Everyone Wants to be a Model Teacher Part I: Observations versus Inferences C. L. Schrader Dover High School. Dover, OH 44622 Got A Match? Almost everyone has struck a match and observed the chemical change that results. Furthermore, few individuals have any difficulty "explaining" what happened or making inferences about the event as long as their explanation is tied closely to a direct observation. For example: 1) Rubbing the match on a rough surface caused it to ignite. 2) If a safety match is used, it will ignite only if the head is rubbed on a special surface provided. Thus, there must be something in that special surface that is necessary for ignition to take place. 3) Something in the air must be required for burning, because the match goes out when that something is used up. Difficulties arise, however, when extrapolation from a direct observation to an application is required. Consider an attempt to "exnlain" burn& in terms of an atomic-molecular model that "hagines" both the match and the surrounding air as made un of atoms arraneed in a oarticular molecular order. ~ u r n i n ginvolves a rearrangement of those atoms into a new molecular order that is more energetically favorable. This explanation requires thinking a b o i t situations that cannot be directly observed, logically analyzing the consequences of each imagined possibility, checking the result of each analysis against the fact acquired through observations, and keeping track of all such analyses so as to know when all possible explanations have been exhausted. The thought processes involved above are described by Piaget as "formal operations." Although some people may not agree that such reasoning can be taught, I believe that students can be shown examples of formal operations and should be given exercises which require the application of the same reasoning patterns as they apply to the subject matter of chemistrv. Perhaos mv ereatest cballenee " in mv more than 20 years of chemistry teaching is relating chemistry to students who are thinkine on the concrete level and who, thus, have difficulty understanding abstract ideas. Teaching strategies that have proven successful for me under these conditions include a systematic link between facts and the managing and examining skills required to process these facts. In a discussion of this type, however, the limitation of humans to attend consciously to several items a t once cannot he overlooked. Extensive research evidence (1, 2) as well as common sense indicates that there is a practical limit to the number of things to which all humans can consciously attend a t any one time. When we are pushed beyond our limits, confusion and error often result. Although having too much on one's mind is a common excuse for "careless errors," it may in many cases be a reality. As a nerson becomes an exnert in a field, the amount of information in that field that he or she can process at one time increases greatly over that of the novice or apprentice. For the experienced chemist, the facts and relationships implied by the microsconic explanation of a burning match, and the questions that need& he asked, require littie if any conscious attention. For example, 1) What is the composition of the air? 2) What is the difference in an atom and a molecule? 3) What is heat? 4) How is a rise in temperature related to the movement of molecules? A
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How is the movement of molecules related to the energy of callisions? 6) How is the energy of collisions related to the breaking of chemical bonds? 5)
The answers are automatic and, consequently, the chemist can focus his efforts on making conscious connections. Thus, an explanation for this phenomena can he readily arrived at. The beginning student, on the other hand, is far less familiar with the facts and nrincinles. In the student's analvsis of the burning match, far more conscious attention must be given to the fundamentals. The ouestions are not automatic. As a result, the student may he &able to make (or even follow) the logical analysis and explanation for the event. The student's "working memory" is said to he overloaded (3); i.e., the number of things to which the student must consciouslv attend exceeds the processing capacity of the brain. A logical conseauence of this argument is that there are a limitednumber ofvariables that c& effectively be introduced a t any given point. Ifstudents are presented with new thowht proc&es, new facts, and new principles all a t the same time, their working memory will become overloaded and they will quickly become confused. They learn neither the