You can easily describe composition- and temperature-dependent fluid properties using the thermodynamic properties database, available as of version 5.3a of the COMSOL Multiphysics® software. For reacting systems, the database computes enthalpy of formation and enthalpy of reaction. For fluid flow and heat and mass transfer, the database can compute viscosity, density, heat capacity, thermal conductivity, and diffusivity of liquids and gases. For systems with several phases, the thermodynamic properties database computes the composition of the phases at equilibrium.