NCERT Solutions for Class 8 Science Chapter 18 Pollution of Air and Water

Ans : Water gets contaminated by the addition of: 
(i) Agricultural chemicals: Farmers use excessive amounts of pesticides and fertilizers to increase crop production. These chemicals get carried away to the later bodies due to rains and floods which lead to water pollution. 
(ii) Industrial wastes: Industries release harmful chemical wastes into water sources, thereby polluting them. 
(iii) Sewage wastes: Waste materials from kitchens, toilets, and laundry sources are also responsible for contaminating water. 

Ans : An individual can reduce air pollution by: 
(i) Avoiding the use of cars as much as possible and by using public transport whenever possible. 
(ii) By not using vehicles for short distances. 
(iii) By using clean fuels such as LPG and CNG instead of diesel and petrol. 
(iv) Always disposing the garbage properly and not burning it. 
(v) Controlling the emissions from vehicles and household chimneys. 

Ans : No. Clear and transparent water is not always fit for drinking. Water might appear clean, but it may contain some disease causing micro-organisms and other dissolved impurities. Hence, it is advised to purify water before drinking. Purification can be done by water purifying systems or by boiling the water. 

Ans : To ensure the supply of clean water to all residents the following steps must be taken: 
(i) The main water source must be built in clean surroundings and should be maintained properly. 
(ii) Chemical methods such as chlorination must be used for purifying water. 
(iii) The area around water pipes must also be clean. 

Ans : Pure air contains around 78% nitrogen, 21% oxygen, and 0.03% carbon dioxide. Other gases such as argon, methane, ozone, and water vapours are also present in small quantities. When this composition of air is altered by the addition of harmful substances or gases such as nitrogen dioxide, sulphur dioxide, carbon monoxide, and particulate matter, then the air is said to be polluted.