Environmental Chemistry II: Water, Occurrence, importance, properties and composition

Environmental Chemistry II: Water

Properties of Water

Occurrence

Water is one of the most important substances on the earth 🌎. It is present in enormous quantity on earth. It has been estimated that the total amount of water on earth is about 1.33 billion cubic meters which approximately covers 71% of the earth's crust.

Despite of an enormous amount of water on earth surface, fresh water available for drinking is only 3% of the total. This small amount of water is not evenly distributed on earth. Some areas are rich in fresh water while certain areas have little or no fresh water. Of this fresh water, 69% resides in glaciers, 30% underground 🚇 water and less than 1%is present in lakes, rivers, and swamps.

Sea water that is almost 97% of total water, contains large amount of dissolved salts. The sodium chloride is the most abundant salt in sea water 🌊. It is present upto 3.4% in it.

Importance of water

Earth 🌎 is the only planet in the solar system that contains water.

There are following important features of water.

I. All living things need water for their survival.

ii. Our body cannot work without water just like a can cannot run without fuel.

iii. Water acts as a lubricant in digestion and joints.

iv. The water in saliva helps chewing and swallowing.

v. Water is crucial for sustaining the reaction that keep us alive. For instance, digestion, distribution of food through blood, removal of waste matter from the body.

vi. It cools automobile engines, nuclear power plants, steel Mills and parts of heavy machinery in industrial units.

vii. It provides means of transportation on earth surface.

viii. Farmers need a large amount of water for their fields for growing fruits, vegetables and crops.

ix. We need water for drinking, cooking 🍳 and cleaning.

x. It is also used to generate electricity.

Properties of Water

i. Water is the only substance that exists in three different states on earth 🌎.

ii. Pure water is transparent, colourless, odorless and tasteless. Its boiling point is 100 oC and melting point is 0 oC.

iiii. Water shows an irregular behaviour on cooling. For instance,On cooling, its volume decreases and its density increases which becomes maximum at 4oC. On further cooling, its volume increases and density decreases. Due to this behaviour, ice 🧊 floats on top of water surface. This ice acts as blanket on the surface of lakes and insulate the lower layer of water. This enables fish and other aquatic life to survive during winter.

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