letters Demonstrating Simultaneous Boiling and Freezing To the Editor: The April 1992 Tested Demonstration of simultaneous boiling and freezing can be much more simply carried out by placing 20 rnL of water in an expanded polystyrene cup along with a small, 3 4 i n . long thermometer, and then using a vacuum pump and bell jar to reduce pressure. The water quickly begins to boil, the temperature of the water slowly drops, and after about 5 min, the water freezes. I've found that freezing water by boiling it in this way does much to illustrate the concepts of internal energy and the energy to boil water came out of the water itself (hence the need of an insulated cup or the water would remain at room temperature), and they seem amused by the somewhat perverse logic that boiling water in an insulated cup at reduced pressure must result in the water freezing. Mark R. Hiza Westtown School Wesnown. PA19395
introduction of the metric svstem after the French revolution, the ~ranco-Americaniiaison, and the comparatively recent introduction ofthe S.I. with its thousandfold steps. A. A. Wolf Facultyof Applied Science, Bristol Polytechnic Bristoi BS 16 lQY,U.K.
Graphical Grade Scaling To the Editor: I am writing to call attention to a graphical equivalent for the grade scaling procedure described by Baily (J. Chem. Educ. 1992.69.221). It eives the same result. but I find it even simpler than thealgebraic procedure. The scale on the X-axis of the graph represents raw scores, and the scale on the Y-axis scaled scores. Draw a straight line determined by the two points (100,100)and (raw class average, desired class average). Each raw score can then be converted to a scaled score bv readina- the Y-values directlv from the line.
To the Editor: Mark Hiza is certainly correct that it is simple to freeze water in an expanded polystyrene cup and the role of the insulation is interesting. It took our "feeble"vacuum pump 15 min to freeze about a third of 20 mL of water in an expanded polystyrene cup. However, the white background and the sides of the cup made visual observation more diF ficult and less satisfylng. When the cup was cut down to a hcinht of3 cm to improvovisibilitv, 15mLof water froze on the-surface only after 40 min and 5 mL of water froze on the surface after about 22 min. The connection between bumping and freezing noted previously is much more difficult to observe. An attempt to remedy this by maldng the interior of the cup blue with a permanent felt-tip marker was largely unsuccessful. It is interesting that cutting off the top of the cup seems to reduce its insulating capacity significantly. Mlke Elllson Evergreen H ~ g hSchool 143W NE 18th St. Vancouver, WA 98684-7899 The Quest for Mistakes Contrary to Carvajal's belief [J. Chem Educ. 1992,69, 4981 the English and the Spanish billion are identical! According to the Oxford English Dictionary the Latin numerical prefixes bi, tri, quadri, etc. have been used commonly since the 17th century to denote a million raised to these Dowen. It was French arithmeticians who reduced the raiio in the geometric progression to a thousand and so devalued the billion, a practice followed in the United States and nowadays inireasingly imitated in the United Kingdom. Perhaps to avoid confusion science students could adhere to the defined S.I. prefixes. Thus the tera prefix could replace the original billion or the equivalent "American" trillion. However as Greenwood has pointed out, the derivation of some S.I. prefixes is "almost unbelievably grotesque" and certainly unsystematic compared with the old expotential notation. For teaching purposes a historical perspective can be given to the billion-dichotomy because it has links with the 536
Journal of Chemical Education
Trevor Robinson University of Massachusetts at Amherst Amherst, MA01003 A Suggestion for Regulation-Sized Posters
To the Editor: Our department receives several kilograms per year of posters announcing- opportunities for off-campus research - experiences, summer undergraduate research, graduate study, etc. We genuinely appreciate receiving this material. Since these are worthwhile activities and we wish to encourage our students to participate, we purchased two 48 in. x 96 in. (122 cm x 310 cml bulletin boards. had them mounted in locations, and use them &clusively for displaying academic program announcements. The posters in our collection average 11in. wide x 17 in. high (28 cm x 43 cm). With slight overlapping, we can display 27 such posters on a bulletin board, completely covering its surface. Still, only a small fraction of the total posters can be accomodated; consequently, we rotate our display twice a year. Unfortunately, some items are oddly shaped andlor much-larger-than-average; the largest poster we have seen measures 17 in. x 25 in., and the most irregularly shaped one measures 9 in. x 21 in.. Since we always have more material than we can use, oversized posters are less likely to be selected; if they are chosen, fewer total posters can be diplayed. we think academicdepartments shouldvoluntarily adopt a standard size for their promam announcements.We sueeest maximum dimensions bf 10.7 in. wide x 16 in. high (27& x 40.6 cm); any attachments (e.g., reply postcards) should lie completely within the borders of the poster. Potential benefits to de~artmentsfrom observine the proposed size limit would include lower printing expenses, decreased postage costs. and meater likelihood of their in hew Gits intended audience. material b&ng
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Joseph H. Lechner Mount Vernon Nazarene Colleoe 800 Man nsburg R O Mount Vernon. Oh43050
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