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  Home > JCE Print > Journal of Chemical Education > Issues > 2005  > October  >
In the Classroom
JCE DigiDemos: Tested Demonstrations
A Device To Emulate Diffusion and Thermal Conductivity Using Water Flow
Harvey F. Blanck
Department of Chemistry, Austin Peay State University, Clarksville, TN 37044

checked by Thomas P. Gonnella
Department of Chemistry, Mayville State University, Mayville, ND 58257
Cover
October 2005
Vol. 82 No. 10
p. 1523
Abstract
Time places severe limitations on which experiments can be demonstrated in the classroom. Since diffusion in liquids is a slow process, most classroom demonstrations of diffusion involve gaseous diffusion. They do not show quantitatively the relative concentrations of the diffusing substances nor do they demonstrate the various different general methods of determining diffusion coefficients. An acrylic plastic device has been designed using water flowing through a series of cells to visually emulate diffusion and thermal conductivity. Water height emulates concentration or temperature. It can emulate a steady-state condition in which there is a constant gradient of concentration or temperature change with distance as well as the approach to this steady state. It can emulate experiments in which mass diffuses across a boundary showing the resulting 1 - error function curve. It can emulate diffusion from a plane (point) source forming a Gaussian curve. Results are obtained in a matter of a few minutes. The lightweight, rugged plastic model is easy to transport, easy to use, easy to store, has no moving parts, and requires only water to operate. This mechanical device should be quite helpful in both classroom and laboratory discussions of diffusion and thermal conductivity.
More Information
*  Citation
 Blanck, Harvey F. J. Chem. Educ. 2005 82 1523.
*  Keywords
 Analogies / Transfer; Demonstrations; Physical Chemistry; Physical Properties; Solutions / Solvents; Transport Properties; Upper-Division Undergraduate
*  History
 Created:
Last Updated:		 August 30, 2005
September 8, 2005
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