Characteristics of Water

Water is a unique liquid, without which no life can survive. This is attributed to the following characteristics.

(i) Water is regarded as a universal solvent. No other liquid can be compared to water as solvent.

(ii) Water possesses the highest heat of fusion and heat of evaporation, collectively known as the latent heat, of all known liquid substances at ordinary temperature. The latent heat of water is responsible for moderating the temperature of the biosphere. It also plays a vital role in the evaporation of water and its condensation as rain and as dew (see hydrological cycle, sec. 2.8.1.1)

(iii) Compared with other common liquids water has a high surface tension, a characteristic that is very important in many physical and biological processes involving movement of water through and into organisms.

(iv) Water is a poor thermal conductor as compared to metals.

(v) Water has a high viscosity which allows organisms to swim using simple movements.

(vi) Water protects the aquatic animals and plants from the mechanical disturbances.

(ix) Water exerts pressure. Organisms living at sea level experience a pressure of about 15 psi (~1 atmosphere, which is equal to 760 mm mercury). With depth, the pressure increases at the ratio of about one atmosphere for every 10 meters of descent. The physical characteristics like solubility, ionic dissociation and surface tension - all are influenced by the pressure.

5.4