The Science and Art of Science Demonstrations Thomas O'Brien State University of New York at Binghamton. Schoo of Eoucat~onana H ~ m a nDevelopment P.O. Box 6000, Binghamton, NY 13902
The Webster's New ColleginteDictionary defines the word "demonstrate" as: 1. show dearly, 2a. to prove or make clear by reasoning or evidence, b. to illustrate and explain especially with many examples, 3. to show or prove the value or efficiency of to a prospective huyer.
All three definitions are relevant to teaching, for a s the philosopher John Dewey suggested: Teaching may be compared to selling commodities. No one can sell unless someone buys. We should ridicule a merchant who said he had sold a great many goods although no one had bought any. But perhaps there are teachers who think they
have done a good day's teaching regardless of what pupils have learned. Clearlv. science "teacher-merchants" need to "demonstrate" the"rea1-world phenomenalevidence, reasoningltheories, attitudeslideals, and valudbeauty of science to their "students-customers~." During the 1950's expert science demonstrators such a s Don Herbert (Mr. Wizard, general science), Hubert Alyea (chemistry), and Julius Sumner Miller (physics) inspired a generation of future scientists and teachers. Unfortunately however. the much needed 1960's nush for "hands-on" science was accompanied by a decline in the art of "minds-on" demonstrations. More recently, summer workshops offered by the Institute of Chemical Education; the Woodrow Wilson Foundation, etc.; the publication of a number of demonstration sourcehooks (1-9); and the renewed popularity of demonstrations featured in science teacher journals and meetings suggest that a reconsideration of the science and art of demonstrations is in order. This paper will provide a n overview of the constructivist theory of learning, a discussion on the demonstrationllaboratory debate, and guidelines for effective use of demonstrations. Student Construction of Learning and Teacher Instruction Cognitive science research suggests that teachers' educational "sales" efforts should acknowledae - students'active role in learning. Knowledge cannot be poured out from the teacher's mind (or iniected under ~ r e s s u r e )into the must be engaged to perceive, learner's. The le-er'skind filter. and transform sensorv datainto wncepts and models within hisher own partic& mental framework. Even prior to formal instruction, students are actively involved in the construction of "naive theories" in a n effort to make sense oftheir world (10-11). Thesetheories are often incomplete, disjointed, and fraught with misconceptions due to developmental immaturit.~,limited experience, inattention to relevant variables, e t d . They &e also resistant to change, even in the face ofinstruction in the "correct" ideas. When confronted with a discrepancy or anomalous phenomenon, students may unwittingly explain away conflicts bv reinternretine the event to fit their ore-existine theorv or by making only minor modifications in their pre-existing theorv. " Or.,if the teacher relies nrimarilv on abstract words. symbols and equations (i.e., places the theoretical principles cart before or in place of the real-world horse of
-
observable events), students may not even sense a discrepancy. In their minds, science concepts . apply . - to the science cla~sroom,not the "real" world! For manv high school and introductory college students still a t a &ncr&e operational stage with;espec? to science concepts, words alone are not sufficient to promote "mindson" c&ceptual learning. Nor can we hope toinstill enthusiasmorunderstandinginto the beginner by merely talkingto him about chemistly, without actually showing him some of the processes and materials which are chemical. First-hand information about a subject is more important the less we know about it. When we have more factual background our imagination has a little something to stand on. . . Granted that our ultimate abject is the ability to think abstractly, this can be attained only by learning first ta think concretely. (12)
Attemnts to "cover" the textbook do not necessarily result in "uncovering" key concepts and processes in the k i n d of the student. To learn science one must learn the language of science, but the reverse is not necessarily true. Learning science words, syntax, and grammar does not automatically translate into comprehension or the ability to apply knowledge in a practical context. To achieve understanding, greater realism or concreteness in teaching strategies and instructional materials are necessary (13,141. Teachers must provide opportunities for students to see, become involved with and reflect on scientific phenomena. Or a s Leonardo da Vinci, stated in his Notebooks -1500: "Iron rusts from disuse, stagnant water loses its purity, and in cold weather becomes frozen: even so does inaction sap the vigors of the mind." Meaningful, cognitive changes occur when students are challenged to "reveal their prior conceptions and test them in a n atmosphere in which ideas are openly generated, debated and tested. . ." (15). Generating and aiding the resolution of cognitive conflict is a primary job of a teacher. Conventional "two by four" teaching too often limits students' exoeriences to answers found between the two covers of the'textbook and the four walls of the classroom and produces '%ored" students. Such "teacher instruction without student construction" has been characterized a s words transferred from the lecturer's notes to the students' notebooks without passing through the minds of either. The DemoILab Debate
Not Either/Or, But When and for What Purposes Given the belief that the laboratory should play a central role in science classes, why bother with demonstrations? Both laboratory experiences and demonstrations are powerful means of activating student interest, focusing attention, and initiating learning. Arguments in favor of demonstrations have included (among others) safety, cost, time, and efficiency. Counterarguments favoring the laboratory have eauated demonstrations with expositom teaching and rote, reception learning and represented thelab a s theonly place where meaningful, discovery learning occurs (see figure). Research from the early 1900's onward has explored the relative effectiveness of the two methods. CritiVolume 68 Number 11 November 1991
933
ExpositorylReception Student receives & assimilates what is to be learned without obligation to independently discover new relationships not presented by the
Rote 4 Content is not integrated into the studenfs cognitive structure, does not lend itself to flexible expression and if not overlearned,is easily forgonen.
