A real solution consists of randomly moving solvent and solute particles, and solvent behavior in a solution is governed by the same forces that affect solute movement (see Simple Diffusion). To examine solvent behavior, let's see what happens when a solute dissolves in a solvent, creating a solution. In the cartoon below, an undissolved crystal composed of many solute particles is surrounded by many, many more water molecules. When first placed in water the crystal is relatively static; in contrast, the water molecules are engaged in rapid Brownian motion:
The crystal begins to dissolve as the interactions among solvent and solute particles exceed those among the solute particles in the crystal. In other words, solute particles in the crystal become "solvated" and go into solution: the crystal dissolves into individual solute particles, each surrounded by associated water, as illustrated in the cartoon at the top of the next page.