The Subject Matter Knowledge in Physics Related Topics of Hong ...

Journal of Science Education and Technology, Vol. 7, No. 4, 1998

The Subject Matter Knowledge in Physics Related Topics of Hong Kong Junior Secondary Science Teachers D. Y. Yip,1 C. M. Chung,1 and S. Y. Mak1,2

The subject matter competence in physics related topics of 147 inservice junior secondary science teachers in Hong Kong was identified using a true-or-false instrument based on a framework conceptualized by the authors. The findings of this study showed that teachers are weak both in factual knowledge and conceptions in these topics. Although physics majors outperform nonphysics majors significantly in the test, their own performance is by no means satisfactory on criterion referenced terms. Items incorrectly answered by over 40% of the teachers are listed with corrections given. The sources of conceptual mistakes and specific remedial measures were elaborated for items incorrectly answered by more than 60% of the teachers. General implications and possibilities for improvement in tertiary education, science teaching, and teacher education were discussed. KEY WORDS: Alternative conceptions and misconceptions; subject matter knowledge of teachers; physics.

Both theory and common sense support the argument that teachers' inadequacy in subject content knowledge will affect teaching performance as well as pupils' learning (Ball and McDiarmid, 1989). The complexity and multiplicity (Berliner, 1984) of a lesson event, such as selecting suitable content, planning and conducting productive learning activities, asking meaningful questions, answering unprepared questions, diagnosing learning difficulties, and assessing students' progress demand teachers to have a good command of subject knowledge. As a teachers' role is more than delivering the information from a textbook, her/his subject content knowledge should extend beyond the cognitive level and specific topics of the curriculum. According to Shulman (1986),

INTRODUCTION

Not until recently, science education researchers have changed their focus of interest in research on children's learning from exhausting and classifying pupils' preconceptions and misconceptions, to identifying sources of conceptual errors and searching for new strategies that facilitate concept changes (Driver et al., 1994 Wandersee et al., 1994). Research on teacher development, on the other hand, has concentrated on changes in teacher cognition (Pajares, 1992) and other macroscopic dimensions related to the teaching profession (Kagan, 1992). Although concerns has been reported on the low level of subject content knowledge among science teachers (Trumper, 1997; Wenner, 1995), prominent contemporary research paradigms seem to have obscured the importance of teachers' mastery of subject content in science teaching.

Teachers must not only be capable of defining for students the accepted truths in a domain. They must also be able to explain why a particular proposition is deemed warranted, why it is worth knowing, and how it relates to other propositions.

1Department

of Curriculum and Instruction, The Chinese University of Hong Kong, Shatin, N.T. Hong Kong. 2Correspondence should be directed to S.Y. Mak, Department of Curriculum and Instruction, The Chinese University of Hong Kong Shatin, N.T. Hong Kong.

Specifically, in teaching Newton's 3rd law, only if a teacher is equipped with an understanding in depth of conditions imposed by the law and its rela319 1059-0145/1200-0319$15.00/0 © 1998 Plenum Publishing Corporation

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tion with other physical laws can s/he possess the pedagogical content knowledge in teaching the law. That is to say, s/he knows the best way to introduce the law to a particular group of pupils (Frazer, 1994), how is it applied, what pupils' common misconceptions are, and how to clarify misunderstandings with both empirical or thought examples and nonexamples (Gagne, 1977). A number of researchers have reported testing preservice teachers' knowledge on science and mathematics (Goodwin, 1995; Linder and Erickson, 1989; Willson and Williams, 1996); however, little research was done to test the subject matter knowledge of inservice secondary school teachers. The present report is part of our research project launched to review the situation in Hong Kong schools, identify the nature of conceptual errors shown by science teachers, and propose possible actions for improvement. Dimensions of Incompetence in Subject Content Knowledge

Based on research findings on children's understanding of science concepts, together with studies on the subject matter knowledge of preservice teachers and differences in problem solving skills between experts and novices, we categorize teachers' incompetence in subject matter into four dimensions. Alternative Conceptions. Driver and Easley (1978), Good (1991), Hashweh (1988, and Wandersee et al. (1994) refer to naive explanations of phenomena in the physical world developed before learning the scientific views. These alternative views are created by the learner, based on subjective experience and everyday meaning of words. They are more commonly detected in basic physics concepts, like force and momentum, because these terms were borrowed from everyday language but bear a special meaning in the science discipline. Alternative conceptions may be very persistent in that many college physics majors and even physics teachers may hold both the scientists' view and their alternative view without being aware of the inconsistency between them. Misconceptions. Ausubel (1968), Lawrenz (1986), and Yip (1996) include all incorrect descriptions, misinterpretations, or inaccurate explanations of a scientific concept created by the learner during the learning process. Misconceptions often have a diversity of causes. These include a partial understanding

