Chemical Education Today
Commentary
Should We Put Observations First? Mansoor Niaz Chemistry Department, Universidad de Oriente, Apartado Postal 90, Cumaná, Estado Sucre, Venezuela 6101A;
[email protected] Understanding Chemistry According to Gillespie (1), most students feel that they do not have to understand chemistry but rather memorize the different concepts. Thus it is not difficult to appreciate why students do not like chemistry. The interesting point is that many general chemistry courses and textbooks present material in a manner that does not call for much conceptual understanding. In a recent study, Niaz (2) has shown that most textbooks present J. J. Thomson’s cathode ray experiments by emphasizing experimental details at the expense of conceptual understanding (i.e., what was Thomson trying to do). Was Thomson simply interested in obtaining an accurate value of the mass-to-charge ratio of the cathode rays? Of the 23 fairly well-known textbooks analyzed, only two made a simple mention of the fact that Thomson’s experiments were conducted against the backdrop of a conflicting framework— cathode rays could have been charged particles or waves in the ether. Again, only two textbooks described satisfactorily that Thomson determined mass-to-charge ratio in order to decide whether cathode rays were ions or universal charged particles. No wonder students do not understand what Thomson was up to and they end up memorizing the experimental details found in most textbooks! Observations Are Laden with Theory According to Gillespie, “Putting observations first shows students that the theories and principles that are so large a part of General Chemistry are there not just to be learned, but to help in understanding these observations” (1, p 485). At first sight this seems reasonable. Nevertheless, “putting observations first” requires some clarification. Modern philosophy of science has shown that all observations are theory-laden (3). In other words reporting of an experiment necessarily involves interpretation. An episode in the history of chemistry illustrates the tension between those who wanted scientific theories to be verifiable by direct experiment and those who worked with hypothetical models. Rutherford explained the importance of this controversy (4, p 176): The great majority of scientific men now regard the atomic theory not only as a working hypothesis of great value but as affording a correct description of one stage of the subdivision of matter. While this is undoubtedly the case today, it is of interest to recall that less than 20 years ago there was a revolt by a limited number of scientific men against the domination of the atomic theory in chemistry. The followers of this school considered that atomic theory should be regarded as a mere hypothesis, which was of necessity unverifiable by direct experiment, and should, therefore, not be employed as a basis of explanation of chemistry.… This tendency advanced so far
734
that textbooks of chemistry were written in which the word atom or molecule was taboo, and chemistry was based instead on the law of combination in multiple proportion.
This statement from Rutherford (an experimentalist par excellence) cogently illustrates the relationship between theories and observations. At this stage it is interesting to recall the historical controversy between Del Monte and Galileo, with regard to understanding pendulum motion. In this context Matthews asks a very pertinent question: “why it was that the supposed isochronism of the pendulum was only seen in the sixteenth century [Galileo], when thousands of people of genius and with acute powers of observation had for thousands of years been pushing children on swings, and looking at swinging lamps” (5, p 111). Matthews goes on to respond: “No amount of looking will reveal isochronic motion; looking is important, but something else is required: a better appreciation of what science is and what it is aiming to do; an epistemology of science” (p 118). This shows that while “putting observations first”, the theoretical rationale is often ignored. General Chemistry Textbooks for the Future In the last decade of the 19th century chemistry textbooks faced a dilemma. Atomic theory and the role of hypotheses based on unseen entities was questioned, and the word atom itself was taboo. French schools were not permitted to teach atomic theory because it was a “mere hypothesis” by decision of the Minister of Education, the well-known chemist Berthelot (6 ). Apparently, following the policy of “putting the observations first” this was justified. Now, after almost 100 years, we are still faced with a dilemma—how to make students understand chemistry. Shall we make the same mistake again? Our contribution to chemistry textbooks for the next millennium could very well be a presentation of material that is more conducive to greater conceptual understanding. This of course would require not observations first but rather a glimpse of why the scientist is doing the experiment and how scientific theories have developed in the past. Thus the theoretical rationale in which the experiment is conducted is more important than the experiment itself. Literature Cited 1. Gillespie, R. J. J. Chem. Educ. 1997, 74, 484–485. 2. Niaz, M. Sci. Educ. 1998, 82, 527–552. 3. Lakatos, I. In Criticism and the Growth of Knowledge; Lakatos, I.; Musgrave, A., Eds.; Cambridge University Press: Cambridge, UK, 1970; pp 91–195. 4. Rutherford, E. Proceedings of the Smithsonian Institution; Smithsonian Institution: Washington, DC, 1915; pp 167–202. 5. Matthews, M. R. Science Teaching: The Role of History and Philosophy of Science; Routledge: New York, 1994. 6. Chomsky, N. Mind 1995, 104, 1–61.
Journal of Chemical Education • Vol. 76 No. 6 June 1999 • JChemEd.chem.wisc.edu
