What is the term for the tendency of molecules to spread out spontaneously in a solution?

The term that describes the tendency of molecules to spread out spontaneously in a solution is diffusion. This process involves the movement of molecules from an area of higher concentration to an area of lower concentration, driven by the kinetic energy of the molecules. As molecules collide with one another, they disperse evenly throughout the available space, resulting in a more uniform distribution over time.

Diffusion occurs across a permeable membrane and does not require energy input; this spontaneous movement continues until equilibrium is reached, where the concentration of molecules is the same throughout the solution. Understanding diffusion is fundamental to concepts in biology, particularly in cellular processes and transport mechanisms.