Fog is a colloidal solution of

Liquid in gas

The correct answer is option 3. Liquid in gas.

Fog is a type of aerosol, which is a colloidal solution consisting of fine particles dispersed in a gas. In the case of fog, the dispersed phase consists of tiny liquid water droplets, while the continuous phase is the surrounding air.

Here's a detailed explanation:

1. Formation of Fog:  Fog forms when air near the ground cools to the point where it reaches its saturation point, leading to the condensation of water vapor into small droplets. This process can occur through various mechanisms such as radiative cooling, advection, or mixing of warm and cold air masses. As a result, fog consists of numerous tiny water droplets suspended in the air.

2. Colloidal Nature: A colloidal solution, or colloidal dispersion, is a heterogeneous mixture in which particles of one substance (the dispersed phase) are dispersed evenly throughout another substance (the continuous phase). In the case of fog, the dispersed phase comprises liquid water droplets, while the continuous phase is the surrounding air. The droplets are small enough to remain suspended in the air rather than settling out due to gravity.

3. Characteristics of Colloids: Fog exhibits several characteristics typical of colloidal systems:

Particle Size:  The water droplets in fog are very small, typically ranging from about 1 to 100 micrometers in diameter. These fine droplets are dispersed throughout the air, giving fog its characteristic appearance of suspended moisture.

Stability:  The suspended droplets in fog remain dispersed throughout the air due to the continual movement and mixing of air masses. While individual droplets may collide and coalesce, the overall foggy appearance is maintained.

Tyndall Effect:  Fog exhibits the Tyndall effect, which is the scattering of light by colloidal particles. When light passes through fog, it is scattered by the suspended water droplets, making the beam of light visible and giving fog its characteristic appearance of diffused light.

4. Properties and Behavior: Fog can vary in density and visibility depending on factors such as the concentration of water droplets, temperature, and atmospheric conditions. Dense fog reduces visibility, impacting transportation and outdoor activities. It can also affect local weather patterns and contribute to the hydrological cycle by providing moisture for plants and ecosystems.

In summary, fog is a colloidal solution consisting of liquid water droplets dispersed in the air. Its formation involves the condensation of water vapor into fine droplets suspended near the ground. Fog exhibits characteristics typical of colloidal systems, including small particle size, stability, and the Tyndall effect. Understanding the colloidal nature of fog helps explain its appearance, behavior, and impact on the environment.