Straw Men and False Dichotomies: Overcoming ... - ACS Publications

Research: Science and Education

Straw Men and False Dichotomies: Overcoming Philosophical Confusion in Chemical Education Keith S. Taber Science Education Centre, University of Cambridge Faculty of Education, Cambridge, CB2 8PQ United Kingdom [email protected]

Many of the ideas taught in chemistry are abstract and counterintuitive, and present considerable challenges to students and those charged with teaching them (1). Progression in learning chemistry often involves developing more sophisticated and nuanced understanding of topics that were initially introduced at a simplified level. Such simplified teaching models are certainly necessary to provide students with ideas with which they can meaningfully engage (2). Unfortunately for many students, our teaching models can themselves become impediments to further learning. The purpose of the present paper is to argue that the philosophical perspective of “instrumentalism” could usefully inform teachers' thinking in ways that could help avoid some of these learning difficulties. Moreover, it is argued here that instrumentalism deserves particular consideration as it has been proposed as the philosophical basis for constructivist approaches to science education that have been widely adopted in the chemical education community, but have also been severely criticized. In particular, the present paper responds to the criticisms of Scerri (3) who has argued in this Journal that constructivism in chemical education is based on a confused philosophical basis, and is associated with the antiscientific position of relativism. This is much more than an academic debate, for instrumentalism provides a perspective that could usefully be adopted by teachers and students in making sense of chemistry courses. While much of the challenge of learning chemistry is inherent in the subject matter, it is becoming clear that aspects of pedagogy also contribute to students' learning difficulties. In particular, students commonly have a weak appreciation of the status of the theories and models that they meet in a chemistry course, and often adopt a naive realist approach and so see them as proven, factual accounts of how the world is. This stance can later lead to new teaching appearing to be in direct contradiction to prior learning: something that can lead to frustration and disengagement, as well as making further learning problematic. It is argued here that teachers who encourage their students to take an instrumentalist approach to learning chemistry may facilitate more effective learning. The Basic Constructivist View of Learning Constructivist approaches to teaching chemistry have been discussed in this Journal over a number of years (4-6). The basis is that:

• Meaningful learning (7) requires students to actively link what they are being told and shown by a teacher to their prior knowledge.

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• Learners will come to classes already holding ideas relevant to the material to be taught. • Some of these ideas will be at odds with the accepted scientific ideas. • As students will interpret teaching in terms of prior knowledge, what they learn will often be a distorted version of what the teacher intended. • Teachers therefore need to take learners' ideas into account so that they can effectively channel learners' thinking toward the intended scientific models.

This basic view, with various formulations, is widely accepted in science education (8, 9), and beyond (10). Scerri's Accusation of Relativist Leanings Eric Scerri has argued in this Journal that constructivism in science education is associated with relativism, a perspective that “implies that the forms of knowledge derived from chemistry, black magic, or voodoo, for example, are all equally valid” (3). Internationally, constructivism has become the most important perspective for considering teaching and learning in science, and has been considered as a paradigm or dominant research program in science education research (9). Scerri is a knowledgeable commentator who has been highly influential in promoting the subdiscipline of the philosophy of chemistry, and his comments reflect those of other notable commentators, in particular Michael Matthews, editor of the influential journal Science and Education (11). Scerri's premise, that constructivism is founded on a philosophical basis that would be rejected by virtually all practicing scientists and science teachers, suggests reason to be concerned about the strong influence of constructivist thinking in chemical education. Rejecting Relativism as a Widespread Influence on Constructivist Science Educators Scerri acknowledged that, despite his reservations about the philosophical underpinnings of constructivism, many of those who claim to be constructivist science educators do so without espousing relativist views. The distinction between being a constructivist in terms of how human learning occurs (i.e., holding the views outlined earlier in this article), and in terms of how science develops new knowledge is well recognized (12). Although it is possible to find constructivist science educators who talk of scientific knowledge as a human construction (13), it is difficult to find any science educator who has ever

