Question

Fog is an example for colloidal system of

• A. Liquid in gas
• B. Gas in liquid
• C. Solid in gas
• D. Gas in solid

Answer 1

Answer:

A. Liquid in gas

• A colloidal system, or colloid, is a heterogeneous mixture in which the particles of one substance (the dispersed phase) are distributed uniformly throughout another substance (the dispersion medium).

• The size of the particles in a colloidal system typically ranges from 1 nanometer (nm) to 1000 nm. This intermediate size distinguishes them from true solutions (particles < 1 nm) and suspensions (particles > 1000 nm).

• Colloidal particles do not settle out on standing, unlike suspensions, and cannot be easily separated by simple filtration.

• Colloids are classified into eight types depending on the physical state (solid, liquid, or gas) of the dispersed phase and the dispersion medium. Note that gas in gas forms a homogeneous mixture and is therefore not a colloid.

• One important classification for competitive exams is Aerosols, where the dispersion medium is a gas.

• If the dispersed phase is a liquid and the dispersion medium is a gas, the colloid is specifically called a liquid aerosol.

• If the dispersed phase is a solid and the dispersion medium is a gas, the colloid is called a solid aerosol.

• Fog consists of tiny water droplets (liquid) suspended and uniformly dispersed in the air (gas).

• These water droplets are of colloidal dimensions, which means they are small enough to remain suspended but large enough to scatter light, reducing visibility.

• Therefore, fog is an excellent example of a colloidal system where the dispersed phase is liquid and the dispersion medium is gas. Clouds and mist are similar examples.