Imagine that we have two identical pistons of ideal gas in the same initial states at room temperature. Piston 1 is free to move up or down. Piston 2 is fixed so it maintains a constant volume. We put both systems into a reservoir of hot water and let them come to equilibrium. Which statement about this situation is true?

1. Both the heat Q and the change in internal energy will be the same for the two pistons
2. The heat is the same for the two pistons but piston 1 has a larger change in internal energy.
3. The heat is the same for the two pistons but piston 2 has a larger change in internal energy.
4. The changes in internal energy are the same for the two pistons but piston 1 has more heat.
5. The changes in internal energy are the same for the two pistons but piston 2 has more heat.
6. None of the above

They will both come to the same final temperature (the reservoir temperature) so the changes in internal energy will be the same. More heat is needed for piston 1, however, because it does work.