In the Classroom
JCE Concept Connections: An In-Depth Look at Surface Chemistry JCE offers a wealth of materials for teaching and learning chemistry that you can explore at our Web site, JCE Online (http://www.jce.divched.org/). In the list below, Randall J. Wildman of the Editorial Staff suggests additional resources on surface chemistry that are available through JCE. Demonstrations The previous article “Marangoni Flowers and the Evil Eye: Overhead Presentations of Marangoni Flow” is a spectacular demonstration of surface tension as it changes over distance and over time. It brings to mind other spectacular phenomena that result from surface tension and will make students go “wow!”: The “classic” surface tension demonstration, showing things floating that would otherwise sink (in this case, metal “needles”): The Floating Needle. Condon, F. E.; Condon, F. E., Jr. J. Chem. Educ. 2001, 78, 334. Demonstrations of surface tension (solid–liquid as well as liquid–air) using magic sand: Chemistry Comes Alive! Vol 8; Bonus Topics: Magic Sand (http://www.jce.divched.org/JCESoft/CCA/CCA8/ MAIN/8/98/04/menu.html)
JCE Classroom Activity #23: Magic Sand. JCE Editorial Staff. J. Chem. Educ. 2000, 77, 40A. Overhead Projector Demonstration: Illustrating the Properties of Magic Sand. Goldsmith, R. H. J. Chem. Educ. 2000, 77, 41.
A “magic sand”-like process applied to glass beads and capillary tubes also opens the door to demonstrating surface tension phenomena: Enchanted Glass. Szabó L., S.; Mazák, K.; Knausz, D.; Rózsahegyi, M. J. Chem. Educ. 2001, 78, 329.
The effect of glycerol and soap on surface tension and viscosity and an introduction to surfactants: JCE Classroom Activity #32: Bubble, Bubble, Toil and Trouble. JCE Editorial Staff. J. Chem. Educ. 2001, 78, 40A. And what better outreach to young “future chemists” than soap bubbles? Here’s a beautiful immersion into the colorful, ethereal world of soap bubbles and kids and an activity on basic surface phenomena: Soap Films and the Joy of Bubbles. Saecker, M. E. J. Chem. Educ. 2005, 82, 1447. JCE Classroom Activity #23: On the Surface: Mini-Activities Exploring Surface Phenomena. JCE Editorial Staff. J. Chem. Educ. 1998, 75, 176A.
And finally, a demonstration showing that small bubbles need a higher pressure of enclosed gas to form due to the increase of surfaceto-volume ratio. (Note the compelling discussion at the end of this article for how quantifying this pressure difference can lead to in-situ measurements of surface tension. Independent study project, perhaps?) Overhead Projector Demonstrations: Demonstration of Surface Tension. Rosenthal, A. J. J. Chem. Educ. 2001, 78, 332. Analysis After seeing all this, how can a student not want to analyze these systems? Here’s some help in doing just that. Foams, from beer head to insulating polymer foams, can be analyzed in terms of surface tension. Here are two articles that analyze foam. The first shows how a student can measure the rate of the collapse of a foam in a liquid, and the second shows how a student can measure a dynamic surface tension and how it better predicts foaming tendency (which the student can also measure) better than a static surface tension: Playing with Liquid Foams: Learning Physical Chemistry. Ritacco, H. J. Chem. Educ. 2008, 85, 1667. A Low-Cost Dynamic Surface Tension Meter with a LabVIEW Interface and Its Usefulness in Understanding Foam Formation. Spanoghe, P.; Cocquyt, J.; Van der Meeren, P. J. Chem. Educ. 2001, 78, 338.
How does one actually measure surface tension? The student manual in the supplemental material for the following article has a concise description of a standard technique for doing this: Surfactant Adsorption: A Revised Physical Chemistry Lab. Bresler, M. R.; Hagen, J. P. J. Chem. Educ. 2008, 85, 269. Dynamic surface tension can be measured in at least two ways—minimum bubble size with corresponding pressure and maximum drop size before said drop detaches from the formation point: A Simplified Method for the Determination of Critical Micelle Concentration. Castro, M. J. L.; Ritacco, H.; Kovensky, J.; Fernández-Cirelli, A. J. Chem. Educ. 2001, 78, 347
A Low-Cost Dynamic Surface Tension Meter. Spanoghe, P.; Cocquyt, J.; Van der Meeren, P. J. Chem. Educ. 2001, 78, 338.
Qualitative analysis showing that things with greater surface tension have rounder droplet shapes: A Demonstration of Surface Tension and Contact Angle. Gesser, H. D. J. Chem. Educ. 2000, 77, 58. The shape of a drop at various stages of growth depends on surface tension: Axisymmetric Liquid Hanging Drops. Meister, E. C.; Latychevskaia, T. Y. J. Chem. Educ. 2006, 83, 117. Molecular model of glycerol—the actual structure differs from what a student might expect after looking at the Lewis structure: JCE Featured Molecule: Glycerol. http://www jce.divched.org/JCEWWW/Features/MonthlyMolecules/2002/Oct/index.html The JCE articles and Web pages cited above have access dates of Apr 2009. All articles from Volume 1 to the current issue are available in full-text PDF at JCE Online. Going to the JCE Previous Issues home page (http://www.jce.divched.org/Journal/Issues/index.html) is a convenient way to browse articles by year, month, and page. To search for articles by title or author in all issues of JCE, go to the JCE index (http://www.jce. divched.org/Journal/Search/index.html).
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© Division of Chemical Education • www.JCE.DivCHED.org • Vol. 86 No. 7 July 2009 • Journal of Chemical Education
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