CHAPTER 21

Teaching Physics

Reinders Duit

Leibniz-Institute for Science Education, Germany

Hans Niedderer and Horst Schecker

University of Bremen, Germany

A deliberate subject-specific view is employed in the present chapter. We attempt to provide an overview of research on teaching and learning physics—in particular from the perspective of what is special in this domain as compared with biology, chemistry, and earth science. We would like to point to two issues where physics education appears to be “special” already.

First, according to the bibliography on constructivist-oriented research on teaching and learning science by Duit (2005), about 64% of the studies documented are carried out in the domain of physics, 21% in the domain of biology, and 15% in the domain of chemistry. There are various reasons for this dominance of physics in the research on teaching and learning. The major reason appears to be that physics learning includes difficulties that are due to the particular nature of physics. We just mention the abstract and highly idealized kind of physics (mathematical) modeling. Research on students’ conceptions has shown that most pre-instructional (“everyday”) ideas students bring to physics instruction are in stark contrast to the physics concepts and principles to be achieved—from kindergarten to the tertiary level. Quite often students’ ideas are incompatible with physics views (Wandersee, Mintzes, & Novak, 1994). This also holds true for students’ more general patterns of thinking and reasoning (Arons, 1984).

Secondly, physics clearly is the domain that is greeted with the lowest interest by students among the sciences. This is true in particular for girls (Parker, Rennie, & Fraser, 1996). It appears also that the nature of physics mentioned is at least partly responsible for these findings. Students, especially girls, perceive physics not only as very abstract, complicated, and difficult, but also as counterintuitive and incomprehensible.

The review presented draws on European views of science education, more precisely, continental European views—with German views somewhat predominant. On the one hand, the issue of scientific literacy is discussed from a position including the German idea of Bildung, with its emphasis on issues that are beyond functional scientific literacy (Bybee, 1997). On the other hand, European ideas of Didaktik (Westbury, Hopmann, & Riquarts, 2000) are used to analyze the particular role of designing the content structure of physics instruction in such a way that it meets students’ perspectives (e.g., pre-instructional conceptions and interests) and the aims of instruction.

THE INTERDISCIPLINARY NATURE OF PHYSICS EDUCATION AS A RESEARCH DOMAIN

As illustrated in Fig. 21.1, physics education research is interdisciplinary in nature. There are several “reference domains” that are needed to meet the challenges of investigating and analyzing the key issues of teaching and learning physics. Philosophy and history of physics provide frameworks make it possible to identify what is usually called the “nature of physics” in the literature (McComas, 1998). Hence, these domains play a major role in discussing what is special in physics and therefore also what is special in teaching and learning physics. But also social sciences, especially pedagogy and psychology, are essential reference domains. Research and development that aims at improving practice has to address issues of physics as a specific way of knowing as well as general issues of learning. This is the underlying position of the present review.

CHARACTERISTICS OF PHYSICS EDUCATION RESEARCH

Dahncke et al. (2001) argued that there is a split in the science education community. On the one side the major focus is on science—here physics. This group usually is at home in organizations that are close to the “mother” discipline, like physical societies. Research work in this group is in most cases restricted to issues of subject matter structure or presentation techniques, more or less neglecting the way in which the ideas developed may be learned by students. On the other hand, there are science educators who try to find a balance between the mother discipline and educational issues. The latter position is the background of Fig. 21.1.

FIGURE 21–1. Reference disciplines of physics education.

Jenkins (2001) provided another distinction of research in science education, namely pedagogical versus empirical. The pedagogical tradition aims at improving practice. Research and development are intimately linked. Research is usually carried out in actual classrooms or at least in settings that are close to a classroom situation. The major concern of the empirical tradition is acquiring “objective data” that are needed to understand and influence educational practice. This distinction has much in common with the differentiation between “applied” and “basic” research. It has been argued in science education (Wright, 1993) as well as in research on teaching and learning in general (Kaestle, 1993) that basic research in education is viewed as irrelevant by practitioners and hence is in danger of widening the gap between research findings and practice. Therefore, a fine-tuned balance between the two positions is needed in research that aims to improve practice.

The German Didaktik Tradition

The meaning of the German term Didaktik should not be associated with the Anglo-Saxon meaning of didactical. Whereas the latter primarily denotes issues of educational technology, Didaktik stands for a multifaceted view of planning and performing instruction that is based on the German concept of Bildung. Bildung shares certain features of scientific literacy but also includes particular views of aims of schooling and instruction (Westbury, Hopmann, & Riquarts, 2000).

A literal translation of Bildung is “formation.” In fact, Bildung is viewed as a process. Here appears to be a first significant difference to scientific literacy, which primarily denotes certain competencies, that is, outcomes of a process. Bildung stands for the formation of the learner as a whole person, that is, for the development of the personality of the learner. Bildung hence includes not only the achievement of domain-specific knowledge, but also the formation of what may be called “cross-curricular competencies” (including competencies allowing rational thinking and various social competencies). There is an emphasis on these cross-curricular competencies, which stand for a well-educated personality.

The meaning of Didaktik is based on the above conception of Bildung. It concerns the analytical process of transposing (or transforming) human knowledge (the cultural heritage) like domain-specific knowledge into knowledge for schooling, which contributes to the above formation (Bildung) of young people. Fensham (2001) claims that many recent attempts to improve science teaching and learning (e.g., based on constructivist perspectives) put a strong emphasis on improving the way science is taught (i.e., focus on the improvement of teaching methods and media). He thinks that science content should also be seen as problematic, that the neglected content structure for instruction should also be given attention. He is of the opinion that the Didaktik tradition allows such an improvement of instruction by developing a content structure for instruction that addresses students’ learning needs and capabilities as well as the aims of instruction.

Briefly put, the content structure of a certain domain (e.g., physics) has to be transformed into a content structure for instruction. The two structures are substantially different. The physics content structure for a certain topic (like the force concept) may not be directly transferred into the content structure for instruction. It has not only to be simplified (in order to make it accessible for students), but also enriched by putting it into contexts that make sense to the learners. Two phases of this process may be differentiated. The first may be called elementarization. It leads to a set of “elementary” ideas comprising the key features of the content in question. For the energy concept the following elementary ideas may result: conservation, transformation, transfer, and degradation. On the basis of this set of elementary ideas the content structure for instruction is constructed. It is a key claim of the Didaktik tradition that both processes, “elementarization” and “construction of the content structure for instruction,” are intimately interrelated to decisions on the aims of teaching the content and the students’ affective and cognitive perspectives. Kattmann, Duit, Gropengieβer, and Komorek (1995) have called the whole process “educational reconstruction” (for an example of the use of the model, see Duit, Komorek, & Wilbers, 1997).

The essence of the content analysis outlined in Fig. 21.2 may be well illustrated by a set of questions comprising the Didaktische Analyse proposed by the German educator Klafki (1969; see also Fensham, 2001):

1. What is the more general idea which is represented by the content of interest? What basic phenomena or basic principles, what general laws, criteria, methods, techniques or attitudes may be addressed in an exemplary way by dealing with the content?
2. What is the significance of the content for students’ actual and future life?
3. What is the structure of the content if viewed from the pedagogical perspectives outlined in questions 1 and 2?
4. What are particular cases, phenomena, situations, experiments that allow the teacher to make the structure of the referring content interesting, worth questioning, accessible, and understandable for the students?

