Our Environment class 10 notes


1. What is environment ?

 Ans. The sum total of physical and biological factors that directly influence the survival , growth , development and reproduction of organisms is called Environment. 

2. What is atmosphere ? 

Ans. Our earth is surrounded by a blanket of air. This layer of air is called the Earth’s atmosphere. 

3. What is environmental chemistry ? 

Ans. The branch of chemistry deals with the study of various chemical phenomena occurring in the the environment is called Environmental chemistry. 

4. What are the different layers of the atmosphere according to variation in temperature. Describe each of them along with the characteristics. 

Ans. The different layers of the atmosphere according to variation in temperature are:

 I. Troposphere: The lower most layer of the atmosphere or closet layer to the earth’s surface is called Troposphere. Characteristics: a) In this layer temperature decreases at the rate of 6.4°c for every 1000 meter or 1 km ascent. b) 75% of the gaseous elements of the atmosphere belongs to this layer. 

II. Stratosphere: the second layer of the earth’s atmosphere which lies above tropopause and extend upto 50 km above the surface of the earth is called Stratosphere.Characteristics: a) In this layer temperature increases with increasing altitude due to the absorption of solar radiations by the ozone layer. b) Water vapour or cloud is absent in this layer except the noctilucent clouds. 

III. Mesosphere: The third layer of the earth’s atmosphere which extends upto 80 km above the surface of the earth is called Mesosphere. Characteristics: a) In this layer temperature decreases with increasing height. b) Meteors that come from the outer space towards the earth get burn’t in this layer. 

IV. Thermosphere: The layer above mesopause where temperature rises rapidly and becomes nearly 1200°c at an elevation of 500 Km is called the Thermosphere. In this layer, ionisation of gas molecules take place and as such this layer is also called Ionsphere. 

Characteristics:      a) In this layer temperature increases with increasing height due to the absorption of x-rays and short wave radiation of the sun by the gas molecules present in this layer. 

b) from the ionosphere radio – waves are reflected back to the earth. It helps in maintaining the world radio communication system. 

5. What is ozonosphere? 

Ans. Ozone is a colourless gas with a strong smell. The highest concentration of ozone lies within the altitude of 12 km to 35 km in the stratosphere. This zone is called ozonosphere or ozone layer. 

6. Write a short note on depletion of ozone layer. 

Ans. The destruction of ozone layer takes place by two process— 

a) Natural process: Photochemical decomposition of ozone molecule takes place by the absorption of light of short wavelength . O3 + hv →*O+ + O2 by atmospheric nitric oxide (NO) O 3 + No→ O2 + NO.

 b) Anthropogenic reason: oxides of nitrogen (NOx) emitted by supersonic aircrafts during combustion of fossil fuels NOX produced during nuclear explosions chlorine liberated from chlorofluoro carbons (CFC) break ozone molecules CFCl3 (g) + hv →CFCl2 (g)+Cl(g) Cl+O3→ClO+O2 ;ClO+O3→2O2+ClThe released Cl-atom again convert O3 to O2 in the stratosphere. NO + O3 → NO2+ [O] ;NO+ O2 →NO2+ [O] .

7. what do you mean ozone hole? 

Ans. The phenomenon of thinning of the ozone layer of the Stratosphere is known as depletion of ozone layer or ozone hole.

 8. What are the harmful effects of ozone depletion? 

Ans. The harmful effects of ozone depletion are as follow— a. Human Health — UV radiations are sufficiently energetic to break apart important biological molecules. b. Skin — Exposure to UV radiation causes the connective tissue of the skin damage. Thus skin becomes wrinkled loses it elasticity. If the exposure continues, the skin becomes Coarsely furrowed and lumpy. Besides, it has been estimated that a 1% decline in ozone layer could lead to 4 to 6% increase in the probability of skin cancer. c. Eyes — uv radiation can damage the lens of eye. cataract even blindness can result. i. Leaves of the plant will be discoloured as photosynthesis will be affected. ii. In Marine organisms will be destroyed.. iii. Agricultural Productivity will be reduced. iv. ozone depletion will cause increase of temperature as ultraviolet rays will reach the earth’s surface easily.

 9. What is the full form of UNEP?

 Ans. United Nation Environmental programme. 

10. What is green house effect?

Ans. The natural Process by which a layer of green house gases present in the atmosphere surrounding the earth’s surface, instead of allowing the infrared radiation reflected by earth’s surface to pass out into the outer space , partly absorb the radiated heat and reflected back to the earth’s surface and thus keep the surface of the earth and the adjacent atmosphere warm, which is not suitable for the existence of the living beings, is known as greenhouse effect. 

11. What is green house?

 Ans. Green house is a large Chamber made of glass on the soil.When the plants of tropical countries are taken to cold countries,they cannot adapt themselves to the climatic conditions of the cold Countries. 

12. Name some green house gases.

 Ans. Carbon dioxide(CO2), Methane(CH4), Water vapour(H2O), Chlorofluoro carbon(CFC), Nitrous oxide(N2O), Ozone(O3). 

13. Name the two gases which are not greenhouse gas. 

Ans. Oxygen(O2), Nitrogen(N2). 

14. What are the major sources of anthropogenic greenhouse gases? 

Ans. The main sources of greenhouse gases due to human activities are: 

I. A number of factories all over the world burn immense quantity of coal, oil and natural gases and produce huge quantity of carbon dioxide. 

II. Power stations based on to sail fuels are major sources of man-made carbon dioxide.

III. A large fleet of automobiles , railways, aircraft etc use an immense quantity of diesel and Petrol reasoning huge amount of carbon dioxide every year. 

IV. Burning of fire woods and deforestation are the major sources for the production of Carbon dioxide. 

V. chlorofluoro carbons are released from coolants. 

 15. What are the consequences of greenhouse gas? 

Ans. Climatic Changes:   i. Due to global warming the oceans get warm up and gear sea level would rise flooding low-lying reasons. ii. In temperate regions , the winter will be shorter and warmer but the summer will be longer and hotter. iii. There will be enormous increase in rainfall but the problems of desertification, drought and soil erosion will further’ Worgen.iv. The tropics may become wetter but the Subtropics, which are already dry, are expected to be drier. 

Other changes: i. Melting of ice- caps will be found over Polar regions. ii. Due to greenhouse effect and much warmer tropical oceans, there may occur cyclones and hurricanes and snow melting mountains will cause more floods during monsoon. iii. A rise in atmospheric temperature will increases the evaporation of sea water increasing the humidity. 

16. What are the measures to control greenhouse effect? 

Ans. → To reduce the consumption of fossil fuel such as coal and petroleum.→ To depend more on non-conventional renewable source of energy such as wind, solar, biogas, etc. → There should be restriction on the emission of CO2 and CFCs from the factories and utomobiles.

 17. What is global warming? 

Ans. The phenomenon of gradual increases of temperature all over the world is called global warming. 

18. What do you mean by sustainable development? 

Ans. Sustainable development is the development that meets the needs the present without compromising the ability of future generations to meet their own need.

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