view from my classroom
FRANK CARDULLA Niles Township High School 9800 Lawler Skokie, IL60077
Chemical Demonstrations Learning Theories Suggest Caution Michael D. Roadruck Ottawa Hills High School, Toledo, OH 43606
After more than two decades of teaching chemistry I am still amazed at what I do not know, not only about chemistrv. .. but..more imoortantlv.",about teaching chemistrv. With me, a s I suspect with many other chemistry teachers, there are things I do simply because they seem 'the right thing to do" a t the time or, "it's always been done that way." Once in a while. though, i t is a ~ o r o ~ r i ato t estor, - and reflect on our techniques and their effeckveness. One technique that many chemistry teachers employ is the use of demonstrations. Some teachers of chemistry avoid demonstrations maintain in^ that they are too timeconsuming both to prepare and t o Demonstrations often involve undue hazard. And, the most condemning, demonstrations entertain rather than teach. Other chemistry teachers contend that the effort is worthwhile, that hazards can be minimized, and that demonstrations are an integral part in transmitting both the content and the spirit of chemistry. The use of demonstrations is seen as a powerful tool by the Woodrow Wilson Foundation.
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Demonstrations are a valuahle tool for every eh~mistry reacher. Displaying chemical phenomena, amwing ruriu~it,~, atimulatmi: thought pn~wses,developmg obaervatmn skdls, and introducing coneepts can be accomplished while both student and teacher enjoy the activity. However, a demonstration only becomes a teaching tool when the teacher helps the students assimilate concepts by carefully choreographing and oracticine the demonstration. olannine to be asked. .. ouestions . and fnllowlng up the demnnstrat~nnwlrh n thornugh discusD r t y f u ~Inst~tutron Hlgh sion. Phrlmuphy ofD~trumafrofmnu, School Chemistry, Woodrow WII-
But, like any powerful tool, demonstrations also can be the agent of harm. The issue I will address in this article is the application of learning theories to t h e use of demonstrations in chemistry. I will attempt to show that although chemical demonstrations can inhibit student learning, a n understanding of cognitive psychology a n d Piaget's developmental learning theories can guide the chemistry teacher in selecting and presenting demonstrations in a manner t h a t promotes concept attainment.
From my earliest exposure to the world of Mr. Wizard I always have been fascinated by demonstrations of science. When I was young, science demonstrations seemed like magic. As I grew, I recognized that the magic was in the knowledge that the demonstrations represented. Naturally, in my career as a chemistry teacher, I always have used demonstrations to trv to imitate Don Herbert and. later, Hubert Alyea. In theaffective domain, I try to recre: ate for my students the wonder and childlike enthusiasm these masters displayed. At the same time, I also intend for the demonstration to teach some of the content. Earlv in my career I did demonstrations just because they were "neat" and the students seemed to pay attention to them better than they did to my lectures. Ergo, they learned better. In the sophistication of my graduate studies in education, however, I began looking for a "theoretical framework" to guide my teaching. Just as the atomic theory guides the work of chemists, perhaps learning theories could guide and improve my use of demonstrations. As a leading figure in learning theory, Piaget's work as it relates to the discipline of chemistry has been described many times in this and other professional journals (1-9). More recently, the application of constructivist learning theories also has been discussed (24-27). Piaget's Research in Cognition
Piaget's training was in the natural sciences, having earned a PhD in Zoology in 1918. He drew upon this background by explaining knowledge in terms of the biological
Rbout the Ruthor
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Michael Roadruck holds a PhD in science education from the University of Toledo and MA and BS degrees from the Ohio State University. He teaches chemistry at Ottawa Hills High School and at the University of Toledo. He is a 1985 Dreyfus Teacher and a member of the Woodrow Wilson National Fellows h i ~Foundation's CHEM8 summer Droaram team. He received t h e Chemical Manufacturers ~ssociaiionReaional Catalvst Award in 1991. He has served as District ~epreshative, ~ewsletter editor, Journal editor, and President for the Science Education Council of Ohio. He is a life member of both the Ohio Academy of Science and the National Science Teachers Association. He has received NSF, Ohio Board of Regents and other grants to provide in-service training to chemistry teachers. He is a co-founderand director of a Norlhwest Ohio alliance arou~for chemistry teachers called the "Le ChAtelier Society... ljiikeilso appears as "Professor Science'' on a local children's TV program in Toledo.
