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Q1. Explain the effects of acid rain on: 1. Aquatic life 2. Statues and bridges

Solution

1. Acid rain disrupts the reproductive cycle of aquatic species. It also leaches aluminum from the soil into the water, clogging the fish's gills and altering their blood chemistry. As a lake becomes acidified, one species after another disappears. 2. Acids present in the acid rain corrodes metals resulting in weakening of the bridges. Acid rain dissolves marble and stone and hence damages the statues.

Q2. What is marble cancer?

Solution

The corrosion of the marble of monuments due to acids present in acid rain is called marble cancer.

Q3. What happens when algae growing in water die?

Solution

Once the algae die, they serve as food for decomposers like bacteria. A lot of oxygen in the water body gets used up. This results in a decrease in the oxygen level which may kill aquatic organisms.

Q4. What is an industrial effluent and what does it contain?

Solution

Wastewater from industries is called industrial effluent. It contains toxic chemicals including oils, greases, dyes, acids, alkalis and toxic metals such as cadmium and lead.

Q5. Expand DDT.

Solution

DDT - Dichlorodiphenyltrichloroethane

Q6. (i) Which phenomenon causes global warming?(ii) What is the minimum increase in temperature that can cause global warming?

Solution

(i) Green house effect (ii) Increase in the earth's temperature by even as little as 0.5ºC can have such a serious effect of global warming.

Q7. Explain why, hot water released by industries and power plants considered a pollutant?

Solution

Hot water from the power plants and industries is released into the rivers. It raises the temperature of the waterbodies, adversely affecting the animals and plants living in it. Hence, it is considered as a pollutant.

Q8. Name the different types of air pollutants? Give one example of each.

Solution

Types of air pollutants: 1. Solid pollutants for example, dust. 2. Gaseous pollutants for example, carbon monoxide.

Q9. List some pollutants released in the air by industries.

Solution

Industries and factories release sulphur dioxide, carbon dioxide, particulate matter and dust into the air.

Q10. What do you mean by leaching? Give its consequence?

Solution

The process of washing away of fertilizers into water bodies is called leaching. The entry of nutrient rich water results in a thick growth of algae called algal bloom which causes eutrophication.

Q11. At what temperature are microorganisms present in water killed?

Solution

Most microbes found in water are killed at a temperature of 100^oC, i.e. the boiling point of water.

Q12. What do the bacteria present in the faeces of mammals indicate?

Solution

The bacteria present in the faeces of mammals are indicators of the quality of water. If water has these bacteria, it means that it has been contaminated by fecal matter. If such water is used by us, it can cause various infections.

Q13. What are the major sources of the following pollutants: 1. Particulate matter 2. Chlorofluorocarbons

Solution

1. Particulate matter- Volcanic eruptions, dust storms, burning of fossil fuels are the natural sources of these pollutants. 2. Chlorofluorocarbons- Coolants in refrigerators and air conditioners and propellants in aerosol apray cans, plastic foams are common sources of these CFCs.

Q14. According to the Ganga Action Plan, how is river water cleaned?

Solution

The polluted water of the Ganga is cleaned by intercepting and diverting waste water to sewage treatment plants instead of letting it flow directly into the river.

Q15. What is responsible for destroying the beauty of the Taj? What measures are being taken to save it?

Solution

Gases like Sulphur dioxide and nitrogen dioxide are responsible for destroying the beauty of Taj. These gases are emitted by Mathura oil refinery and other rubber processing, automobile chemical industries working in and around Agra. These gases react with moisture and produce sulphuric acid and nitric acid. These acids fall on earth along with rain due to which colour of white marble has started to fade and marbles are getting corroded. Various measures are being taken to save the beauty of Taj. The Supreme Court of India has ordered the industries to switch over to cleaner and pollution free fuels. Automobiles have been ordered to use CNG and LPG as the fuel. Unleaded petrol will only be made available to be used as fuel in vehicles.

Q16. What are sources of pollution for the river Ganga?

Solution

Large quantities of garbage, untreated sewage, dead bodies, industrial waste and many other harmful things are directly thrown into the river. All these things act as sources of pollution.

Q17. How does amount of CO₂ rise in atmosphere and become excessive?

Solution

Amount of CO₂ rises in atmosphere and become excessive due to following human activities: (i)Burning of fuels like coal, petrol or diesel etc. (ii)Deforestation which leads to an increase in amount of CO₂ in the air because the number of tress which consume CO₂ is reduced.

Q18. Which industry has particularly lead to the yellowing of the marble of the Taj Mahal?

Solution

Soot given out from the Mathura oil refinery has lead to the yellowing of the Taj Mahal marble.

Q19. How is acid rain caused?

Solution

When rain water becomes acidic in nature, it is called acid rain. Different industries produce pollutants like sulphur dioxide and nitrogen dioxide. These gases react with moisture present in the atmosphere and produce sulphuric acid and nitric acid. These acids fall on earth along with rain and this is called acid rain.

Q20. How is global warming caused?

Solution

Undue increase in temperature of earth's atmosphere due to excessive greenhouse effect is called global warming. The green house gases such as CO₂, water vapours, methane etc. form a thick layer around the earth. When the heat rays coming from the sun fall on earth's surface, some of these rays are absorbed by earth and some are reflected back. Thus, cover of greenhouse gases does not allow these heat rays to leave earth's atmosphere completely. This effect keeps the earth's atmosphere warm. Rising amount of CO₂ causes more and more heat rays to be trapped in the earth's atmosphere. This results in excessive heating of earth's atmosphere, and therefore, temperature of earth's atmosphere rises. This results in global warming.

