Page 88 - ICSE Chemistry 6

Boiling

Boiling is the easiest and the most recommended purifi ca on technique. Boiling water for 5–10 minutes
kills most types of disease-causing microorganisms. This method is feasible only at a small scale and can
be used in our homes. Boiling can also be used as a stage prior to other methods for extra precau on.

Aeration

Aera on helps to kill harmful microorganisms present in water. In this method, air under pressure is
blown into fi ltered water to purify the water.

Ozonisation

These days ozone is used to sterilize water and this process is called ozonisa on.

Water Purifiers and RO System

The water purifi ers used nowadays for purifying water at
fi ltration activated ultraviolet
home provide three stage purifi ca on. In the fi rst stage, through charcoal lamp
water is fi ltered through a candle fi lter. In the second candle
stage, the fi ltered water is passed through ac vated
charcoal which absorbs impuri es. In the third and fi nal
stage, water is irradiated with ultraviolet radia on which
kills the germs present in it.

Reverse osmosis is a method of water purifi ca on tap water
in which water is forced out of the waste through a purifi ed
water
semipermeable membrane by applying pressure. A lot
Fig. 4.9: Water purifi cation in a purifi er
of impure water is le during the process which can
be used for other ac vi es. Bo led drinking water is
prepared using this technique.

Distillation

Dis lled water is tasteless as it does not
distillation
contain any dissolved salts and minerals. fl ask thermometer

Dis lled water is obtained by evapora on of Liebig's
water followed by condensa on of vapour. condenser
This process of obtaining pure water is
known as dis lla on.
salt solution water in
Dis lled water is used for preparing solu ons
for medicinal purposes and in laboratories. water out pure water
It is also used in ba eries of inverters and burner (distillate)
cars.
Fig. 4.10: Distillation

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