The intermolecular interactions play a vital role in the properties of different systems and determine the behavior of them. This book consists of three different parts. In the first part, a new equation of state has been used to predict the density and other thermodynamic properties of three different categories of industrial fluids including glycol ethers, ionic liquids and liquid air. In the second part, MD simulation has been performed to compute the pressure, internal energy and second virial coefficient of binary mixtures of argon with neon, krypton and xenon at different temperatures and compositions using two-body HFD-like, total (two-body+three-body) HFD-like and LJ potentials. We have also analyzed the variation of RDF of the argon-krypton mixtures with density, composition and temperature. In the third part, the stable ZnO/EG and ZnO/G nanofluids in the presence of ammunium citrate, as a dispersant, have been prepared and some physicochemical properties of them including thermal conductivity, viscosity and surface tension have been measured as a function of volume fraction and temperature and the results have been compared with some existing theoretical models.