Chemical Education Today
From Past Issues
1964 and 1984 by Kathryn R. Williams
In 1964 and 1984 I continue looking at JCE issues at 20-year intervals, as begun in the August 2004 issue (1) for 1924 (JCE’s inaugural year) and 1944. I now progress to modern times—the years I remember—1964 and 1984 (Volumes 41 and 61). From Volume 41, 1964 Although computerized databases have contributed immeasurably to our ability to locate specific information, I still rely on the fingerwalking method, which results in my most interesting finds. Strolling through volume 41, I paused briefly at “Data Correlation Experiment” (2), which describes a contraption reminiscent of the “5-0-2” featured in a previous article in From Past Issues (3). But I decided to focus on “The Calorimeter and Its Influence on the Development of Chemistry” (4). Here the author, George T. Armstrong, traces calorimeter design from the first comparative measurements in the mid-1700s (for example, the ice calorimeter in Figure 1) to the high precision and specialty instruments of the 20th century, like Dickenson’s 1914 version, shown in Figure 2. While the details of calorimeter construction may fail to stimulate the average JCE reader, what captured my interest was the second part of the title—Armstrong’s reflections on the importance of calorimetric data in the formation of physical laws, in particular those of Hess and DuLong and Petit. In most texts, the Hess law of heat summation is introduced as a useful result of the first law of thermodynamics. The historical events happened in the opposite order, however. In the 1830s and 1840s, Hess measured heats of dilution and neutralization for acids in various stages of dilution.
The consistency of the sums (reaction + dilution) led him to form his original heat summation hypothesis. Further measurements of greater accuracy and precision verified Hess’ findings for a variety of chemical systems, and led to the establishment of the first law several decades later. Here we have a classic example of the scientific method (data collection, hypothesis, further experimentation, verification, physical law). With just a small change in the order of presentation, the Hess hypothesis can be taught in historical context to show students one aspect of how thermodynamics developed in the 19th century. Armstrong also reminds us that a theory does not necessarily have to survive the rigors of the scientific method to contribute to the advance of knowledge. In 1819, DuLong and Petit based their hypothesis that “atoms of all the elements have exactly the same capacity for heat” on the seeming constancy of the product of specific heat capacity and atomic weight. Later in the 19th century, more accurate and extensive data on both properties showed that the hypothesis was not valid. However according to Armstrong, the proposal “provided a working criterion with which to compare measurements, and a stimulus for improving calorimetric measurements to ascertain whether the calorimetry, the atomic weights, or the law was in error…”. Essential to these developments was the extension of heat capacity measurements to very low temperatures. Those results eventually led to Einstein’s 1905 explanation on the basis of absorption of energy in quanta. The take-home message for all scientists: even a failed theory can have a very positive impact on the progress of science. From Volume 61, 1984
Figure 1. Ice calorimeter designed by Lavoisier and Laplace in 1784. The hot object or reaction in the innermost cup caused ice in the concentric funnel to melt. The water was collected and weighed, and the heat liberated by the process was calculated using the heat of fusion of ice; J. Chem. Educ. 1964, 41, 298 and cover.