FIGURE 21–2. Educational reconstruction of physics content structure.

The concept of educational reconstruction outlined in Fig. 21.2 adds to Klafki's set of questions the idea of a fundamental interplay of all variables of instruction, namely, the Aims, the Content, the Teaching and Learning Methods and the Media, which is also a key figure of thought in the German Didaktik tradition (Heimann, Otto, & Schulz, 1969). In the process of instructional planning this fundamental interplay has to be taken into account. Students’ perspectives must also be taken into consideration as a key point of reference for construction of the content structure for instruction and for developing the phases of instruction, the methods, and the materials and media used.

In a nutshell, the German Didaktik tradition as well as similar traditions in other European countries critically take the content issue into account. It is a key assumption that a content structure has to be developed which addresses students’ pre-instructional perspectives and that the learning environment has to be designed in such a way that students may achieve the content in question. Improving instruction includes both critical analysis and reconstruction of content and development of supportive learning environments.

Clearly, major ideas of Shulman's (1987) approach of content specific pedagogical knowledge are in accordance with the European Didaktik tradition. However, whereas Shulman puts the main emphasis on teacher competencies, the Didaktik tradition has also developed strategies for taking the content issue seriously in instructional planning.

OVERVIEW OF THE CHAPTER

In the following chapter we first discuss major fields of research on teaching physics. The emphasis is on issues that are special for physics teaching. In the subsequent section, research on three content domains, the force concept, the electric circuit, and atomic physics, is reviewed. These three topics allow us to discuss major learning difficulties and major attempts to improve learning that are particularly relevant for physics instruction. Finally, we want to summarize major concerns and desiderata of physics education research.

TEACHING PHYSICS: MAJOR FIELDS OF RESEARCH

As detailed below, we provide a brief overview of major fields of research. We draw on the perspective of the above Didaktik tradition where normative research on the aims of instruction, analytical research on subject matter clarification and elementarization, as well as empirical research on teaching and learning processes are closely linked.

Aims of Instruction

The international science achievement studies TIMSS (Third International Mathematics and Science Study) and PISA (Programme for International Student Assessment) have had a strong impact on the discussion about the proper aims of instruction, in particular for lower secondary education (cf. the discussion on scientific literacy in Chapter 26). Science is seen as a major factor influencing the daily lives of individuals as well as economic progress in technology-based societies (e.g., Beaton et al., 1996, p. 7). Physics forms the basis of information technology, transport, and energy production. In order to make sensible use of technological means, to find a place in a technology-based economy, and to participate in political processes about technology-related decisions, citizens need a certain amount of physics knowledge. The PISA consortium has agreed on a notion of scientific literacy that consists of understanding basic scientific concepts, familiarity with scientific thinking and processes, and the ability to apply this knowledge in concrete situations (cf. OECD, 1999). Students should be able to identify issues that can be understood by the application of scientific knowledge, to draw conclusions from scientific investigations, and to assess the scope of scientific findings. As these competencies apply for all citizens, they have to be targeted during the obligatory phase of science education. Important physics concepts are energy, conservation/devaluation, particle/matter, and interaction.

From a European perspective, in the upper secondary level physics education has to contribute to three major goals of higher education: further general education (Bildung), scientific thinking, and providing a foundation for learning at the tertiary level. In this voluntary phase scientific literacy has to be broadened in these aspects (cf. Schecker, Fischer, & Wiesner, 2004):

• Insights into modern physics world views (basic ideas of quantum physics, relativity, nonlinear physics)
• A systematic view of the cultural and social consequences of physics and technology (e.g., in energy production and consumption)
• Awareness of the specific physics conception of the world, aiming at a small set of general and universally applicable concepts and laws
• Sustainable knowledge of standard physics procedures (e.g., using lab instruments, formal problem solving) as a basis for university studies and vocational training in science and technology

Competencies of applying physics concepts and processes have to be embedded in a proper understanding of the nature of science (NOS; cf. McComas, 1998). Standards for curriculum development based on Scientific Literacy and the NOS can be found in AAAS (1993) and in NRC (1996).

Compared with the American tradition with its pragmatic and optimistic view of science as a means for social progress, the European view as outlined above puts more weight on the contribution of scientific knowledge to the formation of students’ personalities. Students have to decide the extent to which they integrate scientific thinking into their world views. This belongs to the process of Bildung. It includes the critical reflection on problematic outcomes of the scientific enterprise.

Science Processes and Views of the Nature of Science

Learning about science processes and the nature of science (NOS) has to be an integral part of physics education. There is a wide consensus about this thesis among science educators (see Chapter 29). Some central elements of a proper understanding of the NOS are (cf. McComas, 1998; AAAS, 1993) the following:

• Scientific knowledge has a tentative character. Scientific concepts and theories are the result of a historical genetic process.
• Observation, experimental evidence, rational arguments, and skepticism play an important role in generating scientific knowledge.
• Observations are theory-laden. There is no direct path from an experiment to a theory.

Physics is distinguished from other sciences by its extremely high level of abstraction and idealization. Complexity is strongly reduced in order to make quantitative predictions possible. For this purpose physics produces its own prototypical phenomena in lab settings. From the physics point of view the true order of nature lies beyond the “touch and show reality.” The book of nature is written in the language of mathematical models. Theories should contain a very limited set of laws that are all-applicable. Before an everyday world phenomenon with its complexity of influences and parameters qualifies for a physics analysis, it has to be “cleaned.” It is nearly impossible to calculate the path of a leaf falling from a tree; but it is easy to predict precisely the motion of a feather in an evacuated tube. Physics thinking does not originate from the minute observation of the world around us but from the reconstruction of this world under the assumption of theoretical principles. This shift of perspectives (cf. the following section on conceptual change) is a major factor that makes it so difficult for students to learn physics.

There are good reasons to take account of epistemological and concept-genetic aspects in physics teaching (cf. McComas, 1998). They range from a better understanding of physics concepts (e.g., Galili & Hazan, 2000) enabling students to make rational decisions in a democratic society (Driver et al., 1996).

Still, there is often a gap between the strategic aims formulated in the preambles of science curricula and the actual content of textbooks and teaching (cf. Kircher, Girwidz, & Häuβler, 2000, p. 38). The NOS is seldom taught explicitly (Duit, Müller, Tesch, & Widodo, 2004). NOS items are hardly included in physics exams. Teachers do not feel competent in this domain (cf. Abd-EI-Khalick, Bell, & Lederman, 1998). Empirical studies reveal widespread misunderstandings of the NOS. Students’ epistemological beliefs can be characterized as naive-empiristic: scientific theories are seen as everlasting truths, derived from precise observations and theory-free experiments. Creative speculation and theory-laden construction are not taken into account (cf. the analyses of data from TIMSS, population 3, in Köller, Baumert, & Neubrandt, 2000).

