The effects of conformerisation and internal molecular dynamics (IMD) of n-dodecane conformers on energy transfers between gas and liquid phases are investigated. Bond energies, Gibbs free energies of internal dynamics of a set of n-dodecane conformers, and energies of the molecules colliding with the surface of an n-dodecane nanodroplet are studied using quantum chemical calculations (DFT with B97X-D/cc-pVTZ and semi-empirical PM7) and ReaxFF method. The results of the analysis show that the accuracy of the methods increases as we move from the application of PM7 to the application of ReaxFF and then to DFT. Different temperature dependencies of internal Gibbs free energies of conformers in the gas and liquid phases are expected to affect the heat and mass transfer processes between them. The calculations for the gas and liquid (using the quantum solvation model; SMD) phases show significant differences in the internal dynamics of conformers and demonstrate an entropy-enthalpy competition in the evaporation/condensation of an ensemble of the conformers. The Effects of Internal Molecular Dynamics on the Evaporation/Condensation of n-Dodecane.