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International Journal of
Science Education
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Concepts of a higher
hierarchical level require
more dual situated learning
events for conceptual
change: A study of air
pressure and buoyancy
Hsiao-Ching ShePublished online: 26 Nov 2010.
To cite this article: Hsiao-Ching She (2002) Concepts of a higher hierarchical level require more dual situated learning events for conceptual change: A study of air pressure and buoyancy, International Journal of Science Education, 24:9, 981-996, DOI: 10.1080/09500690110098895
To link to this article: http://dx.doi.org/10.1080/09500690110098895
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RESEARCH REPORT
Concepts of a higher hierarchical level require more
dual situated learning events for conceptual change:
a study of air pressure and buoyancy
Hsiao-Ching She, Institute of Education, National Chiao-Tung University,
1001 Ta-Hsueh Rd., Hsin Chu City, Taiwan, ROC
This article examines the process of students’ conceptual changes in respect of air pressure and buoy-ancy as a result of instructing with the Dual Situated Learning Model. The dual situated learning events of this model were designed according to the students’ ontological viewpoint on the science concepts as well as on the nature of these concepts. Results demonstrated that the notion of buoyancy required more dual situated learning events for conceptual change to occur than that for air pressure. Instead of attributing the difficulty involved in conceptual change to the mismatch of ontological category of the concepts, the author proposes that the hierarchical level of the scientific concepts would determine how easy or difficult it is to bring out a conceptual change. Concepts of higher hierarchical level subsume more essential underlying concepts, thus making it more difficult for conceptual changes to occur.
Introduction
Previous empirical findings have shown that students’ misconceptions in science are highly resistant to change through classroom instruction (Osborne and Gilbert 1980, Osborne and Cosgrove 1983, Carey 1986). Several reasons have been pro-posed to account for this. They include: (1) that students’ intuitive concepts are grounded in everyday experiences (Osborne and Freyberg 1985, Driver 1989); (2) that students have difficulty understanding abstract concepts (Murray et al. 1990, Brown 1993); and (3) that students have problems perceiving the invisible mol-ecule (Brook et al. 1984, Gabel et al. 1987). The mismatch of ontological categories for students’ intuitive concepts has recently been proposed to explain why some conceptual changes can occur easily while certain alternative conceptions persist from preschool through college (Carey 1991, Thagard 1992, Chi et al. 1994). The Dual Situated Learning Model (She 2001) was employed to examine the concep-tual change process among students for the concepts of air pressure and buoyancy and to explore the reasons why some concepts are harder to change than others.
Theoretical frameworks
Vosniadou and Brewer (1987) state that there are actually two types of restructur-ing which can take place durrestructur-ing conceptual change, namely weak restructurrestructur-ing and radical restructuring. Weak restructuring allows new information to be
accumu-International Journal of Science Education ISSN 0950–0693 print/ISSN 1464–5289 online # 2002 Taylor & Francis Ltd
http://www.tandf.co.uk/journals DOI: 10.1080/09500690110098895
lated and new relationships to be formed between existing ideas without changing the core concepts. On the other hand, radical restructuring involves changing both the core concepts and structure of knowledge. Such change is similar to the Kuhnian scientific revolutionary paradigm shifts in science (Kuhn 1970).
Carey’s (1985, 1986) theory of change is related to ‘weak restructuring’. She argues that a lack of knowledge forces younger children to fall back on the use of a similarity-to-person-as-exemplar model, or to employ the modes of higher level thinking. Tytler’s (1998) study tends to support the notion that children’s concep-tions, rather than being theory-like, are essentially responses to contextual situa-tions. In addition, they are much more layered and complex than previously thought. This implies that conceptual change is better represented as a gradual accretional phenomenon rather than as a Kuhnian scientific revolution.
