Chemical Education Today
Letters Assessment of Knowledge The article “Assessment of Knowledge Acquired in an Organic Course”, recently published in this Journal (1996, 73, 231), constitutes a representative example of how easy it is to obtain erroneous conclusions in this class of studies. The authors posed to 108 students four options to explain why glycerol is a polar compound, namely: 1. Alkane is classified as nonpolar and glycerol as a polar compound because all alkanes are nonpolar. 2. The hydroxyl functional group is polar. 3. The differences in electronegativity of the different bonds can be analyzed. 4. Based on its polar bonds, glycerol is a polar compound, which distinguishes it from alkanes.
After analyzing the responses they conclude that 83% of students “…could give a description of the problem, analyze it… . ...we consider these results to be acceptable in terms of knowledge demonstrated by these students… .” This conclusion seems to me unacceptable. I imagine 108 students thinking which of the four few consistent options will be considered correct by their teachers, the 83% deciding for 3 (because analyzing something is always appropriate) or 4 (basing on something is also convenient). Alternatively, the 83% of the students decide according to what they have learned from their teachers. Indeed, the authors consider that the best alternative to explain the fact that glycerol is a polar compound is option 3. Probably a printer’s devil replaced atoms by bonds but, as written, a normal student would never select this option. The second-best alternative, also according to the authors, is option 4. Maybe they ignore that the polarity of the bonds is not a condition sufficient to make a molecule polar. Consequently, a plausible interpretation of the results of the study is that 83% of the students followed the course, in this case unfortunately, with sufficient attention. How-
ever, 18 students (those moving against preoccupation with their teachers by having selected option 2) showed resistance to accepting erroneous concepts and selected the unique statement as correct. Interpretations apart, the main conclusion I have obtained after reading this article is: also in a Facultad de Ciencias Agropecuarias, chemistry courses should be conducted by a Department of Chemistry instead of—as recognized in the article—by the Applied Biology Department. Francisco J. Arnáiz Laboratorio de Química Inorgánica Universidad de Burgos 09001 Burgos, Spain
✍ Redox Rap In Laura Kolonie’s letter “Redox Rap” (J. Chem. Educ. 1997, 74, 22), she inadvertently attributes the song “Rock Me Gently” to Neil Diamond. In fact, this song (Capitol #3895) was a number-one hit for Andy Kim in July of 1974. Kim, a Canadian-born artist, also co-wrote the Archies hit “Sugar, Sugar” (with Jeff Barry, #1 in August 1969). Many have compared Andy Kim’s singing voice to that of Diamond, but the interest of accuracy, in what is an otherwise interesting letter, I thought I should correct this case of mistaken identity! Dean Ellerton Suffield Academy Suffield, CT 06078 continued on page 1396
Corrections We apologize for the following errors that appeared in our article (J. Chem. Educ. 1997, 74, 1117–1121): The caption for Figure 4b (the HPLC separation) should read: 1 = 4acetamidophenol, 2 = caffeine, 3 = acetylsalicylic acid, 4 = salicylic acid. Secondly, the capacity factor (k') listed in Table 1 for norephedrine is for caffeine, not for norephedrine. Timothy G. Strein Department of Chemistry Bucknell University Lewisburg, PA 17837
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Unfortunately, a structure error appeared in my article (J. Chem. Educ. 1997, 74, 1055–1059). Structure 5 should have been methyl ohydroxybenzoate (shown at right), and not the methyl p-hydroxybenzoate shown in the article. The boiling point given, 222 °C, is correct for methyl salicylate (methyl o-hydroxybenzoate) and this material is an oil under ambient conditions with a freezing point of -8.6 °C. Methyl phydroxybenzoate is a solid under ambient conditions with a melting point of 131 °C, a boiling point of 280 °C at 708 mm Hg, and no special flavor attributes. Martin Hocking Department of Chemistry University of Victoria Victoria, BC V8W 3P6 Canada
Journal of Chemical Education • Vol. 74 No. 12 December 1997
CO2CH3 OH
5 methyl salicylate b.p. 222 °C wintergreen
Chemical Education Today
Letters continued from page 1384
Egg in the Bottle Revisited Doris Kolb (J. Chem. Educ. 1996, 73, A189) regretted the error that appeared in the June 1995 issue of the Journal regarding the real reasons for reducing the internal pressure in a bottle after the flame of a burning paper inside is extinguished. Not the loss of oxygen inside the bottle, but the cooling of the gas (inclusive of the produced carbon dioxide!) and the condensation of water vapor allow the egg to be pushed into the bottle. In the reply the error was explained as a mix-up with a related demonstration in which an inverted drinking glass is lowered over a burning candle, which is floating in a cork on a dish of water. In the cited demonstration, mostly the same effects as in the experiment with the egg reduce the pressure inside the drinking glass, even though in this demonstration the gas is in contact with water. Under the described circumstances (without shaking), carbon dioxide is not very water soluble. Besides, the candle flame goes out before the oxygen inside the glass gets used up. Concrete tests come to 16% of remaining oxygen. You can check my claim about the solubility of carbon dioxide in a very simple way: fill the drinking glass with pure carbon dioxide at the same temperature as the water; cover the drinking glass, then open it when the rim is below the surface of the water. The level inside the glass rises only a little during one hour, although there is pure carbon dioxide inside and not a mixture of mainly nitrogen, a lot of remaining oxygen, and only a little bit of carbon dioxide as in the demonstration with the candle. When the dish is filled with limewater, the level inside the glass rises faster,
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of course. But in this case the reduced pressure is due to the formation of solid calcium carbonate. Nevertheless, the note about getting the egg out of the bottle with vinegar and baking soda is very useful. Viktor Obendrauf A-8342 Gnas 136 Austria The author replies: Thank you. I certainly appreciate the information that Professor Obendrauf has provided in his note. Doris Kolb Bradley University Peoria, IL 61625
About Letters to the Editor Letters to the Editor may be submitted to the editorial office by regular mail (JCE, University of Wisconsin–Madison, Department of Chemistry, 209 N. Brooks, Madison, WI 53715-1116), by fax (608/2627145), or by email (
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Journal of Chemical Education • Vol. 74 No. 12 December 1997