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of a concept due to an inadequate prerequisite knowledge, or a negligence on the conditions and assumptions behind a rule, or an over-generalization of principles from inadequate evidences. Misconceptions may also be resulted from an interference of learnt materials, an uncritical acceptance of incorrect information, or a wrong deduction due to fallacious reasoning. For instance, misconceptions associated with Newton's 3rd law are often produced by an incomplete understanding of the conditions prescribed by the law. It cannot be a naive explanation created solely by the learner. "Lack of Substance." Claxton (1993) and Lucas (1995) include the lack of commonsense knowledge, the scarcity of examples and nonexample for concept illustration and the ignorance about applications of physical laws. This dimension also includes more subtle inabilities (Beers, 1988; Kuhn, 1962; Lawson, 1994) like a lack of skills to look for patterns, make hypotheses, design experiments, validate results, and identify the linkage and hierarchical order of physical laws. A failure to see the linkage between the "internal resistance of a source" and the 'Voltage drop across the external circuit" belongs to this category. Unlike preconceptions and misconceptions which contain an active schema in the brain, a lack of substance is an emptiness in the mind, or a schema too isolated or too remote to be retrieved from long term memory. The latter often happens in teachers who are required to teach a topic beyond her/his specialization. Lack of Problem Solving Skills. The final form of incompetence is a lack of problem solving skills (Helgeson, 1994). Sometimes, teachers do not possess the ability to solve cognitively demanding problems in science and mathematics. Although, this type of incompetence is very common in teachers of matriculation level and beyond, they occur less frequently in those teaching junior secondary level. The first three dimensions define the nature of conceptual deficiencies that we want to detect with our instrument. As far as the width of coverage is concerned, the instrument includes all topics related to SI and S2 levels (equivalent to grade 7 and 8 in the U.S.) in junior science curriculum. Only physics related topics are discussed in this paper. They are Energy, Making Heat Flow, Force-and-Work, and Electricity. The performance on topics related to chemistry and biology will be reported in a separate paper.

Knowledge in Physics Related Topics of Hong Kong Science Teachers METHOD Instrument The physics part of the instrument consists of 36 true-or-false (T-F) items of which 26 are false statements and 10 are true statements. The authors are fully aware of the limitations of the T-F format in that the responses for each item cannot the underlying thinking process of the participants. Nevertheless, T-F format is employed because it is the most efficient means to reveal areas of incompetence. Compensations against the shortcomings of the T-F format are made in the selection process and the pilot study described below. Reliability and Content Validity The instrument was developed through a 4-step content validation process. In item selection, items in related topics but beyond the junior science cognitive level have been included. This is based on the assumption that a teacher should be well versed in the content knowledge at least 3 grade levels higher than the level s/he is teaching. The reliability of the physics subtest is 0.76. 1. The false statements are collected from 3 sources: a. Common conceptual errors related to the junior science curriculum can be detected from candidates taking the Hong Kong Certificate of Education Examination (HKCEE) and on a smaller proportion the Hong Kong A-level Examination (HKALE), which are one grade lower and one grade higher than the SAT level in the U.S. respectively. b. Classroom discourses recorded by the authors through teaching supervisions and videotaped integrated science lessons. c. Teacher-made tests at the same level as the junior integrated science course collected from teachers taking the PGDE and MEd courses of the Faculties of Education of two local universities. 2. The true statements were selected from textbooks at the junior secondary level. The main purpose of adding these statements is to reduce the chance of scoring by response set (e.g., Ebel, 1991) which is common in the T-F format.

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3. A pilot test was carried out on a sample of 50 teachers enrolled in Teaching of Integrated Science Course under the PGDE Program of the Chinese University of Hong Kong. Teachers were asked to go through and decide on the correctness of each statement in the draft instrument. They were also asked to rewrite for correction and make justifications if they thought the item was incorrect. 4. The teachers' responses were marked and a follow-up discussion was conducted immediately after the pilot test. Items that were correctly done by more than 80% of the teachers were deleted. Items that were considered to be inaccurate or answered wrongly by a high percentage of student teachers were dropped or modified after careful scrutiny. Construct Validity Although it is not possible to identify the nature of conceptual errors solely from the response in a T-F item, some reasonable guesses can be made to reveal possible causes. For instance, if an item is unanswered, the most likely cause is lack of substance. If however a wrong answer is given, as can be seen from the itemwise discussion in the next session, the nature of incompetence can still be found from some extrinsic clues. These include the source of the item, the content of the item, the cognitive level of the item, the written justifications collected in the pilot, markers' reports in past public examinations, and items of similar nature recapitulated in the literature. Sample The research sample included 147 junior secondary science teachers from 55 schools. The academic qualification of our sample was better than the average junior science teacher in Hong Kong as 64% of the subjects held at least a B.Sc. degree and 68% of the sample were trained. In contrast, about 70% of local junior science teachers at large were nongraduates. The teaching experience of the sample ranged from 1 to 32 years, with a mean of 7.6 years. On an average, each teacher taught 2 classes of junior science lessons. As a reward, the participants were told in advance that they would receive a model answer with

