About Water

Water is the common name applied to the liquid state of the

hydrogen-oxygen compound H2O. In 1804, the French chemist Joseph Louis

Gay-Lussac and the German naturalist Alexander von Humboldt

demonstrated that water consists of two volumes of hydrogen to one of

oxygen, as it is shown in the present-day formula H2O.

· Properties

Pure water is an odorless, tasteless liquid. It has a bluish color,

which may be detected, however, only in layers of considerable depth.

Under standard atmospheric pressure (760 mm of mercury), the freezing

point of water is 0° C and its boiling point is 100° C . Water attains

its maximum density at a temperature of 4° C and expands upon

freezing. Like most other liquids, water can exist in a super cooled

state.Which means that it may remain a liquid although its temperature

is below its freezing point. Water can easily be cooled to about -25°

C without freezing, either under laboratory conditions or in the

atmosphere itself. Super cooled water will freeze if it is disturbed,

if the temperature is lowered further, or if an ice crystal or other

particle is added to it.

Almost all the hydrogen in water has an atomic weight of 1. Water is

one of the best-known ionic bonds. Because most substances are

somewhat soluble in water, it is frequently called the 'universal'

solvent. Water combines with certain salts to form hydrates. It reacts

with metal oxides to form acids. It acts as a catalyst in many

important chemical reactions.

· Occurrence

Water is the only substance that occurs at ordinary temperatures in

all three states of matter, that is, as a solid, a liquid, and a gas.

As a solid, or ice, it is found as glaciers and ice caps, in winter,

as snow or hail. It occurs in the liquid state as rain clouds formed

of water droplets, and on vegetation as dew.In addition, it covers

three-quarters of the surface of the earth in the form of swamps,

lakes, rivers, and oceans.