Amount of energy needed for phase change of water
A lot of energy is needed to change the state of a substance. For our purpose I will use water.
1 Lb of liquid water @ 32° F takes 180 BTU to get to 212° F liquid water.
1 Lb of liquid water @ 212° F takes 970 BTU t get to 212° F water vapor.
The water vapor will retain this energy until it is released and the water vapor condenses into liquid water. This energy is latent heat
The British thermal unit (BTU or Btu) is a traditional unit of work. It is the amount of work needed to raise the temperature of one pound of water by one degree Fahrenheit