thought processes nor the new facts and principles. T o be effective, a lesson that focuses on the development of new logical procedures must be done in the context of "simple"situations that students easily understand. Only then will students be able to use what they have observed, develop mental models which will explain their ohservations, and apply formal operational thought to such "abstract" concepts as atoms and molecules. My course has been developed around a series of activities that use a kind of cyclical process. When I am trying to help the students develop a new thought process, they are assigned tasks that are not very demanding in terms of new facts and principles. Likewise, when I am trying to teach new or complex facts and principles, the thought processes are simple and familiar. Models A common misconception is that students who can summarize a concept in their own words have a sufficient understanding to apply the concept in a meaningful way. Research shows, however, that this is unfortunately not the case (4-6). Understanding a t the level of application requires the develonment of mental models to which students at the hieh school level have little prior exposure. Students thus must c e taught how to develon and test models. The studv of cbemistw which itself depends very heavily on models oifers a natural focus for introducine students to modeline techniaues. A model is mental picture, which by its-nature may be unverifiable but which explains exnerimental observations. allows the prediction of additional experimental results, and provides a mechanism for relating abstract concepts to concrete objects or ohservations. Some models are so powerful a t explaining well understood ohservations that they are regarded as facts. An example is the kinetic molecular model of gases; however, it was well into this century before the concept of atomicity was fully accepted (7). I t is not surprising that the first formal study of chemistry would naturally lend itself to exposing students to these much needed skills. In this paper I will describe several activities
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that I used with my students to help them understand what a model is, how to construct and use models, and how to test their reliability. Dr. Watson Because scientific modeline techniaues deoend ouite heavily on being able to distinguish ohservations from inference. I introduce mv students to this idea in the first week of schobl. Other exercises besides the one presented below are eiven throuahout the vear in an effort to extend the idea to numerous settings. Students are first given a definition and common examples of observations and inferences. They are then read an excerpt from Sir Arthur Conan Doyle's novel "The Hed-Headed Leaeue" 18) . , in which Dr. Watson desrrihed Mr. Wilson. a visitor, a commonplace British tradesman about whoa Watson could observe nothing remarkable except blazing red hair. Sherlock Holmes, to whom Watson had been talking, countered with his own detailed accounting of the visitor, including
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11 he had a t a t w "fa t k h with drliratr pink scaler 21 his right hand was larger than rhe left 31 hcwore an arr-and-compassbreast-pin I ) on his wareh chain there was a Chinesewin 5, his right ruffwasshiny for i ~ mrhes e and there waua smooth
patchon the left elbow Holmes then continued "hevond the obvious facts" that the visitor had a t some time doie manual labor, had taken snuff, was a Freemason, had been in China, and had done a considerable amount of writing as of late, "he knew nothing." "What else can be indicated bv that rixht cuff so verv shinv for five inches, and the left onewith thesmooth patch-near the elbow where you rest it upon the desk, except that he has been writing?" Holmes then explained the other inferences. After reading this selection, I ask a student to give an ohservation made by Holmes. Many students respond, "Mr. Wilson had been to China." If I wait and do not respond too quirkly,other students will indicate that the statement ahout Mr. Wilson having been in China was an inference rather than an observation. ~ h u sI, encourage the class to critique each proposed ohservation. Once true observations have been identified. the students are asked t o indicate the inferences that were drawn from those observations. At the wnclusiun, I ask whv Sherlock Holmes'inft~enreswere all corrert.Tvoical student replies include: 1) "Mr. Wilson said the inferences were correct." 2) "Sherloek Holmes is intelligent." 3) "The author wrote the story so all inferences would be correct."
