Techniques of separation

Impure substances: Mixtures

A mixture is a substance which consists of two or more elements or compounds which are not chemically combined together.

Examples -: milk, air, soil, glass.Mixture are not pure as it contains many particles in it.Two types of mixtures:- Homogeneous and

Heterogeneous.It does not have a definite melting or boiling point….

Separation Of MixturesThe method to be used for separating a mixture

depends on the nature of its Constituents.The various processes used to separate constituent of

mixture are : Evaporation , Sublimation, chromatography,

Distillation, Fractional distillation, Crystallization…….By these we can separate the non-volatile component

(solute) from its volatile solvent …

EvaporationEvaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid.

The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid.

With sufficient heat, the liquid would turn into vapor quickly.

APPLICATIONS:-When clothes are hung on a laundry line, even though the ambient temperature is below the boiling point of water, water evaporates. This is accelerated by factors such as low humidity, heat, and wind..

Separation of mixtures by Evaporation

Activity-: Aim: To obtain coloured component(dye) from its volatile

solvent by the method of evaporation. Materials : A beaker, a watch glass, a burner, water and some

blue ink. Procedure: 1. Fill half a beaker with water.o 2. Cover it with a watch glass, put a few drops of ink on it and

heat it.o 3. Evaporation starts from the watch glass. o 4.Continue to heat till you see that there are no further changes

on thewatch glass. Observation: The water gets evaporated from the watch glass and residue is left . Therefore it is not a single substance but a mixture of dye in water.

By Separating FunnelA mixture of two immiscible liquids can be separated by using a Separating Funnel.The Separation of two immiscible liquids by a separating

funnel is based on the difference in their densities…..APPILICATION: The mixture is put into a separating

funnel, shaken and allowed to settle. The oil and water from two separate layer. The liquid with higher density, in this case water forms the lower layer. Remove the stopper and open the tap after standing. The water runs out through the tap. The oil remains in the funnel and can be run out into another beaker.

Separation of mixtures by separating funnel

Activity:- Aim: To separate kerosene oil from water using a

separating funnel… Procedure: 1. Pour the mixture of oil and water in a separating

funnel. Do not disturb it till layer of oil and water is formed. Opening the stop clock of the funnel, pour the lower level of water

carefully. Close the stop clock as the soil reaches the it and is left behind in

the separating funnel. Conclusion: We conclude that immiscible liquids can be separated

with the help of separating funnel…

Sublimation

Most of the solids substances when heated changes into liquid and finally into Vapours (or gas).

This vapour on cooling ,first forms liquid and finally the solids.

On the other hand there are some solid substances like ammonium chloride which directly changes into vapours on heating and the vapours gives back solid substance on cooling.

The change of a solid directly into a vapour on heating and of the vapuor into solids on cooling is known as Sublimation ….

Separation of mixtures by SublimationACTIVITY:- Aim:-To separate a mixture of salt and ammonium

chloride.. Procedure:- 1 The mixture of ammonium chloride and

salt is taken in a china dish and covered with an inverted funnel.

A loose cotton plug is put in the stem of the funnel to prevent the ammonium chloride vapours from escaping in the atmosphere.

On heating ammonium chloride changes into vapours. These vapours condense on the cold inner side of the funnel to

give back solid ammonium chloride.. Sodium Chloride does not vaporise on heating so it remains behind in the china dish….

Distillation

Distillation is the process of heating a liquid to form vapour and then cooling the vapour to get back the liquid…

Liquids

The liquid obtained by condensing the vapours is called distillate. Process in which the components of a substance or liquid mixture are separated by heating it to a certain temperature and condensing the Resulting Vapors…..

Vapours(or gas)Heating

Cooling

Separation of mixtures by DistillationActivity:-Aim: To separate alcohol and water from their solution.Procedure: 1 Take the solution in a distillational flask fitted

with fractionating column. Fit it with a thermometer.Arrange it like the that done in the picture..Heat the mixture slowly keeping a close watch at the

thermometer reading.The alcohol evaporates, condenses in the condenser and can be collected from the condenser outlet.Water is left behind in the distillation flask…..Observation: By this method alcohol and water are separated…

Picture on next page!!!

ChromatographyThe process of separation of component of a mixture is know as

Chromatography .Chromatography is the technique used for the separation of those solutes

that dissolve in the same solvent…..

The substances when present in well defined geometrical shapes Are called crystals. These are formed when a hot saturates solution of salt is allowed to cool slowly and undisturbed.

The process of preparation of crystals is termed as crystallization…..

Crystallization

Made By-:Chhavi Bansal Of---IX-D

Roll No.-12