Major restructuring that required changing the ontological category of a con-ception has been found to be much more difficult to bring about than simple change within an ontological category (Chi et al. 1994). Chi et al. (1994) define conceptual change as the reassignment of a concept to another ontologically dis-tinct category, such as from matter to process. They particularly define ‘acausal interaction’ as a subcategory of process, arguing that many scientific concepts, such as heat, force, mutation, or genetic equilibrium, fall into this subcategory. They suggest that the difficulty children have in learning scientific conceptions ‘stems from the existence of a mismatch or incompatibility between the categorical representation that students bring to an instructional context, and the ontological category to which the science concept truly belongs’ (p. 34). However, DiSessa (1993) offers a substantial critique of the theory of Chi et al., stating that there are many important concepts in physics that cannot be classified as ‘acasual inter-actions’.
Thagard (1992) uses case studies of scientific revolutions to build a model that describes different types and degrees of scientific conceptual changes. His analysis of scientific conceptual systems involves tree-like structures including kind-rela-tions (birds, mammals and reptiles are all different kinds of animals) and part-relations between concepts (birds have feathers and beaks), and rules that link concepts and are in turn parts of the concepts (whales eat sardines). He uses these notions to create a ‘hierarchy of types of changes’.
The studies described above all share the same focus, i.e., there are different categorizations available for science concepts and this would govern whether some conceptual changes are radical, while some are weak. However, these studies fail to support their theory with empirical data, or to suggest how to actually foster conceptual change.
Duit (1995) suggests that conceptual change has to do with restructuring what is already known. His view is supported by Piaget (1974), Toulmin (1972) and Jung (1993). Another view posed by Linder (1993) and Marton (1993) stresses that new ideas are related to the context in which they are used. Duschl et al. (1992) suggests that radical restructuring requires the learner to acquire new procedural knowledge with which to re-evaluate existing knowledge before changes can occur. Strike and Posner (1992), in a revision of their original model, emphasize the importance of a student’s conceptual ecology in controlling the process of change. A student’s conceptual ecology includes a fundamental organization of concepts that serves as the changing conceptual environment in which reconstruction of knowledge occurs (Demastes et al. 1995). These findings suggest that conceptual
change requires students to re-evaluate their existing knowledge, for students who are provided with context-situated ideas, and a conceptual change environment which motivates them, restructure their concepts.
I have developed a Dual Situated Learning Model (She 2001) for conceptual change. This is built upon well-known theoretical frameworks from science edu-cation and cognitive psychology theories (Piaget 1974, Posner et al. 1982, Sternberg and Frensch 1996, Steinberg and Clement 1997, Rea-Rramirez and Clement 1998). This approach emphasizes starting both with students’ ontological view of the concept and with the attributes of the concept, these serving as the bases for the development of dual situated learning events. Each dual situated learning event has two functions: creating dissonance with students’ pre-existing knowledge, providing a new mental set with which to construct more scientific concepts. The new mental set should, as Posner et al. (1982) suggest, enable students to see the new concept as intelligible, plausible, and fruitful. The dual situated learning events can be any types of instructional activities, such as ana-logy, modeling, discrepant events and inquiry activities.
Purpose and participants
This study employs the Dual Situated Learning Model to examine the nature and process of students’ conceptual change related to air pressure and buoyancy. The process of restructuring these two different concepts is extended to demonstrate how this model contributes successfully to bringing about the conceptual change, even for concepts categorized as involving the understanding of both matter as well as process.
Twenty 9th grade students (age 14–15) randomly selected from an average achievement class of a Taiwanese middle school participated in this study. All the participants have learned the concept of air pressure and buoyancy at 8th grade physical science course.
Dual situated learning model
The Dual Situated Learning Model involves six stages.
