Class 9, Science, Chapter-2, Lecture-2, Separation of Mixture Components (Notes)

METHODS OF SEPARATING COMPONENTS OF MIXTURE:

1. Evaporation:
   Principle : the volatile components vaporize whereas non-volatile components are left.
   Application : in separating volatile components from non-volatile components
2. Centrifugation: 
   Principle : denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly.
   Application : (i) for blood test, urine test.
   (ii) to separate butter from cream
   (iii) in washing machines to squeeze out water from wet clothes. 
3. Using Separating Funnel: 
   Principle : immiscible liquids separate out in layers depending on their densities.
   Application : (i) to separate oil from water
   (ii) to separate carbon disulphide from alcohol 
4. Sublimation:
   Principle : the sublimable components sublime and separate out from non-sublimable components.
   Application : to separate ammonium chloride form salt.
5. Chromatography: 
   Principle : the component that is more soluble in water, rises faster and gets separated from the components that is less soluble
   Application : to separate two or more solutes that dissolve in the same solvent.
6. Simple Distillation: 
   Principle : the component having lower boiling point vaporises and separates from the component having high boiling point
   Application : to separate acetone from water.
7. Fractional Distillation:
   Principle : the component having lowest boiling point vaporises and separates firs followed by the component having higher boiling point
   Application : to separate components of crude oil.
8. Crystallization: 
   Principle : the solvent of saturated solution evaporates and leaves crystals of pure solid behind.
   Application : (i) to purify salts.
   (ii) to separate crystals of alum (phitkari) from impure samples.

Crystallization is better than evaporation:

Reasons:

1. During evaporation, some solids may decompose or get charred on excessive heating.
2. Some impurities may remain dissolved in the solution even after filtration. On evaporation, these contaminate the solid.

Fractional Distillation of Air:

1. Air is filtered to remove dust particles.
2. Air is compressed to convert it into liquid.
3. Hot and compressed air is passed through Liquid Nitrogen .
4. Cooled compressed air is allowed to expand to become liquid air at .
5. CO₂ is separated as dry ice.
6. Expanded air is passed through Fractionating Column.
7. Nitrogen gas escapes from the top .
8. Liquid Oxygen is collected at the bottom .