DEMONSTRATIONS as a SUBSTITUTE .for LABORATORY PRACTICE in GENERAL CHEMISTRY* HERSCHEL HUNT Purdue University, Lafayette, Indiana
W
E MUST modernize our methods of teaching are much better fitted to a procedure wherein a skilled in accordance with the backgrounds and habits teacher performs the experiment whiie they observe. of our students if we are to be effective in- The objective in general chemistry is to give the stustructors. Students who are trained from childhood dents a broad background so that they have a knowlto learn by radio, talking picture, or from the window edge of, and can think in terms of, chemistry. The purpose of this paper is to discuss a form of of a speeding auto rather than by working and reading demonstration that may replace the laboratory exerA d i i s s i o n based upon two years' experience handling cises for college freshmen in chemistry. I t is to be gmups of 100 students by both methods, presented before the correlated with the regular lectures but it is not intended Division of Chemical Education of the A. C. S. at Cleveland, to supplant the lecture experiments as now given in Ohio, September 11, 1934.
our better universities. The demonstrations are to be given at regularly scheduled periods and are not to consist of the spectacular experiments common to the formal lecture. A minimum of two hours is necessary for each period since many of the experiments will involve quantitative procedures. A special room containing both a well-equipped lecture table and regular classroom facilities is desirable, though not necessary. Mimeographed sheets with blanks to be filled are used for note-taking. This scheme obviates copying or the giving of credit for beautiful samples obtained unethically. The stndent grade is based upon a written achievement test given a t the end of the demonstration. Since the students are allowed to ask questions as frequently as they desire or to step up front for close inspection, all formality is removed, and the teacher is only a skilled technician and learned salesman. In order to facilitate oral quizzing, better attention, and closer contact between student and instructor, small groups are necessary.
first few weeks in a succeeding course but they know how things should be done and quickly master the manual skills. A student who has seen that small tubing is bent after being heated with a fish-tailed burner, that pyrex tubing is worked with a mixture of oxygen and air by means of a blast lamp, that a roughly broken piece of glass can be smoothed with a wire gauze, that large tubing is easily cut if first scratched with a file, then heated with a hot wire, and suddenly cooled by a drop of water upon the scratch, that soft glass should be heated and cooled slowly, that soft glass cannot be sealed to pyrex, that ground-glass joints are shaped with carbon tools and ground with carborundum, that beeswax prevents brass tools from sticking to hot glass, that a hand torch is best for sealing glass that is mechanically supported, etc.-all of which can be demonstrated in a two-hour period-is better trained for future work as a chemist or as a layman than the boy who has burned his fingers in trying to follow directions to make a wash bottle which looks like the diagram in the manual. We admit that he cannot do all these POPULARITY O F THE DEMONSTRATION METHOD things just because he has seen them done, and we also 1. Student Reception. Students miss the social realize that he cannot after he has tried once. The atmosphere of the laboratory. Because a greater con- number of ideas gained and facts remembered should centration upon the subject is required, the method is be much greater. There is plenty of time left for the not the most popular with the mentally dilatory. The chemical major to learn how to follow directions in class can be kept together by this method, therefore analytical chemistry. 3. Administration Supfiort. Some administrations a part of the class is not discouraged and lost because it cannot keep up with the better students. Time is will be reluctant to make a change from the laboratory not taken from other courses by an over-zealous pro- system to a new system. However, as changes are fessor's requiring the student to stay after hours and do made necessary because of outside reasons this method extra experiments. If a stndent fails to understand should be seriously considered. Departments which some part there is always opportunity to repeat it for are equipped with suitable roomsshould find the change his benefit. The interest of the outstanding student one which will involve no difficulties. Teachers who can be held by allowing him to demonstrate some phase can sell a subject to a student seldom have trouble in of the experiments. using their salesmanship on the deans. Let us hope Relief from the hazards of corrosive acids and break- that administrations universally will reward the teacher ing glassware is insured. The student with a maimed so that those with research minds can furnish a set of body is encouraged but the student who loses time experiments most suited to this method. through sickness is handicapped in that he has no ECONOMY OF THE DEMONSTRATION METHOD means of makine n~ his work. These aye the reactions 1. The Student Saves Time and Money. We x a k e of students whoUha;e had both systems for a semester. Those students who have had high-school chemistry a charge of 50c per semester, which covers mimeofeel that the same subject is new since it is presented graphed work, depreciation of apparatus, etc.; ordidifferently. It gives students who are not going ahead nary laboratory expense would include 75c for an apron, with chemistry more time for their major interest. $5.00 breakage deposit, $1.00 10$3.00 for a manual, More time is made available for the cultural opportuni- and 35c for a notebook. There is thus an actual saving ties of broad reading, a factor much neglected in our to all and especially to those who might have accidents. crowded curricula. The experiments now appearing in our freshman 2. Faculty Reaction. The professor who has used manuals can be demonstrated in 5% to 40% of the time the laboratory method for twenty years rebels a t losing that it requires a student to perform them. Experience it. Others have vested interests and refuse even to has shown us a t Purdue that we can demonstrate thorlet it be tried. It requires young teachers who can oughly in two hours the same material on which the student will spend six hours in the laboratory, perhaps put a lot of enthusiasm into the demonstrations. The feeling that students so trained are incompetent missing the point or getting poor results. (Non-chemito goon with chemistry is questionable since the students cal engineering students.) Any pause in the succeshave seen a considerable number of technics performed sion of events may be utilized for quizzing in order to correctly. Experience shows that demonstration- make sure that each student understands thoroughly trained students have a greater ability to think in terms what is being done. Although manual skills are not practiced by the of chemistry. It is true that they are not apt for the
