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Student Alternative Conceptions in Chemistry
(Published without Appendix 2 and with abridged References in the
California Journal of Science Education, 7(2) 2007 )
Christopher Horton
Worcester, Massachusetts with other members of the Modeling Instruction in High School Chemistry Action Research Teams at Arizona State University: June 2001, August 2002 and August 2004
“Chemical equations ... it took me ages to pick it up as I found it quite confusing ... but having been taught by a teacher one way I tend to relate to it in the same way but in my own thinking ... in an exam I would probably get it wrong. You see when we are told to swot for a test we have to go swot in our book all the stuff the teacher’s way ... we go home and we try to learn that ... but as soon as it hits our eyes it goes in our brain and it goes out the other way ... and so when we come to write it down and we think ... and we write it down all our way ... because of course it still means the same thing ... there is no difference ... but to the teacher there is a distinct difference between our way and the teacher’s way ... and the teacher’s way is the right way ... that’s what I find so hard.” 15-year-old science pupil in New Zealand, in Osborne and Freyberg (1985).
Learning is an active process, and what students do with facts and ideas with which they have been presented depends to a very high degree on what they already think and believe. Being able to recognize and work with these student-held ideas and conceptions is thus a key component of an effective educational strategy. Mulford and Robinson (2002) expressed the problem thus: Alternative conceptions play a larger role in learning chemistry than simply producing inadequate explanations to questions. Students either consciously or subconsciously construct their concepts as explanations for the behavior, properties or theories they experience. They believe most of these explanations are correct because these explanations make sense in terms of their understanding of the behavior of the world around them. Consequently if students encounter new information that contradicts their alternative conceptions it may be difficult for them to accept the new information because it seems wrong. The anomalies do not fit their expectations. Under these conditions the new information may … be ignored, rejected, disbelieved, deemed irrelevant to the current issue, held for consideration at a later time, reinterpreted in light of the student’s current theories, or accepted [while only making] minor changes in the student’s [previously held] concept. Occasionally anomalous information could be accepted and the alternate conception revised. If anomalous new information is presented in a learning situation where the student is rewarded (with grades) for remembering it, the information may be memorized in order to earn the reward, but it is likely to be quickly forgotten because it does not make sense.
Table of Contents
A.5.1 Nature of heat A.5.2 Heat capacity A.10.1: Electrical charge A.10.2 Electrical force A.10.3 Electrical potential A.10.4 Electrical current and circuits
- Foreword
- Table of Contents
- Introduction - Alternative conceptions – the problem: Discussion - Nature and origins of alternative conceptions in chemistry - Difficulties with abstract concepts - The search for key or central alternative conceptions - Implications for teaching. - Organizing the common chemistry alternative conceptions - Rating the alternative conceptions
- Recommendations
- Acknowledgments
- Table 1: Key or Central Misconceptions: The Expert Observers’ Selection
- Table 2: Key or Central Misconceptions: a Classroom Teachers’ Selection
- Appendix 1: Online Resources
- Appendix 2: The Alternative Conceptions in Detail with Notes - Key
- A. Essential Physical Concepts
- A.0: Size, displacement.