Stage 1 (S1): examining the attributes of the physics concept. The first stage is to examine the attributes of the science concepts. This provides information about which essential mental sets are needed to construct a scientific view of the concepts. Two physics concepts, air pressure and buoyancy, were chosen for this study. A panel of eight was involved, including science educators, scientists, and middle school physical science teachers. These two concepts involved the understanding of invisible and abstract attributes. Both air and water exert pressure and they are made of tiny particles (molecules) that are constantly moving (invisible attribute). For air pressure, students need to understand that air particles exert pressure on all sides of the system including whatever is inside the system. The more you push the system, the more the air particles push against whatever inside the closed system (abstract attribute). The concept of buoyancy is at a higher hierarchical level than air pressure, because it deals with the understanding of more concepts. For instance, it requires the student to know that (1) water particles (invisible attribute) exert pressure on all sides of an object (abstract
attribute), and water also exerts a net upward force on the object which is buoyant force (abstract attribute) and (2) this upward buoyant force is equal to the weight of the volume of fluid displaced by the object. In addition, (3) students should also have knowledge of the factors related to the floating and sinking of objects.
Conceptual changes related to air pressure and buoyancy can be categorized as radical changes because these concepts involve the understanding of both matter (for instance, both air and water are made of tiny molecules) as well as process (for instance, air particles move constantly and exert air pressure on all sides of the system and on the object inside; the balance of buoyant force and the weight of water displaced would determine whether an object would sink or float) according to Chi et al. (1994).
According to the evaluation of the experts on the panel, in order to construct a more scientific view of the notion of air pressure, two mental sets are needed. Mental set 1 states that air molecules exert pressure within a closed system, while the pressure exerted on the system will reduce the space between air mol-ecules, which in turn changes the air pressure in the system. Mental set 2 states that air pressure exists everywhere within a closed system, and that air pressure has no direction. In order to understand that water molecules exert a net upward buoyant force, students need to know that water molecules exert pressure on all sides of an object which is a concept similar to that they would learn from air pressure events (mental set 1 and 2). Four mental sets are needed to help students constructing their understanding of buoyant force. Mental set 3 states that the buoyancy of an object is not related to its mass. Mental set 4 states that the buoy-ancy of an object is not related to the presence of air molecules or with cracks or holes inside it. Mental set 5 states that the buoyancy of an object is related to the density of the liquid (water, or other). Mental set 6 states that the buoyancy of an object is related to its volume and that of the displaced liquid (water, or other).
Stage 2 (S2): probing the misconceptions of the physics concept. The second stage involves probing the students’ ontological view concerning the concept of air pressure and buoyancy. This study used the interview-about-events technique (Gilbert et al. 1982) to elicit students’ understanding of the concepts. Each student spent about 30–40 minutes discussing their ontological view of the concepts of air pressure and buoyancy. Almost all of these ninth grade students have learned the concepts of air pressure and buoyant force in eighth grade. Therefore, we decided to present the students with event 2 as described in Appendix 1 without demon-stration and to ask them to predict what would happen to the foam rubber if we push the plunger of the syringe and to provide possible reasons. This is to detect the students’ knowledge of the attributes of mental sets 1 and 2. We also presented the students with event 1 as described in Appendix 2 without demonstration and asked them to predict whether the object would float, provide a possible explana-tion and to describe the factors which determine whether the object will float or not. This is to detect the students’ knowledge of the attributes of mental sets 3, 4, 5 and 6. This qualitative method allowed us to investigate the nature of students’ understanding about semantically rich concepts (Goetz and LeCompte 1984). All these processes were recorded and the 12 videotapes were then transcribed for further analysis.
Stage 3 (S3): analysing the attributes of concepts that students lack. Results from Stages 1 and 2 will indicate which mental sets students specifically lack for the construction of a more scientific view of the concepts, thus providing specific information to teachers for the design of a series of dual situated learning events to promote conceptual change.
Analyses of the results from Stages 1 and 2 show that 70% of the students lack Mental set 1 for restructuring the notion of air pressure since they perceive that air cannot be compressed or exert pressure. About 90% of the students lack mental set 2 because they either believe that air pressure has direction or that it cannot make a substance change shapes. As for buoyancy, 90% of the students lack mental sets 3, 4, 5 and 6 since they believe that buoyancy has to do with the shape and mass of the object or the presence of air, cracks and holes inside the object. The remaining 10% of the students lack mental sets 5 and 6 because they perceive that buoyancy has to do with the object’s contact surface with water or its weight.
