A piston-cylinder device is used to vaporize saturated liquid to saturated vapor under 100 kPa. The volume change and the amount of energy added need to be determined.

Assumptions:

• The pressure is kept as a constant during the process
  

Volume Change V_g - V_f

(1)Volume change

The total volume of the saturated liquid

      V_f = v_fm

The total volume when all the water becomes saturated vapor.

       V_g = v_gm

The volume difference is:

      V_difference = v_gm - v_fm

                     = 10 (1.673 - 0.001) = 16.72 m³

(2) Amount of energy added

Latent heat of vaporization of water under 100 kPa is L_V = 2257.0 kJ/kg. It is the same amount of energy needed to change 1 kg saturated water to saturated vapor under 100 kPa.

      Q = m L_v = 10 (2257.0) = 22570 kJ