Hi all. Lets look at the following scenario: We have an object called A which is kept at 300 K at all times (e.g. a hot plate). Now we have an object B, which is initially 200 K (e.g. a frying pan), and object A and B are now moved together, so they touch eachother. Of course, object B will now be 300 K as well, and object A is still 300 K. When I explain this to someone, I would just say that it is intuitively clear that this is how it must be. But can one explain this using conservation of energy, or some other physical law? I thought about using the first law of thermodynamics: Q = U, but how does one explain that the heat provided by A will make the internal energy of B rise enough, so that the temperature of B is also 300 K? - Niles.