8. Pollution
Complete solutions to the Exercises. Maharashtra State Board (Balbharati), Grade Eight General Science.
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Exercises
(a) Fog seems to be appearing in Delhi during day hours. Air pollution
(b) Many times, vomiting and dysentery occurs after eating ‘pani puri’. Water pollution
(c) Problem of sneezing occurs sometimes during visit to garden. Air pollution
(d) Crop does not grow up in some areas. Soil pollution
(e) People living in the busy squares face the problems like short breathing and other respiratory problems. Air pollution
- Heavy traffic while going to school and problem of asthma – Air pollution.
- Heaps of garbage at many places in the village – Soil pollution.
- Foul smell of human and animal wastes – Air pollution.
- Blackish water with foul smell flowing in a stream – Water pollution.
| Column ‘A’ | Column ‘B’ |
|---|---|
| 1. Water containing cobalt | b. Paralysis |
| 2. Methane gas | d. Skin cancer |
| 3. Water containing lead | a. Mental retardedness |
| 4. Sulphur dioxide | e. Irritation of eyes |
| 5. Nitrogen dioxide | c. Inflammation of lungs |
These pollutants enter our body through air and water. They damage the nerves, brain, skin, eyes and lungs.
(a) Water does not get polluted by washing the clothes in running water of river. False
Soap, detergent and dirt from clothes mix with river water. So the water gets polluted.
(b) More the use of electric appliances, more will be the pollution. True
Most electricity is produced by burning coal. More use of appliances means more burning of coal. So pollution increases.
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(a) What is pollution?
Contamination of the natural environment in a way that is harmful to ecosystems is called pollution.
(b) What are pollutants?
The factors that cause harmful effects on biotic and abiotic components of an ecosystem are called pollutants. Examples: Smoke, sewage, pesticides.
(c) What is acid rain?
Oxides of sulphur and nitrogen are released by burning fuels. They mix with water vapour in air and form acids. When these acids come down with rain, it is called acid rain.
(d) What is green house effect?
Carbon dioxide, methane, nitrous oxide and CFC trap the heat radiated by the earth. So the temperature of the earth rises. This is called green house effect.
The green house effect — heat from the earth is trapped by green house gases.
(e) Which are visible pollutants known to you?
Smoke, dust, garbage, plastic waste, sewage and oil floating on water.
(f) Which are invisible pollutants?
Carbon monoxide, sulphur dioxide, oxides of nitrogen, germs and dissolved chemicals in water.
(a) Give two examples of each of water, soil and air pollution from your residential area.
- Water pollution: Sewage flowing into a stream. Washing clothes at the river.
- Soil pollution: Heaps of garbage on open land. Plastic thrown on the ground.
- Air pollution: Smoke from vehicles. Burning of garbage.
(b) How does the pollution occur due to vehicles? Give the names of vehicles causing least pollution.
Vehicles burn petrol and diesel. The smoke contains carbon monoxide, oxides of nitrogen, sulphur dioxide and fine particles. This causes air pollution. Vehicles also cause noise pollution.
Vehicles causing least pollution: Bicycle, electric vehicles and CNG vehicles.
(c) What are natural reasons for water pollution?
- Growth of aquatic weeds.
- Decomposition of dead plants and animals.
- Mud and sludge brought by rivers.
- Soil erosion.
- Excessive growth of algae.
(d) Suggest four preventive measures for air pollution.
- Fit filters to factory chimneys.
- Do not burn garbage in the open.
- Control the production of CFC.
- Use public transport, bicycles and CNG vehicles. Plant more trees.
(e) Explain relation between green house effect and global warming.
Green house gases trap the heat of the earth. This is green house effect.
Due to industries and burning of fuels, these gases are increasing. So more heat is trapped. The average temperature of the earth is rising. This is called global warming.
Thus, increased green house effect causes global warming.
(f) Construct two slogans each on air, water and soil pollution.
Air:
- Plant a tree, breathe free.
- Clean air, healthy life.
Water:
- Save water, keep it clean.
- Pure water, healthy life.
Soil:
- Keep the soil clean, it gives us food.
- Waste in the bin, not on the land.
| Natural pollutants | Manmade pollutants |
|---|---|
| Dust | Sewage |
| Pollen grains | Chemical fertilizers |
| Algae | Vehicular smoke |
| Waste of animals and birds | Pesticides |