Hi all, Let's say we have 2 closed cylinders A and B, same volume, containing air inside. Two cylinders are connected to each other with a tube, with valve. Initially the valve is closed. cylinder A: P=100 Pa, T= 350 k. cylinder B: P=50 Pa, T= 300 k now if the valve is opened, and closed when their pressure are the same. assume no heat loss to or gain from surrounding. here my problem: will their temperature be the same when their reach the same pressure? my guess are.... 1. yes. By ideal gas law, PV/T = mR, if P1=P2, V1=V2, then T1=T2, so the temp will be the same. 2. no. When the valve is opened, the air flows from A to B, which means the air does some flow work. By conservation of energy, the temp in B will be higher than A. which one of me should I believe?? thanks.