Abd-EI-Khalick, Bell, and Lederman (1998) thus strongly argue for including more NOS elements in teacher training and teaching (see also Schecker, Fischer, & Wiesner, 2004). McComas's book (1998) gives examples of how to introduce students and teachers into epistemological issues. Matthews (1994) stresses the historical perspective in teaching science. Meyling (1997) provides empirical evidence for how an explicitly epistemology-based physics course can change students’ ideas toward a proper understanding of the NOS.

Conceptual Change

The dominating perspectives of research on teaching and learning science have been constructivist views of conceptual change since the 1980s (Mintzes, Wandersee, & Novak, 1997; Duit & Treagust, 2003). A problem-solving perspective on teaching and learning physics that addresses slightly different facets is provided by Maloney (1994). Both research perspectives have been rather influential in developing new teaching and learning approaches that deliberately take students’ preinstructional views, beliefs, and conceptions into account (for proposals on teaching and learning physics see the following volumes: Viennot, 2001, 2003; Redish, 2003; Arons, 1997).

TABLE 21.1
Number of Publications on Students’ Ideas in the Bibliography by Duit (2005)

Biology—total	748
Chemistry—total	548
Physics—total	2,274
Mechanics (force)*	792
Electricity (electrical circuit)	444
Optics	234
Particle model	226
Thermal physics (heat/temp.)	192
Energy	176
Astronomy (Earth in space)	121
Quantum physics	77
Non linear systems (chaos)	35
Sound	28
Magnetism	25
Relativity	8

^* Predominant concept in brackets.

As mentioned above, physics is the domain in which most research studies on investigating students’ conceptions and on conceptual change have been carried out. Table 21.1 presents the number of studies documented in the bibliography by Duit (2006). It becomes obvious that there is a particular emphasis on mechanics and electricity. In both domains there is a strong focus on the force concept or the (simple) electric circuit, respectively. Clearly, these subdomains are somewhat over-researched. Other domains, especially the domains of modern physics, need further attention. More details on research findings in the domains of mechanics, electricity, and atomic physics are given below. General findings of research on conceptual change are reported elsewhere. The particular difficulty of conceptual change in the process of learning physics appears to be that usually students’ preinstructional conceptions about phenomena are deeply rooted in everyday experiences and are therefore in stark contrast to physics conceptions. Radical idealization and decontextualization, the reduction to pure phenomena accompanied by particular mathematical modeling, seems to be a major hurdle for students to understand physics concepts and principles. Furthermore, in quantum physics and relativity the physics view is incomprehensible in principle from everyday world perspectives. Interestingly, this also holds for the “classical” particle view, which is usually introduced in early school grades. Also here the world of the particles is fundamentally different from the world of our everyday experiences.

Viewed from the perspective of scientific literacy (Bybee, 1997), understanding physics includes understanding physics concepts and principles on the one hand and physics processes as well as views of the nature of physics on the other. As argued in the previous section, these views about physics are not only essential features of scientific literacy, but are also essential in understanding physics concepts and principles. Looking at teaching and learning physics from a conceptual change perspective should therefore include conceptual changes on the level of concepts and principles and on the level of processes and views of the nature of physics as well. Research has shown that students’ ideas of processes (like modeling) or views of the nature of physics are “naive” in the same sense as their views of phenomena and concepts (Treagust, Chittleborough, & Mamiala, 2002). A multiple conceptual change view has to be employed (Duit & Treagust, 2003).

Students’ Interests and Gender Issues

Research has shown that emotional factors play an essential role in learning science. Conceptual change, for instance, is not successful if it is based merely on “cold cognition” (Pintrich, Marx, & Boyle, 1992). A recent study on introductory electricity teaching (Laukenmann et al., 2003) has shown the significance of emotional factors. It became obvious again that positive emotions promote achievement. Interestingly, this is especially the case during the first phase of learning the new topic, where students need to be convinced that it is worthwhile to achieve the understanding intended. Kroh and Thomsen (2005) point out the significance of attitudes toward physics and students’ self-concepts for learning physics. They argue that teaching and learning methods that take students’ cognitive and affective variables into account and provide them with significant responsibility for their own learning will develop more positive attitudes and self-concepts and hence will result in more pleasing outcomes of instruction.

The issue of emotional factors (like interests, motivation, attitudes, and self-concept) in learning science and gender differences are more fully discussed elsewhere in the present Handbook (Chapters 5 and 11). Here only a few issues are added that are characteristic of physics instruction.

International comparison studies reveal that girls’ achievements and interests in physics are substantially lower than those of boys (Keeves & Kotte, 1996). However, there are significant differences between the countries concerning the gap between the genders. Nevertheless, physics is usually the science domain that is greeted with the lowest interest in particular by girls. It appears that students’ views of physics play a certain role. Science in general but physics in particular is seen as a male domain (Baker, 1998; Harding, 1996). Stadler, Benke, and Duit (2000) argue that girls and boys hold different (tacit) notions of what it means to understand physics. Briefly put, girls do not think that they understand a concept until they can put it into a broader (nonscientific) context. They try to understand the relations of the system of physics to the world seen as a whole. Boys, in contrast, seem to be more “pragmatic.” They tend to regard physics as valuable in itself. They appear to be pleased with the internal coherence of the system of physics itself. It appears that boys’ views of physics and their notions on understanding physics are somewhat nearer to the above-mentioned characteristic of radical idealization and decontextualization in physics than girls’ views.

In order to improve the situation, several studies have been carried out to embed physics in contexts that make sense especially to girls, that is, to address their particular notion of understanding physics. Briefly, such studies have shown that instructional materials addressing girls’ interests, such as the human body and issues of social relevance, significantly enhance girls’ interests and achievement (Baker, 1998; Häuβler & Hoffmann, 2002; Reid & Skryabina, 2003) and have also proved successful for boys. Research has also revealed that the way physics is taught is another major factor. Teaching strategies that enhance the self-confidence of girls, like collaborative work in single-sex groups, have also improved interests and achievement for girls and boys alike (Baker, 1998; Häuβler & Hoffmann, 2002).

Labwork and Multimedia

Student work with real apparatus in the physics lab and student work with computer-based tools can be regarded as two ways of active engagement with physics phenomena. In modern teaching strategies the two modes are gradually integrated (cf. Goldberg & Bendall, 1995; Laws, 1997; Schecker, 1998). Redish (2003) describes the relevant teaching methods together with available resources.

Labwork

The experiment plays a major role in science classes. In physics instruction most of the teaching time appears to be oriented in some way toward experiments with a certain emphasis on teacher demonstrations (Duit et al., 2004). Learning with hands on in laboratory work or from demonstrations has a particular meaning for physics instruction with respect to the nature of physics. Leach (2002) has formulated empirically supported hypotheses about how students’ actions during lab work are based on their image of the nature of science, thus setting up a basis for analyzing learning processes in the lab with respect to students’ epistemological beliefs. It is further argued that a limited practice in which straightforward demonstration experiments dominate leads to rather limited views about the nature of science. The tension between theory with its general and sharply defined concepts and practice setting up a context with many aspects of everyday life language is a specific issue (Woolnough, 1991; Hodson 1993). In a large Delphi-type study, teachers from universities and high schools gave the following objectives high priority (Welzel et al., 1998):

For students:

1. to link theory to practice,
2. to learn experimental skills,
3. to get to know the methods of scientific thinking,
4. to foster motivation, personal development, and social competence.

