Water

Water is the most dominant feature of our planet and it covers around 71% of the surface. Water is denser than ice. The Britannica defines the word density as “Mass of unit volume of a material substance expressed as kilogram per cubic meter in S.I. units”. Water is one of the very few substances, which are actually denser in the liquid state than in the solid form. This large volume of water, in ice form results in the phenomenon ice floating on the surface of water.

When ice melts some of the Hydrogen Bonds are broken and molecules pack more closely together so that water has a higher density. This breaking down process is not complete until a temperature of 4 Degree Celsius is reached at which water has the maximum density. On this basis, anomalous behaviour of water can be explained, that is, water when heated from 0 to 4 Degree Celsius contracts and when cooled from 4 to 0 Degrees Celsius, water expands (contrary to the behaviour of other liquids).

The water molecule is bonded by Covalent Bonds. However the molecules in water have Hydrogen Bonding as Inter Molecular forces of Attraction, which are the result of Ionic Character, and in turn depend upon Electro-negativity. Thus Electrostatic forces of Attraction also act on these molecules and hence these molecules are said to be ‘Polar Molecules’. The presence of Hydrogen Bonding greatly affects the general properties of water. It is due to Hydrogen Bonding that the physical properties of water such as Viscosity (internal resistence to the flow of the liquid) and Surface Tension exist. Stronger the Hydrogen Bonding, higher would be the viscosity and surface tension. The high boiling point of water as compared to other similar liquids is also due to Hydrogen Bonding.