7th Class Science Water: A Precious Resource Scarcity of Water

       Scarcity of Water

The reasons for the scarcity of water are:

Pattern of Rainfall: The rainfall occurs mainly in rainy season. Therefore, there is scarcity of water in the other seasons.

Loss of Water: All the rain water that falls on the ground cannot be utilized and is lost due to evaporation and runs off the land into streams.

Overuse: Overuse of water is another reason for its scarcity.

Pollution: Pollution of water bodies is one of the main causes of scarcity of water.

Deforestation: Deforestation of hill slopes and other areas leads to excessive runoff of water. In addition to this, negligence and non-proper maintenance of old water tanks, ponds and wells leads to water shortage

       What is the chemical formula of water?  

(a)

(b)  

(c)

(d)

(e) None of these  

Answer: (b)    

       In which one of the following states water is present on earth?

 (a) Solid

(b) Liquid

 (c) Gas

(d) All of these

(e) None of these

Answer:  (d)

Water is a chemical substance with the chemical formula.

A water molecule consists of one oxygen and two hydrogen atoms.

Only 2.5% of the water available on the earth is fresh water.

Approximately 70% of the fresh water used by human beings is for agriculture.