322 explanations after they returned the questionnaire. Our response rate was 75%. To avoid possible embarrassment of participating teachers, the name and the school of the subject were not identified.

RESULTS AND DISCUSSION

The participants were asked to put a "T" in the answer space of each item if they thought the item was correct, and an "F" if they thought it was incorrect, or leave the answer space empty if they did not know the answer. As far as the 37 questions are concerned, the percentage of correct answers for the 13 physics majors is 63.2% and that for nonphysics majors (including nongraduates) is 45.0% with an overall value of 47.1%. Less than 2% of the answers were null answers. Although physics majors significantly outperformed teachers in other disciplines, their performance was by no means satisfactory. In the following discussion, the parenthesis (T or F, D = 0.X) after each item number shows the answer and Item Difficulty index of the item. The latter is defined as the ratio of number of incorrect answers to total number of participants. Due to space limitations, only items with 0.6 > D > 0.4 are reported with corrections. Further elaboration, including the source of the item, the nature of failure and remedial strategies will be given only to those with D > 0.6.

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Item EN4 (F, D = 0.4) states that all energy sources except nuclear energy come from the sun. Besides nuclear energy, there are at least 3 more exceptions. Geothermal energy comes directly from the mantle of the earth. Also, wind is produced partially due to the spinning of the earth and tidal movement comes mainly from the attraction between the earth and the moon. Making Heat Flow

This is a relatively simple unit about the three ways of heat transfer—Conduction, Convection, and Radiation. The performance was above average. Only two out of six items had D > 0.4. Item H2 (F, D = 0.46) states that a greenhouse allows heat radiation to travel only from the outside to inside. The correct answer is that the EM radiations from the sun around the visible region can pass the windows of the greenhouse. This part of the spectrum is absorbed by plants and the soil inside the greenhouse. The energy is reemitted as long wavelength infrared radiations (heat rays). The heat rays cannot pass through glass and so cause an increase in temperature inside the greenhouse. Item H3 (F, D = 0.52) states that heat conduction in a metal is mainly caused by the vibrational motion of metal ions. The correct answer should be "Heat conduction in a metal is mainly caused by the random translational motion of free electrons." Force and Work

Energy

This unit includes the following subtopics: Different Forms of Energy, Energy Converter and Conversion, Energy Stories, Energy Conservation, and Energy Resources. The performance of this unit was satisfactory. Three out of 4 items tested had D > 0.4. Item EN2 (T, D = 0.4) states that the nuclear fuel in a power plant gives out heat energy. Although, it is a true statement, 40% of teachers thought that it was false. Despite that all teachers know the existence of the term "nuclear energy," only a fair proportion know its meaning. Item EN3 (F, D = 0.49) states that wind is produced solely by the convection of air. The correct answer is that the spinning of the earth has a dragging effect on the atmosphere which in turn produces air movement.

The Effects of Force, Friction, Gravity, the Turning Effect, Newton's' 3rd law, and Work are included under this heading. The syllabus does not include the 1st law and 2nd law. The same structure of topics is adopted in our questions. The performance of this unit was below average. Eight items were tested, of which 3 items had D > 0.6 and 4 items had 0.6 > D > 0.4. Item Fl (F, D = 0.69) is a tricky statement which says that the work done to move a weight of 10 N by 10 m is 100 J. The correct answer should be "to lift a weight" instead of "to move a weight." The direction of displacement must be specified because W = Fs is correct only when the force and the displacement go in the same direction. It is difficult to determine whether a wrong answer to this item was due to a careless mistake or a misconception. Even the

