Wednesday, March 7, 2012

Entropy Machinations

Entropy* is a difficult concept to grasp. It's like the silent chaos created when ice melts to water. The crystalline phase disappears; internally, frustrated solid-phase lattice vibrations silently convert into liquid liquid-phase translations and rotations; degrees of freedom are conserved but increase their measure. Proton transfer becomes possible. And yet nothing has changed chemically because ice is still water except in degree. Entropy increased. Disorder ensued.

Entropy can also decrease--enzymes do this unto entropy all the time as does anything which expends energy ordering things around. This video animates making order out of chaos--decreasing entropy: the red and green blocks sort themselves and separate. The ordering happens because the red blocks differ slightly from the green blocks and fit together better.

1868, from Ger. Entropie "measure of the disorder of a system," coined 1865 (on analogy of Energie) by German physicist Rudolph Clausius (1822-1888) from Gk. entropia "a turning toward," from en "in" (see en- (2)) + trope "a turning" (see trope). Related: Entropic.


  1. The red blocks could share a common attraction (magnetic?) different than the green ones. The attraction is weak enough that the thermal energy (fast rotation) can overcome it.

    So it's also a nice demonstrative for spatial preference (fit) or intermolecular attraction.

  2. I don't understand why Clausius didn't just call entropy "disorder" or, by analogy to the published etymology, enchaos = en + kaos, or something similar. Maybe they had no intuitive grasp of the concept. Maybe I'm missing something.