Properties of water and steam

This chapter discusses the properties of water and steam. Fluids consist of a very large number of molecules moving in random directions within the fluid. When the fluid is heated, the speeds of the molecules are increased, increasing the kinetic energy of the molecules. There is an increase in volume because of an increase in the average distance among molecules, causing the potential energy of the fluid to increase. The sum of the internal energy and the pressure energy of a fluid is called the enthalpy of the fluid, denoted by the symbol H and measured in joules. When water is heated at a uniform rate, a stage is reached where the addition of more heat does not result in a corresponding increase in temperature. The temperature at which this occurs is called the saturation temperature, and the water is called saturated water. As heat is added to saturated water, it is turned into saturated steam. The amount of heat required to turn one kg of saturated water into saturated steam is called the specific latent heat of vaporization.