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Corrections and Updates

  1. "plus" should be "or".
  2. "at constant pressure" should be omitted.
  3. "energetic" should be omitted in this and all following expressions of "energetic microstates". It is redundant to prefix the adjective "energetic" to "microstate" because a microstate is always energetic! A microstate describes both the momentum and the location of each molecule at one instant, i.e., each molecule in its one unique energy-location arrangement of all the enormous number that are possible for the system with that total energy. All microstates of a system have the same total energy, i.e., that of the whole macrosystem.
  4. The word "all" must be deleted from this sentence. It is clearly impossible for a mole of particles in any system at any one instant to occupy or be in more than 6 x 10 23 energy-locations. It is equally impossible in millions of years for all of the particles to have been in more than a tiny fraction of the almost incredibly enormous number of microstates that are possible for them in any system above 0 K ( far more than "googols"of possibilities).

    A better substitute sentence is "Isolated systems (or any universe of system plus surroundings) of atoms and molecules at one instant or over a long period of time can only occupy a fraction of the microstates that are accessible to them. However, if not hindered from doing so, an isolated system (or universe) spontaneously changes to any macrostate in which a greater number of accessible microstates are possible." (See "What is a microstate" at

  5. "available microstates" is better expressed as "accessible microstates".
  6. "few microstates" is misleading. There are no molar systems above 0 K that have few microstates. Even every femtomole system above 0 K has far more than astronomical numbers of microstates.
  7. "are" should be "is".
  8. "transports" should be "that transports".
Originally published: J. Chem. Educ. 1999 76 1385
Last revised and updated: August 2004