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Area of Expertise - thermodynamics
Term for the pressure that steam exerts on the enclosing walls in a closed system in dynamic equilibrium with the condensed phase.
See also: lowering the vapor pressure
Learning units in which the term is dealt with
Phase transition45 min.
If a substance changes its physical state, a phase change takes place. For example, the substance changes from a solid to a liquid state, it melts. The temperature at which the substance melts is called the melting point. Further examples of phase changes are evaporation, boiling, sublimation, solidification.
State diagrams35 min.
In general, it can be stated that, depending on the values of the state variables pressure and temperature, a substance can exist in one or more phases. An animation in this lesson shows this for the 92 chemical elements in standard printing for increasing temperatures. It is also shown how the type and number of phases of pure substances can be represented by two or even three-axis coordinate systems. In these so-called state or phase diagrams, the triple and critical point represent important features of the pure substance. Phase rule, polymorphism / allotropy and diamond synthesis are further topics.
Vapor pressure15 minutes.
The phase equilibrium of pure substances is described. The measurement of the vapor pressure can be understood with the help of an animation.
Mixed phases15 minutes.
The phase equilibrium in multiphase multicomponent systems is considered. The lowering of the vapor pressure is explained and the vapor pressure over a solution is considered according to Raoult's or Henry's law.