Stage 4 (S4): designing dual situated learning events. The fourth stage is to design a series of dual situated learning events. Researchers believe that in order for conceptual change to take place, disequilibrium must occur in the form of dissa-tisfaction with the current model (Posner et al. 1982). At the same time, providing a new mental set for students is deemed necessary for conceptual change to occur. Therefore, each dual situated learning event has two functions: creating dissonance with students’ pre-existing knowledge; providing a new mental set for them to construct more scientific concepts. Dissonance is aroused by presenting the students with events and asking them to predict what would happen and to provide possible reasons. Then new schema is created by allowing the students to see and experience what actually happens and suggest new explanation. Two dual situated learning events concerning air pressure were chosen to help students construct mental sets 1 and 2 (Appendix 1) as well as to create dissonance. Similarly, three dual situated learning events concerning buoyancy were chosen to help students construct mental sets 3, 4, 5 and 6 (Appendix 2) as well as to create dissonance.
Stage 5 (S1): instructing with dual situated learning events. In this stage, the inter-view-about-events technique (Gilbert et al. 1982) was employed to examine the process of conceptual change. In each dual situated learning instruction event, the students were asked to predict what would happen and also to provide the expla-nation for their prediction before the events were presented. After the presentation or demonstration of the events, the students were asked to explain why the events were different from their preconceptions and to construct a more scientific view of the concepts according to the events presented. In order to understand the process of conceptual change among students during the instruction, they were asked to ‘think aloud’. The whole process of making prediction, providing explanation, confronting dissonance, and then constructing a more scientific view of the con-cepts, was video-recorded. It took at least 60–90 minutes for each student to finish this process, and these 30 tapes were transcribed for further analysis.
Stage 6 (S6): challenging situated learning events. The last stage is to present the challenging situated learning events which are to provide an opportunity for students to apply the mental sets they have acquired to other situations in order
to ensure that successful conceptual change has occurred. Therefore, students were simply asked to predict what would happen and also provide the explanation for their prediction without presenting events.
The challenging situated learning event (Appendix 3) served to check whether students had acquired the mental sets required for understanding the notions of air pressure and buoyancy. The design of the floating dropper is that of a closed system, so that students need to know that air exerts pressure within it (mental set 1) and that air pressure has no direction (mental set 2). The mass of the floating dropper is kept constant (mental set 3) and it always contains the same amount of air (mental set 4). When the bottle is pressed, the water pressure exerted on the floating dropper will reduce the space between the air molecules, as well as the volume of water displaced by the floating dropper (mental set 6), therefore it sinks. This challenging event can also be applied to liquid with different density. It also helps to demonstrate how the density of liquid determines whether the floating dropper will sink float (mental set 5).
Results Air pressure
Table 1 shows the students’ concepts of air pressure before the use of dual situated learning event 1. As can be seen, 75% of the students held the perspective that air inside the syringe could not be compressed. Table 2 shows that after dual situated learning event 1, all the students changed to believe that air inside the syringe could be compressed. About 60% of the students either thought that the air mol-ecules inside could be compressed or there was space between the air molmol-ecules.
As seen in table 3, before the use of dual situated learning event 2, 40% of the students believed that the shape of foam rubber would be not changed, 50% of them thought that only the shape of the top and bottom parts would be changed and 10% of them believed that the whole shape would be changed. These 90% of the students either thought that air pressure had to be exerted directly on the objects to change the shape of the foam rubber or that air pressure had direction and changed the shape of the top and bottom parts only. As shown in table 4, after
Table 1. Students’ perceptions of air pressure before discrepant events of pressing syringe.