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development of the individual adapting as a n organism to its environment (10). Knowledge is constructed, according to Piaget, by the individual based on his interactions with the environment and his understanding of it. Piaget used the word structures to describe the or~anizationor coordination ofthe individual's experiences chat give the individual a viable understandina of the world. As the individual has new experiences he assimilates these into his existing structures. The experiences thus become a part of his understanding of the environment, altering Gs structure in the process. Piaget terms this change accommodation. This self-reeulatow orocess or eauilibmtion enables the individual & build-nkw mental $trudures, conserve and enrich existine structures. and coordinate eauivalent schemes in order to d e v e l ~ i k n o w l e d that ~ e bettkr fits the environment. Likewise, constructivism emphasizes the role of the indim that the vidual and the senses. ~ o n s ~ r u c t i v i sasserts learner interacts with the environment and constructs meaning out of these experiences. The individual learner paints a picture of the world that is congruent with his or her experiences, revising and expanding with greater and more varied experience (27). Piaget proposed four successive stages in the development of knowledge as one grows to maturity. The highest Piagetian stage is known as formal operational. It is characterized by the ability to go beyond observable data and familiar objects, and to apply mental operations to concepts, abstractions and theories in qualitative and quantitative ways. Applying Piaget's Work to Chemical Demonstrations I t seems clear that most subiect matter taueht ., in chemistry courses is developed on an abstraa, conceptual level. This sus~icionis horne out bv the investieations of several researchers who conclude chat understinding the basic concepts taught in typical introductory secondary and college chemistry courses requires formal thinking (11-13). How manv of our students are a t the formal operational Icvel? ~tu-diessuggest that a large proportion'of college student.; do not function at a formal reasoning level. Some question whether, in fact, outmoded educational practices by high school teachers actually cause a regression in the level of thoucht - .(14.151. Moreover. those caoable of formal thinking often functionon a pre-fohal levef when they are confronted with science concepts and problems (20). Before we bemoan the situation as hopeless, We should he careful not to use Piaget as an exme to rebel
the complexity that gwes ehcm~stryits value, or the frustrnt~onthat comes from domg a drfficult job wcll It would bemmlc~fPlaget'smethods. that hnvr rhr Dower to help us become better thinkers were used to diminish the academic expectations we have far our students. ( I ) against against
Is there some way to use demonstrations so that students a t a lower cognitive level will gain a n understanding of conceptual topics on a formal level, and perhaps even facilitate development of formal operations?
J. Dudley H e m n of Purdue University, wrote: . .. [Tlhe inclusion of concrete experienceAe., opportunities to actually touch, smell, see, and manipulate materials that
would lead to the concepeappears to be important. But concrete experiences are not particularly useful if all the student does is touch, smell, see, and manipulate without being forced to think about what he is doing. . . . It would appear that those educational expeliences which encourage the intellectual dehate of ideas, the weighing of evidence, and an emphasis on making sense out of observed facts are ones that lead to the development of formal thought. (3)
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Journal of Chemical Education
Here, then, was the answer. Chemical demonstrations can be classed with "those educational experiences" that teachers should be using to promote concept attainment and the development of formal thought. Embedded in this answer was a caveat: unless presented orooerlv. manv students do not, and perhaps cannot, benekt f;om"demo&rations. At least one contributine factor to the difficultv many students have with chem&try is the mismatch between the student's comitive develo~mentalstaee and the level a t which chemistry content is presented. ~ G l e s dems onstrations help hridge that gap, they remain only an attention-getting, motivational device. While this is not all bad, it is possible to use Piagetian and constructivist leaming theories to help us extend the use of chemical demonstrations. Students Must Interact with Significant Chemical Content Well done demonstrations, dramaticallv presented. are attention getting. Many excellent articles have been published in this Journal and elsewhere over the years detailing the steps for producing engaging demonstrations (2830). Demonstrations must, however, be more than show. If they are to be educationally defensible, they must involve the student in a n interaction with significant chemistry content. In Understanding Causality, Piaget considers