- A.1: Solid, liquid, matter, substance
- A.2: Air, gas, pressure (see also D.4.5, Thermodynamics of gasses)
- A.3: Mass and weight:
- A.4 Displacement and buoyancy, surface tension
- A.5: Heat
- A.6 Temperature A.5.3 Insulation and conductivity
- A.7 Molecular model of heat
- A.8: Force (limited inventory)
- A.9: Energy (limited inventory)
- A.10: Electricity (limited inventory)
- B. Basic Chemistry A.10.5 Batteries and cells - B.1 Atoms (See also E.1: Atomic structure)
Introduction Controversy has existed over whether to refer to student conceptions that aren’t in accord with those held by scientists as "preconceptions" or "misconceptions". "Misconceptions" seems excessively judgmental in view of the tentative nature of science and the fact that many of these conceptions have been useful to the students in the past. "Preconceptions" glosses over the fact that many of these conceptions arise during the course of instruction. Use of the expression "student alternative conceptions" was finally agreed upon. The following review of the literature on student alternative conceptions in chemistry, and the compilation that came from it, was begun by participants in the Summer, 2001 Integrated Chemistry and Physics course at Arizona State University, who, on their own initiative, organized an action research team to begin the design of a new chemistry curriculum. Work on it continued during the 2002 and 2004 summer meetings of the Modeling Instruction in Chemistry action research teams and their consultants. The Modeling Instruction in Chemistry action research team members were largely high school teachers who had been influenced by the Modeling Instruction in Physics workshops (Wells, et al. , 1995). The Modeling Method of Physics Instruction (described at http://modeling.asu.edu ) focuses on scientific models as central units of knowledge. The original modeling program, for first-semester physics, was motivated by the role that major student alternative conceptions play in blocking understanding of Newtonian mechanics. The program uses a patient guided-inquiry approach to leading students into confrontations with results of experiment, getting them to articulate their thinking, and managing student discourse as they argue their way to a new interpretation. Dramatically higher levels of success have been achieved in this phase of physics instruction. A key feature of this program is use of research-validated concept tests such as the Force Concept Inventory (Hestenes et al., 1992) to measure student conceptual change during the course of instruction. In recent years, high school, college and university teachers involved with modeling instruction in physics have been working to apply these insights and methods to other content areas of physics (e.g. Swackhamer, 2001), to AP physics instruction, to middle school and high school physical science instruction, and since 2005 to chemistry instruction. Among the purposes for studying and cataloging student alternative conceptions in chemistry as part of a project to design a new curriculum were the following:
- Identifying key misconceptions can help in designing curriculum, by identifying where student breakthroughs are needed and alerting designers to pitfalls. Key misconceptions are those which, if left unresolved, have the potential to block or impede further progress.
- Teachers and curriculum designers need to be aware that instruction can actually foster misconceptions that are later problematic and difficult or impossible to erase. This knowledge may lead to different choices in how initially to teach topics.
- Understanding student conceptions is essential for designing effective questions and “distracters” for concept evaluation instruments and tests in chemistry and physical science (e.g. Yeo et al. (2001).)
- An awareness of student alternative conceptions provides teachers with a window into
their students' thinking, helping them listen to their students more powerfully, and thereby helping them to more skillfully manage student discourse.
- We sought to provide teachers, curriculum designers and researchers with a broad bibliography of student alternative conceptions for further research.
- The process of compiling student alternative conceptions served as a stimulus to discussions about what conceptions and models we most want our students to master, and how to frame them. If it is true – and we believe it is - that students must construct their own understanding, and must build new understanding out of the conceptions that they already possess, then it is inescapable that students will need to draw on their “alternative conceptions” for pieces that they can rearrange and reuse to form new concepts. Identifying the concepts the students possess contributes to the search for “bridging” concepts. These are concepts initially accepted by students that are close enough to scientifically accepted ideas to be useful in transitioning to the use of the latter, as proposed by Clement (1982) and de Vos (1987). An example of this might be Linn and Songer’s use of a heat-flow model similar to the “caloric” theory, but stressing that heat lacks mass, for working with middle-school students. (Linn (1991)) Beneath the expressed student alternative conceptions may lie a set of what Halloun and Hestenes (1985b) call "commonsense concepts", which students may not even be able to articulate. Andrea diSessa has proposed that students can be seen as possessing a large set of phenomenological primitives or p-prims (diSessa (1983,1993)), a “rich system of elements that are organized only in limited degree …. relatively simple and usually abstracted from common experiences. For example, ‘people expect that greater effort is accompanied by greater results.’” (diSessa and Sherin (1998) p.1177). Other examples include “closer is stronger”, and “maintaining agency”, meaning a continuing cause that maintains motion. (Hammer (1996)) It is proposed that that these p-prims are never discarded but are rearranged to form new concepts. That level of analysis is beyond this work, but it may help explain the observation that groups of students holding alternative conceptions and struggling with discrepant facts can – with guidance and some appropriate questioning - discuss their way into a very different and stable conception. The list “Student Alternative Conceptions In Chemistry” in Appendix 2 is certainly not complete. The literature on the subject is extensive and has been far from completely mined. Researchers continue to discover new alternative conceptions by asking new questions. Educators and textbook writers continue inadvertently to generate new misconceptions. Finally our understanding of what alternative conceptions are and what is important about them is changing. It can be argued with justification that reducing the cited literature to a list of misconceptions strips away much of its value. Teachers and researchers would be well served to find and read the sources. For example, Rozier et al. (1991) in a study of student reasoning in thermodynamics, involving 2000 students and 29 teachers at the University of Paris, explored the following: student difficulties in thinking about situations involving three variables; their difficulty in following their own chain of reasoning in the reverse direction; their appeal to sequential intermediate states to justify their reasoning; and their willingness to consider that systems will obey different laws during a transition between states. Out of this insightful and thought-provoking work I have lifted for this list such student alternative conceptions as I was
