original form by physical and chemical processes. In this way, not only is waste reduced but resources are also conserved.
c) What are the special features of an eco-city or green city? Give two examples.
= Efforts should be made to hasten the development of green cities or eco-cities. These cities are urban areas around the world striving to lessen the environmental impacts of urbanization by reducing waste, encouraging recycling, lowering emission levels as well as reducing levels of air, water and soil pollution. Some notable green cities include Copenhagen, Amsterdam, Stockholm, Vancouver, London, Berlin, New York, Singapore, Helsinki and Oslo.
d) Why are renewable source of energy preferred over fossil fuels? Give two examples of renewable sources of energy.
= We need to decrease the emission of greenhouse gases by reducing the burning of fossil fuels such as coal and petroleum. Instead we should switch over to renewable sources of energy such as wind, sun, water, and tides. They are not only cheap and abundant but are also non-polluting.
e) State four initiatives you as a student can take to improve the environment in which you live.
= As a student, I can improve the condition of the environment by planting more trees to increase forest cover. We can reduce excessive release of carbon dioxide in the air. the government also distributes tree saplings and organise afforestation programmes to spread awareness regarding the beneficial effects of trees.