the nature of such scientific concepts as work, force, heat, light, space, and their relation to the "knower" in terms of causality. He concludes that to "know" the causal nature of these concepts, the knower must he active (both mentally and physically) in interacting with the "causal events," and maduallv become aware of the processes involved in causality &owledge is not a simplk matter of reflection (16). The demonstration, in so far a s it is performed by the teacher and not the student, is a t best a vicarious experience for the student. A demonstration cannot simply be presented. To achieve its purposes in developing a n understanding of the content, a demonstration must be part of a lesson that gets students actively involved with the event and the content it seeks to impart. The demonstrator must involve the students in the ;xperience through questioning, predicting, redesigning, the ofiering - of explanations and the t e s t i s of those explanations. Demonstrations Must be at the Correct Cognitive Level of the Audience Second, the content of a demonstration must be accessible to the student. Given that most of our students are functioning below the formal operation level, the content level needs to bekn a t best a t the concrete level. This. a t least in this author's experience, requires deliberate at&tion. As teachers of chemistry we have had manv more experiences with, much more knowledge about, ahd considerably wider conuectious with the phenomenon being demonstrated. To us it is perfectly transparent. The demonstration may he opaque, however, to the student whose structures are incompl&e, whose experiences are limited and whose knowledge is uncoordinated. Exploding a mixture of oxygen and hydrogen gases may be t h e attention-getting demonstration for stoichiometry, or activation energy, or exothermic reactions, or any number of other concepts. Put the gases in a goose egg and you have entertainment worthv of the David Letterman show. All the student sees, however, is the flash. Deliberate care must be taken to examine explicitly the chemical concepts this performance illustrates (as the originators of this twist on the demonstration-the Weird Science group from Illinois-do in their own classrooms). Without explicit attention, demonstrations are nearly always abstract, intellectually inaccessible to our chemically naive students. In all seriousness, a former honors student
of mine, believing my assertion that water was made in the reaction, asked after this hydrogen explosion demonstration if this was the wav thunder was produced. He was clearly trying to connect this experience with his past experiences of rain- storms. How many others had made this association and failed to ask if it was true? What can be done? Two clear liquids are added to form a precipitate. Do our students really see in their minds the collisions of ions. the rearrangement of matter already present? Or, are they surprisedthat the mass is the same before and after the reaction? Have we even thought to ask t,hem? It ~is -so- obvious to us.-Who could misunderstand? .--.--- ~ Two clear liquids are added to form a gas. Do our students "see" the eas being formed or do thev think it is air fizzing out? Do we ask how to identify thegas and then actually perform the tests that students suggest? There are indeed many exemplary teachers who do ask the obvious, many who do have students make drawings of atomic and molecular level interactions, and many who do bring students into the demonstration as intellectual participants. I am to insure only suggesting that unless we take expCcit otherwise. demonstrations can obscure rather than enlighten. I am suggesting that learning theories can productively guide our actions in front of the class.
mismatch between the learner and the concept by utilizing concrete models in the instruction were conducted and reported in this Journal by Goodstein and Howe (2).The results showed that ". . . the cap between the concrete and formal levels was not bridged by the provision of concrete exemplars. . . ." Instead, they continue, "[Ilt seems clear that the real beneficiaries of the use of concrete exemplars were the students a t the highest cognitive levels rather than, as we had supposed, those a t the lowest level." So, what I have always done because it had seemed the right thing to do was probably not as beneficial as I had believed. I had missed the point of concreteness. I was the one benefitting from the use of models and analogies. Because I understood the concept, I was able to find approximate examples in the concrkte world. I am not k i n g to advocate abandoning the use of such techniques. Rather, I believe learning theory suggests that we shift the job of creating concrete analogies to the student. We must wme to recognize the powerful tendency of students to misinterpret what we say and do, so that our words and their observations conform to their current understanding of reality. It is when a student recognizes a state of equilibrium, or any other abstract concept, in his or her own world that I believe the student has begun to grasp the concept.
