An aluminum can, with negligible heat capacity, is filled with 485 g of water at 0°C and then is brought into thermal contact with a similar can filled with 517 g of water at 48.5°C. Calculate the change in entropy of the system if no heat is exchanged with the surroundings. 1) I find avg temp, which turns out to be: ~298 2) I calc change in temp for both sides, and find Q. (deltaT)(4.184)(mass) 3) Divide each Q (they're the same, with one being negative) by each starting temperature 4) I come up with .163599 J/K, which is wrong Where am I messing up? I have 4-5 problems identical to this but can't figure any of them out!!!