Concepts %
1. The syringe cannot be pressed 30
1.1. The syringe cannot be pressed because it is full of air that has nowhere to go 20 1.2. The syringe cannot be pressed because air occupies space 5 1.3. Air inside the syringe cannot be pressed because there is air inside the syringe 5 1.4. The syringe cannot be pressed because air pressure exists inside the syringe 10 1.5. The syringe cannot be pressed because the air molecules inside the syringe
were already compressed to the extreme level 5
2. The syringe can be pressed 5
2.1. The syringe can be pressed because it is full of air that can be pressed 10 2.2. The syringe can be pressed because it is full of air that can move 5 2.3. The syringe can be pressed because there is still some space inside the syringe 5
the dual situated learning event 2, about 95% of the students began to believe that air exerted pressure on all sides of the foam rubber, making it smaller on all sides.
Buoyancy
As seen in table 5, before the use of dual situated learning event 3, 90% of the students believed that the solid object would sink while the boat-shaped one would float. Among these 18 students, half of them thought that the shape and the pres-ence of cracks and holes determined whether an object would sink or float; while the other half thought that either the submerged volume of the object or its contact
Table 2. Students’ perceptions of air pressure after discrepant events of pressing syringe.
Concepts %
2. The syringe can be pressed 25
2.1. The syringe can be pressed and the air molecules become more compressed 35 2.3. The syringe can be pressed because there is still some space inside where air
exists 10
2.4. How long the syringe will take to be pressed will depend on the air pressure
inside the syringe 10
2.5. The syringe can be pressed because air can escape from the syringe 5 2.6. The syringe can be pressed because air can be compressed 10 2.7. The syringe can be pressed because air can move and can be compressed 5
Table 3. Students’ perceptions of foam rubber changes due to air press-ure before discrepant events of pressing syringe with foam rubber inside.
Concepts %
1. The shape of foam rubber will not change
1.1. The shape of foam rubber will not change because there is air inside the
syringe 5
1.2. The shape of foam rubber will not change because when the syringe is pressed, the air molecules inside the syringe will be compressed to the
extreme level 25
1.3. The shape of foam rubber will not change because air is saturated inside the syringe or the air pressure inside the syringe creates resistance, so the
syringe cannot be pressed any further 10
2. The shape at the top and bottom parts of the foam rubber will change
2.1. The foam rubber contains space or air occupies space 10 2.2. The foam rubber will be compressed as the volume of the syringe is decreased
and air pressure increases (air molecules become compressed) 20 2.3. Air would press the foam rubber when the syringe is pressed 10 2.4. When the syringe is pressed at the top, only the shape of the top and bottom
parts of the foam rubber will change 5
2.5. The shape of the foam rubber will change only when the syringe touches the
foam rubber 5
3. The shape on all sides of the foam rubber will change 5 3.1. The shape on all sides of the foam rubber will change because air pressure has
no direction and it exerts on all sides of the foam rubber 5
surface with water accounted for its buoyancy. As shown in table 6, after the use of dual situated learning event 3, all the students began to believe that the solid object would sink while the boat-shaped one would float. About 35% of the students held the belief that the object’s contact surface with water contributed to the its buoy-ancy; 45% of them thought that the shape of the object and the presence of cracks and holes within the object governed its buoyancy; and only 10% of them believed that the submerged volume of the object determined whether it would float or sink.
Those 45% of the students who held the belief that buoyancy was governed by the presence of cracks and holes within the object were instructed with dual situ-ated learning event 4. As shown in table 7, before discrepant event 4 was instructed, 15% of the students thought that the sample cans would float, while 30% of them believed that these cans would sink. As seen in table 8, after the use of the dual situated learning event 4, all these 45% of the students changed to believe
Table 4. Students’ perceptions of foam rubber changes due to air press-ure after discrepant events of pressing syringe with foam rubber inside.