Presenting Concrete Demonstrationsto Concrete Thinkers Many of us try to do a s Herron suggests. Conceptual chemistw must be expressed in terms of concrete exemplars. argues that concrete thinkers will acquire approximations of the concept that will serve until a later t g e when they are developmentally more prepared to accommodate a better version of their environment (3). Boulanger also found that greater realism or concreteness of supporting instructional materials was associated with greater cognitive achievement (24).
Helping Students Turn Concrete Exemplars into Abstract Concepts
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The Problem with Analogies
However, concrete demonstrations are hard to fmd. This type of demonstration tends really to be an illustration or analogy. Using beans to stand for atoms to demonstrate Avoeadro's number: usine Stvrofoam balls to show atoms " rearranging during a reaction; using magnets to represent bonding are all approximations of the wncept. And, as approximations, they are inaccurate in many details. While this does not present a problem to the sophisticated learner, the naive learner does not always make the distinction between the accepted view and the model. Uncritical acceptance of the analogy can lead naive students to inappropriate generalizations. Learning theories sensitize us to this distortion. The student is doing exactly what constructivist and Piaaetian theories sugges~onstructing new structures to aiwmmodate the concrete experiences, but the novice does not necessarily know where to stop. Where does the analogy depart fmm reality? This is a good question for determining how well a student understands the concept and how much he has distorted it. We need to ask this question and explore with the students the areas where the analogy breaks down and where it is most appropriate. Demonstrations often involve reactant molecules (a transparent concept to the teacher, but translucent a t best for nonformal ooerations student). The reacting mole- ~ the cules do somethini (that we cannot' see) and are transformed into oroducts-addine two clear liauids toeether to make a preApitate, for exaGple. For the concrete learner these demonstrations are nothine - but .pure mazic. .. The orecipitate appears out of nowhere! Intuitively, 1 would expect that usine models should help students m a w the meanme of a d e m k r a t i o n . ~nvestigationsaimed a t reducing the
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When a student recognizes and can express the limitations of the analogy, that is a student who owns the concept. This is the point of the wucreteness that learning theorv sueeests we use. It is insufficient to be merelv ex(i.e., touchable) models and analogies posed to (built from the teachers world of experience). Constructivist learning theory suggests that it the learner who must actually manipulate the wncrete examples. It is experience with the concrete that allows the d&elopment o? the abstract. Seeing a tetrahedral methane molecule held up in fmnt of me is not equivalent to building it and holding it myself. In playing with it on my own I discover the symmetry of the tetrahedron. I actually have had students who had to toss it on the table a few times to convince themselves a tetrahedron always lands the same way. On the other hand, I have had students who recognized the same concept in the glassblower who makes miniature horses stable by placing three of the horses feet on the ground with the fourth one raised.
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DemonstrationsAre Not a substitute for Hands-on Laboratory Work Using - Piaget's - learning theories as a mide, chemistw teachers have been urgezto use experim&l data and develop the use of demonstrations in their lectures to simulate laboratory experience (3l,32). Certainly encouraging students to become active learners is what learning theories suggest. Nevertheless, lectures accompanied by demonstrations, Piaget says, are not as effective as having the child discover or invent wavs of dealine with obiects for himself. "[Bly canying out exp"eriments inthe chilks presence instead of makine the child carrv them out. one loses the entire informational and formative value offered by action proper as such" t 171. Uemonstrations should not be a s u b s k i t e for the hands-on laboratory work. It is in the lab that students can have the concrete experiences discussed above. Piaget cautions us to design theiaboratory program carefullv because ". . . t h e repetition of past experiments is still a iong way from being the best way of exciting the spirit of invention" (18).Turning the student loose in the lab, however, to reinvent modem chemistry is certainly a recipe for disaster. Some guidance is needed. Demonstration; can provide the teacher an appropriate compromise