.
Meaningful Content is related to the Rudent.smgnitivestructureinnon-
verbatim & nonarbitrary ways, can becreatively appiiedto novelsituations, and is more stable.
Guidelines for Presenting Effective Demonstrations Demonstrations canguide students to construct accurate c o u c e ~ t u a l i z a t i o n sa n d become comuetent, science 's~E.:E&" ifthey are Safe, Simple, ~conohtcai,F:njoy;thle, F:ffrctive and Relevant for the particular student audience. Pre-DemonstrationPlanning
Exploratory/Discovery St~dentdi~~~e~theprincipaiCOntentofwhat
is to be learned which is withheld by the teacher who "simply' helps set the problem and guides the student's inquiry. I
Types of TeachingILearning cisms of experimental and statistical designs, instruments and criteria1 tasks, and the purity and wnsistency of the . treatments notwithstanding, the main wnclusion drawn from well over 50 studies is that they fail to establish the superiority of one approach over the other (16 -17). I n light of this research, some educators have questioned whether the 1960's, NSF-funded, science curricula and inservice nroerams emuhasized the laboratow a t the expense of dem&strations (18-19). Perhaps beeause of the deplorably low occurrence of laboratory science in today's schools, "hands on" activity is oRen automatically equated with enhanced wenitive urocessine- or "minds-on"learning. For instance, a major ACS tahk force recommended'.ut least 3 W class timc be devoted to student laboratory exercises"' but only mentioned demonstration.. parenthetically a s "an imuortant and effectwe mode of instruction" r201. One problem with the laboratory versus demonstration debate a s typically framed is the lack of clear defmition of terms. Eccles (21) .~ armed that: "A teacher may carry out a true experiment a s the agent ofthe class, or a student may, bv following directions. uerform demonstrations for his individual Lstruction." $he relative position of the two techniaues on a receution-diswveni continuum (see fimre) depends on how and where in the-instructional sequence they are presented. Aproperly delivered demonstration can be more discovery-oriented and meaningful than a "cookbook" verification laboratow activity. An optimal learning environment maximizes meaningfd learning by utilizing a mix of different degrees of both reception and discovery learning. Thus, the critical question becomes not which of the two approaches is the "right" one in a universal sense, but what criteria should guide a teacher when choosing between the two. "Minds-on" demonstrations with teacher-controlled experimental wnditions provide a n environment where: (1) student ideas, hypotheses, and possible misconceptions can be tested immediately or challenged-by contrast, "handsonZlaboratoryexperiments are typically designed to "limit" (or even eliminate) action on independent ideas, (2) students can be taueht how to observe, formulate questions, and reason about science by way of teacher example and Socratic questioning, (3) "limiting reagents" that restrict the numbkr and type of "hands-on" experiments such as ~
-
-
934
student ability, safety and waste disposal issues, availability and expense of equipmenffsupplies, cumculum time, and preparation and cleanup time are more easily controlled, and (4) the teacher can demonstrate a love of and enthusiasm for science. Thus, demonstrations can complement and extend (but not replace) more direct laboratory experiences.
