Table of Mechanics Demonstration

List of Mechanics Equipment & Supplies

Lecture Demonstrations

Maxwell Demon Bottle, 4F10.26




The Maxwell's Demon Bottle consists of a sealed flask which contains 5 white and 5 black spheres. This demonstration demonstrate the statistical nature of an irreversible processes. Key words, Kinetic Theory, Probability, and



ID Number


TD, Bay B7, Shelf #1

**Moved from ME, Bay A2


  1. Begin with all the balls in the stem of the flask in the unmixed condition.

Cautions, Warnings, or Safety Concerns:

  1. Demonstration is a Glass Flask which can Brake
  2. This Demonstration will require some practice to make it work.


Begin with all the balls in the stem of the flask in the unmixed condition. Inverting the flask mixes the balls and a discussion of the probability of the balls unmixing on inverting the flask again can follow. With 5 black and 5 white balls the odds against reproducing the initial array are 252 to 1.

Maxwell's Demon can now be introduced. This task is illustrated in the following manner. 1st Rotate the flask to a stem up position and impart a swirling motion to the spheres. Turn the flask to the stem down position and slowly reduce the rotation rate. The balls will spiral back down the neck of the bottle. With a little practice the initial array can always be restored, violating the 252 to 1 odds.

The "demonability" resides in the fact that the black spheres are constructed so as to rapidly lose momentum. They are hollow and contain a small ball bearing within.




ed043p105.pdf (A PDF Report Demonstrating concepts of statistical thermodynamics: More on the Maxwell Demon bottle)


  1. The University of Melbourne ABN

  2. Towson University

  3. Wikipedia


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