Unit 12 - Mixture - Class 8

UNIT 12: MIXTURE

-          We use different types of substances in our daily life.

-          Among them, some are pure substances and some are impure substances (mixture).

-          The substances from which mixture is made are known as components.

-          The physical combination of two or more substances is known as mixture.

-          Mixture are of two types:

o   Homogeneous mixture

o   Heterogeneous mixture

Homogeneous Mixture

-          The mixture in which components of the mixture are distributed equally throughout the mixture.

-          And these components can’t be seen with our naked eyes.

-          Homogeneous mixture is also known as solution.

-          Sugar + Water, Salt + water, metallic alloy etc. are some examples of homogeneous mixture.

Heterogeneous Mixture

-          The mixture in which components of the mixture are not distributed equally throughout the mixture.

-          And these components can be seen with our naked eyes.

-          Sugar + Salt, Sand + water etc. are some examples of heterogeneous mixture.
-     Heterogeneous Mixtures are of two types:
     Suspension: diameter particles are up to 10^-5  cm or more. sandy water, muddy water are examples of suspension.
    Colloid: diameter of particles are between 10^-7 cm to 10^-5 cm. blood, gum, milk etc. are example of this.
-

Separation of Mixture

-          When we need to get pure substances, we have to separate them from the mixture.

-          The pure substances are obtained when the components of a mixture are separated on the basis of their property.

-          There are different ways of separating a mixture. There are different types of method to separate mixture. In this unit, we will discuss about:

o   Distillation

o   Fractional Distillation

o   Chromatography

Distillation

-          It is the process of conversion of liquid into vapor on heating (evaporation) and conversion of vapor into liquid by cooling (condensation).

-          Distillation process is used to separate the components of solution of solid and liquids.

-          For example, Solution of sugar and water, solution of salt and water can be separated from distillation process.

-          It is also used to separate the solution of only two miscible liquids have different boiling point.

Fractional Distillation

-          When a mixture contains two or more miscible liquid substances, it is difficult to separate the components.

-          In this situation, the boiling point of those liquids is determined and substances are separated by using fractional distillation process.

-          The mixtures of different miscible liquids which having different boiling points are separated by fractional distillation method.

-          In this method, the liquid having lower boiling point is separated out first rather than those having higher boiling point.

-          This method is used to separate petrol and petroleum products from crude mineral oil.

Application of Distillation/ Fractional Distillation

-          To separate solution of a solid and a liquid.

-          To separate mixture of two miscible liquids having different boiling points.

-          To prepare distilled water.

-          To prepare distillery products like beer, wines etc.

-          To separate petroleum products like petrol, diesel, cooking gas etc. from crude petroleum mineral.

Chromatography

-          Chromatography is derived from the Greek word "kroma" and "graphy".

-           In Greek language, kroma means color and graphy means write.

-          Therefore, chromatography is used to separate different colors from their mixtures.

-          The term 'chromatography' was first discovered by Russian botanist Tswett in 1906 for the separation of colored plant pigments.

-          Now-a-days, this method is widely used for separation, purification, identification and characterization of the components of mixture, no matter they are colored or colorless.

Application of Chromatography

-          It is used to separate different colors from a mixture.

-          It is used to separate and identify the medicine mixed with blood and urine.

-          It is used to separate the color from the mixture of natural and artificial coloring materials.

-          It is used to identify contents of blood in laboratories.

-          It is used to separate even very small quantity of a substance present in a mixture (solution).

Difference Between Homogeneous and Heterogeneous Mixture

Homogeneous Mixture	Heterogeneous Mixture
·         Components are mixed uniformly	·         Components are not mixed uniformly
·         Components can’t be seen with our naked eyes.	·         Components can be seen with our naked eyes.
·         For example: Sugar + Water, Salt + water, Alcohol + Water etc.	·         For example: Sand + Water, pea + gram etc.