   For teachers:

5. to evaluate the knowledge of the students.

Especially with respect to objective (A), a lot of empirical work has been done. Lunetta (1998) summarized some of the findings: “To many students, a ‘lab’ means manipulating equipment but not manipulating ideas.” He consequently speaks of a “mismatch between goals, behavior and learning outcomes.” Niedderer et al. (2002) have developed a “category-based analysis of videotapes from labwork” to analyze the amount of students’ talking physics during lab work. Results show that students often use lab sheets like recipes without thinking and talking physics.

Multimedia

Multimedia tools for physics instruction can be divided in six categories:

• Micro-based labs (MBL): probes, interfaces, and software for on-line data acquisition, evaluation, and graphing (cf. Tinker, 1996).
• Content-specific simulation programs: Learners vary the parameters and explore the behavior of physical systems on the basis of a given mathematical model; numerous packages are available for all domains of physics.
• Microworlds: Learners can set up their own simulation settings interactively by combining given object-like building blocks, such as lenses and screens on a virtual optics bench (e.g., Goldberg & Bendall, 1995; Interactive Physics, 2004).
• Model building systems (MBS): Students generate a quantitative model describing the behavior of a system (e.g., the motion of bodies) either by putting in a set of equations or by constructing a computer-based concept map, while the software generates the equations (cf. Schecker, 1998).
• General tools: For example, spreadsheets with tables and graphs.
• Targeted tools: For example, tools for analyzing digitized motion videos (e.g., Beichner, 1996).

Multimedia packages integrate tools from several of these categories. The tools can be bound together with nonlinear interactive multimedia hypertext to so-called hypermedia systems.

The effectiveness of multimedia tools in physics education has become a major field of empirical research. Redish, Saul, and Steinberg (1996) found significant positive effects of MBL-based tutorials in teaching mechanics. Schecker (1998) reports that the use of MBS has a positive effect on semiquantitative reasoning about force and motion. A review of the literature on teaching and learning with the computer (Urhahne et al., 2000) draws a positive picture for science. There is a general agreement that the learning effects of multimedia in science education crucially depend on the instructional approach in which the materials are embedded (e.g., Linn et al., 1993).

TEACHING PHYSICS: PEDAGOGICAL CONTENT KNOWLEDGE IN THREE DOMAINS

In this section we want to outline characteristics of teaching and learning physics by reviewing the literature in three domains, ranging from a rather basic topic— simple electric circuits—to modern physics.

Teaching Electricity

Electricity is one of the physics domains where a huge number of research studies are available (Table 21.1). Particular emphasis lies on simple electric circuits. It becomes rather obvious that simple electric circuits are neither simple for students in the early grades of school nor for those at the tertiary level as well (Duit & v. Rhöneck, 1998).

Physics Concepts

The simplest circuit of all is presented in Fig. 21.3. A bulb is connected to a battery. The same geometrical (better: topological) structure holds for all kinds of “sources” and “consumers”.

There are several levels of theoretical frames to allow predictions of whether the circuit will properly work or not.

(1) Level of connecting conditions. “Source” and “consumer” have two connection points each; they have to be connected by conductors in such a way that the two connecting wires do not have direct contact (no short circuit). The voltages printed on source and consumer need to be (nearly) the same, otherwise the consumer will not work or will be destroyed. Note that voltage is simply a connecting condition. All the students need to know here is: the higher the voltage, the stronger the effect, and that voltages above 20 V are dangerous for humans.

FIGURE 21–3. The simple electric circuit.

(2) Level of current flow. Usually the current view as indicated by the two arrows in Fig. 21.3 is also seen as an essential part of theoretically framing the electric circuit from the outset. There is a closed current flow, that is, a flow of electrically charged particles. The intensity of current is the same all over the circuit. In introductory physics instruction the particular nature of charges is usually not further discussed. There are good reasons for that because it depends on the source, the consumer, and the wires which kind of particles compose the charge flow. There is another essential feature of the current flow that needs attention in instruction. The charged flowing particles may not be viewed as moving independently from one another. Rather, the whole current flow forms a strongly coupled system—which can be compared to a bicycle chain. Whenever the current flow is changed at a certain spot the current all over the circuit is also changed.

(3) Level of simultaneous current and energy flows. It is important to enrich the above current flow view with the view of energy flow. If a current is flowing in the circuit of Fig. 21.3, the bulb glows. Hence energy is transported from the battery to the bulb. Therefore, every current flow is accompanied by an energy flow. Whereas the current flow is easy to locate, namely in the wire, this is more complicated for the energy flow. It seems that two different views are possible, namely energy flow in the electromagnetic field around the wires or within the wires. In any case, energy flow and current flow are fundamentally different in two regards. First, the energy flow is fast (nearly the speed of light), whereas the speed of charges (like electrons) is less than a few millimeters a second. Furthermore, the current flow is closed, the energy flow is not. Either on the path to the consumer or on the way back, energy and current flow in opposite directions.

The sketch of different levels of theoretical framing of the simple electric circuit presented above has revealed that the simple electric circuit is not so simple and easy to conceptualize also from the physics point of view. The issue of Educational Reconstruction discussed earlier (Fig. 21.2) comes into play here. The “elementary ideas” of the simple electric circuit may appear simple, but research on students’ conceptions and on learning processes presented in the following show that too simple ideas may deeply mislead students in their attempts to understand the function of the electric circuit.

Students’ Ideas

The following overview draws to a certain extent on the review by Duit and von Rhöneck (1998).

(1) Everyday meanings of current. Everyday talk about electricity is markedly different from physics talk. The meanings of words for current, for instance, are, at least in English and most major European languages, closer to the meaning of energy than to current as used in physics. Misunderstandings in class are likely if these differences are not taken into consideration.

(2) Consumption of current. Already students at the elementary level establish a causal connection between the battery and the bulb and explain that there is an agent moving from the battery to the bulb. The agent may be called electricity or electric current. It may be stored in the battery and is consumed within the bulb. Hence, there is no idea of conservation of electricity or current among children. A number of children think that one wire between battery and bulb suffices and that the second wire simply serves to bring more current to the bulb. Some students believe that two different kinds of currents, called “plus” and “minus” current, travel from both sides of the battery to the bulb. In the bulb then there is a clash of the two currents producing the light (“clashing current”; Osborne, 1983) or a sort of chemical reaction. The idea of consumption of current is commonly held also by students beyond elementary level. Research has shown that it is very difficult to change this idea; it does not vanish through formal science education. It appears that the above way of talking about current is at least partly responsible for this dominance of the consumption conception.

