Page 57 - ICSE Chemistry 8

Activity 3.4

Aim: To separate a mixture of kerosene and water
Materials required: Mixture of kerosene and water, separa ng funnel,
separating funnel
beaker
kerosene
Procedure and water

• Take the mixture of kerosene and water in a separa ng funnel. stopcock
• Leave the mixture for some me to let the water se le down such that
the liquids clearly separate into dis nct layers.
• Carefully open the stopcock and drain out the water, which is heavier,
into a beaker.

Observa on: The water se les down on being le undisturbed and kerosene fl oats above the water.
Conclusion: This shows that a mixture of kerosene and water can be separated using a separa ng funnel.

Fractional Distillation
thermometer
The process of separa on of a mixture into its
components or frac ons by hea ng the mixture is fractionating column
called frac onal dis lla on. This method is used to
water out
separate a mixture of miscible liquids.
condenser
The principle on which the method of separa on is
based is that diff erent miscible liquids have diff erent
distillation
boiling points and the liquid having a lower boiling fl ask water in
point evaporates fi rst as compared to the liquid
having a higher boiling point. Bunsen
burner
Frac onal dis lla on apparatus consists of a
Fig. 3.13: Fractional distillation
dis lla on fl ask, a heat supply, a frac ona ng
column, a condenser and a laboratory thermometer. In this process, the mixture of miscible liquids is
heated to obtain diff erent components of the mixture. Since heat energy is involved in the process, boiling
points play a signifi cant role in the process. The mixture to be separated is put into the dis lla on fl ask and
is heated. The vapour rise up into the frac ona ng column as the mixture begins to boil. The temperature
across the column is variable. The temperature at the top is lower as compared to the temperature at
the bo om which is higher. The vapour of the liquid having a lower boiling point rise to the top of the
frac ona ng column whereas the vapour of the liquid having a higher boiling point condense at the
bo om of the frac ona ng column. A er this, the vapours are allowed to pass into a condenser where
on cooling, they form a liquid which is then collected in a container.

Frac onal dis lla on is used to separate crude oil into various useful components such as kerosene,
gasoline, diesel, paraffi n wax, lubrica ng oil and other fuels. It is also used for separa ng alcohol from
water as the boiling point of alcohol is lower than the boiling point of water. It also has industrial uses in
petroleum refi neries, chemical plants, natural gas processing, separa on of pure gases from mixture of
gases and for purifi ca on and separa on of many organic compounds.

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