scientifically accepted concepts. Students instead graft new knowledge onto a conceptually faulty base. For example, Nurenburn and Pickering (1987, reported in Mulford (1996)), found that of a selected group of college students who were all successful at solving algorithmic questions, many had a very low understanding of the chemistry involved. Lythcott (1990, reported in Mulford (1996)) found that of a group of high school students who were able to balance an equation, most could not draw a diagram of what was happening. Peterson and Treagust (1989) found that of a group of secondary school students, 74% were unable to answer conceptual questions about electron repulsion in valence shells, but 78% were able to successfully answer test questions designed to test this understanding. Similarly Yarroch (1985) found that of "A and B level" high school chemistry students virtually all could balance the equation H2 + N2 -> NH but half could not draw a correct molecular diagram to explain this result. Many investigators report on the ineffectiveness of didactic teaching at altering or replacing misconceptions. For example, Herbert Beall (1994) lectured college freshmen on the second law of thermodynamics and the ideal gas laws. After the lecture only 11% were able to correctly predict the effect that opening a cylinder of compressed gas would have on the temperature of the gas. Douglas Mulford (1996) in his Master of Science thesis at Purdue University observed that student gains on his Chemical Concepts Inventory given before and after their general chemistry courses were marginal, and even students receiving an “A” were able to answer on average only 12.2 out of 22 concept questions correctly. He commented that "a student can earn a high grade ... while still having a high level of misconceptions" and that the gains in concept mastery they made (on the order of one point for the class as a whole), while statistically significant, were of "doubtful educational significance." Marilia Thomaz et al. (1995), L. Lewis et al. (1994) and Clough and Driver (1985) focus on students' concepts about heat and temperature. Clough and Driver (1985) find the whole subject of student preconceptions on this topic to be a "steaming swamp", a morass of wrong and contradictory ideas that are not worth struggling with. They argue for ignoring preconceptions and focusing on building a new coherent structure. Thomaz et al. argue that this has been proven to be ineffective and that to be able to affect student thinking, teachers “need to go into that swamp” and work with student preconceptions. Nature and Origins of Alternative Conceptions in Chemistry Hesse and Anderson (1992) and Tabor (1998) point to the strong preference of most of their subjects for common-sense reasoning, everyday analogies, visible effects and changes, and common (non-scientific) word usage. They observed that students actively rejected the use of scientific vocabulary ("fancy scientific words") in favor of colloquial speech, which led the students into many misunderstandings. They called for teachers to lead students in careful examination of the limits of analogies and metaphors. They predict that some classes of preconceptions will be culturally specific, a product of the analogies and metaphors common in particular cultures or built into particular languages, rather than being universal. Along this line, Schmidt (1997) discusses how misconceptions form a meaningful and
coherent alternative framework in students' minds, which is very robust and difficult to change. He then focuses on the role of everyday meanings of words in fostering misconceptions. He traces some of these misuses of words--for example “oxidation” -- to the way they were historically used in chemistry. Nakhleh (1992) points out that “words such as ‘atom’ and ‘neutralization’ are actually labels that stand for elaborate cognitive structures stored in the brain … sensible and coherent understandings of the events and phenomena in their world from their own point of view.” These cognitive structures are not dictionary definitions; they have visual components and many of the investigators reviewed used student drawings (or sculptures!) to explore them. DiSessa (2004) points out that these often appear to be organized in the students’ minds as stories that unfold as the students sketch and explain their ideas. Tabor (1997) points to anthropomorphic thinking in students' (and teachers’) reasoning about the behavior of electrons in chemical interactions. It was also observed in students' reasoning about chemical reactions. What electrons "want" to do is used as a primitive force concept. (Many teachers and researchers, myself included, still reason this way sometimes, a cause for reflection.) Harrison and Treagust (1996) classified the kinds of models that can be built of a physical phenomenon, and then observed how students used various models and types of model to build a picture of the phenomenon. They deduced that none of the 48 students completing a chemistry course had come to understand that the models they were using were only models, which "... served the development and testing of ideas, not the depiction of reality." Only one of the 48 seemed to even be "on the verge of achieving this understanding." The authors call for teachers to lead their students in a thorough study of the process of model construction and to an understanding of the limitations of the models so constructed. Many authors observed that the ways in which students confuse models and images with reality and the ways in which concepts learned (or misunderstood) in earlier grades form the framework for later misconceptions. For example, Harrison et al. (1996) discuss at length the model of the atom as being like a living cell with a nucleus that divides, a model which a significant minority of students use as their framework for understanding chemistry throughout their school careers. This can have serious consequences. D. Cros, et al. (1986) noted that university students who used the Bohr model to describe an atom failed to move beyond this picture, and this apparently stunted their development as chemists, causing their understanding of interactions between subatomic particles to fail to grow. Kmel et al. (1998) points to a " ... hierarchy of increasing cognitive demand [in describing chemical processes:]
- Disappearance
- Displacement
- Modification
- Transmutation
- Chemical reaction (interaction)." They observe the gradual progress of students from age 8 through 18 in moving up this hierarchy, which is also a movement away from a "model of matter which is homogeneous, static and continuous."