(3) Local and sequential reasoning. Many students focus their attention upon one point of the circuit and ignore what is happening elsewhere. A “system” view of the current flow as described above is usually missing. An example of such local reasoning is the view that the battery delivers a constant current, independent of the circuit that is connected to the battery. Another variant of local reasoning may be called sequential reasoning. A number of students analyze a circuit in terms of “before” and “after” current passes a certain place. If, for instance, in the simple circuit of Fig. 21.3 a resistor is put into the connection leading from the battery to the bulb, students are correctly of the opinion that the bulb shines less brightly. But if the resistor is put into the other connection leading back to the battery, many students think that in this case the bulb shines as bright as before, because only the current leading back is influenced by the additional resistor.

(4) Current and voltage. Voltage has proved to be particularly difficult concept for students across different age levels. Before instruction voltage is usually related to the “strength of the battery” (or another source) or is viewed as the intensity of force or current. Usually there is not much progress after instruction. Many students still have severe difficulties in differentiating the two concepts.

(5) Learning processes. Many studies (e.g., Shipstone et al., 1988) have shown that the success of physics instruction in developing students’ ideas about the electric circuit toward the physics view is rather limited. Most of these data draw on pre-post-test designs. However, there are also studies that follow the learning processes in detail. It becomes obvious that the learning pathways students follow are very complicated. There are forward and backward movements, there are parallel developments, and there are dead-end streets. In a study by Niedderer and Goldberg (1995), for instance, a group of three college students approaching the physics ideas of the electric circuit in a guided inquiry approach was involved. These students started with typical, alternative conceptions. On the level of connecting conditions they had many difficulties connecting a bulb to a battery in the correct way. On the level of current flow they viewed current as a kind of fuel that flows from the battery to the bulb and is consumed there. They further referred to previous knowledge taught in their science class on positive and negative charge. They merged these two concepts (the consumption idea and the notion of plus and minus current) in such a way that they constructed a new intermediate conception, similar to the well-known clashing currents concept which provided them with fruitful explanations. It was their own cognitive construction, which was not intended and not even realized by the teacher. During their further learning process these students developed more intermediate concepts: “Electron current” helped them to see current as moving electrons. The “electron gas pressure” idea provided a first understanding of the difference between the concepts of current and voltage. At the end of the whole teaching sequence, however, these students still had difficulties seeing voltage as analogous to pressure difference, not merely to pressure.

A case study by Clement and Steinberg (2002) provided evidence that a student can start from an analogical source such as air pressure and flow and follow a learning pathway that builds a dynamically imaginable model of electric potential differences that cause current flow. There the learning pathway consisted of a series of partial models generated by dissonance-driven evaluations and revisions of the student's original model, and the student was able to apply the final model to a transfer problem. However, they still found intermittent difficulties with the distinction between potential and current.

Teaching Approaches

A substantial number of studies have been carried out investigating possibilities to guide students from their ideas to the physics concepts of the electric circuit. Basically, the same kinds of approaches as used in other science domains have also been employed here. There have been attempts to support conceptual change by specially designed multimedia learning environments and by a number of constructivist-oriented teaching and learning settings. It appears that such attempts usually (but not always) have proved superior to more “traditional” kinds of physics instruction. Still, the success is often disappointingly limited. There is, however, one exception. Almost all students, after appropriate experiences with electric circuits, are convinced that two wires are necessary to make the consumer work.

Students’ pre-instructional conceptions of the electric circuit are—as outlined— in stark contrast to the referring physics concepts. Often new teaching and learning strategies start with the elicitation of students’ ideas and with establishing their experiences in question. Students carry out experiments (e.g., with batteries and bulbs) and develop and exchange their views of the phenomena investigated. From such a basis the teacher tries to guide students toward the physics view. Challenging students’ ideas is often a crucial period; that is cognitive conflicts play a certain role. Cognitive conflict strategies, though successful in a number of cases, bear one of several difficulties. The most important is that it is often difficult for students to experience the conflict. It may also happen that elicitation and long discussions of students’ pre-instructional views may strengthen just this view. Therefore, also in the domain of electricity, various approaches have been developed that attempt to avoid cognitive conflicts. These approaches usually start from students’ ideas that are mainly in accordance with the physics view and try to guide students from this kernel of conformity to the physics view via a continuous pathway. One such strategy Grayson (1996) calls “concept substitution.” Instead of challenging students’ views of current consumption, she provides the following reinterpretation: The view that something is consumed is not wrong at all—if seen in terms of energy as outlined above: energy is actually flowing from the battery to the bulb while current is flowing. Energy is “consumed,” that is, transformed into heat and light.

Briefly summarized, understanding the simple electric circuit has proved rather difficult for students both in school and at the tertiary level. It appears that these difficulties are due at least partly to the fact that students’ ideas are deeply rooted in certain everyday experiences (predominantly everyday speech about electricity, current, and electric circuits) and that these conceptions are not adequately addressed in instruction. The case of teaching and learning about electric circuits also shows that instruction may support “false” ideas. In general, the somewhat limited success of conceptual change approaches points to the issue that the content structure for instruction has to be carefully developed in a process called educational reconstruction above (Fig. 21.2). Also seemingly simple topics need substantially deep understanding of the physics “behind” that simple topic.

Teaching Mechanics

Within the domains of school physics, mechanics has the most substantial body of empirical research on students’ conceptions (Table 21.1). There are various proposals for teaching approaches and a variety of multimedia tools. Nevertheless, mechanics remains one of the most difficult domains to teach and to learn. “Force” and “velocity” are subsumed by everyday interpretations of motion phenomena that differ substantially from physics concepts.

Physics Concepts

The concepts of classical mechanics—kinematics and dynamics—are displacement, velocity, acceleration, force, and momentum. Mechanical energy (kinetic and potential energy, work) belongs to the intersection between mechanics and thermodynamics. Mechanics is canonized by Newton's three laws. A trivialized version still found in many classrooms goes along the following lines:

1. If there are no forces acting on a body, it remains in its state of motion—at rest or with uniform velocity (“inertia”).
2. The (resultant) force acting on a body is proportional to the body's mass and acceleration (F = m · a).
3. To each force exerted on a body (“action”) there is an equal but opposite force (“reaction”).

Many students reproduce Newton's laws in similar phrases without understanding their conceptual content. F = m · a is probably the best known and least understood equation of physics. A sound way of expressing Newton's ideas is:

(1*)	The motion of a body can only be changed by forces acting from outside. If there is no change, then there are either no forces at all or the vector sum of the single forces (FR = ΣFi; the resultant force) is zero.
(2*)	The state of motion of a body is described by its momentum (p = m · v). In order to change momentum, a resultant force has to be exerted over a certain time interval (Δp = FR · Δt).
(3*)	Forces result from the interaction of bodies. Whenever a body A exerts a force on another body B, then B simultaneously exerts an equal but opposite force on A (FA→B FB→A).

Although the problems of teaching and learning mechanics cannot be solved simply by the use of proper formulations, the second set of laws helps to work out the conceptual core of mechanics. Law 1* opposes a widespread misunderstanding that inertia is only true in the absence of any force. Law 2* stresses the aspect of a time process of changing motion by forces. Law 3* underlines that interaction forces act on different bodies. An important aspect of conceptualizing mechanics is to distinguish clearly between the resultant force and single forces. Although the equations F = m · a (Newton's resultant force that changes the motion of a body) and F = m · g (for the single force of gravity) look very similar, the meanings of the “Fs” are completely different.

