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Visualizing Entropy

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Joseph H. Lechner

Mount Vernon Nazarene College, Department of Chemistry, 800 Martinsburg Road, Mount Vernon, OH 43050

J. Chem. Educ., 1999, 76 (10), p 1382

DOI: 10.1021/ed076p1382

Publication Date (Web): October 1, 1999

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 (ii) When U.S. currency is withdrawn from circulation, intact bills (low entropy) are shredded into small fragments (high entropy).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 SÂ =klnW.

Keywords (Audience):

High School / Introductory Chemistry

Keywords (Domain):

Demonstrations

Keywords (Pedagogy):

Analogies / Transfer

Keywords (Subject):

Statistical Mechanics

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This article has been cited by 1 ACS Journal articles (1 most recent appear below).

Thermodynamics for Visual Learners
Todd M. Hamilton
Journal of Chemical Education2003 80 (12), 1425
- Thermodynamics for Visual Learners
  Todd M. Hamilton
  Journal of Chemical Education2003 80 (12), 1425
  One of the difficulties in learning physical chemistry is mastering the many abstract concepts. Some students are visual learners and for them a picture is truly worth a thousand words. I have developed several examples for visual learners in the area of ...
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