The thermodynamics of mixing can be described according to the theory of Flory and Huggins; with so called ideal solutions, there is no heat of mixing and the Flory-Huggins parameter chi = 0. A solution always shows a lower vapor pressure than the pure solvent which can be calculated with Raoult's 1st law. A solution has both a higher boiling point and a lower freezing point than the pure solvent. The properties mentioned are colligative, which means: only the number of dissolved particles is decisive, not the chemical nature of the solute. osmotic pressure is another colligative property; it can be calculated using van't Hoff equation and it especially plays an important role in biology.