Chemical Education Today
Reports from Other Journals
The Physics Teacher: To a Physics Teacher a Mass Is Mass. To a Chemistry Teacher a Mass Is a Mess by Roy W. Clark
With this in mind, I searched JCE Index for “fluorescent light” and found only three articles, none of which explained how fluorescent lights worked. One was a suggestion as to what a chemist might do with discarded fluorescent tubes (no, not as Darth Vader swords!) (1), another reported an analytical hazard of fluorescent lighting (it darkens precipitated silver chloride) (2), and the third was a short biography of Elliot Quincy Adams, a chemist who worked for General Electric Co. during the development of these lamps (3). Perhaps one of our readers will soon submit a chemists’ view of fluorescent lighting.
Fluorescent Lights
The thermometer article by Gash is a good reminder of two trends in both chemistry and physics. One unfortunate trend is that we often forget about emergent stem corrections for our old glass/mercury thermometers. The other is that in the rush to thermocouple and thermistor thermometers, the trend seems to be to trust the calibration to the manufacturer rather than to do it yourself. Unless you have done some calibration, the digits in an electronic thermometer display are not all significant figures. Gash’s article is a good review of the glass thermometer as an active instrument, one that exchanges thermal energy with the mass being investigated.
Silverman’s article is a very clear explanation of how fluorescent light works. Chemistry teachers have little difficulty explaining tungsten filament incandescent light bulbs to an audience. But do your students ever ask how a fluorescent light works, and can you tell them? Why do some have “starters,” whereas others do not (the lights, not the students)? Do the bulbs have filaments? Why are they called fluorescent lights? Why are the bulbs a hazardous waste disposal problem, if they are? The physicist Silverman will tell you how fluorescent lights work, why some need starters, and that they contain a phosphor, but he won’t tell you about the chemical composition of the phosphor. He will tell you that there is mercury inside that is vaporized during operation, but he won’t tell you how much, or if it is a hazard during disposal of these popular lamps. So a chemist needs to look elsewhere for these answers.
14
“Power, Reaction, and Excitement… in an AC Circuit” by Mark P. Silverman (TPT, 2002, 40, 302–307) “So You Thought a Glass Thermometer Measured Temperature?” by Phillip Gash (TPT, 2002, 40, 74–76) “An Archimedes’ Principle Activity” by Hasan Fakhruddin (TPT, 2002, 40, 376)
Glass Thermometers
Archimedes’ Solution Finally, the third article from TPT by Fakhruddin illustrates that the world is not always as simple to the chemist as it is to the physicist. This article postulates the case of a large beaker containing water. Within this beaker is a smaller beaker containing only a block of wood. The small beaker is a
Journal of Chemical Education • Vol. 80 No. 1 January 2003 • JChemEd.chem.wisc.edu
TPT Featured Aticles
Is the study of light physics or chemistry? What about the study of electricity and electrical conductance? How about heat and temperature measurement? These questions seem reasonable in a world that has classified scientists into many separate groups so that the public might have a vague idea about what they do for a living. The answer to these questions is that any reproducible phenomenon is a proper subject for study by any of the natural philosophers of the world, to use an old term. Nevertheless, it is fair to say that physicists prefer to study and explain phenomena in which the composition of the materials utilized in the experiment is less important than the behavior of those materials. Physicists know, for example, that “iron bars do not a prism make.” But glass makes a fine prism. So physicists study the light, not the glass. Chemists, on the contrary, immediately ask how and of what is glass made? To a physicist constructing a circuit a wire is a wire. Copper or stainless steel, or silver, who cares? To a chemist dipping this wire into solutions to construct an electrochemical cell, the type of wire matters very much. If a falling object is a bowling ball or a bottle of hydrochloric acid, who cares? In physics a mass is a mass, its composition to be ignored. In chemistry a mass is a mess, a mess that is to be sorted and configured as a variable parameter in a chemistry experiment. With this as a theme, I suggest three recent articles from The Physics Teacher (see box).
Chemical Education Today
ship containing a wooden cargo. The question is then asked, if the block is removed from the smaller beaker and allowed to float in the larger beaker, will the level of the water in the larger beaker (a) rise (b) fall (c) stay the same? I’m sure you have the answer in mind already. If it is wood and floats the answer is different from the same question using a block of iron, which doesn’t float. But being a physicist, Fakhruddin neglects to consider the case of the cargo being an equal volume of salt (notice that I don’t say NaCl here because the physicists might not recognize this peculiar notation). Now what will happen? It seems to matter what the mass is composed of, so we chemists best take over
here and leave the physicists eating our dust. Hey, I wonder what’s in dust? Literature Cited 1. Bishop, J. A. J. Chem. Educ. 1956, 33, 372. 2. Blackmon, M. C. J. Chem. Educ. 1945, 22, 292. 3. Tarbell, D. S. J. Chem. Educ. 1990, 67, 7.
Roy W. Clark is in the Department of Chemistry, Middle Tennessee State University, Murfreesboro, TN 37132;
[email protected].
JChemEd.chem.wisc.edu • Vol. 80 No. 1 January 2003 • Journal of Chemical Education
15
