SOME ASPECTS OF THE UNIT METHOD OF TEACHING CHEMISTRY* RUSSELLS. HOWARD, LYONS TOWNSRIP HIGH SCHOOL AND JUNIOR COLLEGE. LA GRANGE. ILLINOIS
If a universal human trait can be found and utilized to promote a desire for learning then the problems of education narrow down to learning how to best utilize this trait. I f we look within ourselves for a n imfielling motive we wefind that we must have a reason for the tasks we Wrsue with enthusiasm. The pupil of high-school age has a natural desire to learn something and i t becomes our duty as teachers to turn this natural tendency in the direction of our subject by pointing out a worthwhile reason for performing the tasks we set. The unit method offers the means of directing pupil activity by keeping him oriented in the subject and supplies a worthwhile objective that i s not too far removed from the present.
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I am sure that all of us have, a t times, come to the conclusion that it does not make much difference how we present our subject since some seem to learn and others do not. Probably we shall never entirely free ourselves from that conviction, hut hope springs eternal in the human breast and from year to year we do strive to find a better way of doing things. Dissatisfaction with things as they are is, I believe, a blessing in disguise for without it life takes on a settled and drab appearance, the push is gone, and every day is like the one before. Some argue that "newfangled" methods of teaching are just so much waste of time and this argument is backed by the observation that youngsters have learned all right in the past when less "fuss" was made about how to teach them. Those who argue thus probably have in mind the group that learn in spite of how they are taught and forget about the ones that have always failed to measure up to a reasonable scale of accomplishment. Since our educational system has taken on the task of mass education on such a grand scale, the proportion of more gifted pupils to the total has dropped materially and we are faced with the problem of extending the benefits of education to those who have more dC5culty in learning and to those who have little inclination to try. If we are to accept the thesis that we as teachers have just as much obligation to the less gifted as to the brilliant student then it becomes necessary to give serious consideration to our methods of teaching in order to extend, in the best possible manner, the benefits of education to the larger group. It would seem to follow that if we are able to improve the methods for teaching the less gifted, we may benefit better students as well. Whatever view we take, it is a fact that teaching methods are now under investigation and will continue to be for a long time to come. There are too * Presented before the Illinois Association of Chemistry Teachers. November, 1930 910
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many teachers who are dissatisfied with the results of their effortsfor teaching to remain static for any length of time. It is true in other lines of endeavor that effort expended-in investigation is not wasted, but results in better use of the efforts of those engaged in the undertaking. It is futile to attempt to build an educational structure that will be complete and will remain so. As long as ideas and life are in the flux we shall be forced to modify the curriculum and the content within each subject in order to meet the changing conditions, but it is not impossible to devise methods of teaching that are based upon something fundamental and will meet the needs of education under greatly changed conditions. That fundamental something upon which to erect our teaching methods should be an impelling trait common to the human mind. We have reason to believe that the mind of man has remained pretty much the same in its basic attributes for the last five thousand years, at least. Once we have laid hold of that impelling trait or force that is responsible for human action and, if properly directed, for progress as well, our task is not yet accomplished since we must then learn how to use this force for the purposes of education. In the manner of all evolutionary process, growth will be attended with waste, seeming progress will end in blind alleys. However, if these forces which are the cause of striving after better things are maintained they shall in time free us from irrelevant beliefs and. give us a more complete understanding of those means of approach to the mind which we call teaching methods. Where shall we begin our task of laying bare for inspection and study the avenues of approach to this most complex result of Nature's handiwork, the human mind? I t seems logical that we must begin and end with the study of the behaviors of the individual as affected by various stimuli, since the mind, as far as our ability to influence it is concerned, does not exist as a separate entity apart from its container. The study of the behaviors of the individual has certainly not been neglected. The tons of educational studies turned out by the press each year is witness to the fact that he is being studied from every conceivable angle both inside and out, but it is always a study of the other fellow. Why not turn the searchlight of analysis within ourselves and it may reveal there the causes for the actions of others? When we find the causes for our own behaviors we may find the key that will unlock the doors that now often separate us from intellectual contact with those whom we attempt to influence with our teaching. Stop and think a moment-am I always responsive to those appeals for action that come to me although they may be intended for my own good? Do we not all need a reason for doing things before we do them with enthusiasm? Do we go about our daily tasks without a cause? Let us f i s t clearly define in our own minds the reasons for performing the
