posted by Angel .
One gram of water is placed in a cylinder and the pressure is maintained at 2.0 x 105 Pa. The temperature of the water is raised by 31oC. Determine the change in internal energy when, a) the water is in its liquid phase and causes an expansion of 1.0 x 10-8 m3. b) Water is in its gaseous phase and expands by the much greater amount of 7.1 x 10-5 m3. Assume that there is no phase change for both cases. (cliquidH20 =4186 J/(kgoC); cgasH20 = 2020 J/(kgoC))
This looks like a situation where you should use the formula
dU = Qin - P dV
The heat in is Qin = C*dT. the two cases have different values of C and different values of the volume expansion, dV.
dU is the change in internal energy.