student, much more thinking is done, many more scientific observations are made, and many more chemical phenomena are seen. The professor calls attention to every point so that principles are observed that would be overlooked if the student were working alone. There is much more to be learned in chemistry than any individual can master. The conscientious teacher should want to introduce his students to the methods, the apparatus, the practices, the compounds, and the uses of this wonderful science rather than have him spend from six to eighteen precious hours trying to prepare pure barium hydroxide from witherite, a common procedure in some of the largest engineering schools in the United States. The only memory retained by the student after many hours in the "sweat box" over the furnace is that his wet crystals of barium hydroxide changed back to the carbonate before he could get them checked. Why is anyone convinced that this method of teaching is perfect because the student has had an indelible impression that barium hydroxide reacts with carbon dioxide? In the same amount of time, with the same effort, such reactions could be demonstrated repeatedly in different ways, with the incidental introduction of different principles. 2. Facul~yTime. Practically the same amount of time is required to prepare and give a demonstration as to hold a three-hour laboratory session. The apparatus should be set-up and all routine procedurescompleted before the period opens. In large schools the most efficient method is to have classes scheduled consecutively so that the apparatus need not be moved until the entire class has finished. Then if the classes are scheduled properly one hundred students can be handled in two periods. This will not be an overload for the teacher, as most experiments can be set-up in one hour and dismantled in one-half hour. On the other hand, six hours of laboratory direction in one day is an overload. The demonstration requires more concentrated efforton the part of the teacher. Students with access to a laboratory can learn without either a manual or a teacher. Observation $roves that few teachers converse with the students upon chemistry throughout the entire laboratory period. Our method does not permit notebook grading during the period, keeping of records, chats with other assistants, a glance at the morning paper, a trip to the office for the mail, reporting absences, a session with an old grad back for homecoming, the filling of bottles forgotten because of a late dinner, or the 101 diversions with which we have all learned to pass the three hours allotted us for lahoratory instruction. Because of the freedom and lack of responsibility of the laboratory method, it will always have many strong supporters. Smce one can conveniently handle forty to fifty students a t one time by the demonstration method, the number of laboratory assistants is cut in two. However, a more experienced and capable instructor is required. 3. Laboratory SNce, A f i m t u s , and Chemicals. There can be an actual saving of 99% in chemicals if
no more work is demonstrated than the student would do. However, we are against this procedure. A minimum of three times as much as the student would do can be demonstrated in an hour; therefore, one can anticipate a saving of only about 75%. The apparatus saving is still greater. In order to give a good set of demonstrations we will need equipment different from that which the normal freshman locker will contain. It is possible for two sets of equipment to keep 500 students moving a t the proper rate in a large school, or to care for 200 students easily under adverse schedule conditions. In small schools one set will suffice. All the equipment can be put back into general use after the class has completed a cycle. Most of the elaborate set-ups desirable for the demonstrations may be temporarily taken from research stock or advanced class stock without any inconvenience. This is the only possible way to introduce chemistry into our small high schools which cannot equip a laboratory. The average cost of the equipment in a freshman locker is $12.00. In our school this means a capital investment of $19,200. Records show that about $2.00 is spent each year per student on chemicals, non-returnables, and depreciation of equipment not covered by the student breakage charge. Another $2.00 per student is spent on storeroom help. Since the ideal demonstration room can he used as a recitation room, another real economy is offered in building space. WHICH METHOD IS THE BETTER TEACHING MOL?
The answer is: "The method most preferred by the instructor." Unless the teacher works enthusiastically and untiringly, either method fails. It would be impossible to learn by the demonstration method from an instructor not capable of making, and eager to make, the plan a success. It is practically impossible to find a large number of equally good teachers who are equally enthusiastic about both systems with .the same types of students. Therefore, any data of a statistical nature should be scrutinized carefully if they are to be used as an argument for the adoption of a new system. However, I would urge every freshman teacher to give the demonstration system a trial for two semesters to see how $uccessful he is, if he likes it, and if the students do not respond better to his teachmg by'this method. The method described here is not the method formerly used a t Indiana University.* SUMMARY
The biggest advantage of the demonstration method is the saving of student time. The second important feature is the saving of money by the student and university. To date there are no reliable statistics proving that the student learns a great deal more by one system than the other; however, those teachers who have used both systems do not contend that the only way for a student to learn chemistry is for him to perform the experiment. See PAYNE, V. F.,J. CHEM.EDUC., 9,932 (1932).