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tasks we propose t o have our pupils do. Let us put ourselves, as best we can, in the places of those we attempt to teach and try to find how we would read under the conditions which we ourselves impose. If we do not do so, we shall remain content t o allow the incentives for education to be only those set up by school administrations in the forms of grades, credits, and diplomas, which are but poor substitutes for more genuine reasons for school endeavor. It might seem, to us who are interested in chemistry, that this subject would have a natural appeal t o all boys and girls, but our experience certainly will not hear out such a supposition. The early years of life, a t least through the high-school age, are those in which the normal individual is interested in learning, although the interests that engage his attention may be far removed from the content of school subjects. It is the age, however, when a desire for knowledge of some sort does exist and i t is the function of the teacher to utilize this fundamental tendency and direct it into proper channels. To those who lack their own motives for the study of chemistry we must attempt to supply them definite objectives and worthwhile reasons for their labors. We have all heard much of the need for developing in our students an interest in the subject we teach and all will agree that this is a necessary prelude t o successful teaching, but this interest will come only when in some manner or other satisfactory reasons have been established for learning. If the reasons for study are strong enough, genuine interest will manifest itself and the other desirable qualities that we associate with successful learning and teaching will naturally take their place. If we accept as a fact the need for definite and strong motivation for successful work then the problem narrows down t o finding the right conditions and the necessary stimuli that will bring about in our pupils the desirable attitudes toward learning. Is i t not true that we in our own experience have gone blindly through the motions attendant to study and have performed tasks that were required of us without interest and without knowledge of their purpose? The objectives we were expected t o reach, if any, were so remote and obscure as t o furnish little incentive for ever reaching them. Would our enthusiasm for the work not have been increased had we but known where we were, where we were going, and why we were on the way? Let us remember that folks of secondary-school age are usually unable to wander alone far from home intellectually. I n the strange surroundings they cannot orient themselves with certainty. The vastness of the unknown into which they are often sent without a reliable compass or chart confuses them. They lose their way, becoming intellectual derelicts subsisting upon what they happen to find and wandering without purpose and without hope. This dark and gloomy picture is not over-
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drawn. We do not know just how dismal the outlook can become until we have either experienced i t ourselves or have come into contact with others who are experiencing it. The objectives to be attained from study should be definite and not so far removed that they will be lost sight of before their attainment. The successful accomplishment of a task, the purport of which is fully known and understood, is in itself a reward that brings a sense of satisfaction. Moreover, it furnishes an incentive for further eEort. The background of the proposed organization and plan of carrying it into execution herein outlined takes into consideration the need for a definite purpose as a compelling motive in education, the need for motivation that is not too far removed from the present, and the necessity for the orientation of the learner with respect to the work in hand.
The Unit* In recognition of the complexity and scope of the science of chemistry we begin by organizing the field for study into related parts or units which enable the student to keep himself within a more limited area and make the objectives immediate. The objectives within each unit are primarily those of understandings of principles and appreciations of relationships. The gathering of information by the student is for the purpose of attaining the objectives chosen for each unit. The divisions for study should be as few as possible, since a multiplicity of units causes confusion rather than clearness of purpose. The choosing of the units comes as the result of experiment, because there is much more involved than the mere collection of related ideas. For example, there enters into the problem the right sequence of the units, in order to have the background that is adequate for the building of the understandings that follow. The attempt to master a principle without adequate preparation will result in failure, and with failure a possible loss of morale. True learning for the best results comes as the result of growth, and, like that natural process, must have the conditions a t the optimum. Following are the titles of eight units that may be used to cover the field of general chemistry. 1. 2. 3. 4. 5. 6.
Matter undergoing changes. Water, solution, and aystallization. The general properties of gases. The uses of the idea of atoms and molecules. Ionization, acids, bases, and salts. The non-metals and their relatives.
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* For full details of the unit method of teaching see MORRISON,"The Practice of Teaching in the Secondary School." University of Chicago Press, Chicago, IUinois, 1929.
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7. The general properties of metals and their compounds. Organic chemistry, the compounds of carbon.
8.
If these are to he made real units far study, they must contain objectives that are worthwhile. Here must reside clear-cut principles, the mastery of which will he a challenge to the pupil. They must contain more than just piles of fads set out for inspection like exhibits in a museum. The facts as such must be the means of gaining an understanding of natural laws and an appreciation of the fineness of natural adjustment. There will be found, of course, an abundance of material within the scope of each unit that can be learned, but does not need to be taught. There is no need of wasting the time of the pupil or the teacher rehearsing the properties of the elements, for example, unless the use of these properties leads to something more fundamental. There is certainly enough food for real thought in the great field of chemistry without wasting time memorizing words unless some real purpose is to he served. Since it is not possible to discuss here the understandings that are to he sought for each unit, we shall illustrate only the case of Unit I. The underlying purposes of the study of the materials that come within the range of the first unit, "Matter Undergoing Changes," may he taken as: I. An understanding of how matter is composed and some of the changes it undergoes. 11. A knowledge and understanding that energy is the cause and result of chemical change and that the amount of matter and energy is constant. 111. An understanding of some of the chemical relations of the elements, oxygen, hydrogen, and carbon, and their utilization in chemical changes. It is, of course, evident that the understandings proposed here will not be as deep and broad in the first unit as will ultimately result after more chemical experience has been gained. However, if the ideas contained within these objectives are made the conscious goal of the student during the time spent upon this unit, as study progresses, an appreciation of their importance will grow beyond this point.
