Page 56 - ICSE Chemistry 8

fl ask. When the mixture in the dis lla on fl ask is heated, the liquid vaporises and the solid component is
le behind in the fl ask. The vapour of the liquid component condense into pure liquid upon cooling. The
pure liquid obtained is collected in a conical fl ask. This method is used to obtain dis lled water which is
used in laboratories for conduc ng experiments and in ba eries.
Centrifugation

The process of separa ng fi nely suspended solid components
in a liquid by spinning the mixture in a closed container is called
centrifuga on. The spinning of the mixture occurs in a machine
called a centrifuge.

The principle of centrifuga on is that the heavier par cles
experience larger centrifugal force as compared to the lighter
par cles. In this process, the centrifuge spins rapidly to speed
the process. The mixture is put in the test tubes which are kept
in the centrifuge. A er spinning the mixture in the centrifuge, (a) centrifuge (b) blood sample
the suspended components in the liquid get collected at the Fig. 3.11: Centrifugation
base of the container followed by the separa on of liquid by the process of decanta on.

Centrifuga on is used to separate bu er from milk. It is also used in laboratories to separate blood cells
from plasma.
Separating Liquid-Liquid Mixtures

Using Separating Funnel separating
funnel

A separa ng funnel is a device made up of glass with a tap called oil
stopcock. The stopcock is a ached to the bo om of the funnel and
water
controls the fl ow of liquid.
The separa ng funnel is used to separate a mixture of immiscible liquids,
i.e., an emulsion. The principle behind the separa on of immiscible
liquids is that the lighter liquid fl oats above the heavier liquid.

• The mixture to be separated is put into a separa ng funnel and water
is allowed to se le.
Fig. 3.12: Separating
• A er some me, it is observed that the liquids form separate immiscible liquids
layers one above the other.
• The liquid forming the lower layer is collected Know Your Scientist
in a container by opening the stopcock.
Thomas Graham (1805–1869) worked on the
• The stopcock is closed once whole of the diff usion of gases. His work on diff usion of
liquid in the lower layer is collected in the gases is called Graham's Law.
container.
• The liquid forming the upper layer is collected in another container in the same way.

The separa ng funnel can be used to separate a mixture of oil and water.

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