Chemical Engineering - Chemical Engineering Basics - Discussion

In winter season due to low temperature moisture in air get condensed but not in large amount to become a droplet rather they suspend in air forming fog.

Actually, in fog dispersed phase is liquid and dispersion medium is gas (liquid dispersed in gas).

Because the air here acts as a gas due to morning therefore the liquid is dispersed in gas.

Fog phase is liquid and dispersed medium is gas.

Colloidal system.

(Also called colloidal dispersion, colloidal suspension. ) An intimate mixture of two substances, one of which, called the dispersed phase (or colloid) , is uniformly distributed in a finely divided state through the second substance, called the dispersion medium (or dispersing medium).

The dispersion medium may be a gas, a liquid, or a solid and the dispersed phase may also be any of these, with the exception of one gas in another. A system of liquid or solid particles colloidally dispersed in a gas is called an aerosol. A system of solid substance or water-insoluble liquid colloidally dispersed in liquid water is called a hydrosol. There is no sharp line of demarcation between true solutions and colloidal systems or between mere suspensions and colloidal systems. When the particles of the dispersed phase are smaller than about 10-3 μm in diameter, the system begins to assume the properties of a true solution; when the particles dispersed are much greater than 1 μm, separation of the dispersed phase from the dispersing medium becomes so rapid that the system is best regarded as a suspension. According to the latter criterion, natural clouds in the atmosphere should not be termed aerosols; however, since many cloud forms apparently exhibit characteristics of true colloidal suspensions, this strict physicochemical definition is often disregarded for purposes of convenient and helpful analogy. Condensation nuclei and many artificial smokes may be regarded as aerosols.

Gas +liquid=aerosol.