GEL

About

A gel is a semi-solid substance with properties that can range from soft and weak to hard and tough. Defined as a substantially dilute cross-linked system, gels exhibit no flow when in a steady state, although the liquid phase may still diffuse through the system. Despite being mostly liquid by mass, gels behave like solids due to a three-dimensional cross-linked network within the liquid. The cross-linking within the fluid provides the gel with its structure and hardness, while also contributing to its adhesive stick, known as tack. In this way, gels function as a dispersion of liquid molecules within a solid medium. The term gel was coined in the nineteenth century by Scottish chemist Thomas Graham, who created the word by clipping it from gelatine. The process of forming a gel is called gelation.