Students’ Ideas

Driver et al. (1994, p. 149) summarize the empirical findings about students’ ideas on force and motion in these statements:

• if there is motion, there is a force acting;
• if there is no motion, there is no force acting;
• there cannot be a force without motion;
• when an object is moving, there is a force in the direction of its motion;
• a moving object stops when its force is used up;
• a moving object has an own force within it which keeps it going;
• motion is proportional to the force acting;
• a constant speed results from a constant force.

One can add:

• friction is no “real” force but a resistance to motion;
• objects at rest or non-active objects (like tables or roads) do not exert forces;
• objects in circular motion “sense” a centrifugal force (independent of the system of reference).

These findings have been confirmed in empirical studies all over the world. They form the body of intuitive mechanics.

Research on students’ ideas in mechanics was stimulated by Warren's book Understanding Force (1979). From a physicist's perspective Warren worked out the inherent difficulties and the conceptual stepping stones—sometimes caused by imprecise instruction. Warren developed a set of test items for university beginners that were also used in many follow-up studies with younger students (see Fig. 21.4 for an example). He showed that many students failed to solve seemingly “simple” problems.

Students are asked to mark the forces acting on the ball at points P and Q and to indicate their probable relative magnitudes (Warren, 1979, p. 34). Most students see a “force” in the direction of motion instead of a (resultant) force in the direction of the change of motion (in P vertically downward).

FIGURE 21–4. Diagram from a tutorial test on student ideas of forces.

Viennot (1979) expanded on the question of how students conceptualize mechanics alternatively. She claimed that students’ “spontaneous reasoning” was consistent and could be formed into an intuitive law of force in which “force” depends on velocity v (instead of acceleration a). Viennot found a coexistence between the idea of “force” as an interaction force impressed on a body and a “supply of force” stored in a body.

McCloskey (1983) drew parallels between students’ “intuitive physics” and medieval “impetus theory”, based on the idea that force impressed on an object can be stored in the body and is later used up in its motion. Students’ impetus reasoning is very resistant to instruction. It leads to wrong predictions of the path of moving objects, like a cannon ball traveling in a straight line before the impetus is used up, so that it falls down vertically. Students even use impetus ideas when they are asked to drop a ball on a target on the ground while they are running.

Jung, Wiesner, and Engelhard (1981) worked out that “inertia” is conceptualized by students as a sort of “lameness”—a resistance to motion that has to be overcome by force. It is often associated with static friction. For students “force” has a polyvalent meaning that integrates facets of the physics concepts of energy, momentum, and Newtonian force. This is comparable to the ambivalent meaning of “force” in physics up to the mid-1850s. Students organize their mechanics knowledge in episodes (cases of force and motion) rather than in generalized principles.

There are a great number of further details on student difficulties, misunderstandings, and alternative concepts in mechanics:

• the problem of distinguishing between points of time and time intervals, which makes it difficult to understand the concepts of momentary velocity and acceleration: “If the velocity is zero, there can be no acceleration” (see, e.g., Trow-bridge & McDermott, 1981).
• the misunderstanding that “action” and “reaction” refer to the same body (thus students believe that in order to cause motion, “action” must be stronger than “reaction” (see, e.g., Viennot, 1979).

A controversial issue is whether students’ intuitive physics forms a systematic and coherent scheme—a sort of “alternative theory” (e.g., Viennot, 1979). diSessa (1988) strongly opposes this notion. He argues that students’ knowledge consists of single loosely connected phenomenological primitives like “force as mover” or “more effort begs more result.” According to diSessa, the transition to scientific understanding involves a major structural change toward systematization. In contrast, Vosniadou (2002) has argued on the basis of patterns in student responses that students construct their own narrow but coherent explanatory frameworks in mechanics. Chi, Slotta, and de Leeuw (1994) propose to organize students’ thinking along ontological categories: In students’ minds “force” belongs to the category “matter” (something that can be stored), while it should be re-assigned to the “constrained-based interaction” category. Jung, Wiesner, and Engelhard (1981) claim that it is more effective to address students’ general categories of reasoning than to address specific alternative conceptions. Such categories are:

• functional descriptions of motion—in contrast to seeking the “cause” of motion
• relationships and interactions between bodies—in contrast to the properties of bodies

Research on students’ understanding of mechanics culminated in the 1980s and has since reached a high degree of consensus. There are standardized instruments to assess students’ reasoning:

• Force Concept Inventory (FCI; Hestenes, Wells, & Swackhamer, 1992)
• Force and Motion Conceptual Evaluation (FMCE; Thornton & Sokoloff, 1998)
• Test of Understanding Graphs in Kinematics (TUGK; Beichner, 1994)

Teaching Approaches

Under subject matter aspects Warren (1979, p. 13) points out that the Newtonian system of mechanics should be fully developed in terms of “real” forces. A “real” force can be attributed to a concrete body in a definable interaction which is subject to a recognizable law, such as gravitational forces caused by a planet or elastic forces caused by a deformed ball. Imaginary forces (“pseudo” forces) like centrifugal force only confuse students. Herrmann (1998) builds a mechanics curriculum around the concept of “momentum” that can be stored, shared between bodies, or flow from one body to another.

Minstrell (1992) reports on positive effects of high school mechanics courses where students are explicitly asked to express their intuitive ideas about force and motion. The students’ ideas are then juxtaposed with the physics concepts. A similar strategy is presented by Schecker and Niedderer (1996) under the term “contrastive teaching.” After introducing Newton's laws, the teacher poses an open-ended problem like “investigate forces in collisions.” Students often make statements like “a force is transferred from body A to body B“—even though they nominally know the Newtonian definition of “force.” This elicitation of students’ own ideas (cf. Driver & Oldham, 1986) helps to contrast their intuitive views with the scientific notion of “force”. Clement (1993) shows how students’ intuitive ideas can be used as starting points (“anchors”) for teaching sequences that lead to a proper understanding of related Newtonian concepts by way of “bridging analogies.” Camp and Clement (1994) present a series of student activities that help them to overcome known learning obstacles.

Hake (1998) carried out a meta-analysis of studies done with the Force Concept Inventory-FCI (6,000 students involved). He found that so-called “interactive-engagement courses” score higher than “traditional” teacher-centered methods. Interactive engagement can be effectively assisted by multimedia. Laws (1997) and Thornton and Sokoloff (1990) have developed activity-based mechanics curricula that center around microcomputer-based labs with a range of new sensors, interfaces, and software. In a collaborative learning environment where students investigate “real” motion phenomena the approach leads to a considerable increase in the understanding of kinematics (Thornton, 1992). Motion in sports (like high jumping) can be analyzed by digital video tools like Videograph (cf. Beichner, 1996). The active construction of virtual microworlds from a given set of building blocks (bodies, springs, ropes, etc.) is another means of prompting students to explore mechanics phenomena (leading software package: Interactive Physics, 2004).

