Chemical Education Today
Report: My Favorite Element
Professor Gallium by Mary E. Saecker
photos by Jim Maynard
“A Demo a Day!” was a motto of Norman Craig, my physical chemistry teacher at Oberlin College. Every class period, he devoted himself to making us think rigorously about chemical principles, while also bringing concepts, equations, and constants to life with thoughtful and often dramatic demonstrations. I loved that semester of chemistry and always looked forward to finding out what new idea would be on display. Twenty-three years later I can still feel the sense of surprise at seeing 50 mL of ethanol added to 50 mL of water to produce only 97 mL and give meaning to ΔVmix. I can still hear the whoosh of the tank of pressurized N2 as the valve was opened and a drop in temperature was measured to help us see the Joule–Thompson expansion in action. I can still feel the cool rubber band on my lips after stretching it to give us an introduction to the development of the second law of thermodynamics. And I’m still indignant about the seemingly endless osmotic pressure demonstration showing a carrot pierced with a long hollow tube and standing in a beaker of water—it counted for several days of demonstrations, and even though the solution height in the column did increase, I wanted more! During one lecture, our demonstration turned out to be a story. At that point in the semester, we were in the midst of studying phase changes and Professor Craig said he had remembered an interesting fact about gallium: it has the wonderful property of melting just below body temperature (29.8 °C; 85.6 °F). He decided he would demonstrate this to our class in a way we would always remember. He would hide a bag containing some gallium next to his body and in the middle of class he would whip out the bag and reveal this marvelous metal and its memorable melting point. In order to prepare for the next day’s class, he told us that the night before he decided to try out his novel gallium demonstration. He prepared the bag, concealed it, waited for the sample to melt, and, voilà!, pulled out the bag. Only, the bag ripped and the gallium dripped all over him. While quite aware of the melting point of gallium, he realized he wasn’t sure of its toxicity. In a measure of precaution, he removed his galliumcoated trousers and donned a lab coat. A fellow professor came to his rescue and quickly found the Material Safety Data Sheet for gallium (1). As he ended his tale, he told us the moral of the
story: never perform a demonstration without knowing the dangers of the materials involved! Although we never actually got to see gallium melt at body temperature or even the trousers as evidence of this unfortunate mishap, the demonstration worked: I will always know gallium’s melting point. Gallium has many additional amazing properties and uses (2), and it is worthy of being anyone’s favorite element (3). For me, it is my favorite because it symbolizes a teacher completely dedicated to helping his students understand and appreciate chemistry as much as he did (4). Literature Cited (all sites accessed Jul 2009) 1. Gallium MSDS available at http://www.actiocms.com/msdsxchange/ english/index.cfm. 2. Banks, A. J.; Davis, E. M.; Holmes, J. L.; Jacobsen, J. J.; Kotz, J. C.; Moore, J. W.; Schatz, P. F.; Robinson, W. R.; Tweedale, J.; Young, S. Periodic Table Live! 3rd edition; JCE Software: Madison, WI, 2002. Gallium information and images available at http://www. chemeddl.org/collections/ptl/PTL/elements/Ga/frames.html. 3. It’s Elemental: The Periodic Table. Chem. Eng. News 2003, 81 (36), cover story; 89 essays celebrating the elements, each written by a different author, is available online at http://pubs.acs.org/ cen/80th/elements.html. Oliver Sacks’s essay on gallium is available at http://pubs.acs.org/cen/80th/gallium.html. 4. Sabatier, J. News: Craig Precipitates from Department. The Oberlin Review 1999, 128 (6; Oct 8); available at http://www. oberlin.edu/stupub/ocreview/archives/1999.10.08/news/craig.html; See also http://new.oberlin.edu/arts-and-sciences/departments/ chemistry/norman-c.-craig.dot; http://www.oberlin.edu/alummag/ oamcurrent/oam_fall_00/tappan03.html; http://www.oberlin.edu/ library/news/fall1995/observer_17_5.pdf.
Supporting JCE Online Material
http://www.jce.divched.org/Journal/Issues/2009/Oct/abs1134.html Abstract and keywords Full text (PDF) with links to cited URLs
Mary E. Saecker is an Associate Editor of the Journal of Chemical Education;
[email protected].
Gallium melting at body temperature.
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Journal of Chemical Education • Vol. 86 No. 10 October 2009 • www.JCE.DivCHED.org • © Division of Chemical Education
