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you are here->home->Chemistry->Class 9->Separation
of Mixtures Using Different Techniques

Separation of Mixtures Using Different
Techniques

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Our Objective

To separate the components of a mixture using the following techniques:

Separating funnel

Chromatography

Centrifugation

Simple distillation

Fractional distillation

The Theory

How is a homogeneous mixture different from a heterogeneous mixture?

Most materials in our surroundings are mixtures of two or more components.
Mixtures are either homogeneous or heterogeneous. Homogeneous mixtures are
uniform in composition, but heterogeneous mixtures are not uniform in
composition.

Air is a homogeneous mixture and oil in water is a heterogeneous mixture.
Homogeneous and heterogeneous mixtures can be separated into their components by
several physical methods. The choice of separation techniques is based on the
type of mixture and difference in the chemical properties of the constituents of
a mixture.

What are types of separation techniques?

Various types of separation processes are:

Crystallization

Filtration

Decantation

Sublimation

Evaporation

Simple distillation

Fractional distillation

Chromatography

Centrifugation

Separating funnel

Magnetic separation

Precipitation

Let’s discuss some of the separation techniques

Using a separating funnel:

A separating funnel is used for the separation of components of a mixture
between two immiscible liquid phases. One phase is the aqueous phase and the
other phase is an organic solvent. This separation is based on the differences
in the densities of the liquids. The liquid having more density forms the lower
layer and the liquid having less density forms the upper layer.

Applications:

To separate a mixture of oil and water.

To separate a mixture of kerosene oil and water.

Chromatography:

Chromatography is a separation technique used to separate the different
components in a liquid mixture. It was introduced by a Russian Scientist Michael
Tswett. Chromatography involves the sample being dissolved in a
particular solvent called mobile phase. The mobile phase may be a gas
or liquid. The mobile phase is then passed through another phase called
stationary phase. The stationary phase may be a solid packed in a glass plate or
a piece of chromatography paper.

The various components of the mixture travel at different speeds, causing
them to separate. There are different types of chromatographic techniques such
as column chromatography, TLC, paper chromatography, and gas chromatography.

Paper chromatography is one of the important chromatographic methods. Paper
chromatography uses paper as the stationary phase and a liquid solvent as the
mobile phase. In paper chromatography, the sample is placed on a spot on the
paper and the paper is carefully dipped into a solvent. The solvent rises up the
paper due to capillary action and the components of the mixture rise up at
different rates and thus are separated from one another.

Applications:

To separate colors in a dye.

To separate pigments from natural colors.

To separate drugs from blood.

Centrifugation:

Sometimes the solid particles in a liquid are very small and can pass through
a filter paper. For such particles, the filtration technique cannot be used for
separation. Such mixtures are separated by centrifugation. So,
centrifugation is the process of separation of insoluble materials from
a liquid where normal filtration does not work well. The centrifugation
is based on the size, shape, and density of the particles, viscosity of the
medium, and the speed of rotation. The principle is that the denser particles
are forced to the bottom and the lighter particles stay at the top when spun
rapidly.

The apparatus used for centrifugation is called a centrifuge. The centrifuge
consists of a centrifuge tube holder called rotor. The rotor holds balanced
centrifugal tubes of equal amounts of the solid-liquid mixture. On rapid
rotation of the rotor, the centrifuge tubes rotate horizontally and due to the
centrifugal force, the denser insoluble particles separate from the liquid. When
the rotation stops, the solid particles end up at the bottom of the centrifuge
tube with liquid at the top.

Applications:

Used in diagnostic laboratories for blood and urine tests.

Used in dairies and home to separate butter from cream.

Used in washing machines to squeeze water from wet clothes.

Simple distillation:

Simple distillation is a method used for the separation of components of a
mixture containing two miscible liquids that boil without decomposition and have
sufficient difference in their boiling points.

The distillation process involves heating a liquid to its boiling points, and
transferring the vapors into the cold portion of the apparatus, then condensing
the vapors and collecting the condensed liquid in a container. In this process,
when the temperature of a liquid rises, the vapor pressure of the liquid
increases. When the vapor pressure of the liquid and the atmospheric pressure
reach the same level, the liquid passes into its vapor state. The vapors pass
over the heated portion of the apparatus until they come into contact with the
cold surface of the water-cooled condenser. When the vapor cools, it condenses
and passes down the condenser and is collected into a receiver through the
vacuum adapter.

Applications:

Separation of acetone and water.

Distillation of alcohol.

Fractional distillation:Fractional distillation is used for the separation of
a mixture of two or more miscible liquids for which the difference in boiling
points is less than 25K. The apparatus for fractional distillation is similar to
that of simple distillation, except that a fractionating column is fitted in
between the distillation flask and the condenser.

A simple fractionating column is a tube packed with glass beads. The beads
provide surface for the vapors to cool and condense repeatedly. When vapors of a
mixture are passed through the fractionating column, because of the repeated
condensation and evaporation, the vapors of the liquid with the lower boiling
point first pass out of the fractionating column, condense and are collected in
the receiver flask. The other liquid, with a slightly higher boiling point, can
be collected in similar fashion in another receiver flask.

Applications:

Separation of different fractions from petroleum products.

Separation of a mixture of methanol and ethanol.

Learning outcomes

Student understands the following terms: solvent extraction,
chromatography, RF , centrifugation, simple  distillation, fractional
distillation, etc.

Student acquires skills to perform experiments using the following
techniques in the chemistry lab:

Solvent extraction using separating funnel

Paper Chromatography

Centrifuge machine

Simple distillation & fractional distillation

Student can identify the components in the mixture based on the knowledge
of Rf value, boiling point, density, etc.

Student is able to select & design the  above techniques based on
the  chemical and physical properties  of the components in the
mixture.

Students  acquire the skill  to arrange the requirements for
each technique through the animations, simulators and videos.

Students will be able to select and perform suitable separation techniques
based on the available information about the nature of the components in the
mixture.

Let’s try out these separation techniques……

Cite
this Simulator:
amrita.olabs.edu.in,. (2012). Separation of Mixtures Using Different Techniques. Retrieved 10 February 2018, from amrita.olabs.edu.in/?sub=73&brch=2&sim=96&cnt=1

Developed by Amrita
Vishwa Vidyapeetham &
CDAC Mumbai. Funded by MeitY (Ministry of Electronics & Information
Technology)

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