Knowledge in Physics Related Topics of Hong Kong Science Teachers

pilot study could not reveal the cause because participants did not justify their answers if they thought it was a T statement. Whatever the causes, a careless mistake like this is inexcusable for teachers because the erroneous view would be passed to students and becomes a misconception. Item F2 (F, D = 0.74) is a very common misconception about Newton's 3rd law. It states that for a block resting on the floor, the 3rd law reaction of its weight is the normal reaction exerted by the floor on the block. Since the weight of the block is the gravitational force exerted on the block by the earth, its reaction should be the gravitational force exerted by the block on the earth. This is a common misconception found in several textbooks (e.g., Doyle and Minns, 1991) and also in teacher-made tests for this level. This type of misconception should be corrected using the concept change learning model. For instance, the teacher should ask the class to examine and compare carefully the details of the 3rd law and the physical conditions laid down in the statement. Students should be encouraged to find out by themselves that this pair of forces is not an action-andreaction pair because they act on the same object. A slight alternation of the problem situation, such as changing the stationary level floor into an incline plane or an accelerating platform will help students to understand why the statement is incorrect. When this question was discussed in the pilot study with student teachers, many teachers expressed their concern that the context might be too difficult for S2 students. We agree that this test item is beyond the average ability of students and so should not be included in the S2 level, but the teacher should at least appreciate the difficulty level of this item in order to avoid using it in teacher-made tests. Nevertheless, we consider that it is a good item to stimulate conceptual changes in the physics course at grade 11 or 12, to illustrate the application of concept change teaching strategy in the PGDE course. Item F3 (F, D = 0.48) states that the force needed to move a cart is larger than its 3rd law reaction. The truth is that action and reaction are always equal in magnitude. Item F4 (F, D = 0.42) and item F5 (F, D = 0.55) are related. The former states that Newton's 3rd law is true when there is no acceleration. The latter states that when a body falls freely under the action of gravity, the weight has no reaction. Like item 2, the reaction of the weight of a falling body is still the

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gravitational attraction exerted by the body on the earth. To facilitate accurate concept formation, in addition to the remarks suggested in items 2, physics teachers should provide examples, including bodies at rest and in motion, to illustrate the principle of action and the reaction. Also, the difference in the system of interest between the 2nd law and the 3rd law should be discussed with students in the physics course. The 2nd law is a law which governs the motion of a single body but the 3rd law is about the interaction of two bodies. During the discussion, a pair of free body diagrams, one for each body, should be drawn for all examples to illustrate the 3rd law. Curriculum developers can also help to correct the misconception. Thus far, the term "free body diagram" is not found in any part of the physics syllabuses in Hong Kong. This should be added under the 3rd law or elsewhere. Item F7 (F, D = 0.56) states that the grooves on a tire help to prevent sliding on a dry road. The scientific view is that the grooves help to prevent skidding only on a wet road. Their presence makes room for the water to escape between the tire and the road. Electricity

The units on electricity include the following subtopics: Static Charges, Simple Circuit (except voltage), Heating Effect of Current, Magnetic Effect of Current, Electrolysis, Safety in Using Electricity, Vacuum Tube, and Cathode Rays. The performance of teachers was very disappointing. Fourteen out of 17 items had D > 0.4 within which 8 items were incorrectly answered by over 60% of the participants. Item ELI (F, D = 0.76) states that most of the charges on an insulated oval-shaped conductor accumulate at the sharp point. The correct answer should be that the charge concentration (or density) instead of the amount of charge is highest at the sharp point. It was not known how many teachers were trapped by the tricky question and how many really did not know the answer. In any case, understanding can be improved if more exact wordings are used in textbooks and the correct concept is made accessible to teachers through different channels in their training. Item EL2 (T, D = 0.48) states that a person will not encounter an electric shock if s/he touches a bare

324 neutral wire in a mains cable. This is a true statement because the neutral wire carries no potential. Item EL4 (F, D = 0.67) states that the voltage of a cell is the pushing force per unit charge provided by the cell. The correct answer should be "energy per unit charge" instead of "force per unit charge." The error can be attributed to two causes. First, only "electric current" but not "voltage" is included under the subtopic simple circuit in the teaching syllabus at this level. As a result, only a loose definition, like "driving force of a cell," or "strength of a cell", or no definition at all is given to the "emf" of a cell by many textbooks. Second, due to an incomplete understanding or an interference between learned materials, many teachers had never made clear before or failed to internalize the meanings of "voltage", "emf" and "potential difference" they came across in their school days. They relearn the concept in the wrong way from junior science textbooks. It may be very difficult or even unrealistic to help all science teachers get hold of all these concepts (Mak and Young, 1988). However, at least two things can be done to prevent the propagation of misconceptions. First, as far as the syllabus is concerned, it seems reasonable to introduce at least the concept of "the voltage of a cell" in the introductory level while the "potential difference across a resistor" and the "emf of a cell" may be skipped from the early stage to avoid confusion. Second, careful wordings should be used to explain the "voltage of a cell" in students' textbooks. Item ELS (F, D = 0.83) and item 6 (F, D = 0.84) are both about free electrons in a conductor. Item 5 states that all free electrons drift with the same speed along the whole circuit. Item 6 states that free electrons move in a direction opposite to the conventional current. The correct answer is that in the freeelectron model of metallic conduction, free electrons move with a very large thermal random speed (106 ms-1) inside a metal and a small directional drift speed (10-2 m.s-1) is superimposed on the top of the random motion when a voltage is applied across the conductor. The extremely poor performance on these two items may be attributed to three factors. First, most nonphysics teachers may have forgotten the mechanism of metallic conduction covered in the pre-university physics course. Another cause of the misconception may come from misleading diagrams on this topic in some textbooks (e.g., Nelkon and Parker, 1977) across all grades. Free electrons are often drawn moving at the same speed along the

