NCERT Solutions Class 8 Science
The NCERT Solutions in English Language for Class 8 Science Chapter – 18 (Pollution of Air and Water) has been provided here to help the students in solving the questions from this exercise.
Chapter – 18 (Pollution of Air and Water)
1. What are the different ways in which water gets contaminated ?
Answer – The different ways in which the water gets contaminated are listed below:
(i) Industrial waste: The harmful chemical wastes get released by the industries into water sources.
(ii) Sewage waste: Kitchen, laundry, and toilets release waste materials, and this pollutes water.
(iii) Agricultural chemicals: Excessive amounts of pesticides and fertilizers are used by farmers to enhance crop production. Rains and floods carry these harmful chemicals to water bodies, which results in water pollution.
(iv) Land waste: Due to improper disposal of day-to-day waste, the rain water gets contaminated.
2. At an individual level, how can you help reduce air pollution?
Answer – Air pollution should be checked at individual level in the following ways :
- We can use public transportation and encourage carpooling so that air pollution can be reduced.
- Instead of going by cars and scooters for short distances, we can go walking or by bicycle.
- By saying no to crackers we can minimise air pollution as well as noise pollution.
- We can plant trees as they reduce air pollution.
- By disposing of garbage properly and not burning it. As burning of garbage releases greenhouse gases which are responsible for global warming.
- By taking care that dry leaves are dispose-off properly. As they tend to burn on their own which pollutes the air.
- By using cleaner fuels like CNG and LPG instead of petrol and diesel.
- By controlling the emissions of vehicles and household chimneys.
3. Clear, transparent water is always fit for drinking. Comment.
Answer – No, clear, transparent water may not always be fit for drinking. It may still contain harmful disease causing microorganisms. We should always purify this water, with the help of water purifiers or by boiling them, before using it.
4. You are a member of the municipal body of your town. Make a list of measures that would help your town to ensure the supply of clean water to all its residents.
Answer – We can ensure supply of clean water by
- Using chlorination to purify water.
- Prohibiting Open defecation in water resources.
- Water tanks and pipes should be kept clean.
- We should make a rule that industries in the town should process their waste before throwing it in the river.
- Throwing of plastics in the river should be banned.
- Making people aware as how to keep water clean
5. Explain the differences between pure air and polluted air.
Answer –
| Pure Air | Polluted Air |
| Air which is fit for breathing is called pure air | Air which is not fit for breathing is called Polluted air |
| All gases in the correct ratio | Harmful gases are in higher ratio |
| Smog is present | Smog is not present |
| It is free of dust and harmful gases | It has dust and harmful gases |
| Not harmful for Human Beings and Animals | Harmful for Human Beings and Animals |
6. Explain circumstances leading to acid rain. How does acid rain affect us?
Answer – The harmful gases like sulphur dioxide and nitrogen dioxide, react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. These acids then drop down with rain, making the rain acidic. This is called acid rain. The harmful effects of acid rain:
- Acid rain causes skin irritation.
- Inhibits germination of plants.
- Causes corrosion to bridges and buildings.
- It changes the fertility of the soil.
- Destroys plants and aquatic life.
7. Which of the following is not a greenhouse gas?
(a) Carbon dioxide
(b) Sulphur dioxide
(c) Methane
(d) Nitrogen
Answer – (d) Nitrogen
8. Describe the ‘Green House Effect’ in your own words.
Answer – Greenhouse Effect means warming the Environment. When the sun rays reach on earth, a part of the radiation that falls on the earth is absorbed by it and a part is reflected back into space. A part of the reflected radiation is trapped by the atmosphere. This trapped radiation further warms the earth. This is called Carbon House effect. CO2 is one of the gases responsible for this effect.
9. Prepare a brief speech on global warming. You have to deliver the speech in your class.
Answer – Continuous increase in temperature of the earth is called global warming. There are many reasons for it. One of them is increase in population. Increase in the number of vehicles is also one of the causes. Pollution of air has also increased the global warming. Cutting trees, grazing the plants by animals increase the global warming.
10. Describe the threat to the beauty of the Taj Mahal.
Answer – The major threat to the Taj Mahal is acid rain. When the acid rain falls on the Taj, which is completely made of marble, they react with marble to form a powder-like substance which is then washed away by the rain. This phenomenon is known as marble cancer. In addition, the soot particles emitted from the Mathura oil refinery located near Agra are leading to the yellowing of the Taj Mahal marble.
11. Why does the increased level of nutrients in the water affect the survival of aquatic organisms?
Answer – Excessive quantities of chemicals get washed away from the fields. These act as nutrients for algae to flourish. Once these algae die, they serve as food for decomposers like bacteria. A lot of oxygen in water body gets used up. This results in the decrease in the oxygen level which may kill aquatic organisms.