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suggested we should study learners' ideas in science because they offer alternatives that have equal validity to those in the curriculum (which would be the logical conclusion of a truly relativist position). Yet this is the “straw man” that Scerri implies is infiltrating chemical education. So commentating on Scerri's article, Cardellini suggests that, while teachers may accept that people actively construct knowledge, they are suspicious that constructivism implies that “every construction of personal meaning is acceptable” (14). In another response to Scerri's article, Bernal acknowledges that such a relativist position does not characterize constructivist chemical educators, but warns that some constructivists seem to accept that “reason and evidence play no role in determining the validity of scientific theories, ...that no distinction can be made between science and non-sense” (15). In contrast to such a view, constructivist science educators discuss the significance of students' ideas in the context of their consequences for learning the prescribed curricular science (16). Space only allows consideration of two of the most influential science educators associated internationally with constructivism. The late Rosalind Driver, author of several of the seminal constructivist papers in science education (17, 18), in her influential book, The Pupil as Scientist? (based mainly upon her observations of science teaching in the University of Illinois Curriculum Laboratory), criticized unstructured “discovery” learning methods because they were unlikely to lead to the “conventional” scientific answers (19): The constructivist view of science, on the other hand, indicates the fallacy here. If we wish children to develop an understanding of the conventional concepts and principles of science, more is required than simply providing practical experiences. The theoretical models and scientific conventions will not be “discovered” by children through their practical work. They need to be presented. Guidance is then needed to help children assimilate their practical experiences into what is possibly a new way of thinking about them.

This attitude is typical of most science-educator constructivists' writing; despite the claims of one critic in the United States who argued that “many constructivists [in science education] are pure empiricists because of their ignorance of the scientific process” (20). While Scerri's article did not make such extreme claims about U.S. science educators, he does use something of a sleightof-hand to support his case. One of the sources that Scerri criticizes is Spencer's 1999 contribution in this Journal (4) exploring “new directions” in chemistry teaching. This paper offers a brief overview of a range of related developments, and is not a detailed exposition of a constructivist position. One of the points that Scerri picks upon is how the constructivist position is contrasted with the view that examination questions only have one correct answer. Scerri makes much of this and explores how different answers could be considered correct. He notes that “to claim that knowledge is constructed in general or that the majority of exam questions have more than one answer is, I believe, the height of folly” (3). This clearly implies that the constructivist view is that different students' various diverse answers in examinations should be considered correct (presumably because each is correct relative to that individual's own way of thinking). It is unlikely many chemistry teachers would see this as a reasonable assessment policy. However, this is another “straw man” as Spencer did

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not actually associate a constructivist view with having more than one correct answer. Rather the constructivist view was that “the ability to answer with only one answer does not demonstrate student understanding” (4), namely, that being able to produce the answer in the mark scheme does not provide reliable evidence of understanding the science in the way the teacher intended. This is something that most chemistry teachers will have experienced in their classes, and hardly seems an objectionable claim. Herron has argued that constructivist principles can explain how Scerri, a philosopher, may misunderstand the work of constructivist educators (21). We all inevitably use our existing knowledge as interpretative frameworks to make sense of what we read and what we hear. John Gilbert (a recipient of NARST's “Distinguished Contribution to Science Education Through Research” award), was, like Driver, author of some of the seminal papers championing constructivism (22, 23). In 1985, with David Swift, Gilbert set out a conceptualization for the tenets of the constructivist research program (24). The methodology of scientific research programs is a way of understanding progress in science (itself a notion inconsistent with relativism) devised by the philosopher Lakatos (8, 25). What is revealing is how Gilbert and Swift clearly aligned this area of research with a realist position. The core assumptions of their program included the statements “the world is real”; “the individual tests hypotheses through interaction with reality against personally appealing criteria”; and “reality provides guidance as to the adequacy of these hypotheses so tested”. Again there is little comfort for a relativist here. It has to be recognized that some constructivist science educators do demonstrate “relativist” tendencies (26), and some of Driver's writings appear to entertain conventionalist ideas that the authority of scientific ideas derives from being adopted by the scientific community. However, as Scerri himself acknowledges, “cognitive” constructivism need not be based on a relativist view, and indeed in practice most constructivist writing in science education seems to be clearly based on a view of science teaching in which children's ideas are judged against accepted “correct” answers. Instrumentalism as a Middle Way: Rejecting ObjectivismRelativism as a False Dichotomy Scerri objected to accounts that treat objectivism, realism, and positivism as if equivalent (27). Yet Scerri's own account ignored the highly significant distinction between extreme relativism and instrumentalism. Instrumentalism considers the products of science (theories, models, laws, etc.) not as true descriptions of the world, but rather as useful tools to make sense of, predict, and control the world (28). This distinction is of particular relevance for two reasons. First, although it is difficult to find science educators adopting relativist positions, the constructivist writing that Scerri criticizes is sometimes explicitly linked to an instrumentalist view. A number of science educators, including one of Scerri's prime targets, George Bodner, draw heavily upon the instrumentalist constructivism of Ernst von Glasersfeld (6). Second, whereas total relativism is anathema for science, offering no basis for developing reliable public knowledge, an instrumentalist perspective would seem to be something that is not only compatible with science, but has actually been adopted by many practicing scientists (29). Bernal suggested that “no one