She reports that “about 43% could define ‘element’ and ‘compound’ correctly at the start of a post-16 course and that this figure remained unchanged at the end.” (!) (Barker (1995), in Kind (2004) p.23.) Clearly this is a key conceptual problem and one that poses a major challenge to teachers. Kind proposes a “bridging exercise” of having students observe progressively smaller unseen things, such as insect details, bacteria and viruses, as a way of establishing the reality of the realm of things too small to see, followed by engaging the students in a process of imagining atoms. (Kind, 2004, p.13) Hong Kwen Boo (1998) emphasizes that students have a difficult time understanding the abstract concept of energy, and urges that more emphasis be given to the concept of the "driving force involving the concept of free energy/entropy," and to the difficulty students have in bridging the gap between “perceptual thinking” and the use of "concepts about particles and their interactions." "Students [failed to] understand the nature of science as a process of construction of predictive conceptual models ... and the nature of scientific concepts and principles ... [i.e.] their applicability across the entire range of [chemical] phenomena." Ricardo Trumper (1993) on the other hand argues that "we can start teaching students about energy in about the 5 th grade, since they have good cognitive building blocks associated with a good energy concept." Viennant (1993a), considering student reasoning about heat transfer along a rod, observed that when more than one factor was considered the students would use sequential reasoning – ordered in time. Driver (1985), Anderson (1986) and Guiterrez and Ogborn (1992) (all reported in Viennot (1998)), Sere (1987), and Mehent (1997) all observed pa reluctance of students at all levels to consider more than one cause for an effect. This shows up as extreme difficulty in working with three-variable relationships such as the ideal gas law. The students would either disregard one variable, or if dealing with two at a time they would imagine them as operating sequentially in time, in what Rozier (1991) calls "linear causal reasoning." This way of thinking, he reported, was "extremely resistant to instruction." It conditioned students to cling to alternate conceptions that require only linear or one-step reasoning. Another key difficulty students face is the problem of imagining “nothing”. Many writers (e.g. Griffiths 1992, Novick and Nussbaum 1978) have noted that many students cannot imagine “nothing” between atoms or molecules, and either deny that they can be far apart in a gas or propose a variety of possible substances to fill the spaces. This is even true of many university science students. (Benson et al. (1993), in Kind (2004)) As Kind (p.11) puts it: Students of all ages find space difficult to imagine and intuitively “fill” it with something. Since students depend on visible, sensory information about solids and liquids to develop their naïve view of matter, their difficulty accepting a model proposing that there is “nothing” in the spaces between particles is unsurprising. Difficulty imagining “reversibility” is another stumbling block for students, who come up with many alternative explanations to work around their lack of understanding. Many students fail to see state changes, dissolution and other physical changes as reversible. For example Gensler (1970, in Kind (2004) p.25) observes that students fail to see that re- crystallized sugar is the same stuff which was added to the water originally. This contributes to the students’ difficulty in distinguishing physical from chemical changes. The reversibility of chemical reactions also poses serious conceptual challenges to the students, leading to an inability for example to grasp the reciprocal relationship between acids and bases and the concept of an equilibrium. This to be sure must come in part from the inability to see that “something is happening” at equilibrium when no visible change is occurring, but students in
very high numbers in upper grade classes also view the forward and reverse reactions as two separate reactions. (Johnstone et al., 2007) At a still deeper level, inability to grasp reversibility may be related to student difficulties in general with picturing two things going on at once. Excessive reliance on memorization is a well-known obstacle to student understanding. Bou Jaoude (1992) developed an instrument to divide a high school class into "rote learners" and "meaningful learners". He found similar levels of misconceptions initially in both groups. After instruction the rote learners had failed to progress or even had regressed, while the meaningful learners had made significant gains in concept mastery. Viennot (1998) notes that students generally confuse rates of reaction and rates of change with final states. This may underlie many alternative conceptions, such as the belief he uncovered that since iron heats faster than sand, it will reach a higher temperature. He suggests that students require two additional essential thinking skills that are “opposed to the common threads of their everyday reasoning:”
- They must be able to identify the relevant systems as well as their essential characteristics in order to predict transfers of heat.
