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Characteristics of water:

1. Colourless, odourless
2. Dissolves many substances readily (universal solvent)
3. Tasteless.
4. Occurs in three states: Solid (ice), Liquid (water), Gaseous (water vapour)

The blood of animals and the sap in plants contain a very high proportion of water.

Water available on earth:

1. Water in seas and oceans: 97%
2. Ground water, frozen state (ice): 2.7%
3. Fresh, drinking water: 0.3% Thus, only 0.3% of total water covering the earth’s surface can be utilized for the purpose of drinking. [/responsivevoice]

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Sources of water: ‘Water cycle’ that leads to rainfall is the major source of water on earth.

Water Cycle: Water evaporates from the oceans, gets stored in the clouds and condenses as rain. Thus, fresh water enters the ocean, thereby completing the cycle. Rain water also seeps into the ground, thereby increasing the ground water level. This gives rise to other sources of water like rivers, ponds, springs, lakes, streams.

Uncontrolled use of water for the ever increasing population, industry and farming has resulted in shortage of water.

Tips to save water:

i. Do not waste water, use it wisely.

ii. Allow water to seep into the ground by storing or blocking it.

iii. Reuse water (stored water doesn’t become stale at once).

We get water from natural sources such as streams, rivers, ponds, springs and lakes. Man also digs wells and borewells to lift ground water. Apart from this, man has also constructed bunds and dams of various sizes on rivers.

Sources of Water Pollution:

Household Detergents, Thermal Pollution, Fertilizers, Pesticides, Herbicides, Oil Spills in Oceans, Domestic Waste, Industrial Waste, Sewage. [/responsivevoice]

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• Land is seen in the form of stones, soil, big rocks.
• Both plants and animals need land.
• Humans live on land as well as utilize it for other purposes like shelter, farming etc.
• Buried within the land are minerals, crude oil and natural gas, which are useful for humans in many ways.

Land can be divided into the following layers:

1. Humus: Topmost mature layer. Most fertile layer. Formed by decomposition of animals and plants. Usually found in dense forests.
2. Top soil: Made up of soil, small stones, insects and worms.
3. Sub soil: Made up of sand and small stones. Immature layer.
4. Bed rock: This layer has less of soil and more of rocks. Minerals are obtained from this layer. Responsible for colour and texture of the soil.

Soil is composed of:

1. Biotic components: Living things constituting the soil. Example: plants, microbes, worms etc.
2. Abiotic components: Non-living things constituting the soil. Exmaple: Rocks, small stones, sand, pebbles etc. [/responsivevoice]

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Process of soil formation:

1. It is a slow, continuous natural process.
2. Heat, cold and water are responsible for breakdown of the bedrocks. This process is known as “Weathering” of rocks.
3. Weathering brings about formation of stones, sand and soil particles.
4. Roots of trees also contribute in weathering of rocks.

1. The Sun :       

• Rocks expand because of heat energy from the Sun. At night, rocks cool down and contract.
• Expansion and contraction of rocks are not simultaneous which results in the formation of cracks in the rocks. When the cracks grow further, rocks break into small pieces.

2. Water

• Water gets filled in the cracks present in rocks. At low temperature, this water freezes and expands.
• Expansion of water widens the cracks in rocks. Flowing water wears away the ground surface over which it is flowing. Fast-flowing water always carries small pieces of rocks.
• These small rocks, or pebbles, rub against rock surfaces gradually causing soil to form from the rocks.

3. Wind

• Strong winds strike the surface of rocks and erode or break them.

4. Biological

• Lichens grow on rock surfaces and extract minerals.

5. Weathering    

• This creates crevices on rocks in which a thin layer of soil gets filled. Mosses grow on this soil.
• They deepen the crevices, and cracks are formed. Roots of plants grow deep in the ground in search of nutrients and water. As the roots grow, they form cracks in the rocks and eventually break them. [/responsivevoice]

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Soil degradation/soil erosion: Soil can get degraded/destroyed by natural as well as artificial means.

1. Natural process: Natural calamities like earthquakes, floods, storms etc.
2. Artificial process: Human activities like mining, farming, deforestation etc.

 Effects of soil degradation/soil erosion: The top fertile soil is lost in this process of soil erosion. This results in loss of fertility of the soil which thereby makes the land “barren”.

Ways to prevent soil erosion: Plant more trees, as the roots of trees/plants/grasses and bushes hold the soil particles tightly together, thereby preventing erosion.

Formation of fossil fuels: Geographical upheavals led to burial of the trees and animals deep inside the land. Burial of the remains of plants and animals for many ages led to formation of fossil fuels.

Fossil fuels give us many useful substances. Example: Crude oil, a type of fossil fuel, which gives us petrol, diesel, kerosene, paraffin, tar and wax.

 Utilization of resources: All living things utilize the natural resources for their survival but the availability of natural resources in the environment is limited. For example – Oxygen – 21% Fresh water – 0.3% Land – 29%

These resources although available in fewer quantities are sufficient to fulfill the needs of living organisms, provided these are used wisely and not wasted. [/responsivevoice]