Teaching Atomic Physics

Teaching atomic physics concerns the introduction to various views of the “micro-world” ranging from somewhat “simple” particle models to quantum mechanical views. Many research studies are available on students’ views and the conceptual change processes concerning the particle model. Also, a substantial number of studies on quantum views have been carried out (Table 21.1). For both domains it turns out that students’ everyday conceptions are in stark contrast to the science views. This is already true for the simple particle model which is part of every introductory science course. The microworld of particles is totally different from the world of objects in life-world dimensions. Attempts to make the microworld understandable by introducing analogies to everyday world features usually lead to major student misunderstandings. Students, for instance, tend to view the particles as if they were objects of the life world and hence attach life-world features like color or temperature to them (Duit, 1992; Scott, 1992).

The clash between everyday world views and physics concepts is even more fundamental for quantum views of the microworld. A number of quantum features in principle appear to be inconceivable by everyday world thinking. Examples are particle/wave dualism (Bohr's idea of complementarity) and Heisenberg's uncertainty principle, leading, for instance, to the consequence that it is not possible to know both the speed and location of a particle with unlimited precision.

Concerning models of the atom, students tend to have naĴve realistic views. The majority see models more or less as copies of the reality (Harrison & Treagust, 1996; Treagust, Chittleborough, & Mamiala, 2002). It appears that there is not much development of such views toward awareness of the model character of atoms in lower secondary science teaching (Knote, 1975). In upper secondary physics instruction of the German Gymnasium, Bethge (1992) found that many students differentiated between a model (of an atom) and reality. However, it has to be taken into account that the German Gymnasium caters only to the top level of students and that physics instruction at this level usually includes modern physics and considerations on the philosophy of physics. This is not the case in many other countries. Briefly summarized, the domains under inspection firstly provide further examples of science views fundamentally different from students’ everyday world views. Secondly, it becomes obvious that learning science concepts and principles should include the development of views about the nature of science. Here, proper understanding of particle models and models of the atom only develop if views about models develop accordingly.

Models of the Atom in Physics and Students’ Ideas

The interplay between two different views—the particle view and the continuum view—characterizes scientific ideas of substance and atoms. Already the Greek philosophers (Sambursky, 1975, p. 38) held both views about the constitution of matter. Matter was either seen as consisting of tiny particles called atoms, or as a continuous “something” that fills space and is indefinitely divisible. The basic particle view was further elaborated in the eighteenth and nineteenth centuries, culminating in statistical mechanics. After 1900, various atomic models were developed, proposed different structures of positive and negative charges with respect to particle and continuum. Scientific views of the atom have grown over centuries. Certain stages of this process parallel the models constructed by students.

(1) Atom as a ball. In 1808, Dalton published his book A New System of Chemical Philosophy, in which he viewed atoms as tiny balls (Fig. 21.5). Each element had its own kind of atoms. This hypothesis was suitable to explain fundamental empirical laws about weights in chemical reactions. Later in the nineteenth century Bolzmann's theory of statistical mechanics was also based on atoms as balls. However, in this case the atoms were merely conceptualized as mass points without any other features.

(2) Atom as a plum pudding. In Thomson's “plum pudding” model of the atom (published 1904) the positive charge is spread out across the whole atom continuously, whereas the negative charge sits in the form of particles (electrons) in this positive charge like plums in a dough (Fig. 21.6).

A discussion of atomic models with respect to their texture, using analogies with and without a nucleus, can be valuable. Discussing fruits as analogies with (cherry) and without (kiwi) a nucleus may help students to clarify their thinking. In this respect it is interesting that Harrison and Treagust (1996) found that 76% of their students preferred space-filling models.

(3) Atom as a nucleus with a shell. This model was developed by Rutherford in 1911. A heavy positive nucleus is surrounded by electrons as a shell (Fig. 21.7).

Often this model is presented in science instruction. Harrison and Treagust (1996) found that 38% of lower secondary students view atoms as something with a hard center, and 50% are aware of some sort of electron clouds.

(4) The planetary model of the atom. A most influential model was developed by Bohr (Fig. 21.8) in analogy of the system of planets revolving around the sun.

FIGURE 21–5. Four atoms of Dalton's ball model of atoms.

FIGURE 21–6. The first three atoms of the J.J. Thomson plum pudding model.

This model is still taught in science instruction, and often it is the only model of so-called modern atomic physics students learn. About half of the students in lower secondary as well as the majority in upper secondary and in university actually see the atom as a planetary system with a nucleus being surrounded by moving electrons (Knote, 1975; Harrison & Treagust, 1996; Fischler & Lichtfeldt, 1992). As the model provides a powerful mental model by drawing an analogy to the planetary system, it has proved to be very resistant against the teaching of more advanced models (Bethge, 1992; Fischler & Lichtfeldt, 1992; Mashhadi, 1995; Taber, 2001; Müller & Wiesner, 2002).

(5) Intermediate conceptions of the quantum atomic models. At least in the United Kingdom and in Germany there is a certain tradition to teach quantum atomic physics beyond the Bohr model in upper secondary school. In these teaching approaches, students typically construct intermediate concepts of a quantum atomic model (Bethge, 1992; Mashhadi, 1995; Petri & Niedderer, 1998). One of these models conceptualizes smeared orbits (Fig. 21.9). A number of students at university level appear to hold such models (Müller & Wiesner, 2002).

(6) The probability density conception of the atom. This model is based on Born's interpretation of the Schrödinger equation (Fig. 21.10).

In this conception the Schrödinger term ψ ² is interpreted as the probability of finding the electron at a certain distance from the nucleus: the larger the distance, the smaller is the probability. Studies have shown that students have difficulty understanding this view (Bethge, 1992; Mashhadi, 1995).

(7) The electron cloud model of the atom. This model consists of a nucleus as a particle and an electron cloud as a charge cloud surrounding the nucleus. Its density is calculated by the Schrödinger ψ-function (Fig. 21.11).

FIGURE 21–7. The Rutherford model.

FIGURE 21–8. Bohr's planetary model of the atom.

The charge density in this model decreases when the distance from the nucleus increases. This may be seen analogously to the distribution of the air around the earth. This model of a charge cloud is called “electronium” in an approach by Herr-mann (1995, 1998). Studies (Niedderer & Deylitz, 1999; Budde et al., 2002) show that the electron cloud model (electronium Fig. 21.11) is easier to learn than the Born model in Fig. 21.10. If both models are offered, students prefer the electronium model, and about 90% of them use it in the final test and in interviews.

FIGURE 21–9. Smeared orbits model (Petri & Niedderer, 1998).

FIGURE 21–10. Visualization of an atom according to Born.

FIGURE 21–11. Visualization of an atom according to Schrödinger.

Teaching Approaches

Various approaches of teaching and learning quantum mechanics have been developed and evaluated. Gedankenexperimente (thought experiments) or computer simulations to introduce the concepts of quantum physics, such as the “preparation” of samples of equal particles or the new view of “measurement”, play a significant role in many approaches. In the following a brief overview of different emphases is presented.

