Dissolution is the process by which a solute forms a solution in a solvent.
The solute, in the case of solids, has its crystalline structure disintegrated as separate ions, atoms, and molecules form. For liquids and gases, the molecules must be adaptable with those of the solvent for a solution to form. The outcome of the process of dissolution (the amount dissolved at equilibrium, i.e., the solubility) is governed by the thermodynamic energies involved, such as the heat of solution and entropy of solution, but the dissolution itself (a kinetic process) is not. Overall the free energy must be negative for net dissolution to occur. In turn, those energies are controlled by the way in which different chemical bond types interact with those in the solvent. Solid solutions occur in metal alloys and their formation and description is governed by the relevant phase diagram.
Dissolution process is of fundamental importance to the description of numerous natural processes on earth, and it is commonly utilized by humans. Dissolution testing is widely used in the pharmaceutical industry for optimization of formulation and quality control.