Yip, Chung, and Mak same direction in a conductor. A third explanation is that some teachers may retain a vague idea of drift speed but mistakenly associate the drift speed of electrons directly with the electric current. The latter is the same in different parts of a simple series circuit. The analysis shows that the nature of failure can be either a misunderstanding of drift speed or a lack of knowledge of this term. In the former case, the source of the misconception must be removed to stop its spreading. Physics textbook authors can juxtapose diagrams showing "the random nature of free electron motion" and "the drift motion in the presence of an electric field" in physics texts (e.g., Serway and Faughn, 1989) at higher grades. Also, publishers can provide computer animations and video programs to schools to illustrate the mechanism of metallic conduction. In these topics, audio-visual aids with a dynamic scene are far more useful than static drawings to help learners capture the essence of the model. On the other hand, if teachers do not know or forget the term, perhaps the best way to remind or widen their scope of knowledge is to empower them with information through various possible channels. Item EL7 (F, D = 0.51) states that when a simple circuit is connected, electrons will first pass through one circuit element and then another (depending on the distance between the individual element and the source). The scientific view is that an electric field is set up almost simultaneously across a noninductive DC circuit when the switch is closed and there is no time lag in the flow of electric current in different parts of the circuit. Item EL8 (T, D = 46.9) states that the voltage across a coil (assumed zero resistance) in a steady DC circuit is zero. Possibly due to an interference of learning, about half of the teachers wrongly recalled a finite back emf associated with the coil. Item EL9 (F, D = 0.69) states that circuits are connected either in series or in parallel. This loose statement can be found in many junior science textbooks (Chan et al., 1993). Although, series and parallel connections are often used in simple circuits, other connections, like the bridge circuit is not uncommon. The statement should be changed to "Circuits are often connected in series or in parallel." Item EL10 (F, D = 0.54) states that there is a small amount of gas inside a vacuum tube to provide ions for electrical conduction. The correct answer is that there is nothing in the space of a vacuum tube

Knowledge in Physics Related Topics of Hong Kong Science Teachers before the circuit is connected and the charge carriers are electrons produced by thermionic emission. Item EL12 (T, D = 0.76) states that the maximum current delivered by two dry cells in series is the same as that provided by a single dry cell. In a new carbon dry cell, the emf is 1.5 V and the internal resistance is about 0.5 ohm. Since the maximum current is just the short circuit current, its value is about 3 A. The same short circuit current is obtained when two cells are connected in series because both the emf and the internal resistance are doubled. A lack of understanding on the internal resistance of a cell explains why so many teachers picked the F option. Although, internal resistance is not required in the teaching syllabus at this level and the certificate level (CDC, 1993), some experimental results, like the drop in the voltage across a cell in a closed circuit can only be explained in terms of internal resistance. The teacher should at least know why things happen this way. A reminder in the teachers' guide of a textbook on the existence and effects of internal resistance will equip teachers with the necessary knowledge to resolve these paradoxes. As nonphysics majors may have unlearned the topic due to lack of practice or have never learnt this concept before, teacher trainers must spare some tune to discuss the effect of internal resistance in cells and meters with student teachers in the teaching of the integrated science course. Item EL13 (F, D = 0.50) states that the human body can withstand a current no more than 0.1 A. The truth is that we feel pain when the current through the body is 3 mA and the "not let go current" is about 10 mA, more or less. An 0.1 A current will produce almost instant death. Item EL14 (F, D = 0.62) states that the current goes out from the live connection in a 3-point socket. The fact is that only the live wire carries a voltage (relative to the earth) in the mains circuit and the main current is an alternating current. This wrong description is found in several textbooks in Hong Kong (Doyle and Minns, 1991). Many teachers just followed such wrong descriptions in answering this item. Here, we are not in a position to judge the depth of understanding of the textbook writers, but we are very sure that there is a "bug" in this part of the curriculum (CDC, 1986). Students are required to learn some safety precautions in using mains electricity but they have no prerequisite knowledge on what is "voltage," how large is the voltage of the mains and what is an "alternating current." Thus stu-

