Question

Answer in your own words.
(a) Explain with the help of a diagram how soil is formed.
(b) Why is there a shortage of water even though it occupies about 71% of the earth’s surface?
(c) What are the various constituents of air? Write their uses.
(d) Why are air, water and land considered to be valuable natural resources?

Answer 1

a. Soil is formed by the process of weathering during which rocks break down to form soil particles. This breaking down of rock occurs over a period of millions of years. Weathering can be physical, chemical, and biological. The bedrock breaks down into pieces due to the effects of heat, cold, water, wind and rain. Microbes, insects and rodents also help iin this process. The roots of trees also help in the process of weathering.




b. Although water occupies about 71% of the earth's surface, all of it is not potable water. Most of the water is available in the form of seas and oceans which is salty in nature. This saline water has its limitations and cannot be used for many purposes. Around 2.7% of water exists in frozen state or as groundwater which is unaccessible. Only 0.3% of water is available as potable water which is fit for human consumption.

c.

Constituents of air	Uses
1. Nitrogen	Required in building proteins. Useful in production of ammonia. Used in airtight packaging of food products.
2. Oxygen	Necessary for respiration and combustion.
3. Carbon dioxide	Used by plants to make their foods. Used in fire extinguishers.
4. Argon	Used in electric bulbs.
5. Heluim	Used for obtaining low temperatures. Used for generating lifts in airships.
6. Neon	Used in decorative lights and street lighting.
7. Krypton	Used in fluorescent tubes.
8. Xenon	Used in flash photography.

d. The following points elucidate the fact that air, land and water are valuable natural resources:


Importance of air:

• The importance of air can be understood by the fact that earth supports life becuase of the present of this air in our surrounding.
• It is required for various biological functions and biogeochemical cycles.

Importance of land:

• All terrestrial organisms live on land.
• We use it for the purpose of land farming, building houses, roads etc.
• The plants and animals which we use also grow on the land.
• The minerals which we obtain from deep inside the earth are also important resources. For example, petrol, coal etc.

Importance of water:

• Water plays an important role in various vital processes that are carried out by our body. All cellular processes take place in water medium.
• The availability of water plays an important role in deciding the number of individuals of each species that will be able to survive in a particular area, and also the sustainability of life in the region.
• Fresh water is utilized by humans for consumption.
• Water is central to the lives of aquatic animals which live in water.