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Fast forward to 1984. I flipped through the first 25 pages of this volume and behold: two familiar names, John and Elizabeth Moore. The present JCE editorial team organized the symposium, “Will Computers Replace TA’s? Professors? Labs? Should They?” for the Fall 1983 National ACS Meeting. Their report includes the papers submitted by the key participants and John Moore’s summary of the panel discussion at the meeting (5). The symposium title still intrigues (and plagues) us today. Several of the participants’ papers focused on specific computer uses (for example, spreadsheets for equilibrium calculations, computer-enhanced experiments, simulations of physical models), many of which are commonly used today. Other participants addressed the title questions directly. Although Moore’s summary of the responses is more inclusive, I prefer the sound bite approach of Stanley G. Smith, in particular “A computer is a tool: good teachers cannot be replaced by a computer.” But this blunt assertion must be interpreted in context with his follow-up statements: “…a good teacher will use the computer to be even better. The objective is not to replace anybody, but to do a better job of
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From Past Issues teaching. The computer, as demonstrated by experiments, does serve that role.” Twenty years later, I think we all agree with Smith’s assessment. Computer availability has generated more jobs, and not just for IT personnel. There is also obvious need for more good teachers to design meaningful instructional materials and to oversee chat rooms and other interactive learning scenarios. Satisfied that I would not be losing my day job to a PC, I continued my walk through volume 61. After paging through the entire year, I returned to the April issue, which contains a 16-paper collection on “Chemistry of the Food Cycle—State of the Art” (6). The April cover, reproduced in Figure 3, shows in cartoon form the five stages of the food cycle: food growth, the post-harvest/post-mortem period, processing, storage, and consumption. In their lead article (6), symposium organizers Irwin A. Taub and Marcus Karel provide further background on the cycle and introduce the papers covering each aspect. As an example, consider “Chemical Effects during the Storage of Frozen Foods” (7), parts of which can add interest to lectures in a variety of scenarios. Beginning students and nonmajors should appreciate some of the physical considerations of ice formation, e.g., the freezing point depression caused by polar and ionic solutes and the phenomenon of supercooling. The rate of freezing also has profound effects on stored foods. As in any crystallization process, rapid freezing produces small ice crystals that are much less damaging to plant cell walls than the large crystals formed by slow cooling. Long-term storage at subfreezing temperatures also
Figure 3. Cover from the April 1984 issue of the Journal of Chemical Education showing the five stages of the food cycle; J. Chem. Educ. 1984, 61.
leads to significant chemical changes: free radical oxidation of lipids, aggregation of lipo- and fibrous proteins, and conformational changes in proteins. These reactions, as well as those described in other symposium papers, can add interest to lectures in organic and biochemistry. The food cycle symposium has special relevance in light of the growing public concern about diets and nutrition. Interested readers will be happy to learn that they can find the full text of all articles in the symposium (6) on JCE Online at http://www.jce.divched.org; articles may be accessed by using the Search JCE Index feature, using the information in the citation. Literature Cited
Figure 2. The Dickenson design was the forerunner of many bomb calorimeters in use today. This schematic diagram of an assembled Dickenson calorimeter with jacket shows B, bomb; C, calorimeter vessel; J, jacket wall; P, resistance thermometer; FL, firing leads; CS, calorimeter stirrer; JS, jacket stirrer; TV, tube to thermostat valve; H, jacket heater; TB, thermostat bulb; TH, tubular housing. Drawing from NBS; J. Chem. Educ. 1964, 41, 302.
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1. Williams, Kathryn R. Four Score Years Ago. J. Chem. Educ. 2004, 81, 1090–1091. 2. Cunning, Joe D.; Burnet, George Jr.; Levenspiel, Octave. Data Correlation Experiment. J. Chem. Educ. 1964, 41, 35–37. 3. Williams, Kathryn R. Early Automated Testing: The 5-0-2. J. Chem. Educ. 2002, 79, 16. 4. Armstrong, George T. The Calorimeter and Its Influence on the Development of Chemistry. J. Chem. Educ. 1964, 41, 297– 307. 5. Moore, John W.; Moore, Elizabeth A. Will Computers Replace TA’s? Professors? Labs? Should They? A Symposium Report. J. Chem. Educ. 1984, 61, 26–35. 6. Taub, Irwin A.; Karel, Marcus. Chemistry of the Food Cycle— State of the Art. J. Chem. Educ. 1984, 61, 270–367. 7. Powrie, W. D. Chemical Effects during Storage of Frozen Foods. J. Chem. Educ. 1984, 61, 340–347.
Kathryn R. Williams is in the Department of Chemistry, University of Florida, P. O. Box 117200, Gainesville, FL 326117200;
[email protected] Vol. 81 No. 9 September 2004
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