Concepts %
1. Only the shape of the top and bottom parts of the foam rubber will change 5 2. The shape of foam rubber will become smaller on all sides
2.1. The shape of foam rubber will be squeezed on all sides because air would exert pressure on all sides of the foam rubber 45 2.2. The shape of foam rubber will become smaller on all sides because air escapes
from the foam rubber when the syringe is pressed 30 2.3 The shape of the foam rubber will change on all sides because air
exerts pressure on the foam rubber 20
Table 5. Students’ perceptions of buoyancy before discrepant events (the same amount of clay was used to make both the solid and boat-shaped objects).
Concepts %
1. The solid object will sink, while the boat-shaped one will float
1.1. The submerged volume of both the solid and boat-shaped objects are different 10 1.2. The greater the contact surface of an object with water, the greater its
buoyancy 25
1.3. The boat-shaped object contains empty space, so its volume is greater than the solid one, therefore, the density of the boat-shaped is smaller than that of the
solid one 15
1.4. The shape will determine whether the object will float or sink 15 1.5. The boat-shaped object will float because it is empty inside 10 1.6. The boat-shaped object will float because there is air inside 5 1.7. The solid object will sink because of its mass 10 2. Both the solid and boat-shaped objects will float because they have the same mass 5
2.1. The boat-shaped object will sink because it has greater contact surface and
thus exerts greater pressure 5
Table 6. Students’ perceptions of buoyancy after discrepant events (the same amount of clay was used to make both the solid and boat-shaped objects).
Concept %
1. The solid object will sink, while the boat-shaped one will float
1.1. The submerged volume of both the solid and boat-shaped objects are different 10 1.2. The greater the contact surface of an object with water, the greater its
buoyancy 15
1.21. The greater the contact surface of an object with water, the lower the water
pressure 10
1.22. The greater contact surface with water would disperse the mass of the object 10 1.3. The boat-shaped object contains empty space, so its volume is greater than the
solid one, therefore, the density of the boat-shaped is smaller than that of
the solid one 15
1.4. The shape will determine whether the object will float or sink 15 1.5. The boat-shaped object will float because it is empty inside 10 1.6. The boat-shaped object will float because there is air inside 10 1.7. The solid object will sink because of its mass 5 1.8. The upward water pressure is greater than the mass of the object 5
Table 7. Students’ perceptions of the empty can before discrepant events.
Concept %
1. The empty can will float 10
1.1. The inside of the empty can is filled with air 5 1.2. The empty can will float because of water pressure 5
2. The empty can will sink 5
2.1. The shape will determine whether the empty can will sink or float 5 2.2. The empty can will sink because it looks heavy 10 2.3. The water density will determine whether the empty can will sink or float 5
Table 8. Students’ perceptions of the empty can after discrepant events.
Concept %
1. The empty can in the more concentrated solution (22% salt water) will float 1.1. The empty can in the more concentrated solution (22% salt water) will float,
while that in the less concentrated solution (2% salt water) will sink, because
the density of the solutions are different 10
1.2. The empty can will float because its density is lower than that of the salt
water 25
1.3. The empty can will sink because it is a closed system. It will float while it is
an open system 5
1.4. The empty can will float because of air pressure 5
that the sample cans would float at higher concentration of salt water. About 30% of the students believed that the empty sample can would float because its density was lower than that of salt water.
As seen in table 9, before the dual situated learning event 5, 55% of the students believed that the solid object displaced more volume of water than the boat-shaped one, 35% of them believed otherwise, thinking that the boat-shaped object displaced more volume of water than the solid one, and 15% of them held the belief that both objects displaced the same volume of water. Only this 15% of the students possessed the knowledge that the greater the buoyancy, the greater the volume of water displaced. As shown in table 10, after the use of dual situated
Table 9. Students’ perceptions of the volume of water displacement of the solid and boat-shaped objects before discrepant events.
