CBSE Class 8 Science • Chapter 20 • Detailed Master Notes
Chapter Overview
Water is essential for life, but human activities are continuously compromising its quality. In this chapter, we explore how water gets polluted, its effects on living organisms, and methods for purification and conservation.
A growing population, industries, and agriculture are rapidly consuming our water resources. Along the way, we are adding harmful materials into rivers, lakes, and oceans.
Water Pollution: Whenever harmful substances such as sewage, toxic chemicals, silt, etc., get mixed with water, the water becomes polluted. The substances that pollute water are called water pollutants.
The Ganga is one of the most famous rivers in India, but millions of people living in towns and cities along its route throw large quantities of garbage, untreated sewage, dead bodies, and many other harmful things into it.
To save the river, the Ganga Action Plan was launched in 1985. It aimed to reduce pollution levels in the river. However, increasing population and industrialization have already severely damaged the river.
AI Image Prompt: A scientific educational illustration showing sources of water pollution. A river flows through the center. On one side, a factory is shown discharging green toxic liquid through a pipe into the river. On the other side, an agricultural field is shown with rain washing white pesticide runoff into the river. Clean, educational style.
We must ensure that the water we drink is safe and free from disease-causing microorganisms.
Potable Water: Water which is suitable for drinking is called potable water.
Q1. Why is it dangerous to excessively chlorinate water?
Ans: While chlorination destroys germs, it is a chemical process. Adding more chlorine tablets than specified can make the water chemically toxic and harmful for human consumption.
Water is a precious natural resource. We must learn how to conserve it. The strict mantra is: Reduce, Reuse, and Recycle.