Important Questions for Class 8 Chapter 18 - Pollution of Air and Water

Important questions based on NCERT syllabus for Chapter 18 - Pollution of Air and Water:

Question-1: Describe greenhouse effect.

Solution: 1. A greenhouse is an enclosure of glass in which plants are kept to protect them from the cold air outside. The glass traps the heat of the sun, making the air inside warmer.
2. In a quite similar way, the carbon dioxide in the air traps the heat of the sun radiated back by the earth. This makes the air warm and comfortable for living beings, and in fact, makes it possible for life to exist on the earth.
3. But an excess increase in carbon dioxide has made much warmer than required and this is known as greenhouse effect.

Question-2: What are the methods of reducing air pollution?

Solution: We can reduce air pollution by :

  1. Modifying automobile engines such that complete combustion of fuel takes place and less amount of harmful gases are released.
  2. Using unleaded petrol will generate lead (poisonous) free exhaust and keep air cleaner.
  3. Using CNG i.e. compressed natural gas that burns completely and produces less pollutants when used as automobile fuel.
  4. Using cleaner souces of energy like hydroelectricity, solar energy, wind energy etc instead of burning fossil fuels (coal and petroleum) that on burning produce many air pollutants.
  5. Using better filters at the exaust of vehicles.

Question-3: Why does the increased level of nutrients in the water affect the survival of aquatic organisms?

Solution: 1. The increased in the level of nutrients in the water leads to an excessive increase in the population of algae in the water body.
2. When these algae die, they serve as food for decomposers.
3. A lot of oxygen is utilized in this process.
4. Consequently leading to a decrease in the level of oxygen dissolved in the water body.
5. This in turn causes fishes and other aquatic organisms to die.