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would equate” instrumentalism “with hostility to science”, pointing out that instrumentalists “believe that reason and evidence decide which theories are accepted or rejected” (15). So the distinction between objectivism and relativism is a false dichotomy that obscures a middle path. von Glasersfeld certainly offers an account that Scerri could not accept, as in von Glasersfeld's approach all human knowledge (not just public scientific knowledge) is indeed constructed, and accepted scientific knowledge does arise out of a form of negotiation. This makes his position suspect to such commentators as Scerri and Matthews who seem to see any tendency to relativism as the philosophical equivalent of a slippery slope (30). However, von Glasersfeld does not deny the existence of an external reality in which we all live (31), and accepts that we all share the same physical universe, which has a particular form (regardless of how we construe it), and so constrains the ways we can viably make sense of the world (32). This is basically a realist position, as von Glasersfeld would accept that, although each individual constructs his or her own mental models of the world, ultimately these models must be judged in terms of their degree of fit with experience, which is constrained by the real world (33). We cannot justify believing anything we want, and an individual who believed he or she could pass through walls only has to test this belief for it to be found wanting. However, von Glasersfeld also believes that we can never have certain knowledge of the world, and so we can never be absolutely sure whose versions of that reality are closest to the mark. This is not, however, the same as saying that we should therefore treat all ideas (whether from science or superstition, whether elicited from a science teacher or an elementary pupil) as equally likely to be correct and so worthy of equal consideration. So the contrast between seeing science as a means of providing absolute knowledge and there being no basis for making any kind of judgments about the relative merits of different ideas is another false dichotomy. von Glasersfeld takes a pragmatic stand (34). If we can never be sure whether our mental constructions are “accurate” in terms of corresponding to reality, then we should sensibly adopt a different criterion to judge our ideas. This is the notion of “fit”. From this perspective, the purpose of science ceases to be to know nature, but rather to build models of nature that work for us, to test them out by further experience, and to discard or modify those that do not do a good job of “fitting” (35). We can have grounds to be very confident in some of our constructions that have continued to fit the experiences of thousands of scientists over extended periods. But we can never be entirely sure we have understood nature. Newton's model of gravitation did an excellent job for several centuries, albeit generating some anomalies, but since being superseded by Einstein's model, has been considered an imperfect representation of nature. Einstein's new construction of the nature of gravity suggested further tests, and led to new experiences, so that we now consider the Newtonian model only fits our experience within certain limits. Despite this, the Newtonian description of gravity continues to be a viable model in many circumstances: it remains in use in many areas of science and engineering, and forms the basis of material taught in school and college courses. So half a century after Einstein proposed general relativity, and our “best” understanding of gravitation shifted from being about interactions between massive bodies, to being about the geometry of 554


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space-time, Raymond Wilson, the head of applied mathematics at the U.S. space agency NASA, reported to teachers that (36) [Newton's models were still] used in the solution of all mathematical problems of the Space Age, from rocket design and propulsion to deduction of the path followed by a rocket flying through Earth's atmosphere, a spacecraft orbiting about Earth or the Moon, or a probe approaching some more distant planet.

Wilson also told his audience that (36) Newton's original mathematical theories of bodies falling under gravitational forces... are used nowadays to predict and determine rocket trajectories, manned space capsule orbits, and the schedule of deep space probes to the planets Venus and Mars, as well as to the Moon.

