The Two-Phase Thermodynamic (2PT) model describes an arbitrary system as a superpositon of a hard-sphere gas and a solid, enabling us to calculate the system's entropy, thereby making a connection from the dynamics to the thermodynamics. In this work the 2PT model is used to investigate effects of solutes on the dynamics and thermodynamics of water. The negative excess mixing entropy of water-methanol and water-ethanol mixtures are correctly predicted by the model and accounted to the lowered diffusion of the molecules in the mixture. Ethanol is found to lower the entropy of water more than methanol. A second system analyzed are aqueous solutions of sodium chloride. Increasing salt concentrations are shifting diffusional modes of water to oscillations and lower its entropy. Several problems of the 2PT model are pointed out which are related to the unphysical separation in two subsystems. Deviating separation schemes based on time separation, velocity separation and position separation are proposed and analyzed.