1. The problem statement, all variables and given/known data Each molecule of a substance can exist in either of two states; these states differ in energy by 25 eV. a. What is the entropy of this sample at room temperature? b. What is the internal energy of this sample at room temperature? 2. Relevant equations dU = TdS U =(f/2)nRT (f = degrees of freedom) 3. The attempt at a solution I don't understand how i am supposed to derive the total entropy of the sample from the difference in energy "states" (the DIFFERENCE in entropy between states would be easy): the problem talks about molecules, then atoms.. are these states referring to electronic excitement, or what?.. i need some opinions about this, please..