Instrumentalism is then a form of realism, as the world is out there providing the bounds on our experiences, but it is not objectivist in Scerri's sense of “some permanent, ahistorical framework to which we can ultimately appeal in determining the nature of knowledge, truth, and reality” (3). But nor is it relativism, as it does offer a rational basis for preferring chemistry to magic or voodoo, because chemical knowledge does a much better job of fitting experience. Whereas few science teachers would seriously consider relativism as a viable stance, instrumentalism is a perspective that has been adopted by many in science (37-39), and has indeed been championed by Rudolph as the basis for developing the public understanding of science (40). Models of the Atom as Instruments To draw on an example close to Scerri's heart, it is very common to teach in college that the electrons in many-electron atoms occupy orbitals designated 1s, 2s, 2p, 3s, and so on; that is, those derived from studies of hydrogenic systems (H, Heþ, etc.). Scerri has been critical of the use of this model, which he feels is not well supported theoretically, as the additional interactions in many-electron atoms contravene the assumptions made when deriving the set of discrete atomic orbitals (41). Scerri has been concerned whether orbitals with such characterizations “really” exist in these atoms, and whether they have “really” been observed (42). Yet even though it is recognized that this model is theoretically dubious, it not only continues to be widely taught, but also to be used by many professional chemists outside of the specializm of quantum chemistry (43). For many of these chemists, the issue of whether the model is a true reflection of the fundamental nature of matter is secondary to the usefulness of the orbital approximation model: it may not be well justified on theoretical grounds, so may not be a good description of the “real” structure of many-electron atoms, but it has been found to be an extremely useful model that “fits” with many chemists' laboratory experiences, and allows predictions to be made that further the aims of chemical science (e.g., predicting viable reaction pathways). As one example, in his Nobel address discussing the development of the frontier molecular orbital approach to explaining and predicting patterns of reactivity, Kenichi Fukui refers to drawing upon an analogy with “the principal role played by the valence electrons in the formation of molecules from atoms” (44). Thinking in terms of localized electrons located in discrete orbitals has proved a fruitful tool in this area of chemistry. Like Newtonian gravity, the orbital model is a useful instrument that gives reliable results under a wide range of applications.


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This might lead us to something of an ethical dilemma in chemical education. If we have good reason to believe that the orbital approximation is flawed and cannot be a “true” reflection of reality, but it is nonetheless a useful and widely used approach, then should we teach students that, for example, sodium has an electronic configuration of 1s22s22p63s1? The constructivist who is a pragmatic instrumentalist can offer a clear answer to such a question. Model Confusion, Not Philosophical Confusion, Blights Chemistry Education Chemistry is a discipline that is taught, learned, and practiced with the aid of a vast range of models. As a science, chemistry depends upon these models, such as modeling atomic structures in terms of the “orbital approximation”. In producing a curriculum, scientific models are represented in curricular models that are considered suitable approximations for the age group of the students concerned. To get abstract ideas across to students, teachers will employ teaching models that are often informal and intended to offer links with students' own experiences, rather than necessarily having a strict correspondence with all aspects of the scientific model (45). This often means making compromises to find the “optimum level of simplification” that is within the comprehensions of students at a given level, but still suitable for building progression to more advanced study (2). So students meet a wide range of models of varying status in studying chemistry. It was suggested by Carr, as long ago as 1984, that a major source of learning difficulties in chemistry was “model confusion” (46). Research into the use of models in science teaching has shown that models included in the curriculum may often be incoherent hybrids of different scientific models (47). Students, meanwhile, may often show a limited appreciation of the nature and roles of models in science, often seeing them as little more than scaled versions of what is being modeled (48-50). The widespread use of models in teaching chemistry, without an appreciation of the role and status of models by students, is the source of much confusion among learners. The example of models of the atom, already considered above, offers a useful illustration of the problem. Atoms were proposed as theoretical entities long before they were widely accepted in science as “real” objects (51). Some chemists were happy to use the notion of the atom as a useful instrument or tool at a time when others felt that such conjectured “unobservables” had no place in scientific explanations. For most chemists today, the atom concept has become so familiar that atoms are usually treated as real, that is, as if our concept of the atom corresponds to entities that really exist in the universe. (A strictly instrumentalist view would consider our most advanced notion of the atom as a human construction that has been very useful and shown to have a good fit to the empirical evidence.) However, even an educator who believes that the current scientific understanding of the atom represents true knowledge of the world would not suggest that this knowledge should be made part of the school or college curriculum, as the concept is too abstract and mathematical to make sense to learners at this level. In any case, chemists, historically and even currently, have often been able to “make do” very well with much simpler models of the atom. These models have been useful in explaining the


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composition of pure substances, the ratios of materials that react, the existence of elements, periodicity, and very much more. So for many purposes, much more restricted models of the atom have been found to be excellent tools for thinking about, explaining, and predicting chemistry. Indeed, Sanchez Gomez and Martín have considered how, although quantum theory offers the most sophisticated approach to modeling matter, most chemists continue to work with (and much university teaching of chemistry adopts) what has been termed as “folk molecular theory” (FMT), where (43), [M]olecules are seen as tri-dimensional arrangements of atoms in a classical (Euclidean) space. Atoms are joined together by bonds which have some kind of physical entity (a bonding energy, as well as other physical properties, can be assigned to a particular bond), so that a molecule can be said to be made of atoms and bonds between them. The nature of the bonds, as well as the chemical properties resulting from this nature, can be determined by means of several models and semi-empirical rules (Lewis “forms”; atomic orbitals hybridization rules; VSEPR model; etc.) which must be regarded as the methodological nucleus of FMT.