The Presentation The purpose of the presentation, which precedes the period of assimilation, is to out the fact that something definite is to be accomplished during the p ~ o that d is to follow. It helps in the orientation and points to the goal to be reached and gives reasons for the work that is to come. The presentation need not include every topic that makes up the content of the unit and, in fact, it is much hetter that it should not, since such an
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amount of detail matter would cause mental indigestion. Within the presentation some stress should be laid upon the general values of chemistry, together with the more localized purposes of the unit. As a motive for close attention to the presentation it is well to require that it he reproduced from memory, in outline form. A possible presentation, covering the fourth unit of study, will illustrate these points. T m USESOF ~mIDEA 01. ATOMSAND MOLECULES UNITIV Presentation Before beginning a more detailed study of the atom and the molecule, it will aid us to follow the story if we know beforehand where it leads. Often we fail t o appreciate and understand some part of a subject because we do not, a t the time, know its relation to that which is to fallow I n order t o get a clear picture in his own mind of the composition of matter. John Dalton, an Englishman, definitely formulated his ideas on this subject; these ideas have also aided those who came after him in picturing the way matter is composed. He hit upon some ideas to explain the way things are made that have since proved to be correct. He thought of all matter as made up of very small indivisible particles called atoms, and the various substances of the earth as composed of groups of these atoms held together by what he called "chemical affinity." We shall find how, among other things, these ideas of Dalton's make it possible t o understand why any ~-particular compound is always composed of the same elements in exactly the same proportion by weight. If it were not for the fact that we always find each substance, without regard as t o how it was made or where it came from, composed of elements in this definite way, there could be no science of chemistry. The ideas of Dalton were not entirely original with him. The belief that all things are made of very small particles probably had its origin among the Greeks. If this belief existed before, thereisno written record of it. I t isnot remarkable that they reached this conclusion, but what is remarkable is that they gave the subject any thought. I t illustrates the type of mind developed by the Greek civilization. They liked to speculate about things, but that was as far as they usually went with i t ; they were satisfied to think without carrying their thoughts to the test of experiment. It is doubtful if they would have progressed far had they set out to prove the existence of these tiny indivisible particles. It has taken over 2000 years to develop sufficient knowledge to put this idea to the test of convincing experiment. I t was not until John Dalton (1766-1844) carried the ideas of the Greeks a few steps further that any real progress was made toward an understanding of the way substances are built. He had imagination, that quality so necessary for exploration into the unknown. He summed up his ideas, and that is all they were a t the time, in the following manner. ~
1. All things are made up of very small particles called atoms 2. These atoms cannot be divided by any known means. 3. Each individual atom has a definite and constant weight. 4. Atoms of different kinds vary in weight from those of every other kind. 5. The reawn atoms combine with one another t o form compounds is that they have an attraction for each other, a chemical afinity. This picture of the nature of things, as given by John Dalton, will be our starting point as we begin the study of this unit of chemistry. If John Dalton's ideas are worth
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anything, they should be capable of making clear t o us the meaning of facts that have been found by experiment. We shall have plenty of prwf, before we have completed our study, that without his conceptions most chemical happenings would he unexplainable. The thought may come t o your mind: Why study about the atom and the molecule, they cannot be seen? Why not study chemistry by examining only those things that can be seen with the eyes? Before you can appreciate the importance of the h o w l edge about the atom and the molecule to the advancement of civilization and for an understanding of the world about us, you must have followed the history of man's fight to overcome the obstacles set by nature. You must have learned what an important part this knowledge of atoms and molecules has been, and is, in this struggle. Since you have not had this opportunity of fallowing this history for yourself, you must accept as truth the statement that it is necessary t o understand these things before you are really able t o appreciate and know what chemistry means. After having made the effort necessary t o master this part of chemistry, you can look backward more intclligently and appreciate the bearing these facts have upon a sound understanding of the laws of nature. We shall learn of the work of the Frenchmsn, Gay-Lussac, an experimenter with gases, and the Italian, Avogadro, who made good guesses, and how the experiments of the Frenchman and the guesses of the Italian are combined to explain the molecular construction of the common elemental gases such as hydrogen and oxygen. Without the ideas of Avogadro the results of Gay-Lussac's experiments are not understandable. The history of science knows no national boundaries; men and women of all civilized countries have contributed their part t o the knowledge of nature that we have today. We already have an idea of what a chemical formula means, but we do not yet know how i t is found. Before the h u e chemical formula of a compound can be determined, there are three things