1. The problem statement, all variables and given/known data A student performs a combustion experiment by burning a mixture of fuel and oxygen in a constant-volume metal can surrounded by a water bath. During the experiment, the temperature of the water is observed to rise. Regard the mixture of fuel and oxygen as the system. a) Has heat been transferred to/from the system? How can you tell? b) Has work been done by/on the system? How can you tell? c) What is the sign of ΔU of the system? How can you tell? d) 1g of fuel is placed in the can for combustion. During combustion, the 200mL water bath is observed to increase in temperature by 35.5°C. What is the heat of combustion (energy released per gram) of the fuel? 2. Relevant equations ΔU = Q - W where ΔU = change of internal energy in system, Q = heat gained by system, W = work done on the surrounding BY the system. 3. The attempt at a solution Now I know that for part a), heat has been transferred from the system, as the temperature of the water bath rises (meaning, heat has been transferred from the system to the surroundings). However, I am a little confused about part b). I am not sure if the work is done by the system or not. I am guessing, since the metal can is at constant-volume, no work has been done, but I may be wrong. Please correct me if I am wrong. I am stuck at this point. I can't attempt the other parts of the problem unless I understand part b). Thank you.