Colloids: Properties of True Solution, Colloidal Solution and Suspension (For CBSE, ICSE, IAS, NET, NRA 2022)

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Colloids

The term colloid has been derived from two terms, namely colla and oids. ‘Kolla’ means glue and ‘Oids’ means like i.e.. glue-like.

True Solution, Colloidal Solution and Suspension

  • If the size of the solute particles is less than 1 nm in a solution, then it is true solution.
  • If the size of the solute particles is between 1 to 100 nm then it is colloidal solution.
  • If the size of solute particles is greater than 100 nm it is a suspension.

Properties of True Solution, Colloidal and Suspension

Properties of True Solution

Phases of Colloidal Solution

Colloids solutions are heterogenous in nature and therefore it consist of at least two phases:

  • Dispersed phase
  • Dispersion medium.

Dispersed Phase

It is the substance present in small proportion and consists of particles of colloids size (1 to 100 nm) .

Dispersion Phase

  • It is the medium in which the colloids particles are dispersed.
  • For example, in a colloidal solution of Sulphur in water, Sulphur particles constitute the ‘dispersed phase’ and water is the ‘dispersion medium’ .

Different Types of Colloidal Solution

Following table shows different types of colloidal solution based on the physical state of the two phases:

Types of Colloidal Solutions

Types of Colloidal Solutions

The most common type of colloidal solution are sols (solid in liquid type) , gels (liquid in solid type) and emulsions (liquid in liquid type) .

Classification of Colloidal Solution

Colloidal solutions can be classified in different ways:

  • On the basis of interaction between the phases
  • On the basis of molecular size.

Classification Based on Interaction

Depending upon the interaction between dispersed phase and the dispersion medium colloidal solutions have been classified into two categories:

Lyophilic Colloids

  • The word ‘Lyophilic’ means solvent lover.
  • Lyophilic colloidal solutions are those in which the dispersed phase have a great affinity (or love) for the dispersion medium.
  • These solution can easily formed simply by bringing dispersed phase and dispersion medium in direct contact with each other .
  • They are reversible in nature, i.e.. if they has been formed then dispersed phase and dispersion medium can be separated easily and again formed by remixing the two phases
  • These sols are quite stable.
  • If water is used as dispersion medium, then they are called as hydrophilic colloids.

Lyophobic Colloids

  • The word ‘Lyophobic’ means solvent hating.
  • Lyophobic colloidal solutions are those in which the dispersed phase has no affinity for the dispersion medium.
  • They cannot prepared easily and have to be prepared by special method.
  • These sols can be readily precipitated and once precipitated they have little tendency to go back into the colloidal state.
  • These sols are irreversible in nature.
  • They are not very stable and require a stabilizing agent to remain in the colloidal form.
  • If water is used as dispersion medium, then it is hydrophobic sol.

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