Final answer:
Gelatin is sold in two forms, powder and sheets. These forms, when mixed with water and cooled, form colloidal gels commonly used in desserts and cooking.
Step-by-step explanation:
The two forms in which gelatin is sold are powder and sheets. Gelatin is used in making desserts, such as Jell-O, which is a type of colloid. When gelatin is mixed with water and heated, it disperses to create a colloidal system. Upon cooling, it coagulates into a gel, which is a viscous substance that is neither completely solid nor liquid. Powdered gelatin consists of grains of gelatin that are small in size and disperse easily in water. Sheet gelatin, also known as leaf gelatin, is a thin flat piece of gelatin film that dissolves slowly and is often preferred in professional baking and cooking for its consistent quality. Both forms, when hydrated and then cooled, form a gel—a colloidal dispersion of liquid in a solid, as the proteins form a three-dimensional network with the spaces filled by liquid or a dilute solution.