Page 173 - ICSE Chemistry 8

Purification of Water by Distillation

The process of conver ng a liquid into vapour
distillation thermometer
by hea ng and then condensing the vapour fl ask
back into the liquid is called dis lla on. This Liebig’s
process is used to remove dissolved impuri es condenser

from water. The water obtained a er dis lla on
is called dis lled water. It is the purest form of salt solution water in
water.
water out
Impure water is kept in the dis lla on fl ask and pure water
(distillate)
boiled. The steam produced is made to pass burner
through Liebig’s condenser where the steam Fig. 8.6: Purifi cation of water by distillation
condenses to water which is collected in the
receiver.

The dissolved impuri es are le behind in the fl ask. Hence, the process enables recovery of both pure
water and dissolved solids.
Uses of Distilled Water

• Dis lled water is used in the ba eries of cars and inverters.

• It is used in the prepara on of medicines.

• It is used for conduc ng experiments in laboratories.

Purification of Water at Home

Water can be purifi ed at home using the following processes.
• Boiling: It is the simplest way of purifying water. Boiling water ensures that most of the germs in
it are destroyed and water is safe for drinking. Boiled water should be cooled and fi ltered before
using it. It should be stored in a clean container and kept covered.

• Chlorina on: In this process, chlorine tablets are added to water to kill germs and make water safe
for consump on.
• Water purifi ers: Water purifi ers make water fi t for consump on by using either ultraviolet rays or
reverse osmosis or a combina on of both to kill germs.

• Addi on of alum: Muddy water can be cleaned by adding a crystal of alum. This leads to the
impuri es se ling down in the container so that the water can be fi ltered and used.

PHYSICAL PROPERTIES OF WATER

A molecule of water is made up of two atoms of hydrogen and one atom of oxygen. Its molecular formula
is H O. Some of the proper es of water are described here.
2
• Nature: Pure water is transparent, colourless, odourless and tasteless at room temperature. Water
contains dissolved minerals and gases that give it a pleasant taste.

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