I am going to learn an introductory to thermodynamics in my chemistry book(Senior year) so I thought I could ask some questions here about it to confirm my understanding: 1) Temperature: I have seen a lot of discussions here about what temperature really is. I came up with a summary (Thanks to Dr.Claude): Temperature initially was what a thermometer reads. It is a scale which we use to represent the system tendency to give out heat until it reaches equilibrium. But now because of the kinetic theory, Temperature relates to the average of kinetic energy of the substance. So we say that the temperature now represents the average of kinetic energy of the molecules. 2) Is it wrong to starting thinking about pair of molecules and how they interact during phase changes? I mean the temperature stays the same during phase changes because the heat goes into breaking the chemical bonds instead of increasing the kinetic energy. The question that comes to my mind is all these forces interactions, molecules moving around, some of them gaining energy and other losing (Kinetic) and you are telling me that the kinetic energy stays constant. At this stage should I just work stick to the math and stop trying to imagine all these physics interactions? 3) Does specific heat change with temperature? I have seen also threads about that here but most of them were a bit complicated, talking about quantum mechanics and all. So can someone explain it in kind of a simple way or a bit advanced and I will try to keep up? Just enough to satisfy my desire to know it.. (Just a disease, I am not required to search all of that. We are just required to understand enthlapy and hess' law but the problem they oversimplify things which I dont like) 4) In solutions, My books says that if the mass of the salt is not negligible then you just add the mass of the salt and water together and use the specific heat of water. Is that because the ratio of the mass of the salt to the mass of the solution times the specific heat for the dissolved salt is negligible?