DAVID A. PHILLIPS Wabash College Crawfordsville. IN 47933 PRUDENCE PHILLIPS CrawfordsvilleHigh School Crawfordsville, IN 47933
Why I Do Demonstrations
Lecture Demonstrations
Davld 0. Tanls Holland Christian High Schwl 950 Ottawa Avenue Holland, MI 49423
Bassam 2. Shakhashirl University of Wisconsin-Madison 1101 University Avenue Madision. WI 53706
Chemistry is an experimental science. The teaching of chemistry naturally involves work on the part of the students hut also should include teacher demonstrations. I view demonstrations as valuable classroom tools. Essentiallv a demonstration is a visual aid t h a t h e l ~ mv s " students see ihstract descriptions in concrete form. A demonstration often helps make the connection between theory and reality for my students. I feel a demonstration should always illustrate a concept and then he explained thoroughly through subsequent discussion or lecture. Some of the educational and economic reasons I have for doing demonstrations in my classroom follow: 1. A properly chosen demonstration can illustrate a chemical principle at the precise time needed to clarify the principle. It is much more satisfying to a student to have a concept illustrated when the principle is being discussed in class than to hear the teacher say: "We will he doing a lab experiment next week that illustrates this principle. I'm sure you will understand it better after we do the lab. But in the mean time, I want you to do the problems on page 256 because they illustrate this same principle." 2. Arousing the curiosity of today's secondary school students is a monumental task. The very looks on their faces so often express the challenee: "What vou are mine .. .. to do that will be interestine to me tuday?" Properly chosen demonatrntion~carefully performed canaerveasexrrllcnt introductionsmtopics.Thequedons raised during demonstrations can he used to lead naturally into new topics or concepts. I know I'm on the right track when my stndents come into the rwm when my desk is cluttered with chemicals and equipment and they remark: "Oh, good, you are going to show us something today!" 3. Stimulating the thought processes of students is a constant chsllenge. Many students are looking for short, quick answers to every question. If a demonstration is properly done and ifthe discussion is carefully directed, a teacher can effectively guide students to think critically and to use scientificprinciples and theories to explain the phenomenon demonstrated. In oral and written responses to my questions, my students use phrases such as: "In the demonstration you did . . ." or "It is justlike the day you demonstrated.. . ." 4. Observation skills of students nwd constant sharpenmg. One way l~ hme these skills is to stage a sllcnt dernousrratlon.'The students are asked to record their own observationsas the teacher carefully performs the experiment without any oral description. Student observationscan be collected for examination by the teacher, they can be used as the basis of the discussion of the demonstration by mouos .. . of students or hv the entire class. or thev can be utilized as the basis of n student assignment involving an explanation of the demonstration based on thele observations. 5. Often demonvtrations can serve a vuhatitutes for laboratory experiments that are tw complex o r b expensive for all the students to perform. Because of the cost of specialized equipment or chemicds, certain laboratory experiments may be done as teacher demonstrations rather than as student lahs. Other experiments that are too dangerous in the hands of untrained students can he carefully performed as demonstrations by competent teachers.
Lecture demonstrations help to focus students' attention on chemial hehavior and chemical properties and to increase their knowledge and awareness of chkmistry. T o approach demonstrations simply as chances to show off dramatic chemical changes or oily to impress students with the "magic" of chemistry is to fail to appreciate the opportunity they provide to teach scientific concepts and descriptive properties of chemical systems. The lecture demonstration should he a nrocess. not a sinele event. - In a iecture demonstration, the teacher's knowledge of the hehavior and ropert ties of the chemical svstem is the kev to successful i n s k k i o n , and the way in bhich the teaiher manipulates the system serves as a model not only of technique hut also of attitude. The instructional purposes of the lecture dictate whether a phenomenon is demonstrated or whether a concept is developed and huilt hy a series of experiments. Lecture experiments, which some teachers prefer t o lecture demonstrations, generally involve more student participation and greater reliance on questions and suggestions, such as, "What will happen if you add more o f . . . ?" However, even in a lecture demonstration, where a teacher is in full control of directing the flow of events, the techer can ask the same sort of "what i f ' questions and can proceed with further maninulation of the chemical svstem. In nrincinle and in practice, every lecture demonstration is a situation in which teachers can convev their attitudes about the ex~erimental basis of chemistry,ihus motivating the students'to conduct further experimentation and leading them to understand the interplay between theory and experiment. Lecture demonstrations should not, of course, be considered substitutes for laboratory experiments. In the laboratory, students can work with the chemicals and equipment at their own pace, making their own discoveries. In the lecture hall, students witness chemical changes and chemical systems as manipulated by the teacher. The teacher controls the pace and explains the purposes of each step. Both kinds of instruction are integral parts of the education we offer students. At all levels of instruction, the attitudes and motivations of hoth teacher and student are crucial. The attitude of the teacher is central to the success of interactions with students. Our motivation to teach is reflected in what we do, as well as in what we do not do, hoth in and out of the classroom. Our modes of communicating with students affect their motivation
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1010
Journal of Chemical Education
In plannlng a chemistry canse,same of the he iimpabnl decisions a teacher must make iwob the selectim of material to be -ed and me time to be devoted to each topic. For each column in this serles, a high schwl and a milege teacher have been invited todiscuss why they fee.1a ~ l c u l atopic r is impatam and how it canbibutes ta the students' undersunding of chemistry.
