Abstract

In this paper we find a connection between the long lasting macroscopic classical laws of gases and the quantum mechanical description of non-interacting particles confined in a box, thus constituting an ideal gas. In such a gas, the motion of each individual molecule can be considered to be independent of all other molecules, and the macroscopic parameters of an ideal gas, mainly, pressure P and temperature T, can be defined as simple average quantities based on individual motions of all molecules in consideration. It is shown that for an ideal gas enclosed in a macroscopic box of volume V, the constant gappearing in the classical law of adiabatic expansion law, that is, , can be derived based on quantum mechanics. Physical implications of the result we disclose are discussed.

Key words: Adiabatic transformation, quantum mechanics, kinetic theory of gases.