Journal of Chemical Education
As with other instructional strategies, careful planning increases both the urobabilitv and uotential demee of success. Several issues should he considered: 1. What are the purposes of the demonstration? What concepts will it illustrate? While a given phenomenon may effectively demonstrate a number of disparate concepts, avoid overtaxing student wnceptual abilities by attempting to teach too much a t one time. Consider khethei a laboratory experiment, wmputer simulation, audiovisual program or other method may be preferable or serve as a complement to a demonstration in your particular setting. 2. If a demonstration is to be used, where in the instructional seauence would it be most effective? Ademonstration should be' timely. I t may be used to: (a) excite initial observations and auestionine to challenge student misconceptions [exploration], (b) encourage student (re)construction of a conceut linventionl. (c) illustrate and test student understankng of a p r e ~ o u s l ydiscussed concept [application], or (d) simply to model good technique or process skills in anticipation of a laboratory activity. A recent NARST monograph (15) discusses the theory and provides examples of science lesson plans designed around a learning cycle approach. 3. What prior knowledge should be activated and reviewed before the demonstration? Highet (22) anticipated discussions on concept mapping (23)when he suggested the following analogy:
-
-
-
Suppose you wanted to get to know a tract of country. The worst way to do it would he to jumg into a car, drive straight from one end to the other, then turn your back on it and walk away.Yet that is what many teachers do with complex subjects, and that is why their pupils seem [less infamedl than they really are.. .How much better would they learn the country if, before setting out, they were briefed and given maps to study; if they were tested and reoriented onee or twice during the trip; and ifthey were shown photographs afthe best spots and taken onee more over the map when they reached the end of their journey. Teachers must balance students'need for a sense of focus and direction with the need for a discovery-oriented approach. 4. What design would be most effective given the materials a t hand and the tareet audience? Avoid the elaborate and nonessential. Don't get out a cannon to shoot a fly for the "best education is to be found in gaining the utmost information from the simplest apparatus" (24). Materials should be auurouriate to student backerounds and the conceptual i&d'of understanding desrred. Extraneous equipment may cause students to "miss the forest for the trees." Also, the use ofclearly marked household chemicals, equipment, and "toys" helps students realize that science can be found everywhere, notjust in test tubes andbeakers. Simplicity of materials and design also saves valuable
-
setup and cleanup time, especially for demonstrations that can be stored in plastic boxes or Ziploc bags. 5. Which of the many available demonstrations on the concept of interest will generate the most interest and cognitive dissonance andThe least expense and safetyldisposal problems? While not all demonstrations need be spectacular, they should be "exocharmic" attention grabbers (25). Given the existence of content-specific student misconceptions, discrepant event type designs can be particularly effective. Dependine on how, when. and to whom the demonstration is presentled, almost any demonstration can create comitive conflict. Some newer demonstration soureebooks (3, 4) are organized with this explicit intent. Additionally, most of the "misconceptions" research cites examples used in the experimental studies, a s well a s the common misconceptions encountered (10-11). 6. In addition to the element of surprise, how might a bit of preplanned showmanship and humor be employed? McCormack (5) suggests teachers employ some of the professional magician's showmanship and methods (such as magic signs of phenolphthalein + ammonia, silver nitrate +light or potassium nitrate + fire) to introduce students to the magic of science. As for humor, Highet (26) suggests that: One of the most important qualities of a goad teacher is s D. U.D ~ ~alive S and attentive. . . and helm humor. . . it k e e ~ the to knve a true pierure of many irnpnrmnt sul,,)ects.. . tiny-fivr minurrs of work plus live minutes laughter are u o r t h twme as mwh aa aixrv minutes of unvaried work. Cartoons (ex.. . . .Garv. Larsen and Sidnev Harris). scientific puns and poems, historical skits, participatory simulations (in which students become ths tbme thevarnstudvinesuch " a s moleculesfor examples see ~ a t t i n k(2711, music, and silent demonstrations can sinelv or in combination be m i t e effective. Remember, the ghimical formula of teachindsales success. SW7C-alwavs address the student/custo& question: .'So what, ~ h ( ; c o rWhy, Care?" 7. What steps ol'the demonstration ~ r ~ l c e d u should re be carried out a6ead of time? ~inima1ly;rea~entsand apparatus should he prepared. labelled. and arraneed conveniently to avoid wasting valuable class time. &o, if any steps in the demonstration are excessively long and not pertinent to the actual concept to be demonstrated, carry out these steps ahead of t i e . "A demonstration is 'produced' much a s a play is produced. Attention must be given to many of the same factors a s stage directors consider: visibility, audibility, single centers of attention, audience participations, contrasts, climaxes" (28). Always pretest the demonstration-"prior practice prevents poor presentation" (29). 