that must be known about the compound: of what elements i t is composed, the percentage of each element in the compound, and the molecular weight of the compound. There is a regular way that atoms combine with one another to form compounds, and if we learn the system they have of combining, i t is possible to write the formulas of substances without ever having seen the formula before. The property of atoms that causes them to unite in a definite manner is called the valence of the element or atom. It is going t o be necessary to learn the valence of the common elements just as i t was necessary in arithmetic t o learn the multiplication table, hut after the valences are learned and their use understood, writing chemical formulas becomes a simple operation. The ability t o write and understand chemical formulas is very important in the study of chemistry. We all bave some remembrance of equations from algebra, so the use of the equation in chemistry will not he entirely new. The chemical equation to represent substances interacting chemically with one another and the substances formed by this interaction is another of those guides that chemists bave developed to help them in understanding and in putting to practical use this property that matter has of undergoing chemical change. We must not look upon chemical equations as things put into chemistry books to give trouble, but learn t o know them for what they are, aids to an understanding of nature. Just as soon as we learn t o use the chemical equations, we find ourselves thinkina in terms of them when considerina what takes d a c e in a chemical change . of any kind. The equation must be balanced before it becomes a true equation. By balancing we mean the arranging of the two sides of the equation so that each atom, represented or found in the compounds that act upon one anothrr, will he rrprrrmtrd in e q w l nurnhrr in tlw molwules of the new substances formcd hIntter is nrithcrcrcated nor destroyrd
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when i t is rearranged in new combinations, and since a chemical equation represents the truth, as far as we know it, the equation must talre the fact of the conservation of matter into consideration. Since these and other ideas are so closely associated, it is logical that we consider them together.
In order that we understand the relation of the presentation to the contents of the unit i t is necessary to list here the topics that will come up for consideration during the assimilative period that is to follow. There are collected within this unit those things based upon the atomic and molecular nature of matter that pupils are capable of understanding at this stage in the course. During the previous three units there has already been built up enough background to make their understanding possible. In addition to the use of atomic and molecular structure there is also introduced into this unit the use of the electrical nature of matter as a means of explaining valence. The foundation for thinking of matter as capable of assuming an electrically charged condition was laid down in Unit 11, when colloids were considered. CONTENTS OR UNITIV I 1. The origin of the belief that matter is composed of small indivisible particles 2. The atomic theory of John Dalton 3. Atomic weight, or the relative weights of the atoms 4. The reasons for the union of the elements in definite proportions by weight 5. Molecular weight, the relative weight of the molecules 6. The chemical formula and what i t stands for 7. The use of the chemical formula for the calculation of the percentage composition of compounds 8. The reasons for the chemical union of elements in multiple proportions 9. A use for the formula weight of elements and compounds (a) The meaning of the gram-molecular-weight (mole), and its uses 10. Gay-Lussac's law of combining gas volumes 11. Avogadro's hypothesis concerning the number of molecules in like volumc~of gases 12. Proof that molecules of the common elemental gases contain two atoms 13. The uses of the gram-molecular-volume 14. Methods of finding molecular weights (a) The gram-molecular-volume method (b) The freezing-point and boiling-point method 15. The method for finding the simplest formula of a compound 16. The method for finding the true formula of a compound 17. Equivalent or combining weights 18. The uses lor chemical rquiltims 19. Prohlrms inrolving t h e chemical equation (a) Weight relations (b) Weight and volume relations (6) Volume relations
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I1 1. Valence and its applications (a) Constant valence (6) Variable valence 2. The naming of compounds based upon valence 3. The general meaning of oxidation and reduction
I t would require far more time than that allotted to follow through the procedure during the assimilative and the recitation periods, since a complete survey of the former alone would be considerable in itself. It has been the purpose of this paper to call to your attention but a few of the fundamentals upon which the unit method of teaching depends, and to give a glimpse of its organization by specific examples. There will always be disappointment when we survey the results of our efforts as teachers with any method of instruction that we may use. We must remember that we are dealing with the most complicated and little understood of all things, the human. It has been said that one can tell pretty well what a dog will do if you kick him, hut nobody can predict what a man will do if you knock his hat off. Let us repeat, that the surest way to understand the needs of others is to fist try to understand ourselves, hut who can say that they have yet succeeded definitely in doing that? Our own experience should teach us that the greatest opportunities for teaching lie in consciously utilizing the common human need for definite purposes as a directional force, the need for a motivation that is not too far removed from the present, and a necessity for knowing where we are, where we are going, and why we are on the way.
