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单词 vapour pressure
释义
vapour pressure

Physics
  • The pressure exerted by a vapour. All solids and liquids give off vapours, consisting of atoms or molecules of the substances that have evaporated from the condensed forms. These atoms or molecules exert a vapour pressure. If the substance is in an enclosed space, the vapour pressure will reach an equilibrium value that depends only on the nature of the substance and the temperature. This maximum value occurs when there is a dynamic equilibrium between the atoms or molecules escaping from the liquid or solid and those that strike the surface of the liquid or solid and return to it. The vapour is then said to be a saturated vapour and the pressure it exerts is the saturated vapour pressure.


Chemistry
  • The pressure exerted by a vapour. All solids and liquids give off vapours, consisting of atoms or molecules of the substances that have evaporated from the condensed forms. These atoms or molecules exert a vapour pressure. If the substance is in an enclosed space, the vapour pressure will reach an equilibrium value that depends only on the nature of the substance and the temperature. This equilibrium value occurs when there is a dynamic equilibrium between the atoms or molecules escaping from the liquid or solid and those that strike the surface of the liquid or solid and return to it. The vapour is then said to be a saturated vapour and the pressure it exerts is the saturated vapour pressure.


Chemical Engineering
  • The pressure exerted by the vapour of a solid or a liquid in which it is in contact and at equilibrium for a specified temperature. The vapour pressures of pure substances can be obtained from published data or from empirical equations such as the Antoine equation. The Clausius–Clapeyron equation can also be used but is less accur-ate. The vapour pressure can be lowered by the addition of a solute. This is related to the decrease in freezing point and increase in boiling point.


Geology and Earth Sciences
  • The pressure exerted by molecules of a substance in the vapour state, at equilibrium with molecules of the same substance in the liquid state, within a closed container. The magnitude of the vapour pressure exerted depends on the temperature and the identity of the liquid; it does not depend on the amount of liquid in the container. The saturated vapour pressure of water at 0 °C is 610 N m−2, rising to 2340 N m−2 at 20 °C and 7380 N m−2 at 40 °C. See also partial pressure.


Geography
  • In meteorology, the pressure exerted by the water vapour in the air. This is a partial pressure since pressure is also exerted by the air itself. Moisture content is commonly measured by relative humidity. The absolute value of the water content is not usually the most important issue but its value compared with saturation vapour pressure; thus relative humidity is more relevant than specific humidity.


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