How long can you survive without water? Without water, we cannot survive for more than a few days. Water is called elixir of life. Without it, life on earth would not be possible. Human beings, plants and animals all need water for their survival. Perhaps that is why nature has covered more than 70% of the earth’s surface with water. About 97% of the total water on earth is in the ocean.
Structure of water molecule
Water is a compound of hydrogen and oxygen. It contains two parts of hydrogen and one part of oxygen by volume, as shown in figure. Pure water is colorless, odorless, transparent ad tasteless. We get water Form Rivers, lakes, fountains, wells, rains, oceans, etc. water exists in three state—solid, liquid and gas. Normally, it is found in the liquid state, but when it is cooled to 0 degree centigrade, it freezes into ice. When it is heated to 100 degree centigrade, it turns into steam.
Water obtained form nature is not pure, but contains many slats and minerals dissolved in it. Due to these impurities, it develops a taste slightly different than pure water. Some of the impurities make water hard. Hard water does not form lather with soap. The hardness of water is of two types- temporary and permanent. Temporary hardness is due to the presence of bicarbonates of calcium and magnesium. It is removed by boiling the water. The presence of chlorides and sulphates of calcium and magnesium in water cause permanent hardness. This hardness can be removed by mixing sodium carbonate with the water.
Water has many fascinating properties. For example, ice is lighter than water. That is why ice and big icebergs float on the surface of seas. Water has the maximum density at 4 degree centigrade. Due to this property, during winters, only the upper surface of water in lakes and ponds freezes but the lower portion remains liquid. Hence marine life can easily survive in such lakes and ponds.
The structure of water is such that most substances dissolve in it. Hence, water is regarded as a universal solvent. Seawater is saline because many minerals remain dissolved in it. Air dissolves itself in water enabling aquatic animals to breathe. Water is a liquid which does not evaporate easily. That is why soil retains moisture for a long period; this benefits trees and plants.
Water content in different living organism varies. Trees and plants have 60% to 80% water, fresh fruits 85% to 95% and plants living in water contain 98% water. Human body contains 65% water.
A civilized man on an average used 35 gallons of water every day for drinking bathing and washing. One should be careful about drinking water. Often, water contains germs of dangerous diseases like typhoid, cholera, diarrhoes, dysentery, etc. boiled water is, therefore, hygienic. Water can be made free from germs by filtering, boiling and mixing potassium permanganate or chlorine tablets in it.
