MadSci Network: Chemistry

Re: Quantum tunneling and violation of 2nd law of thermodynamics

Date: Thu Apr 13 17:07:55 2006
Posted By: Ara Kooser, Grad student, Physical Chemistry, Sandia National Labs
Area of science: Chemistry
ID: 1144808429.Ch

Part I.

To my knowledge so far only sub-atomic particles tunnel. Molecules do not tunnel so you can't take advantage of quantum mechanics.

The probability of tunneling occurring is governed by this equation P= e(-2KL). L is the length of the barrier and K is the wave number. [ (-2KL) is an exponent] K contains the mass of the tunneling object so roughly; the exponent of the probability function is proportional to mass and barrier length.

This means the probability of tunneling decreases exponentially as you increase mass and barrier length. The mass of a molecule is orders of magnitude greater the an electron. A good book on physical chemistry will have all the gory and painful details of the math. Physical Chemistry, Atkins 7th Edition.

Part II.

The problem you pose is a slight variation on the thought experiment of James Clerk Maxwell. Maxwell's Demon.

From Wikipedia ('s_demon)
"Maxwell imagines two containers, A and B, filled with the same gas at equal temperatures, placed next to each other. A little "demon" guards a trapdoor between the two containers, observing the molecules on both sides. When a faster-than-average molecule from A flies towards the trapdoor, the demon opens it, and the molecule will fly from A to B. Thus, the average speed of the molecules in B will have increased, while the molecules in A will have slowed down on average. However, since average molecular speed corresponds to temperature, the temperature in A will have decreased and in B will have increased; this is contrary to the second law of thermodynamics."

The demon can either be a real demon or some mechanical means of separating molecules.

There are biological examples of Maxwell's Demon mechanism listed on the Wikipedia site.

Thanks for the question. I hope this answers everything. If not let me know.

Current Queue | Current Queue for Chemistry | Chemistry archives

Try the links in the MadSci Library for more information on Chemistry.

MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci

MadSci Network,
© 1995-2006. All rights reserved.