Hi there, Please, I would like to know if the Thermal Conductivity of a liquefied gas increases or decreases when becomes a supercritical fluid. Also, I would like to know how is the relation between the molecular mass and thermal conductivity of a liquefied gas and a supercritical fluid, because in the gaseous phase, as higher the molecular mass, smaller seems to be the thermal conductivity value. Per example in gaseous phase: Helium Molecular weight : 4.0026 g/mol Thermal conductivity (1.013 bar and 0 °C (32 °F)) : 142.64 mW/(m.K) Methane Molecular weight : 16.043 g/mol Thermal conductivity (1.013 bar and 0 °C (32 °F)) : 32.81mW/(m.K) Hexafluoroethane - R116 Molecular weight : 138.02 g/mol Thermal conductivity (1.013 bar and 0 °C (32 °F)) : 13.47mW/(m.K) Is it the same for supercritical fluids? http://en.wikipedia.org/wiki/Supercritical_fluid Thanks a lot. PS - This is not a homework question, is part of a personal and independent research. I hardly tried to find the answer, but I could not. I did not ask about it in the Chemical Forum because I consider it not a formulation problem, but a question about the characteristics of the state of the matter. Thanks.