Students Learn through Teaching
To the Editor: One of the best ways for students to learn is to teach each other. I would like to share with your readers a mechanism I have been using for this purpose in my course on chemical instrumentation. This procedure can be used in any laboratory course where students rotate'through a number of assigned experiments. At the first meeting of the class each instrument (or experiment) is described briefly. A tour of the laboratory follows. At this time each student picks one instrument to be his own responsibility. He then gets 12-18 laboratory hr to get the instrument working and t o develop, test, and write up two experiments for his instrument. The student is left on his own (insofar as this is possible) to utilize manufacturer's literature, textbooks, and the chemical literature in working with his instrument. This experience in itself is one of the most valuable aspects of the procedure. If the student flounders too long, he is led into more productive channels. After the student completes this first. assignment, he then works his way through the remaining experiments. Should he experience difficulty with an instrument, he first consults the student ''expert" on that instrument. If the "expert" can't solve the problem, then the instructor steps in. Following the initial hectic period of the term, the instructor has little to do. My students have been very much in favor of this procedure. It gives each of them an in-depth experience with one instrument, as well as the traditional "one-shot" experience with each of the remaining instruments.
the Volkswagen 11,900 (miles) (gm)/gm of fuel to 7680 (miles) (gm)/gm of fuel. I n step 4, however, the situation became reversed when the energy content of the two fuels used w a s introduced. Qualitatively, this did not appear correct since I have always considered that similar hydrocarbons have similar heats of combustion. Quantitatively, I was not dissappointed. The "Handbook of Chemistry and Physics" lists the heat of combustion of lard as 9.300 kcal/gm and gasoline as 11.528 kcal/gm. If these values are combined with the (miles) (gm)/ gm of fuel values we find that the hummingbird wins with 1280 (miles) (gm)/kcal to 665 for the Volkswagen, or a ratio in fa.vorof the hummingbird by almost 2 to 1.
T o the Editor: I was interested in the revised calculations concerning the Volkswagen versus the hummingbird offered by G. Nebhia [THIS JOURNAL, 46, 701 (1969)], in which he divided the value obtained for the hummingbird by the heat of comhustion value for gasoline and the value ohtained for the Volkswagen by the heat of combustion for animal f a t to find their efficiencies to be about equal. If instead one matches the hummingbird with the animal fat and the Volkswagen with the gasoline, the efficiencies would he: Hummingbird Volkswagen
The Hummingbird Returns
T o the Editor: The poor little hummingbird has been had. I n "Fuel Conversion in Transport Phenomena," J. CHEM EDUC.,46, 455 (1969), the hummingbird was leading
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11 900 = 1322 (miles) (g)/kcal 9
= 640 (miles) (g)/kcal E0 12
and the hummingbird would he almost twice as efficient as the Volkswagen. I hope this may offer some aid to E. R. Gerlach [THISJOURNAL, 46, 455 (1969)l in his defense against the Volkswagen.
