Lyophilic colloids are also known as reversible sols. These colloidal solutions have an affinity for the dispersion medium, and the particles do not settle down even on standing for a long time. Gum is an example of a lyophilic colloid.

Explanation:

Lyophilic colloids are formed by substances that have a strong affinity for the dispersion medium. The particles of the colloid are surrounded by a layer of the dispersion medium molecules, which keeps them from aggregating and settling down. Lyophilic colloids are thermodynamically stable and can be easily prepared by mixing the colloid-forming substances with the dispersion medium.

Gum is an example of a lyophilic colloid. It is a complex carbohydrate that is obtained from various plants. When gum is mixed with water, it forms a viscous solution that is stable and does not settle down. The particles of the gum colloid are surrounded by a layer of water molecules, which keeps them from aggregating and settling down.

Mil, blood, and fog are not examples of lyophilic colloids. Milk is a colloid, but it is not a lyophilic colloid. Milk is a mixture of fat droplets, protein molecules, and other substances that are suspended in water. Blood is also a colloid, but it is not a lyophilic colloid. Blood is a mixture of red blood cells, white blood cells, and platelets that are suspended in plasma. Fog is not a colloid but a suspension of water droplets in air.

In summary, gum is a lyophilic colloid because it has a strong affinity for the dispersion medium, and its particles are stabilized by a layer of water molecules.