Hello everyone, Below is one paragraphe from my thermo textbook: Equilibrium for Ai but not for T (XiA = XiB but, for example : TA > TB). Thus, for U and S, we have a gap in relation to the equilibrium : UA = UAeq + [itex]\delta[/itex]UA,UB = UBeq + [itex]\delta[/itex]UB Ai is state variables such as V,l, ect. T is temperature. I don't quite understand why there is not a second situation where Ai is the same but T is different? Why it's not mentioned here? Thanks a lot.