Colloid: It is any substance in which small insoluble particles are dispersed over a large amount of another material.
- A cloud or fog is a type of colloid composed of a liquid (water) dispersed in a gas (air).
- Small particles do not dissolve in this atmosphere, but droplets of liquid water are dispersed through the air.
- In fog, The dispersed phase is a liquid and the dispersion medium is a gas.
Hence, Fog is a Colloid.