The first resoonse is scientific. because the inferences have been verified dyMr. Wilson's bibgraphical data. The second response is pseudoscientific because Holmes' opinions are accepted because he is an expert. The third response is most interestiue because it examines not onlv the data and theories, but the entire premise, and it is this so& of analytical thinking I want t o foster. I point out that scientists often make incorrect inferences and that plausible alternatives should always he sought. T o emphasize my point, I often use the story that the leftarm of tennis champion Rod Laver is much bigger than his right arm, yet I do not think he has done manual labor. I ask students to suggest plausible alternative hypotheses. This is an opportunity for them to think creatively and all plausible comments should he warmly reinforced. My objective a t this point is to encourage the students to be analytical and creative in making their inferences. I evaluate the inferences at another time. Candle The following day the students are given a candle and asked to make three ohservations and three inferences. Without 1002
Journal of Chemical Education
failure at least one student in every class will say, "I observed that this candle has heen burned before." This statement is typically picked up on by another student who correctly explains that the statement was an inference and perhaps the kick was made to he partly black. Another student wilistate, "We can't even he sure the object is a candle." When still another asks, "What could i t he except a candle?" we discuss alternative hypotheses, such as: perhaps these are clever sculptures of candles. I stress, however, that we are not yet evaluating the correctness of the inferences, just identifying such statements. This year a student asked, "What is a candle?" After much discussion and some experimenting, the class agreed that acandle is asolid ohject, with a wick, which produces heat and light by burning fuel. One of mv ~ r i m a r veoals in teachine chemistrv is to reouire students to-use the ;Gee highest cognitive processes, which were defined bv Bloom as analvsis. and evaluation . . svnthesis, . (9).The candle discussion requires analysis of statements to determine if thev are ohservations or inferences: and evaluation of statements to determine which are the essential characteristics of a candle. Class discussions of this tvpe are most valuable if they are focused on the reasoning processes, the higher cognitive processes, and require formal operations. I have found that the amount of time I wait for a response is very important as suggested hy Rowe (10). Lamb (11) has stated that, "to enhance student achievement in science, teachers should use more questions related to application, analysis, synthesis, evaluation, convergent production and divergent production." Tisher (12) found that the highest achievement results when the teacher asks equal mixtures of higher and lower level questions. Its Place in Chemistry I t may he correctly argued that we can do analysis, synthesis, and evaluation in connection with almost any ohservation. Why take time in a chemistry class with an excerpt from a detective story and familiar ohservations such a s a burning candle? The answer is simply that analysis, synthesis, and evaluation are relatively new thought processes for beginning chemistry students. The only way that students can &tendcarefullv the imoortant conditions that senarate an observation from an inference or can put together several separate ideas into a single conclusion is to devote all of their conscious attention to the logical analysis. If we ask them to do this kind of analysis of unfamiliar phenomena they will be unsuccessful and will not be able to understand the thought processes that we are trying to teach. Thus, it is important that the early activities focus on analytical procedures in such a wav that thev can be explained in terms of facts and principles that the students will ;eadily understand. Literature Cited (1) Miller, G., The Magical Number Seven, Plus or Minus Taro. Psych. Rou., 63. 81 (19561. (2) Broadbent, D. E.,"TheMagie N u m k Seven AfterPifteenYem,"in"Sfudie3 inLon8 Term Memorv," (Editors: Kennedy,A., and Wilka, A,), John Wilev & Sons, New Yurk, 1915. (31 Johnstone, A. H., "Nyholm Lecture: Chemical Education Research: Fsets, Finding8 and Consequences," Chrm. Sor. Reu.,9, 365 (1980). (41 Anderson, J. R., "Language, Memory and Thought: Lawrence Edbaum Asnciates, Hillsdale. NJ. 1976. Franciam. (5) Anderson. J. R.,"CognitivePsy~holwandIteImplicstions~Fleeman.San 1980. (6) Anderson, R. C. & Shifrin, Z.,'?he Meaning of Words in Context," in "Theoretical 1rsuer inReading Camprehension," (Editors Spiro,R. J..Brurr, B. C., and Brewer, W. F.1, Lawrence Erlbsum Associates, Hillsdale, NJ, 1980. (7) Servos, John W., '"Learis,G. N.: The Disciplinary Setting," J. CHEM. EDUC. 61, (1984). (81 D0yie.A. C.,"The Red-HesdedLeague. The~lluaratedShedmkHHm~Treaaury: Crown Publishers, New York. 1916. (9) Bloom. Benjamin, (editor):Tsronomy of Educational Objstives. The Cl&sdhtion of Eduestiond Goals-Handbook I: Cognitive Domain: David MeKay Co., h e . . New Yark, 195L (101 Rowe,Mary Budd,"RelationofWsit-TimesndRewards ta theDsvelopment of Lsnwage, Lagic. and Fate Contrul, P a n 11: Rewards," J. RPS. Sci. Teach., 11, 291 ,lo"", ,.",-,.
(11) Lsmb, William G.,"Ask s Higher Level Question? Get a Higher Level Answer? The Sei. Teach..43: 22 (April 1976). (12) Tisher, Richard P.. "Verbal Interaction in Science Classes," J. Re8 Sci. T a ~ h .8, 11971).
