Matter exists in three physical states, viz the gas, the liquid and the solid. Gases fill up the
whole vessel in which they are placed and exert pressure on the walls of the vessel they
can be compresssed by applying the pressure and can be lioquefied by cooling along with
compression. The well known laws of gaseous behaviour are Boyle’s law Charle’s law,
Graham’s law, Avogadro’s law and Dalton’s law. There was no theoretical background to
justify these empirical generalizations the ideas developed by joule (1848) Knoning
(1856). Clausius (1857) Maxwell and Boltzmann (1859) laid down the basis of Kinetic
Molecular theory of Gases and this gave conclusing explanation to the various gas laws.