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when used as a starting point for the more direct experience in the lab. Demonstrations are a way to model the investieative approach and techniaues that characterize an edu~ational'l~b component. Demonstrations can steer students to areas of self-directed investigations that are most likely to be fruitful.Lecture and diskssion can then play a more supportive role as students build a base of experience and then need a vocabulary and organizing structure to interpret and integrate the experiences. Throughout it all, learning theories remind us to keep foremost the role of the learner constructing knowledge out of experience. Using Demonstrations as Motivators One argument from learning theory promoting the use of demonstrations is that students attend to them. In 1958 Buell described the results of investigations conducted by S. H. Banks for his dissertation "How Students in a Secondary Modem School Induce Scientific Principles from Scientific Experiments" (Birmingham University, Birmingham, England, 1958). Buell reported that "All children, [in the study1 regardless of success in building and verifying hypotheses, showed genuine interest in the experiments-both the manipulation and the cognitive resultants" (19). I do not think we would find students any different today. Students become interested, motivated, even excited by demonstrations. Demonstrations that are "exocharmic", i.e., generate charm, are compelling to watch. Color changes, flames and explosions hold students' attention and are good "set inducers" preparing students for learning - (20). Demonstrations not only provide motivation, but also learning theories can help us present demonstrations so that they promote learning and induce formal operations. How should we present demonstrations for maximum benefit? Banks cokludes, says Buell, that students should, whenever possible, be encouraged to elaborate their own interpretations of scientific demonstrations rather than being presented with the theories, ready-made,before seeing the illustrations (23). Students like demonstrations and experiments. They pay attention to them. Learning theory urges us to take advantage of students' efforts to assimilate the new experiences that demonstrations can provide. For maximum benefit we need to involve students in the making, testing, and verifying of hypotheses. We should not simply give students the "right answer" when doing a demonstration. Rather, the students must be asked to observe, to interpret, to hypothesize, to analyze hypotheses, and to draw conclusions. In short, students must experience the phenomenon, not just the presentation
Demonstrations can be useful in provoking formal thinking. The presentation of discrepant events which, in Piaeetian krms. are not easilv assimilated. not onlv compels interest but disturbs thg equilibrium requiriig the learner to engage in accommodation. The adding of measured volumes of alcohol and water to get less than the sum of the individual volumes is an excellent examole. It is the learner, however, who should propose the bucket of sand and bucket of golf balls analogy. Using demonstrations to provoke student thought, the teacher also must "provide counter-examples that comuel reflection and reConclusion Piagetian learning theory cautions us that the role of demonstrations in helping the concrete learner understand the fundamental concepts of chemistry is highly complex. Demonstrations are not an elixir for reviving the 1028
Journal of Chemical Education
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flagging spirits and expanding the minds of despondent chemistry students. I am not, however, suggesting that we abandon the use of demonstrations citing the shortcomings that learning theories reveal. Instead, I am suggestinn that we continue and even increase our use of demonstrations provided that we make conscious use of our understanding of how people learn to euide us in the selection and preBeutatioh o? those demonstrations. What learning. theory suggests is that the teacher cease beine a lecturer or demo&trator, satisfied with transmittrng ready-made solutions, but take on the role of a tour a i d e who leads clients to places where they can experience the culture, where they can engage the unfamiliar directly (21). Demonstrations can be a ready vehicle for stimulating student interest and research. Students can present demonstrations, investigate other ways of doing them, extending them, improving them, collecting additional data, n sthe concept demonidentifvine other a ~ ~ l i c a t i o of strated: ti dents ckl;ecome involved intimatAy with the spirit of chemistrv throueh demonstrations. Demonstrations are then just"a stepp';ngoff point. Once the interest is piclued and a direction is set. students should be expected to ingage in their own area bf research, to construct their own knowledge of chemistry based upon their own experiences with chemistry. Anticipating Piaget by half a century, Michael Faraday said that to make a fact his own he had to see it (22).Chemistry must be seen to be believed! Chemical literac, requires Literal chemistry. 1)emonstrations bring chen&try to life. Without them, chemistry instruction would be lifeIcss. dcvoid of the charm that drew us into chemistw i n the first place. Demonstrations are a wonderful tool, key unlock manv minds. The spotlight of learnine theories helps us loocat demonstrati& &m theperspec%ve ofthe learner rather than the presenter. Theories of leamine are a long way from providkg the guidance that the a t k c theory has. Nevertheless, they do suggest beneficial approaches for using the demonstration tool.
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