7. Evaporation and Condensation

Heat transfer to a liquid leads to an increase of the temperature up to the boiling temperature at which evaporation starts. The vapor pressure becomes equal to the pressure of the system. In the case of the evaporation of a liquid mixture all components or only some of them or perhaps only one component can be present in the vapor. Dealing with the evaporation of an aqueous solution of an inorganic salt with a very low vapor pressure approximately pure steam is leaving the liquid. (Note that an entrainment of small drops can take place with the result of small salt contents in the steam.) In general, all components of the liquid mixture will be present in the vapor when there are no great differences of the vapor pressure of the components.