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  Home > JCE Print > Journal of Chemical Education > Issues > 1999  > October  >
In the Classroom
Visualizing Entropy
Joseph H. Lechner
Mount Vernon Nazarene College, Department of Chemistry, 800 Martinsburg Road, Mount Vernon, OH 43050
Cover
October 1999
Vol. 76 No. 10
p. 1382
Abstract
This report describes two classroom activities that help students visualize the abstract concept of entropy and apply the second law of thermodynamics to real situations. (i) A sealed "rainbow tube" contains six smaller vessels, each filled with a different brightly colored solution (low entropy). When the tube is inverted, the solutions mix together and react to form an amorphous precipitate (high entropy). The change from low entropy to high entropy is irreversible as long as the tube remains sealed. (ii) When U.S. currency is withdrawn from circulation, intact bills (low entropy) are shredded into small fragments (high entropy). Shredding is quick and easy; the reverse process is clearly nonspontaneous. It is theoretically possible, but it is time-consuming and energy-intensive, to reassemble one bill from a pile that contains fragments of hundreds of bills. We calculate the probability P of drawing pieces of only one specific bill from a mixture containing one pound of bills, each shredded into n fragments. This result can be related to Boltzmann's entropy formula SÊ=klnW.
More Information
*  Citation
 Lechner, Joseph H. J. Chem. Educ. 1999 76 1382.
*  Keywords
 Introductory / High School Chemistry; Demonstrations; Statistical Mechanics; Thermodynamics
*  History
 Created:
Last Updated:		 September 6, 1999
June 23, 2005
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