I'm really starting to hate this class, the lecture didn't even begin to explain any of this I have no idea where to begin. We've been working on change in internal energy and work done on/by a gas, etc, and we get a question like this on the homework: Water standing in the open at 29.7°C evaporates because of the escape of some of the surface molecules. The heat of vaporization (518 cal/g) is approximately equal to εn, where ε is the average energy of the escaping molecules and n is the number of molecules per gram. (a) Find ε, in calories. (b) What is the ratio of ε to the average kinetic energy of H2O molecules, assuming the latter is related to temperature in the same way as it is for gases? I don't even know where to begin?