Abstract The paper considers the problems of changing the thermodynamic characteristics of a system when dissolving polyatomic particles in a condensed medium. It is shown that the complete measurement of the free energy of a system includes the following main components: 1) Changes associated with the formation of a cavity in the medium in which the impurity particle is located, 2) Free energy associated with the translational and rotational motion of the particle as a whole, 3) The electrostatic part associated with the interaction of the particle with the medium. The paper presents the results of calculations of the thermodynamic characteristics of condensed systems with polyatomic impurity particles, taking into account the effects of frequency and spatial dispersion of the medium.