Different Forms of Water

Water is usually found in a liquid state, which is called fluid state. But when cooled to zero degree, it turns into ice, which is its solid state. If the water is heated to 100 degrees, it turns into vapor, which is its gaseous state.

This means that water is found in all three forms i.e. solid (ice), fluid (water) and gas (vapor).

Composition of Water

In 1781, Henry Cavandish proved by an experiment that water is not an element but a compound of hydrogen and oxygen. Its chemical formula is H2O. When we heat it, it turns into vapor and upon cooling it returns to its liquid state again.

Water molecules need to be heated to 2200 degrees Celsius in order to break into hydrogen and oxygen. But heating the water to 2200 degrees is very difficult, because it turns into vapor at 100 degrees. The only alternative is decomposition of water. When an electric current is carried in water, it breaks down into its elemental elements - hydrogen and oxygen.

Hydrogen and oxygen are found in water in the ratio of 1:8 according to weight and 2:1 according to volume.

Different Sources of Water

The main sources of water which we use are wells, rivers, lakes, ponds, waterfalls and hand pumps.

Although there is a huge reservoir of water in the form of oceans, seas and lakes on our earth, in the same way it is very difficult for us to get water for its use directly.

Water Cycle

Due to the heat of the sun; seas and oceans evaporate and fly into the sky as water vapor. At a high altitude, this water vapor starts to cool and then turn into small droplets of water, thus they take the form of clouds.

Then a situation comes in that these small droplets of water, combine to form big drops of water and then it starts raining. This rain water does not contain the impurities which are found in the seas and oceans.

After the rains, some part of this water soaks in the ground and the rest goes to the lakes and seas through the river and drains.


1. Fill in the blanks:

(a) Solid form of water is called ....... and gaseous form .........

(b) Pure water turns solid on ......... and gaseous form on ..........

(c) Water is a compound of ......... and .........

(d) Water by weight has 1 part ........ and 8 parts ..........

2. What is the easiest method of dividing water into hydrogen and oxygen ?

3. The following sentences are true or false:

(a) Due to decreasing number of ponds, ground-water level is decreasing

(b) The Sun plays the most important role in providing us pure water

(c) The process of large-scale distillation is continuous in nature.

(d) Rain water also has many impurities because it is basically sea-water.


1. (a) Ice, vapor (b) cooling, boiling (c) Oxygen, Hydrogen (d) Hydrogen, Oxygen

2. Electrical decomposition

3. (a) True (b) False (c) True (d) False