Which substance acts as an example of a protective colloid?

The correct answer highlights gelatin as a prime example of a protective colloid. Protective colloids are substances that stabilize emulsions and suspensions by preventing the coalescence of dispersed particles. Gelatin, being a protein derived from collagen, possesses the ability to form a gel-like structure in the presence of water. This characteristic allows gelatin to create a protective layer around dispersed particles, enhancing the stability of colloidal systems.

Gelatin is particularly effective in food products, pharmaceuticals, and cosmetics, where it helps maintain texture and consistency by preventing the settling of particles or separation of phases.

While starch, silica, and gum arabic have their own useful properties in various applications, they do not function as effectively as protective colloids in the same context as gelatin. For instance, starch can thicken and stabilize but is not primarily used for its protective colloidal properties. Silica can be involved in preventing clumping, but it does not create a protective film around the particles like gelatin does. Gum arabic can stabilize emulsions and is a gum that serves as a thickening agent, but it is not as universally recognized for its protective colloid function compared to gelatin.