General Science Solutions Solutions for Class 8 Science Chapter 8 - Pollution

Answer:

a. Air pollution
b. Water pollution
c. Air pollution
d. Soil pollution
e. Air pollution

Answer:

Nilesh is a student of std. VIII and lives in urban area.  It takes about an hour to go to the school by bus. He faces the heavy traffic of two wheelers, four wheelers, rickshaws, buses  (Air pollution) while going to school. He is facing the problem of asthma (Air pollution) since to stay away from urban area. Since then, his mother sent him to the village of his maternal uncle. Nilesh saw the heaps of garbage in many places in village. Foul smell of human and animal wastes (Air and soil pollution) was present at many places. Blackish water with foul smell (Water pollution) was flowing in a stream. He devleoped some abdominal disease (Water pollution) with in few days. 

Answer:

Answer:

A. Water does not get polluted by washing the cloths in running water of river. - False
B. More the use of electric appliances, more wil be the pollution. - True

Answer:

a. Pollution is any undesirable change that takes place in the environment which is harmful to both living and non-living things.

b. Pollutants are the harmful chemicals and substances that cause pollution. For example, nitrogen oxides, sulphur oxides, carbon monoxide, pesticides etc.

c. Gases such as sulphur dioxide, sulphur trioxide and nitrogen dioxide, when present in air, combine with the water droplets present in the atmosphere to form acid droplets. These droplets remain suspended in air and fall down on the earth along with rain, thereby making the rain acidic. Such rain is called acid rain.

d. The increase in the average temperature of the earth’s surface due to the increase in concentration of greenhouse gases such as carbon dioxide, methane, etc. is called greenhouse effect.

e. Pollutants which are visible to our naked eyes are called visible pollutants. For example, sewage, plant and animal wastes, pesticides, plastic, sand etc.

f. Invisible pollutants are pollutants which are not visible to our naked eyes. For example, fungi, viruses, bacteria, gases like carbon monoxide, nitrogen dioxide etc.

Answer:

a. Sources of air pollution:

Burning of fuel like wood, kerosene.
Vehicular emissions from automobiles.

Sources of water pollution:

Washing of clothes in flowing water bodies.
Release of domestic sewage into water bodies.

Sources of soil pollution:

Spraying of pesticides and insecticides on plants.
Mixing of wastes of animals and plants.


b. Most of the vehicles are run on fossil fuels like petrol and diesel. These fossil fuels are burnt in vehicles to produce energy which results in the production of smoke. This smoke conatins harmful gases like carbon monoxide, hydrogen, nitrogen oxide, particulate matter, ammonia and sulphur dioxide. 
There are various other kinds of vehicles which cause least or no pollution at all, for example. bicycle, vehicles run on CNG, electric cars, metro etc.
 

c. The natural reasons of water pollution are :

• Presence of aquatic weeds which depletes the oxygen content of water bodies.
• Excessive algal growth.
• Mud and sludge which are added to water bodies due to river currents and their diversions.
• Growth of microbes like bacteria and fungi on dead and decaying matter present in water bodies.

(i) Use of clean fuels such as CNG, LPG and unleaded petrol in public and private transport.

(ii) Use of renewable sources of energy such as solar, wind, and hydel energy.

(iii) Planting more and more trees to prevent pollution.

(iv) Preventing burning of dry leaves and using them in composting.


e. Greenhouse gases such as CO₂, methane, etc. are gases that absorb the heat of the Sun and the Earth and emit it back to the Earth’s surface. Thus, these gases prevent a part of the heat rays from escaping into the atmosphere. This cycle is repeated several times to maintain the Earth’s temperature to an optimum temperature of 15°C. Therefore, upto a normal level, greenhouse gases help in maintaining the temperature on the Earth.

However, the concentration of these gases has increased because of increased industrialization, which has lead to the heating up of the Earth’s surface. As a result, the overall temperature of the Earth has increased, resulting in climatic changes. During the last century, the temperature of the Earth has increased by 0.6°C. This has lead to global warming.

The greenhouse effect can be controlled by reducing the use of fossil fuels. Fossil fuels produce greenhouse gases on burning.

f. It is an activity based question. Kindly do it yourself.

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