Thermodynamic Entropy and Information

Macrostate of an Ideal Gas

The ideal gas law describes the relationship between observeable properties of an ideal gas at equilibrium:

       PV = nRT

where P = pressure, V = volume, n = number of particles (in mol's), T = temperature, R = universal gas constan t.

    Any three of the four variable quantities are sufficient to specify the macrostate of a closed system at equilibrium. Other related quantities, like the internal energy of the system (E = PV), may be also be used to specify the macrostate. The number of particles, N = n*6.0221415×10²³ is not often directly measured, but can be estimated from the mass of the system and a known mass per particle.