Vob 3, NO. 10
TEACHING FRESEWCB&~S.II(Y
1126
A DEVIATION FROM THE STEREOTYPED METHOD OF TEACHING FRESHMAN CHEMISTRY* W.A. ~ ? ~ L SUI N~ G R ,S I T 08 Y TEXAS, AUSTIN. TEXAS Introduction The object of this paper is to present a brief outline of a course in firstyear college chemistry as given at the University of Texas. In order to emphasize the deviations from the "standard" course, a brief summary of the high points of the usual stereotyped course must be presented. This paper is essentially a criticism of descriptive, informative courses and a plea for a course that stimulates thought and the student's reasoning powers. The Usual Introductory Course If college texts on general inorganic chemistry are a good criterion the usual introductory course may be outlined brieily as follows: The fundamental principles of the science are presented at the beginning in many interesting modi6cations. However, practically all of them are illustrated extensively by a discussion of oxygen and of hydrogen, which lead into symbols, chemical arithmetic, the gas laws, and valence. Thus, almost a t the opening lecture of the course, a general mixture of double decomposition or metathesis and of oxidation-reduction is presented. The course a t this point is subject to about two general procedures, with variations in detail: (a) A discussion of the elements and their compounds according to a division into metals and non-metals, or (b) a discussion according to the groupings of the periodic classification. The order and arrangement of the topics is subject, of course, to the inclinations of the particular teacher or writer. An inspection of the table of contents of college texts of former or recent issue will reveal the similarity of general arrangement and the modifications of detail. Such topics as ionization, chemical equilibrium, atomic structure, electrolysis, battery action, and oxidation-reduction reactions are introduced at widely varying and somewhat unrelated points of the course. Almost unifomly great attention is paid to the minute and multitudinous details of chemical behavior and almost as uniformly there is little attention paid to the fundamental types of chemical reactions which the student meets in the course. In one recent text, oxidationreduction reactions are explained (but briefly) fully 100 pages after a detailed discussion of oxy-halogen and oxy-sulfur compounds. On about page 20 of another text a reaction involving potassium permanganate is given and a discussion of nascent hydrogen is presented to the beginner. * Presented before the Division of Chemical Education of the American Chemical Society at the meeting in Tulsa, Oklahoma. April 7. 1926.
No distinction is made, apparently, in the types of the reactions presented; the conditions under which a metathetical reaction may be predicted to go to completion as contrasted with the conditions which obtain when an oxidation-reduction reaction takes place seem never to be called to the student's attention incidentally, accidentally, or intentionally. As a result he memorizes a large number of reactions of more or less doubtful value, gets no clear concept of the underlying forces driving or bringing about reactions, and sees but little difference in the writing of equations, except in difficulties, for metathetical and for oxidationreduction reactions. Expressed more succinctly, the average student is taught to memorize a series of facts but he is not taught to think and to reason from fundamentals. The course may be informative but is not productive of thought; it is almost a case of not being able to see the forest for the trees. The brilliant student "makes good" in spite of his handicap while the weak student falls by the wayside. The Course Proposed The course to be outlined is, in the main, the course given to first-year students a t the University of Texas. Its inception and the major portion of its development is due to Professor E. P. Schoch; his successors in the course have, of course, added some improvements and some finishing touches. It is not an ideal course by any means hut, based upon critical comparisons of experience, i t is far ahead of the type of course which most of the recent text-books would want given (and which is given, if publishers' representatives are not exaggerating the number of adoptions of these texts). The course presents the fundamentals much as other courses do. Exception is made, however, in that illustrations are drawn from reactions involving merely a double decomposition or change of partners. The gas laws are presented a t this point merely as a source of information to be drawn upon whenever needed. The reaction between a base and an acid presents, of course, an excellent opportunity for the exposition of valence. This is followed by a discussion of the solubility and the extent of ionization of acids, bases, and salts. Based upon these ideas the concepts of reversible reactions, equilibrium, and of reactions that "go to completion" are presented. Here, as before, metathetical reactions furnish the illustrations.' The student is then taught bow to predict whether or not a metathesis may 1 The introduction of such simple oxidation-reduction reactions as the reaction between steam and iron or iron oxide and hydrogen to illustrate a reversible reaction may be justified and would in no wise alter the general scheme of the course. Oxidation-reduction reactions that may be written by inspection are, as a matter of fact, introduced at times by the author for illustrative purposes; he takescare, however, to point out the differencein type.
be expected when two binary substances are mixed in solution; these predictions are based upon his knowledge of the general statements of solubility and of ionization of the common acids, bases, and salts. If a reaction attains equilibrium before progressing as far as to be called "completion," the student must be able to say "why" this reaction cannot be expected to go to completion. This presentation is followed by a brief discussion of the atomic structure of matter. At this point the student learns, for the iirst time, of an " electron exchange" by considering, for example, the ditferences hetwecn a sodium or chlorine atom and the corresponding ions. Such a topic, involving electron exchange, naturally leads into electrolysis and battery action, upon which is built the scheme of writing and, what is more important, of predicting the probability of occurrence of oxidation-reduction reactions. He learns to use a table2 of electromotive reactions to guide him in predicting whether or not an oxidation-reduction may be expected. The simple "pole" or half-cell reactions are the basis for the derivation of any oxidation-reduction reactions which he may meet. He differentiates between simple "ion or partner exchange" and "electron exchange" reactions; he grasps the difference between the fundamental conditions which obtain when these two types of reactions take place. The student learns to $redid from certain fundamentals; he does not have to cram a lot of unassociated facts into his mind. While these topics of electron exchange are being presented in the lecture room, the topic of the general reagents sodium hydroxide, ammonium hydroxide, and hydrogen sulfide are presented as laboratory and drill-room work. This is followed by formal qualitative analysis, in which the arsenic, antimony, and tin determinations are omitted and the alkaline earths are tested spectroscopically. Most of the reactions of the separations and identifications are metathetical and the student knows "why" the reactions take place and how to write the equations. The oxidationreduction reactions are relatively few and the writing of the equations need be postponed merely a matter of a few weeks a t most, until the lecture-room discussion has progressed far enough to enable the student to write equations for all the reactions with which he meets, be they metathetical or oxidation-reduction reactions. This is followed by a presentation of the more common elements of the various periodic groups; a t this stage of learning the student really knows what is meant by the oxy-acids, oxy-compounds, and reactions invoIving the permanganates, manganates, dichromates, etc., have no special difficulties to offer. An extended discussion of the fonrth group, more especially of carbon in the form of elementary organic chemistry, closes the course. a Liddell, "Handbook of Chemical Engineering," Vol. 11, p. 690; this table, slightly abbreviated, is used in the teaching of the first-year course.
