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Is Matter Around us Pure?

Tutormate > CBSE Syllabus-Class 9th Chemistry > Is Matter Around us Pure?

10 Separation of Mixtures II

  • Chromatography is a technique of separating two or more dissolved solids which are present in a solution in very small quantities.




  • This separation is based on the fact that though two or more substances are soluble in the same solvent but their solubilities may be different.
  • This method is based on the different properties of compounds in two phases: stationary and mobile phase.
  • Based on this, chromatography can be classified into:
  • Paper chromatography
  • Column chromatography
  • Thin layer chromatography
  • Gas chromatography



Applications of Chromatography:

The technique of chromatography is used to separate.

  • components of dyes
  • pigments from natural colours
  • amino acids
  • sugars from urine samples
  • drugs from blood




Purification by Crystallisation

  • Crystallization is the process of cooling a hot, concentrated solution of a substance to obtain crystals.
  • It is a better technique than ‘evaporation to dryness’ because of the following reasons:
    • Some solids like sugar decompose or get charred on heating to dryness during evaporation. There is no such problem in crystallisation.
    • The soluble impurities do not get removed in the process of evaporation. But such impurities get removed in crystallisation.
    • Evaporation can be used with completely non-volatile solids.





  • Purification of salt that we get from sea water
  • Separation of crystals of alum (phitkari) from impure samples




Separation by Distillation

  • Distillation is the process of heating a liquid to form vapour, and then cooling the vapour to get back liquid.
  • It is 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.

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