The three broad classification of colloids and three example for each one
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Classification of Colloids
Colloids occur widely in nature as well as are manufactured synthetically. Since these have a wide industrial application, it is important to have a proper system for the classification of colloids. Colloids consist of a dispersed phase and a dispersion medium. They are classified on the basis of different properties of the dispersed phase and the medium. Let us learn about them here.
Classification of Colloids
Based on the Nature of Interaction Between Dispersed Phase and Dispersion Medium
Hydrophilic colloids: These are water-loving colloids. The colloid particles are attracted to the water. They are also known as reversible sols. Examples include Agar, gelatin, pectin, etc
Hydrophobic colloids: These are the 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
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 Val forces
Example: Gold sol, Sulphur sol.
Macromolecular Colloids: Molecules have very high molecular masses that result in the formation of large molecules that 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 concentrations. At a particular concentration, the molecules of dispersed phase align in such a 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.