This set of models derives from the state of chemical knowledge in the first half of the 20th century, but is contrary to the most advanced structural models available today. To someone outside of chemistry, it might therefore seem both surprising and inappropriate that most professional (and even academic) chemists carry out their work as though molecules contain discrete atoms, forming a shape dictated by minimizing the repulsions between pairs of electrons, many of which are considered to be localized in atomic orbitals (which it was suggested above is a questionable construct even in the context of an isolated atom). Yet chemists continue to work with these models for a very good reason: they have often continued to be fruitful; they are useful tools. As Sanchez Gomez and Martín acknowledge, this set of theoretically surpassed models (43), [H]as been especially useful in guiding research in chemistry. If the quality of a theoretical model could be judged by the range of different problems it can deal with, or by the number of sound technological applications it has brought about, then it would be difficult to find, in the whole realm of the experimental sciences, a model better than FMT.

So models that might be considered flawed (such as Newtonian gravitation or FMT), will still be adopted by successful scientists, at least within certain ranges of application, so long as they are still found to be useful. This suggests that such “superseded” models should still be part of a relevant science education, as long as their status as models is well recognized. So one model that is commonly used in teaching is the particle (often not explicitly discriminating between atoms or molecules at this stage) being like a small billiard ball. This model has proved very useful in science, so it is “intellectually honest” (52) to teach this model in school. A billiard ball is a hard sphere of elastic material with a defined surface, and this determines its behavior in collisions, and when packed with other billiard balls. This is a useful model for explaining gas behavior and closepacking solid structures. However, the model breaks down in other circumstances as atoms and molecules are not like the particles (grains of sand, salt crystals) familiar to learners. Rather these entities at the submicroscopic level, “quanticles” (53), are better understood as composed of fields that have no discrete


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surface, and allow interpenetration under some circumstances. So to explain other aspects of their behavior, for example during chemical reactions, we need to abandon the “billiard ball” model. This is fine, provided students understand that we are using models that are designed to represent certain aspects of the target entities, and that models are not scale replicas but tools for thinking that have limited ranges of application. This, of course, is precisely what research suggests most students do not understand. So it is common in school science to ask students to think about thermal expansion in solids using a particle model. Here the particles are usually shown to be well spaced, and thermal expansion is explained in terms of greater vibrations leading to increased spacing. This explanation is itself a sleight-of-hand, as increased vibration per se at the submicroscopic level need not require expansion at the molar scale, and only leads to expansion because of the asymmetry in the way forces between atoms or molecules vary with separation. However, the main learning problem here is that to explain thermal expansion students are expected to use a model of solid structure that is inconsistent with the model they had learned to explain why solid structures lead to rigid materials with fixed shapes. To the teacher who appreciates the nature of the models used, this inconsistency can readily be accepted, but the learner who takes the models literally perceives teaching as presenting contradictory “facts” about the particles comprising solids. These problems continue to higher levels. Students are commonly taught a model of the atom with electrons located in concentric “shells” (K, L, M...) that are often considered as like “orbits”. This can be a useful model for the purposes of much introductory chemistry in school science. However, when students understand this model to be a scaled-up replica of the atom, it can act as a learning impediment for more advanced studies. So students either misconstrue the orbital models introduced in later classes as new terminology applied to the familiar shells and orbits (53), or become very frustrated at having been misled (or even lied to) by earlier chemistry teachers (54). A related example concerns student ideas about bonding. It is common to teach students about covalent and ionic bonding in introductory chemistry courses. For some students, bonding “is” either covalent or ionic, and this leads to difficulties learning about other forms of bonding later. In this particular case, the availability of simple notions of covalent bonding as “electron sharing” and ionic bonding often identified with “electron transfer” (which of course is neither appropriate as a definition, nor even relevant in many reactions that produce ionic products), are often reinforced by being associated with a perceived drive for atoms to “fill their shells” (55). Students who take these ideas literally will tend to interpret later more advanced learning in inappropriate ways; thus, metallic bonding may be considered as a type of ionic or covalent bonding, or as a hybrid, or as just a force and not really bonding (56). Ionic-covalent becomes seen as a dichotomy for classifying bonding, so that polar bonding is not seen as a model of a very common form of bond, but as a subset of covalent bonds. Like the realism-relativism divide, this is a false dichotomy. From this perspective, intermolecular interactions, such as hydrogen bonding, are not considered to be “proper” bonding, as they offer no mechanism for filling electron shells (57). Again, the problem is not with the models themselves. Chemists use a model of “ionic” bonding as an ideal case, and 556