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dents are learning the meaning of grounding and the importance of fusing in the live connection by rote. Moreover, in wiring a 3-pin plug, students are doing something without knowing why they have to do it. Two things can be done to improve the situation. First, the concept of alternating current is not very abstract. Students in junior secondary level can understand its meaning if sufficient examples, models, analogies, and animations are supplied in the lesson to aid learning. Second, the sequence of teaching different topics should be carefully planned and properly arranged in a curriculum. For example, in this case, the mains connection and safety rules are best introduced after the concepts of "voltage" and alternating current are taught. Item EL15 (F, D = 0.76) states that the neutral wire is blue in a socket. The correct international convention is that the neutral wire is blue in a 3-pin plug but black inside a wall socket. This mistake is found in the diagram of many textbooks (Johnson et al., 1995) where a blue line is drawn to represent the neutral connection in a socket. Another cause of the misconception may be a result of an interference of learning. Many teachers do not know the color code in a socket, but the blue color association is formed when the "color code of a 3-pin plug" and "a plug is connected to a socket" are brought out from their long term memory at the same time. Like other misconceptions produced by diagrams, textbook writers and publishers can help to eradicate the cause. Item EL17 (F, D = 0.59) states that the cause of death of electrocution is often due to severe burning. The main cause of death should be heart failure and cessation of breathing. Summary The research shows that most teachers are incompetent in subject content knowledge. In particular, their performance is worst in the two most fundamental areas in classical physics, namely, mechanics and electricity. As far as factual information is concerned, the instrument shows that over 40% of the teachers are not sure about the nature of nuclear energy (EN2), the cause of wind (EN3), and the origin of energy sources on the earth (EN4). Even more teachers do not know the magnitude of fatal current through the human body (EL13), the color code of the neutral wire in a mains socket (EL15), and the main cause of death in electrocution (EL17).

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The context of an item helps to show whether it is an alternative conception or a misconception. Although, the distinction is not 100% exact, the instrument seems to reveal 4 alternative conceptions in physics that teachers might have held before secondary school learning. These include: • grooves in tires for increasing friction (F7); • electrocution by the neutral wire (EL2); • the time lag model of electrical conduction (EL7); • the naive relation between the maximum current and the number of cells (EL12). The instrument identifies at least twelve physics related misconceptions. Each is held by over 40% of the teachers teaching the subject. These include: • explanation of greenhouse effect in terms of the one-way traffic of heat rays (H2); • thermal conduction in metals in terms of vibrational motion of metal ions (H3); • work done as force times displacement in any direction (F1) • action and reaction acting on the same body (F2); • when pulling a cart, the action is larger than the reaction (F3); • uncertainty in the 3rd law reaction for accelerating bodies (F4 and F5); • more charges instead of higher charge density at sharp points (EL1); • voltage as force per charge (EL4); • uniform motion of free electrons in a conductor (EL5 and 6); • no electrical connections other than parallel or series (EL9); • gas ions in a vacuum tube (EL10); • the live connection as the positive terminal of a cell (EL14). Although, it is impossible to exhaust all causes of misconception itemwise, the list appears to be manifestations of the causes we point out in the beginning of this paper. Two additional remarks may be added here. First, a fair proportion of these items (EN4, H3, F2, EL4, ELS, EL9 and EL14) are found in textbooks. This shows that the latter may become a medium for the propagation and perpetuation of misconceptions. Second, a comparison of the Hong Kong physics curriculum and our test instrument shows that neither the CE (CDC, 1993) nor the Alevel syllabus (CDC, 1992) has adequate coverage for

topics EN3, EN4, H2, H3 appearing in the junior science curriculum. Also, the free body diagram (essential for the understanding of Newton's 3rd law) is not mentioned in any part of the curriculum. As a result, what most teachers know about these topics is no more than what they learned in the junior science course.