Fischler's (1999) approach does not begin with the quantum nature of photons which is the starting point in most other courses. Right from the beginning electron diffraction experiments are carried out and interpreted. Surprising results of the experiments catch students’ attention, and mechanistic interpretations of electrons are avoided. In a treatment-control-group design Fischler and Lichtfeldt (1992) found that about 20% of the students in the experimental group developed satisfactory concepts about quantum principles, whereas in the control group (starting from photons) no student reached that level. Also Müller (2003) found positive effects on understanding by introducing a more modern quantum model of the atom and by abandoning the planetary model.

In a number of approaches, major emphasis is put on explaining basic phenomena and interesting technical applications of quantum physics. Niedderer's approach (Niedderer & Deylitz, 1999) aims at understanding the size and spectra of atoms, chemical bonding, and the spectra of solids. An evaluation study (Niedderer & Deylitz, 1999) showed that—apart from problems with understanding the mathematics of Schrödinger's equation—most goals of conceptual understanding could be reached with reasonable success. As mentioned, a majority of the students preferred the “electron cloud” model to the “probability density” model.

Zollman et al. (2002) analyze objects like LEDs and gas lamps, fluorescent and phosphorescent materials, as well as the tunneling microscope. Potential energy diagrams are used to explain these materials. In the “Visual Quantum Mechanics” approach, the emphasis is on conceptual understanding and visualization as opposed to of mathematical formalisms. In an evaluation study, Rebello and Zollman (1999) observed that hands-on activities, computer visualization programs, and constructivist pedagogy enabled their students to build mental models that allowed them to explain their observations. The preliminary study also provided information about difficulties in helping students to learn abstract concepts by the approach used.

Briefly summarized, research has shown that students’ understanding of particle models and quantum models of the atom may be substantially improved by approaches that are oriented toward constructivist conceptual change views of teaching and learning. However, the success rate is still somewhat limited. Much more research-based development is necessary for both domains. It appears that the above views of the German Didaktik tradition (see the idea of educational reconstruction in Fig. 21.2) may help in further improving the existing approaches. The content structure for instruction—seen from that perspective—has to be developed by taking into account (a) physics views of particles and atoms, (b) physics views of the nature of particles and atoms, (c) students’ views of particles and atoms and of the nature of the models provided, and (d) the aims of teaching particles and atoms. From a scientific literacy perspective it appears that through adoption of the Didaktik tradition the purpose of teaching and learning particle views and especially quantum physics views of the atoms may also be further clarified.

OUTLOOK: DESIDERATA FOR PHYSICS EDUCATION RESEARCH

In order to improve physics teaching and learning in school as well as in other institutions, various changes in the present state of practice are necessary. Most changes are not specific to physics instruction. However, they have to be specifically designed for the particular content and content specific pedagogical issues of physics. Other necessary changes are specific for physics instruction, in particular those concerning emphases of the content taught. In the following, major concerns are briefly outlined.

General Concerns

Teachers’ thinking about instruction and their teaching practices. Teachers, of course, are the key players in education reforms (Anderson & Helms, 2001). Research has shown that (a) many teachers are not (well) informed about research findings on teaching and learning, (b) their views about “good” physics instruction are rather topic dominated, modeling of student learning is deficient, and (c) in educational practice there still appears to be a dominance of teacher-centered instruction. It is essential that teachers’ thinking about instruction includes all the facets addressed in the European Didaktik tradition as outlined above (Fig. 21.2). In terms of Shulman's (1987) perspective, there should be a balance between content and content-specific pedagogical issues in teacher thinking. Instructional planning should include considerations on content issues as well as on issues of how students may be able to learn the content.

More research is needed, especially concerning the following two issues (see Chapter 39 on teacher professional development for more details):

• To investigate how teachers may be made familiar with research findings and how their views about teaching and learning physics may be improved and whether instructional practice improves accordingly. Here issues of conceptual change discussed above come into play. Changing deeply rooted views (here teachers’ views) has proved to be a long-lasting process.
• In order to be able to design more efficient instructional approaches it is necessary to be familiar with the actual practice of physics instruction. So far only a few studies that allow deep insight into actual practice (e.g., by analyzing videos) are available (Duit et al., 2004). More studies on the normal practice of physics instruction are needed.

Aims and standards. The present discussion on scientific literacy is focused on the use of physics knowledge for understanding daily life concerns and participation as citizens in decisions on science and technology. The above concept of Bildung adds the idea of forming the learners’ personalities. It appears to be necessary to further analyze whether the actual concepts of scientific literacy are sound and can be put into practice, that is, are not just visions. A broad spectrum of research methods has to be employed, ranging from historical and hermeneutical studies on various views of scientific literacy in different areas and countries, empirical studies on the actual need of physics knowledge to understand daily life issues and to participate in society, as well as empirical studies on students’ capabilities to achieve the envisioned facets of scientific literacy.

Standards have been a key concern for a number of countries since the 1990s (e.g., in the United States and Canada); in other countries (like Germany) this is a more recent issue. Standards usually attempt to make the more general concepts of scientific literacy explicit. This serves two related functions: to provide a frame for setting key issues of scientific literacy into practice and for facilitating construction of test measures that make it possible to determine the extent to which the various competencies stated are put into practice.

Standards are based on implicit or explicit models of the structure and development of competence. More research is needed:

• To design models of students’ competency structures, drawing on data from achievement tests, favorably in a longitudinal perspective
• To design psychometric methods to prove the competency levels achieved

Content, processes, and views about the nature of science. As more fully outlined above, processes and views about the nature of science are given only rather limited attention in physics teaching. Research appears to be needed to investigate the interplay of understanding content on the one hand and processes as well as views of the nature of science on the other.

Holistic approaches. Research has shown that the outcomes of instruction (e.g., the development of achievement and affective variables) are not due simply to a single factor of the instructional arrangement but to an intimate interplay of many factors (Baumert & Köller, 2000; Oser & Baeriswyl, 2001). In other words, it does not make sense to change just one factor to improve physics instruction (e.g., introducing multimedia learning environments, new exciting experiments, or innovative teaching methods). The above idea of educational reconstruction (Fig. 21.2), which is based on the European Didaktik tradition, may provide a frame for designing approaches that take into account the essential interplay of the many factors determining instructional outcomes.

Physics-Specific Concerns

Physics instruction in school includes a certain canon of content that is quite similar all over the world. Interestingly, most topics of this canon concern rather “old” physics, namely physics of the nineteenth century. So-called modern physics plays a certain role only in the upper secondary levels. Most teaching approaches for quantum physics and relativity (Table 21.1) are suited only for rather gifted students. Attempts to make more recent thinking about matter, space, and time accessible to younger or less gifted students as part of their scientific literacy are rare. There is a certain irony in this situation when schools appear to be reluctant to address this issue, while popular science books on modern physics are booming. Serious attempts are needed to make key basic ideas of modern physics accessible to “normal” students. Some studies in the field of nonlinear systems have shown that this is possible (Duit, Komorek, & Wilbers, 1997).

ACKNOWLEDGMENTS

Many thanks to John Clement (University of Massachusetts) and Ron Good (Louisiana State of University), who reviewed this chapter.

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