Hi all, I'm brushing up on some thermodynamics, and having been reading up on the interpretation of temperature as derived from kinetic theory. I can follow the derivation for an ideal, monatomic gas which relates temperature to the average, translational kinetic energy of the molecules. Most textbooks I've been perusing seem to stop there and don't bother extending this to more complicated systems. I understand that more complicated arrangements of atoms have additional degrees of freedom and that the internal energy of such systems increases beyond just the translational kinetic energy as a result of these additional degrees of freedom. I'll be perfectly honest and say that the kinetic interpretation of temperature has always made the most intuitive sense to me. I'm curious about how well this can be extended to say an everyday solid or liquid (not some exotic condensate or something). My question is: as an operational definition, is it still reasonable to think of temperature as a measure of the average translational kinetic energy of molecules in solids and liquids? As a follow-up question, I recall reading somewhere that, while solids and liquids have portions of their internal energy associated with rotational and vibrational motion, it is ultimately differences in the average translational kinetic energy between substances that drives heat flow (since this is what would lead to collisions between substances) - is this correct? Thanks! Alexander.