We have presented a generalized description for the processes of vibration-induced size segregation and mixing of granular materials from a thermodynamic standpoint. We have developed methods for calculating the total energy, enthalpy and entropy increment for the segregation and mixing processes. The calculations are based on the measured indicators of the process and on the fundamental properties of dry granular media. We have established that non-dissipative energy loss or entropy generation occur, without contradicting the second law of thermodynamics, in a system comprising a separator (averaging unit) and a polydisperse raw material in a gravitational field. We have confirmed that the above calculations are valid for the processes of segregation and mixing of both hydrophilic and hydrophobic granular materials. The tools developed can be used in designing different screening surfaces.