CONCLUSION This study is based on a T-F instrument with items modified from examinations, teachers' narration, and textbooks covering physics related topics of the Integrated Science Curriculum. Some of the most popular preconceptions, like the alternative frameworks about force and motion (Gunstone and Watts, 1993), had not been included in the instrument because our selection range was limited by the syllabus content. Despite these limitations, our results reveal a fairly representative sample of concept deficiencies in teachers and suggest that most junior science teachers do not possess sufficient substantive content knowledge to teach the physics related parts of the subject. The following measures may be considered to improve the situation. We believed that the lack of common sense knowledge is the result of a lack of exposure. So the best way to enhance the background knowledge of our teachers is to make the knowledge accessible to them through various channels. A cooperative effort is needed for a successful exposure enhancement program. Supplementary teaching materials, alternative teaching resources, and information related to science topics can be supplied to teachers through written materials like the teachers' guides to textbooks and Curriculum guides published by the Curriculum Development Council. More seminars on resources for science teaching should be run by inspectors of the Education Department. Information can also be disseminated through discussion sessions in the PGDE and Refresher Training Courses held by the teacher training institutes. Teachers should also be encouraged to gather information from the science columns in newspapers, magazines, educational TV programs, and through the world wide web in the computer. More educational multi-medium teaching resources, like computer floppies, CDROMs, and LD's, should be made available in school and university libraries.

Knowledge in Physics Related Topics of Hong Kong Science Teachers Exposure alone is not enough to rectify the misconceptions and alternative conceptions held by teachers. Up to the present, the textbook is still the most popular and efficient means for disseminating information. The result reminds textbook authors to be cautious about the use of words and diagrams. In writing textbooks at an introductory level, the rule of thumb is to simplify but not to falsify. Textbook writers should also check their diagrams carefully because artwork presentations are often drawn by artists who have no adequate science background. All textbooks should be reviewed by experienced teachers as well as university professors to ensure that the level is appropriate, the coverage is suitable, and the concepts are sound before they are released to the market. The spiral learning model should be adopted for designing the science curriculum. The concept of heat flow, greenhouse effect, the free body diagram, and the random nature of free electron motion should be included in the physics curriculum. Also, the order of appearance for different topics should be carefully planned in the curriculum. For instance, the concept "voltage" should be taught under the heading "Simple Circuit" and before the discussion on "Domestic Electricity Supply." This will help students to understand why a voltage sign is printed on each dry cell and why a fuse is installed on alive wire. Also the concept of internal resistance should be included at the certificate level. This is the only means through which learners can understand why there is always a voltage drop across the cell when a load is connected in a circuit. The prevalence of conceptual flaws in secondary school teachers suggests that undergraduate science courses in universities fail to equip their students with the fundamental background knowledge needed for teaching junior secondary science. As a fair proportion of university graduates will enter the teaching profession and choose teaching as their life-long career, many of them will have to teach the Integrated Science course after graduation. The science faculties should offer a course on the Teaching of Integrated Science to these potential teachers so that they can develop a deeper understanding of scientific concepts outside their specialization. The physics departments in universities should also offer a course on General Physics for Teaching Secondary Schools for potential physics teachers. Finally, in teacher training institutes, it is often assumed by science teacher trainers that graduates

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in a discipline should have possessed an adequate background knowledge on that discipline so that the training program will concentrate on the theory of instruction and teaching skill practice. They seldom address the need of student teachers for a deeper understanding on subject matter. Such an assumption is no longer tenable and provisions should be made in teacher training courses to rectify misconceptions and preconceptions of prospective and practicing teachers (Bauman and Adams, 1990; Viega et al., 1989).

REFERENCES Ausubel, D. P. (1968). Educational Psychology: A Cognitive View, Holt, Rinehart and Winston, New York. Ball, D. L, and McDiarmid, G. W. (1989). The subject-matter preparation of teachers. In Brophy, J. (Ed.), Advances in Research on Teaching (Vol. 2), JAI Press, Greenwich, pp. 437449. Bauman, R., and Adams, S. (1990). Misunderstanding of electric current. Physics Teacher 28: 334. Beers, S. (1988). Epistemological assumptions and college teaching: Interactions in the college classroom. Journal of Research and Development in Education 21(4): 87-94. Berliner, D. C. (1984). The half-full glass: A review of research on teaching. In Hosford, R (Ed.), Using What We Know About Teaching. Association for Supervision and Curriculum Development, Alexandra, pp. 51-81. Chan, W. K., Hui, Y. K., Wong, K. F., and Kong, S. W. (1993). Understanding Integrated Science 2A, Aristo, Hong Kong. Claxton, G. L. (1993). Minitheories: a preliminary model for learning science. In Black, P. J., and Lucas, A. M. (Eds.) Children's Informal Ideas In Science, Routledge, London, pp. 45-61. Curriculum Development Council (1992). Syllabus for A-level Physics: Forms 6 to 7, Government Printer, Hong Kong. Curriculum Development Council (1993). Syllabus for CE-level Physics: Forms 4 to 5, Government Printer, Hong Kong. Curriculum Development Council (1986). Syllabus for Science: Forms 1 to 3, Government Printer, Hong Kong. Doyle, R, and Minns, R. (1991). New Integrated Science 2, Longman, Hong Kong. Driver, R., and Easley, J. (1978). Pupils and paradigms: A review of the literature related to concept development in adolescent science students. Studies in Science Education 5: 61-84. Driver, R., Squires, A., Rushworth, R, and Wood-Robinson, V. (1994). Making Sense of Secondary Science. Routledge, London. Ebel, R. (1991). Essentials of Educational Measurement, PrenticeHall, Englewood Cliffs, NJ. Frazer, B. J. (1994). Research on classroom and school climate. In Gabel, D. L. (Ed.) Handbook of Research on Science Teaching and Learning, Macmillan, New York, pp. 493-541. Fung, R C. W, Fung, A. Y. C, and Chung, L H. M. (1989). Integrated Science Today, Jing Kung, Hong Kong. Gagne, R. (1977). The Conditions of Learning. Holt, Rinehart and Winston, New York. Good, R. (1991). Editorial. Journal of Research in Science Teaching 28: 387. Goodwin, A. J. (1995). Understanding secondary science: a perspective of the graduate scientist beginning teacher. School Science Review 76(276): 101-109.