8. What auestions and uractical a ~ ~ l i c a t i owill n s be aDpropriate & motivate and direct &dent observation a i d thought processes? What qualitative and/or quantitative data are crucial to the demonstration? Might a data collection table be prepared for the blackboard or an overhead projector? What potential questions or experimental variations are students likely to pose a s additional probes? How might Socratlc dialogue;; a n d or cooperat h e learnlng groups be employed? ' h u n g people art! not receptacles to be filled:. the" are fires lo be kindled. ldustus von i.iehea. , -19th century German chemist). Intellectual engagement and interaction are limiting reagents for the chemical reactions involved in "minds-on" learning. Consider the demonstration formulation: 15% to Arouse interest. 20% to teach students to Observe, 20% tonlustrate principles and 45% to make students Think (30). Learning cycle theory (15)can help one mix the ingredients in the proper order, so that students learn much more than a n "IOTA" from demonstrations.
-
d
~
~
~~~~~~
~
--.
9. What followup questions and practical applicationscan be used to test and stretch students' constructions of the new concept?
In training a child to activity ofthought, above all things we is must beware of what I will call 'inert ideas' that ~~~-~~ -~ to sav. ~ ~ ideas that are merely received into the mind without being utilized, or tested, or thrown into fresh combinations (31).
-
~~
Lawson et al. em;ihasize the importance of this third and last step [concept application] of the learning cycle (15). In both science research and science learning, new conceptualizations garner stronger support when they are used to make successful predi&ons &an when they-only account for prior data. 10. Could some of the pre-planning or post-demonstration cleanup responsibilities be delegated to laboratory assistants if available? Also, consider how "volunteers from the audience" might be used a s assistants during the demonstration itself. kctive srudent paniclpafion sends a message that demonstrations are not a "commercial break"and increases a demonstration's "exocharmic" character. Demonstrations that involve races, contests, and voting between the teacher and students or between groups of students are especially effective in this regard. Presentation Strategies Although the demonstrator should allow his or her natnral personality to come out in the manner of the presentation, there are several guidelines that are generally applicable: 1.Clear the demonstration table of clutter that presents a safety and/or visibility problem. 2. Model respect and knowledge rather than fear and ignorance of safety and wastedisposal issues and regulations. Precautions including the use of goggles, a safety shield or a fume hood (if necessary), and proximity to a fire extinguisher, shower, first aid kit, and telephone should be made explicit to students. If necessary, warn students against repeating the demonstration on their own. The ACS, NSTA, and recent demonstration books have up-todate safety and waste disposal guidelines (see for example, 32 and 33). 3. Provide a short introduction that connects the demonstration to previous discussions and helps focus student attention, but 'let nature do your talking for you"-"show, don't tell" -adopt a "let's see what happens" approach. If appropriate, ask students to predict the results but avoid forecasting the expected results yourself. Such a presentation encourages more "minds-on" behavior in students and may save teacher credibility if the demonstration "fails." 4. As you perform the demonstration check with your audience to be sure that they can see, hear, smell, etc. Use large scale apparatus, elevated stands or painted boxes, overhead projectors (as light tables or projection devices), spotlights, dyes, chemical indicators, and contrasting backdrops. Avoid blocking visibility with your body unless you are deliberately trying to hide a particular step in the procedure. .', Do not provide a lot ol'srirntific verbiage at the timeof thedemonstr:rtion. Allow sufficienttime for ihcfull sensow impact to be felt before eliciting student response. ~ e m e m ber, "Concentration must be learnt. . . I t should not be imagined a s nothing but a n effort of the will. Concentration is also a n intellectual process" (34). Encourage students to make careful qualitative andlor quantitative observations. Consider appointing a class "reporter" to record results for subsequent discussion and/or have all students take detailed observation notes. 6 . Guide the students to w e the forests iconcepts and throretical princ~ples~ by means of thc trces (observations,. Volume 68 Number 11 November 1991
935
