1. Large scale burning of fuels can have a harmful effect on our environment. Describe the cause and effect of the following.
   (a) Photochemical smog
   (b) Carbon monoxide poisoning
   (c) Acid rain
   (d) Greenhouse effect

2. Compare the effects of greenhouse effect and global warming on the environment.

    The greenhouse gases such as CO₂ in the atmosphere trap the sun's heat and makes the earth hot.
   Global warming occurs when too much of greenhouse gases are released into the atmosphere, thereby increasing the temperature all over the world.

3. What do you mean by Marble Cancer?

    Acid rain corrodes the marble of the monuments. This phenomenon is called Marble Cancer.

4. What is acid rain? Why is it harmful?

    When fossil fuels are burnt, they release gases such as sulphur dioxide and nitrogen dioxide in the atmosphere. These gases react with water vapour present in the atmosphere to form sulphuric acid and nitric acid. This acid then drops down with rain and is called acid rain.
   Acid rain is harmful because it corrodes materials, harms living things and contaminates water supplies.

5. Name one of the poisonous element present in the exhaust of automobiles.

     Lead.

6. Look at the diagram shown below and answer the following questions.

  (a) State man's negative impact on the surrounding environment from the given diagram.
  (b) How can this negative impact be prevented?

    (a) The given figure shows water pollution, since rubbish, such as used cans and leftover food, can be spotted in the water. It has a negative impact on the environment because it may contaminate water sources or harm organisms living in the water.
   (b) The negative impact of water pollution can be prevented by:
   (i) Having proper and hygienic waste disposal systems.
   (ii) Educating people on the importance of keeping the environment clean.

7. Study the diagram below.

   (a) What two types of pollution can the above vehicles cause?
   (b) What can be done to reduce the pollution?

      (a) Movement of vehicles on the road contributes to noise pollution from movement and air pollution (from exhausts). The pollution is most when the number of moving motor vehicles on the road is highest.
     (b) Vehicles must be sent for servicing often. Also, if possible avoid the usage of personal vehicles, by using public transport (this reduces the number of vehicles on the road).

8. Study the given figure. 

  (a) What kind of waste is seen in the given figure?
  (b) What kind of effect does it have on environment?

    (a) The waste that comes out of factories is known as industrial waste.
   (b) It has negative impact on the environment. It causes water and air pollution. Industrial wastes usually contain a lot of toxic chemicals. These enter the nearby water bodies, polluting them, and killing the plants and animals living in the water bodies.
Similarly industries releases gases from burning which in turn causes air pollution. The air pollution in turn causes global warming, besides creating respiratory problems in people and animals living nearby.

9. The carbon and nitrogen cycle maintains a balance in an ecosystem. However, this 'balance of nature' has been disturbed by the action of man. How have the human's activity increased the amount of CO₂ in air and oxides of nitrogen in air?

    (a) Carbon dioxide in air : The level of CO₂ increased in the atmosphere due to
         (i) Burning of fossil fuels such as coal, oil, natural gas.
        (ii) Burning of forests.
    (b) Nitrogen dioxide in air : The level of NO₂ in atmosphere increased due to smoke released from vehicle exhausts.

10. Why do we feel suffocated and uncomfortable in a crowded traffic road?

        The vehicles on the road emit carbon monoxide from their exhaust. This gas is harmful for our body if inhaled. In a road crowded with traffic, there is more release of carbon monoxide gas, which causes suffocation and uncomfortable feeling.

11. List three ways of increasing the oxygen content of the air in an area 'X'?

     Three ways of increasing the oxygen content of the air in an area 'X' are:
     (a) Growing more and more trees.
     (b) Avoiding burning of waste and other harmful substances.
     (c) Minimizing pollution caused by vehicles, by using clean fuel like CNG.

12. The data table below compares cars and light trucks in regard to gas mileage and the amount of gases released into the environment (emissions).

    Based on the information in the table, what conclusion can be made about light trucks?

     Based on the information it can be concluded that light trucks cause greater negative impact on the environment than cars. This is because, they emit greater amount of nitrogen oxide and carbon dioxide in the environment, as compared to cars. Also they consume more fossil fuels (average is less) causing depletion of non-renewable resources.

13. (a) Explain why many scientists are concerned about the increased concentration of carbon dioxide and other greenhouse gases in Earth's atmosphere.
     (b) State one specific action that humans can take to reduce the rate of increase in the concentration of carbon dioxide in Earth's atmosphere.

      (a) Scientists are concerned about the increased concentration of carbon dioxide and other greenhouse gases in Earth's atmosphere because when too much of greenhouse gases are released into the atmosphere it can lead to global warming. Global warming, is an increase in Earth's average temperature. This increases in temperature affects the climate, making storms more unpredictable and severe, causing a rise in ocean level through melting of polar ice caps and similar other problems.
      (b) By growing more and more trees we can reduce the rate of increase in the concentration of carbon dioxide in Earth's atmosphere. Plants take in carbon dioxide to prepare their food and gives out oxygen to the atmosphere.

14. What will happen to the candle when a beaker is inverted and lowered onto a burning candle?

      The candle will stop burning, when the oxygen present inside the beaker is used up.

15. What are the causes of indoor air pollution? How to prevent or minimise it?

       Indoor air pollution means the pollution of air due to human activities inside home. The use of paints, aerosols, acids for cleaning toilets, sprays and deodorants, carpet cleaners, objects made from recycled plastics etc. produces vapours which are quite harmful for our health. Indoor pollution can be minimised by flushing fresh air after the use of above activities.

16. Burning of fossil fuels causes pollution. Comment.

     Fossil fuels such as coal, wood, petroleum oil, natural gas are burnt to provide a source of energy. Their combustion not only produces energy and carbon dioxide but other poisonous gases like carbon monoxide, sulphur dioxide, oxides of nitrogen and smoke particles. Thus lot of atmospheric pollution is caused by burning of fossil fuels. 

17. What are aerosols? How are these dangerous?

        The solid particles or liquid droplets in air are called aerosols. These can enter the buildings and are more dangerous because of their great sticking power to materials.

18. "Hot water can also be a pollutant" explain How?
       Hot water is usually, water from power plants and industries. It is released into rivers. It raises the temperature of the water body. It adversely effects the animals and plants living in it.

19. Explain Ganga Action Plan.

        An ambitious plan to save the river is called Ganga Action Plan launched in 1985. It aims to reduce the pollution level in the river. However, the increasing pollution and industrialisation have already damaged this mighty river beyond repair. Ganga at Kanpur in Uttar Pradesh, has one of the most polluted stretches of the river. Kanpur is one of the most populated town in U.P. People can be seen bathing, washing clothes and defecating in the river. They also throw garbage, flowers, idols of gods and goddesses and non-biodegradable polythene bags into river. The industrial units discharge toxic chemicals and wastes into the river. Due to these causes, the water is polluted in Ganga. Ganga Action Plan is related to reduce pollution in Ganga.

20. Explain the process of water treatment to make it drinkable.

      The water obtained from various sources is pupmped, from sources such as river or lake and is collected in a tank. The water is then cleaned in water work by allowing it to filter through layers of gravel and sand. It removes the dirt from water. Then water is treated with some chemicals like chlorine to kill the germs. The water is then supplied to the localities where it is to be used for drinking purposes.