Solution solute in a solution is the mass of that solute expressed as a percentage of the mass of the whole solution. "Homogeneous" means that the components of the mixture form a single phase. "Heterogeneous" means that the components of the mixture are of different phase. The properties of the mixture (such as concentration, temperature, and density) can be uniformly distributed through the volume but only in absence of diffusion phenomena or after their completion. Usually, the substance present in the greatest amount is considered the solvent. Solvents can be gases, liquids or solids. One or more components present in the
Phase (matter) separate spontaneously. Emulsions and colloids are examples of immiscible phase pair combinations that do not physically separate. Left to equilibration, many compositions will form a uniform single phase, but depending on the temperature and pressure even a single substance may separate into two or more distinct phases. Within each phase, the properties are uniform but between the two phases properties differ. Water in a closed jar with an air space over it forms a two phase system. Most of the water is in the liquid phase, where it is held by the mutual attraction of water molecules. Even at equilibrium