New approach explains well known equations and processes clearly. It is understandable state equation PV=RT has mental basis not empirical. Differential equation via temperature was deduced for specific heat of specie two constant with on the base of derivative formula. Constants are characteristics of concrete specie. The results conform table data well. The equation adds logical description of thermodynamics. Gibbs energy is calculated via temperature on the base of specific heat. Initial value at zero is defined by experimental coordinates. Method of phase equilibrium calculation has been developed. Example of water - vapour equilibrium calculation showed good conformation to experimental data. That probably can explain the difference of real gas to perfect one by the presence of condensation quantity in the mix. New approach joins two method of analysis: functions and processes.