compressibility,vapor pressureof a liquid

• Compressibility of substance is the measure of its change in volume under the action of external forces, namely, the normal compressive forces. The measure of compressibility of the fluid is the bulk modulus of elasticity (K) K = lim DV - 0 (- DP) / (DV/V) The unit of compressibility is N/m2 .

• Liquids evaporate because of molecule s escaping from the liquid surface. These vapor molecules exert a partial pressure on the surface of the liquid known as vapour pressure.