Question

Give the classification of colloids with the applications of colloids.

Answer 1

Classification of Colloids

Based on Nature of Interaction Between Dispersed Phase and Dispersion Medium

• Hydrophilic colloids: These are water-loving colloids. The colloid particles are attracted toward the water. They are also known as reversible sols. Examples include Agar, gelatin, pectin, etc

• Hydrophobic colloids: These are opposite in nature to hydrophilic colloids. The colloid particles are repelled by water. They are also called irreversible sols. Examples include Gold sols, clay particles, etc

Based on Type of Particles of Dispersed Phase

Depending upon how different substances forming colloidal solution acquire the size of particles in this range, colloidal solutions may be classified into the following three categories.  

• Multimolecular Colloids: The solution that is formed as a result of the aggregation of a large number of atoms or small molecules (having diameters of less than 1nm) of the dispersed media. The dispersed particles are held together by Van der waals forces . Example: Gold sol, Sulphur sol.

• Macromolecular Colloids: Molecules have very high molecular masses that result in the formation of large molecules are termed as macromolecules. When such substances are dispersed in a suitable dispersion medium, the resulting colloidal solutions are known as macromolecular colloids. Thus, macromolecular colloids consist of high molecular mass. Generally, lyophilic colloids are macromolecular in nature.  Examples include the colloidal dispersion of naturally occurring macromolecules such as starch, proteins, gelatin, cellulose, nucleic acids etc. as well as synthetic polymers such as polyethylene, polypropylene, synthetic rubber etc. also form macromolecular colloids when dispersed in suitable solvents.

• Associated Colloids (Micelles): Certain colloids behave as strong electrolytes at lower concentrations but exhibit colloidal properties at higher concentration. At a particular concentration, the molecules of dispersed phase align in such as way as to form micellar structures. This particular concentration is known as critical micellar concentration. The colloids that form micelles are known as associated colloids.

Depending Upon the State of Dispersed and Dispersion Medium

Depending upon the state of dispersed particles and the dispersion medium, the following system of Classification of colloids can be employed.  

1] When the Dispersion Medium is Liquid

• Foams – When the dispersed medium is gas. Examples include whipped cream, shaving cream, etc

• Emulsions – When the dispersed phase is liquid. Examples include milk, mayonnaise, etc

• Sol – When the dispersed phase is solid. Examples include blood, pigmented ink, etc

2] When the Dispersion Medium is Gaseous

• Liquid Aerosol – When the dispersed phase is liquid. Examples include fog, mist, hair sprays, etc.

• Solid Aerosol –  When the dispersed phase is solid. Examples include smoke, ice cloud, etc.

3] When the Dispersion Medium is Solid

• Solid Foam – When the dispersed medium is gas. Examples include styrofoam, pumice, etc

• Gel – When the dispersed medium is liquid. Examples include agar, gelatin, etc

• Solid Sol – When the dispersed medium is solid. Examples include cranberry glass

Answer 2

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