AskDefine | Define effusion

Dictionary Definition



1 an unrestrained expression of emotion [syn: gush, outburst, blowup, ebullition]
2 flow under pressure

User Contributed Dictionary




  1. an outpouring of liquid
  2. In the context of "by extension": an outpouring of speech or emotion
    • 1930; George S. Kaufman, Morrie Ryskind, Bert Kalmar, Harry Ruby; Animal Crackers, Paramount Pictures
      Captain Spaulding: My friends, I am highly gratified by this magnificent display of effusion...
  3. the seeping of fluid into a body cavity; the fluid itself


Extensive Definition

For other uses, see effusion (disambiguation).
In chemistry, effusion is the process where individual molecules flow through a hole without collisions between molecules. This occurs if the diameter of the hole is considerably smaller than the mean free path of the molecules. According to Graham's law, the rate at which gases effuse is dependent on their molecular weight; gases with a lower molecular weight effuse more quickly than gases with a higher molecular weight. For two gases at the same temperature (and having the same specific heat), and thus having the same kinetic energy, the average molecular speed of each gas can be found using the equation E=(1/2) mv^2. Thus, lighter molecules have a higher speed. This results in more molecules passing through the hole per unit time. This is why a balloon filled with low molecular weight hydrogen left alone for a reasonable amount of time deflates faster than a separate balloon full of higher molecular weight oxygen.


External links

effusion in French: Effusion
effusion in Hebrew: אפוזיה
effusion in Polish: Efuzja (fizyka)
effusion in Portuguese: Efusão (química)
effusion in Serbian: Ефузија
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