Q21. (i) Name two acids responsible for formation of acid rain. (ii) Which refinery is producing pollutants near Taj Mahal?

Solution

(i) Sulphuric acid and nitric acid are the acids responsible for the formation of acid rain. (ii) Mathura oil refinery

Q22. What is meant by water pollution?

Solution

When water is contaminated by unwanted substances which have a harmful effect on both the living and the non-living, it is referred to as water pollution.

Q23. How water pollution control helps in the conservation of energy?

Solution

Pollution control contributes to energy conservation by reducing the amount of energy needed to clean up very large pollution problems, as they are encountered when they are smaller and easier to correct. Water pollution control also means less water filtration and purification is needed, which will save a lot of energy.

Q24. What is "Ganga Action Plan" and when was this plan launched?

Solution

It is an ambitious plan to save the Ganga river. Ganga Action Plan was launched in 1985. It aimed to reduce the pollution levels in the river.

Q25. List a few disease-causing microorganisms which can be found in sewage water.

Solution

Sewage carries the microorganisms for certain water-borne diseases such as cholera, dysentery, jaundice, typhoid and diarrhoea.

Q26. How boiling helps in the purification of water?

Solution

Boiling can be used as a method for obtaining safe drinking water. Boiling kills the germs present in the water and thus makes water potable.

Q27. How does domestic wet waste contribute to air pollution?

Solution

Domestic wet waste is subject to decomposition and thus releases foul odour and CO₂ into the atmosphere, polluting the air.

Q28. (a) Name any two green house gases.(b) What causes global warming?

Solution

(a) Carbon dioxide (CO₂), methane (CH₄), ozone (O₃) and water vapour (H₂O) are green house gases. (any two)(b) The greenhouse gases do not allow heat rays to escape from the earth resulting in an increase of temperature of the earth. Hence, green house gases cause global warming.

Q29. How does rising content of CO₂ responsible for increasing temperature of earth?

Solution

The sun sends its rays to the earth. Some of these rays are absorbed by the earth atmosphere and some radiations are reflected back. CO₂ traps heat and does not allow it to escape into space. This effect keeps earth's atmosphere warm. Rising amount of CO₂ causes more heat rays to be trapped in the atmosphere. This result in excessive heating of earth's atmosphere, therefore, temperature rises.

Q30. Name the organisms due to which the ponds often look green in colour? What is the source for  growth of such organisms?

Solution

The green colour is because of algae which is produced in the pond's water. The deposition of algae is caused by excessive quantities of chemicals which get washed from the fields in the rivers or ponds. These act as nutrients for algae to flourish.

Q31. What is eutrophication?

Solution

Eutrophication may be defined as the process of increase in the nutrient content of the aquatic ecosystem followed by the excessive growth of algae and weeds on the water surface.

Q32. Expand LPG and CNG.

Solution

CNG - Compressed Natural Gas LPG - Liquefied Petroleum Gas

Q33. How do pesticides and weedicides pollute water?

Solution

chemicals present in pesticides and weedicides dissolve in water and are washed into water bodies from the fields. They also seep into the ground to pollute ground water.

Q34. (i) What are the major oxides responsible for acid rain? (ii) How do these oxides present in air affect buildings?

Solution

(i) Oxides of sulphur and nitrogen are the major oxides responsible for the formation of acid rain. (ii) Gases like sulphur dioxide and nitrogen dioxide present in air react with moisture and produce sulphuric acid and nitric acid. Due to these acids, pH of rain water decreases. These acids fall on earth along with rain. This acid rain reacts with marble and slate and damages the buildings.

Q35. How does deforestation lead to an increase in amount of CO₂ in air?

Solution

Plants utilise CO₂ from the atmosphere for photosynthesis, thereby decreasing the amount of CO₂ in the air. Deforestation leads to an increase in the amount of CO₂ in the air because the number of trees which consume CO₂ is reduced.

Q36. How does the Indian legal system protect the Taj Mahal from pollution?

Solution

The Supreme Court of India has ordered industries in and around the Taj Mahal to switch to LPG and CNG. It has also ordered vehicles to switch to unleaded petrol in the Taj zone to reduce pollution in the area and to protect the monument.

Q37. How green house effect is important to life? Write any three ways.

Solution

(i)The presence of CO₂ and other gases in the atmosphere produce greenhouse effect, which keeps the atmosphere warm. (ii)The warm atmosphere helps in the rapid growth of plants, trees, etc. These are sources of food, shelter etc. (iii)The warm atmosphere is necessary for evaporation of water, formation of clouds, rainfall, etc. All forms of life depend on these resources.

Q38. (i)What is trapping of radiation of sun by the atmosphere of the earth called? Explain the process. (ii)Name any two gases responsible for above phenomenon.

Solution

(i) Green house effect the sun sends its rays to the earth. Some of these rays are absorbed by the earth atmosphere and some radiations are reflected back. Thus, cover of green house gases does not allow the heat rays to leave earth's atmosphere completely. This effect keeps earth's atmosphere warm. (ii) CO₂, Methane(CH₄)

Q39. Write any two effects of water pollution.

Solution

(i) Industrial wastes discharged into the waters contain a lot of toxic substances that make water unfit for drinking and bathing. (ii) Pollution of water also leads to a reduction in the number of aquatic plants and animals due to destruction of habitat and nesting places.

Q40. How is drinking water purified by using chemical method?

Solution

Chemical treatment is one of the most important drinking water purification methods. The most commonly used chemicals for drinking water purification are chlorine and iodine. These chemicals kill almost all the disease-causing microorganisms present in the water and make the water pure.