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  Home > JCE Print > Journal of Chemical Education > Issues > 2005  > February  >
In the Classroom
JCE DigiDemos: Tested Demonstrations
Hard Water and Soft Soap: Dependence of Soap Performance on Water Hardness. A Classroom Demonstration
Viktoria K. L. Osorio, Wanda de Oliveira, and Omar A. El Seoud
Instituto de Química, Universidade de São Paulo, 05513-970 São Paulo, Brazil

checked by Wyatt Cotton
Science Division, Cincinnati State College, Cincinnati, OH 45223

Jerry Easdon
Department of Chemistry, College of the Ozarks, Point Lookout, MO 65726

Cover
February 2005
Vol. 82 No. 2
p. 257
Abstract
We describe a series of classroom demonstrations presented to high school students. The demonstrations were carried out to answer the question: Why does soap not foam in seawater? We generalized the question into: Why does soap performance depend on the hardness of the water used? A sequence of experiments was carried out to compare the performance of soap in soft and hard water and to illustrate the water-softening action of EDTA and zeolites. The experiments permitted the students to identify the species responsible for seawater hardness, to explain the softening action of EDTA and zeolites, and to appreciate the need for water treatment and the use of builders in commercial detergent formulations.
More Information
*  Citation
 Osorio, Viktoria K. L.; de Oliveira, Wanda; El Seoud, Omar A. J. Chem. Educ. 2005 82 257.
*  Keywords
 Environmental Chemistry; Problem-Based Learning; Water / Water Chemistry
*  History
 Created:
Last Updated:		 January 4, 2005
January 12, 2005
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