328 Gunstone, R., and Watts, M. (1993) Force and motion. In Driver, R., Guesne, E., and Tiberghien, A. (Eds) Children's ideas in science. Open University Press, Milton Keynes, pp. 85-104. Hashweh, M. (1988). Descriptive studies of students' conceptions in science. Journal of Research in Science Teaching 25: 121134. Helgeson, S. L. (1994). Research on problem solving: Middle school. In Gabel, D. L. (Ed.) Handbook of Research on Science Teaching and Learning, Macmillan, New York, pp. 248268. Johnson, K., Cheng, I., Mak, T.P., and Sun, S. C. (1995). Physics for Your Certificate, Pilot, Hong Kong. Kagan, D. M. (1992). Professional Growth among preservice and beginning teachers. Review of Educational Research 62(2): 129-169. Kuhn, T (1962). The Structure of Scientific Revolutions, University of Chicago Press, Chicago, Illinois. Lawrenz, F. (1986). Misconceptions of physical science concepts among elementary school teachers. School Science and Mathematics 86: 654-660. Lawson, A. E. (1994). Research on the acquisition of science knowledge: Epistemological foundations of cognition. In Gabel, D. L. (Ed.) Handbook of Research on Science Teaching and Learning, Macmillan, New York, pp. 131-173. Linder, C. G., and Erickson, G. (1989). A study of tertiary physics students' conceptualizations of sound. International Journal of Science Education 11: 491-501. Lucas, A. M. (1995). Playing the notes but ignoring the tune: the narrowness of biology education research. Journal of Biological Education, 29(3): 195-200. Mak, S. Y., and Young, K. (1988). Voltage measurements in a loop surrounding a solenoid: Some further paradoxes due to stray capacitances. American Journal of Physics, 56(3): 254-258.

Yip, Chung, and Mak Nelkon, M., and Parker, R (1977). Advanced Level Physics, Heinemann, Hong Kong. Pajares, M. F. (1992). Teachers' beliefs and educational research: Cleaning up a messy construct. Review of Educational Research 62(3): 307-332. Sanders, M. (1993). Erroneous ideas about respiration: the teacher factor. Journal of Research in Science Teaching 30: 919-934. Serway, R. A., and Faughn, J. S. (1989). College Physics, Saunders College, Philadelphia, Pennsylvania. Shulman, L. (1986). Those who understand: Knowledge growth in teaching. Educational Researcher 15(2): 4-14. Trumper, R. (1997). A survey of conceptions of energy of Israeli preservice high school biology teachers. International Journal of Science Education 19(1): 31-46. Viega, M., Coster Pereira, D., R. (1989). Teachers' language and pupils' ideas in science lessons: Can teachers avoid reinforcing wrong ideas? International Journal of Science Education 11: 465-479. Wandersee, J.H., Mintzes, J. J., and Novak, D.J. (1994). Research on alternative conceptions in science. In Gabel, D. L. (Ed.) Handbook of Research on Science Teaching and Learning, Macmillan, New York, pp. 177-210. Wenner, G. (1995). Science knowledge and efficacy beliefs among preservice elementary teachers: A follow-up study. Journal of Science Education and Technology 4(4): 307-315. Willson, M., and Williams, D. (1996). Trainee teachers' misunderstandings in chemistry: Diagnosis and evaluation using concept mapping. School Science Review 77(280): 107-113. Yip, D. Y. (1996). Misconceptions of Biology Teachers and the Implication for Teacher Education Programs. Paper presented at the International Conference on Basic Education, Hong Kong.