- They must be able to clearly sort out what concerns changes on the one hand, and permanent states on the other. The ability to distinguish between a state and a rate of change can be seen as an underlying or fundamental mathematical ability. Other capabilities whose absence might also block students' ability to grasp chemistry concepts include division, ratio and proportional reasoning, direct and inverse variation, probability, randomness, large and small numbers, and exponential growth. Many alternative conceptions no doubt are developed by students to cope with concepts that are beyond their reach because of such difficulties. The search for key or central alternative conceptions Thomaz et al. (1995), working with groups of secondary students in the UK, reported that 92% to 97% of the students " ... revealed a great difficulty in accepting that different objects are at the same temperature when in contact with the surroundings for a long time." They focused on this as the core concept in their highly successful project using constructivist methods to teach thermodynamics. L. Viennot (1997), E. Clough and R. Driver (1985), and J. Solomon (1985) outline the varieties of student misunderstandings about energy. Solomon discusses how the ways in which teachers word their explanations of energy generate new misconceptions. C. Gayford (1986) and Solomon (1985) outline the ways students confuse energy with the "life force" in biological systems. (This could perhaps be the result of or at least reinforced by using the concept of energy in biology before having properly studied it in physics or physical science.) Kruger (1990) found the same confusion about energy among primary school teachers. deVos, et al. (1994) identify the key concepts in chemistry as being the "chemical substance" and the "chemical reaction". To them the key difficulty faced by students was "the incoherence and incompleteness of all chemistry curricula studied," and they document many
Experts are not in agreement on whether to interpret (and teach) the mole as a “number” (Dierks (1981) in Kind (2004) p.50) or as an “amount of substance” or “chemical amount” that corresponds to 12 grams of carbon-12 (Nelson (1991) in Kind). Kind speculates that “This difference may be at the centre of problems associated with the mole – in teaching the concept we may use 'amount of substance' and 'number of particles' synonymously, contributing unwittingly to students’ difficulties by never really explaining what we mean in either case.” Lists of alternative conceptions that have been proposed as key or central misconceptions by various investigators (Table 1), and by the participants in the Modeling Methods in Chemistry Workshop of 2001 (Table 2) have been provided below. Implications for Teaching When the importance of student alternative conceptions in a subject area has been recognized, what use should the teacher make of this knowledge? There is ample evidence (previously discussed) that instruction that fails to acknowledge and address these alternative conceptions will prove unable to foster real growth in understanding of the subject. Students can still gain "knowledge", in the form of memorizing facts and procedures for solving very limited classes of problems, and teachers may out of frustration become reconciled to settling for this kind of learning, and even to calling it success. But in the words of Mary Nakleh (1992), “knowledge is not understanding.” So how then should the teacher proceed? First, the teacher shouldn’t design a course around dealing with student alternative conceptions. A course has to be built around positive goals. In particular it should be built around the models or fundamental concepts of chemistry to be mastered and understood by the end of the course. An understanding of student thinking will affect the tactics and even the strategy followed, but the course must be about building, not tearing down. Vanessa Kind’s booklet and the Modeling Instruction Program (links in Appendix 1) offer two of what must by now be many such curriculum outlines available. A knowledge of student alternative conceptions will be helpful in deciding where to start and what to cover. As Driver and Bell (1986) put it: “We may need to reconsider the assumptions we are currently making about where students start from in their thinking in science courses. … We may be making unwarranted assumptions that students will have [understood the prerequisite topics], and we can therefore take [these] for granted and build on [them] in lessons ….” Should the teacher confront students with the evidence that their ideas are wrong or lacking in predictive value, and then present them with replacement ideas? This is tempting. It is relatively simple to do, and it’s fun – for the teacher. Pedagogically however it is a very bad idea. It can be embarrassing and devaluing for the students, whose ideas always, at every time, represent the culmination of a lifetime of trying to make sense of their world, and are therefore held as valued possessions. As Smith et al.