Another Approach to Freshman Chemistry The introductory chemistry course for the science major has traditionally consisted of three l-hr lectures and a t least one 4-hr laboratory per week. This format has several problems associated with it, the most important of which is that it is difficult to present chemistry as an experimental science. New principles are almost always first presented in the lecture and then exemplified by a laboratory experiment. As a result of the dominance of expository teaching, students are given no opportunity to act as scientists or learn as a scientist learns. We have attempted to overcome this problem by adopting a new approach to the introductory chemistry course. We have replaced the traditional format with two 4-hr periods per week. The students work in both the laboratory and the classroom during one of these periods. This arrangement makes it possible to intimately involve laboratory experiments and results with the class material. The new format also gives the teacher the opportunity to make the student discover for himself much of what is ordinarily given in the lecture. The student is confronted with a problem and is expected to devise an explanation based on his experimental results. This approach can be illustrated by outlining the treatment of the gas laws. In the first class on the gas laws, pressure is defined and the manometer and barometer are discussed as instruments used to measure pressure. The students then go to the laboratory and measure the volumes of a fixed amount of air a t various pressures. For the next class, they prepare plots of P versus V, PV versus P, and PV versus V from their data and are told to formulate a relation between the pressure of air and its volume. Only in the following period is the class told that their results with air are applicable to any gas and that the general relation is known as Boyle's Law. The Kinetic Theory of Gases is introduced as a model to understand the law. It is shown that the model predicts the PV product of a gas to be constant a t constant temperature. After reaching this conclusion the class returns to the laboratory to determine the relation between the PV product of air and temperature. This result is combined with previous discussion to derive the Ideal Gas 1.w. .X numher of pedngugicol ndwantsges result frum cumbininy Inhornlory and lerrurc. F nrr tnught n i gencralrmr~onsof lohoratury observntion;. Thus. Knoulr s Law i. introduced nftrr the srudenrs have rneawred the vapor premure o i iollllmrm of nun-volatile s o l u t e s . ~ l s osuch , an arrangement makes it possible to use an experiment tointroduce a new topic. Atomic theory is introduced after the students have studied the hydrogen spectrum in the lab. The theory is presented as an attempt toexplain why atoms emit light of discreet energies. We have found the approach to he an excellent tool to introduce the basic concepts of chemistry. Subjects that might seem obscure or abstract to freshmen in a lecture become very real and concrete when introduced or illustrated in the laboratory. Furthermore, by being required to interpret and analyze their experimental results, the students gain a deeper understanding of the methods of science. The better students, particularly, become proficient at formulating hypotheses and then trying to prove them correct. We wish to thank the Division of Chemical Education-du Pont Small Grants Program for a grant helping to initiate this project. Henry Altmiller St. Edwards University Austin, Texas 78704
Volume 50,Number 4. April 1973
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