ABSTRACT
When the temperature, the pressure, or the solute concentration of a homogeneous system is changed, a new phase can be possibly formed. Examples are the formation of a vapor phase when a liquid is heated to above its boiling point and the formation of sucrose crystals when a sucrose solution is cooled to below its saturation temperature. The formation of a new phase is often very slow if the conditions are not far from equilibrium. For the new phase to develop, nucleation has to occur, i.e., the formation of small regions of the new phase that are large enough to grow spontaneously. This is the subject of this chapter. The emphasis is on nucleation of a solid phase in a liquid. Unless mentioned otherwise, the ambient pressure is assumed to be constant at about 1 bar.