(1993) put it, “misconceptions are faulty extensions of productive prior knowledge.” The students have spent a lifetime, starting as toddlers, trying to be right, and they get defensive, angry and wary when being made wrong. In any case, they simply cannot just switch off their own ideas and adopt new ones that are presented to them, even if the evidence is clear. Brains don’t work that way. As Smith
(1993) observes, replacing misconceptions “… is neither plausible nor always desirable; misconceptions thought to be extinguished often reappear.” Hammer (1996) argues that calling a statement a misconception implies that it must be removed from the student’s mind. “To construct from useful conceptions without eliminating misconceptions would leave in place knowledge inherently inconsistent with expert understanding.” This he argues is impossible, making the entire enterprise of dealing with misconceptions flawed. Yet modern practice shows that new conceptions arrived at over time or through guided inquiry and student discourse are in fact stable and do in fact come to replace old conceptions. (e.g. Francis (1998)) Perhaps this is achieved not by an eradication but by the learners’ rearrangement of mental elements at some deeper level. If a teacher decides to follow this path, he or she should get training in how to manage student discourse and guide student thinking in a non-directive manner. To move beyond their previously held ideas students must construct new ones, in interaction with the results of experiment. For the teacher, especially for veteran teacher, this can be quite challenging and counterintuitive. It is a skill that cannot easily be self-taught. For example, after a lifetime of being the expert who explains everything, you’ll have to learn to steadfastly refuse your students (and maybe their parents) when they righteously demand that you do your job and give them “the answer”. It is said that we teach the way we were taught. Hesse and Anderson (1992) commented that “it is likely that the same conceptual-change techniques that are employed by the teacher to promote conceptual change within students must also be applied to the present body of practicing teachers.” The Modeling Instruction program listed in Appendix 1 is one place to look for this kind of training, but there are surely others. David Hestenes (1995), commenting on the dismal performance of physics graduate students on their oral exams, points out that students don’t really start to master the concepts of physics until they start on their dissertation research. He implies that rich interactive inquiry-focused experiences such as working closely with a professor on a project need to be provided much earlier in the curriculum. Lewis and Linn (1994) argue for a curriculum that includes everyday knowledge, to encourage integration of knowledge, to engage students in building on their intuitive conceptions, and to make scientific knowledge easier to remember. Finally, get your principal and your department chair on your side! Any effort to take on a new way of teaching should have their understanding and approval, including an agreement on how you are going to measure the success of your students and of your course. A course based on guided inquiry and discourse aimed at achieving conceptual change will not look like other courses, won’t have the same rhythm, and won’t be able to cover as many topics. To succeed, you need your administrators to understand it and why it is worth doing. Organizing the Chemistry Alternative Conceptions The preconceptions and misconceptions listed in Appendix 2 are categorized by topic. They are divided into essential physical concepts (background), basic chemistry, electrochemistry, thermodynamics and atomic chemistry. For the most part, the essential physical concepts section (“A. “) does not rely on the atomic theory, while the basic chemistry part (“B. ) does..