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have found this very useful despite considering no compounds to have “pure” ionic bonding. Teachers find it very useful to talk about atoms “needing” full shells of electrons as a way of introducing abstract ideas to students (55). But when scientific models are considered as true descriptions of nature, and the teaching models are learned as facts (rather than being used as a way of facilitating learning of the prescribed science), then students may become confused, frustrated, and ultimately disengaged with a fascinating subject. The Value of Adopting an Instrumentalist Perspective in Chemical Education Teaching chemistry as a set of models of varying levels of sophistication and with different ranges of application is certainly not an instant solution to the many learning difficulties that students have in our subject (58). For one thing, students tend to be realists about science and are likely to ask us which model is actually the true representation of reality. Whether this realist attitude is a product of the way we talk about science in class is a question for future investigation. Avoiding talking about atom and molecules, and bonds, and hybridized orbitals, and resonance structures, and so on as if we were talking about “real” entities would make our language clumsy. Even constructivists refer to “billiard balls”, rather than to “perceived regularities in my experience of the world that I construe as a class of objects that appear to me to have sufficiently similar and regular properties to justify assigning to the provisional category billiard balls”! Such a convoluted way of communicating would do little to decrease the level of confusion students experience in chemistry lessons. However, it has increasingly become clear that science education should involve learning about science, that is, the nature of science, as well as learning some science (59). Scientific literacy (60) for a modern technological democracy means understanding the way science works (61, 62). This involves appreciating both the provisional nature of science, and so why sometimes different scientists can rationally disagree without discrediting science, and yet how science offers reliable knowledge that justifies our confidence because it provides ways of understanding the world that have been extensively corroborated. For this, students need to understand that theories are not proven facts, and models are not just scale replicas. Chemistry offers the ideal subject to teach young people about the variety, nature, and role of models: about their value as thinking tools, but also about how they may only allow sound inferences within certain ranges of application. The example of submicroscopic models of matter considered above offers one context for developing these ideas; so, for example, rather than teaching pupils that particles (i.e., quanticles) are tiny hard spheres, or that atoms have shells of electrons, we should teach them that scientists developed these models as ways of making sense of a range of physical and chemical properties, and continued to use these models where they were good guides to predicting material behavior. As the limitations of the models were identified, they were developed, replaced, or supplemented. In this way, an “orbital” model of the atom can be understood by students as a more sophisticated model needed to supplement the “shell” model for some purposes: not as being taught what atoms are really like to replace earlier flawed learning.


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When introducing bonding types, it might be possible to illustrate the limitations of the covalent-ionic bonding dichotomy by comparison with a classifying task in a context more familiar to most students. Athletics is sometimes described as “track and field”, but an attempt to classify athletes into these disciplines demonstrates this is an imperfect typology. Athletes in the pentathlon and decathlon have a metaphoric foot in both camps (akin to polar bonds). Top swimmers and gymnasts are excellent athletes, but, like metallic bonds, do not fit into either category and are not served by the simple dichotomous model. Covalent-ionic can sometimes be a useful classification scheme, but the track and field analogy makes it clear to students that this will be a tool that will have a limited range of application. Through such teaching approaches, model confusion in chemistry can be replaced by an appreciation that learning often involves mastering a sequence of increasingly challenging models offering increments in explanatory power or range of application. Understanding chemistry in this way will allow students to appreciate how now-discredited historical models can be considered as having usefully contributed to the development of current knowledge, as well as how the models that they must progress beyond in their studies can still contribute to their own learning. It will also teach them something of the excitement of the intellectual challenge of building, testing, and developing models in chemistry and other sciences. An instrumentalist approach to teaching and learning can be both pedagogically sound, and philosophically consistent with constructivist approaches to chemical education. Literature Cited 1. 2. 3. 4. 5. 6. 7.

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