been good to have recorded the modeling workshop teachers’ explanations of their choices. Some examples of how some student alternative conceptions might be evaluated: "Anodes are always on the left" is an example of a misconception which is both trivial and non-primitive, a simple artifact of the habit of some textbook writers of always illustrating anodes in this way. This sort of misconception will clear up quickly when students actually understand what an anode is from their own experience, and may disappear when new textbooks come out. An interesting glimpse of what is going on in student learning. “Chemical bonds store energy” (previously mentioned) is not a primitive misconception in the sense that it refers to a concept (the chemical bond) which is several steps removed from the child's experience of the world. However, whether it is taught in school, picked up from the ongoing conversation about energy in the larger world or arrived at by the student through their own thinking, once the concept has been acquired it becomes heavily used and strongly held. This misconception can become a serious obstacle to further progress in chemistry. "Heat has the properties of matter" and "heating an object adds mass to it" (Schmidt, 1997) are both important alternative conceptions, widespread, persistent and having significant consequences. Are they redundant? The former appears to be the fundamental statement of the misconception, and would thus rate designation as a key misconception, but the latter would be the example in which a student would recognize their own ideas. The similarity of this conception to the medieval “phlogiston” and early modern “caloric” are clues that its roots may be very deep. My call would be that the first expression is the better choice. "Temperature is a property of the material from which a body is made" and "two objects in the same environment don't eventually reach a common temperature." Of a group of secondary students, 95% gave each of these responses (Thomaz, 1998). Here we have a misunderstanding that is primitive and fundamental in that it arises inevitably out of observations. It is extremely widespread, extremely persistent and has profound consequences for the student's further progress in chemistry. These are logically equivalent statements. The first summarizes what subjects report, and the second is its expression as a failure to understand a core scientific principle. The first one is the actual alternative conception. However, neither is as fundamental as the conception “metal is cold”. Metal “feels” cold! That is true! Until students can reinterpret this phenomenon (e.g. “what we feel isn’t really how cold or hot something is, but how fast heat is flowing through our skin”), many simply won’t believe their thermometer! This may require first distinguishing heat conductivity from heat capacity and quantity of heat energy. The previously mentioned model of electrical forces within the atom, "force is conserved," was never actually said by any of the subjects, yet once distinguished, its fingerprints can be seen on a number of other alternative conceptions. It seems to be a good hypothesis about what the students are “really” thinking at a deeper level. I called it Key, but it really needs more testing. I contributed my own nominations for key alternative conception where I felt the findings of the investigators reviewed pointed strongly to this conclusion but they didn’t actually call it; or where from my own teaching experience I recognized an alternative conception as one I had encountered in my students and had found stubborn, persistent and troublesome, and where no investigator had called out it or any similar conception.
school districts, by state or provincial education departments, by national departments or ministries of education, or as a service to their neighborhoods by nearby universities or colleges. Journals are always starved for funds and most won’t jump forward with offers of free access for teachers, but they could certainly take on actively promoting this idea and offering to negotiate easy terms for entities representing teachers. Perhaps they could agree to offer free access to teachers in poor countries and communities as a public service. Many concept tests or formative assessments have been or are being developed for many levels of and topics in chemistry. If such a test uses observed student alternative conceptions as distracters (wrong answers), and if it is used as both a pre-test and a post-test for the same class, the resulting data is potentially useful for research. Makers and users of these tests could be identified and invited to join in such projects, particularly for collecting information on the evolution of student conceptions over time. Alternative conceptions concerning a number of topics have yet to be found or evaluated by us, and also do not appear in the CARD index. These include: The periodic table of the elements. The equipartition theorem. Geometry and polarity of molecules. The third law of thermodynamics. Organic chemistry – all of it. References have been found to misconceptions concerning the geometry and polarity of molecules (Furio Mas,1996). It would be very surprising if there weren’t a substantial number of misconceptions concerning the periodic table of the elements, given that students are introduced to this topic in grammar school, long before they are clear about what an atom is.
Acknowledgments This work was made possible in part by grants from the National Science Foundation. Special thanks must be given to Jane Jackson, Co-Director of the Modeling Instruction Program, for her support and facilitation of this project and for the efforts she made, including late-night proofreading, to see it through to publication, and to Thomas Loughran and Guy Ashkenazi for reviewing the article and sharing their comments, suggestions and corrections. Professors Eileen Lewis and Dewey Dykstra were kind enough to share their thoughts and suggestions for this work. Many participants in the Modeling Instruction in High School Chemistry action research teams that formed at Arizona State University in June 2001 and that met again in August 2002 and August 2004 made contributions to this work, and spurred it on with requests for support around developing concept tests. In particular we are grateful for the expert and generous assistance of Guy Ashkenazi, Ph.D., formerly of Hebrew University, and David Frank, Ph.D. of California State University in Fresno, who served at various times as advisors to these teams. Kristen Guyser and Patrick Daisley were essential to the formation of this project, as were Lynette Burdick, Consuelo Rogers, David Boyer and Gail Seemueller. Thanks to Larry Dukerich and Brenda Royce for their many efforts to keep the Chemistry Modeling Instruction project alive and on track. My apologies to those I left out. Finally I would like to thank Christine Bertrand and the California Science Teachers Association for printing an earlier version of this article in their journal, the California Journal of Science, and posting the article with the list of alternative conceptions on their website at http://www.cascience.org/csta/res_teaching_science.asp