Concept %
1. The volume of water displaced by the solid object is greater than that by the
boat-shaped one 5
1.1. The volume of water displaced by the solid object is greater because it sinks
and has a greater submerged volume 45
1.2. The volume of water displaced by the solid object is greater because it sinks 5 2. The volume of water displaced by the boat-shaped object is greater than that by the
solid one
2.1. The greater the buoyancy of an object, the greater the volume of water
displaced by it 15
2.2. The greater the volume of an object or the greater the volume of air inside the object, the greater the volume of water displaced by it 15 3. The volume of water displaced by both objects are the same 5
3.1. The volume of water displaced by both objects are the same because they
have the same volume 10
Table 10. Students’ perceptions of the volume of water displacement of the solid and boat-shaped objects after discrepant events.
Concept %
1. The volume of water displaced by the boat-shaped object is greater than that by the solid one
1.1. The volume of water displaced by the object that floats is greater because it
exerts greater buoyancy force 65
1.2. The volume of water displaced by the object that sinks is less because its
submerged volume is less 10
1.3. The volume of water displaced by the object that floats is greater because it
has greater surface area 5
1.4. The volume of water displaced by the boat-shaped object is greater because
it contains more air 5
1.5. The volume of water displaced by the boat-shaped object is greater because it contains more air and space than the solid one, thus exerting greater
buoyancy force 5
1.6. The volume of water displaced by the boat-shaped object is greater because
it has greater volume than the solid one 10
learning event 5, 80% of the students began to believe that the boat-shaped object would have greater displacement of water than the solid one. Among these 80% students, 60% of them would actually explain that the object that floated exerted greater buoyancy, thus displacing greater volume of water.
Challenging situated learning event
In order to examine whether students have already acquired all the schemas con-cerning air pressure and buoyancy, a challenging situated learning event was pro-vided. The students were asked to predict what would happen to the floating dropper in a bottle (closed system) if the bottle was squeezed on both sides. Their responses were displayed in table 11. As can be seen, all students predicted that the floating dropper would sink. About 65% of them mentioned that the vol-ume of the floating dropper was decreased when the bottle was squeezed from the side. As a result, the density of the floating dropper was increased, thus it sank. Among these students, 25% of them added the view that air inside the floating dropper was compressed when the bottle was squeezed. About 20% of the students believed that the pressure in the bottle would change, and so would that of the floating dropper. The water pressure was increased when the bottle was squeezed. Consequently, the volume of the floating dropper was decreased, thus increasing the density while decreasing the volume of water displacement and the buoyancy. Some other students only predicted that the pressure of the dropper would increase while the volume of water displacement would change or remain the same.
Table 11. Students’ explanations of what cause the floating dropper (closed system) to sink or rise.
Concept %
1. The floating dropper will sink because its density increases
1.1. The floating dropper will sink because its density increases when it is pressed 10 1.2. The floating dropper will sink because its density increases and its volume
decreases when the bottle is pressed 30
2. The floating dropper will sink because its density increases when the air inside it was compressed, resulting in a decrease in air volume 25 3. The buoyancy force will determine whether the floating dropper will sink or rise
3.1. The floating dropper will sink because of the decrease in buoyancy force due to increase in its density. The density of the floating dropper increases
because its volume decreases when the pressure in the bottle changes 15 3.2. The floating dropper will sink because of the decrease in buoyancy force.
The decrease in buoyancy force is due to increase in water pressure and decrease in its volume when the floating dropper is compressed 5 4. The pressure will determine whether the floating dropper will sink or rise
4.1. The floating dropper will sink because its volume changes when the pressure
increases 5
4.2. The floating dropper will neither sink or rise because the density remains constant although the pressure increases resulting in volume change 5 5. The floating dropper will neither sink or rise because the water volume remains
constant
5.1. The floating dropper will sink when the bottle is pressed 5
From the predictions offered by the students, we can see that 90% of them have successfully applied the mental sets they have acquired concerning air press-ure and buoyancy to the new situation.
Conclusions
The ability of this model to bring about conceptual change can be attributed to its properties. First, the model emphasizes the importance of understanding the nat-ure of physical concepts and students’ ontological view of these concepts. These analyses provide teachers with specific mental sets that students lack for construct-ing specific physical concepts and serve as the bases for designconstruct-ing appropriate dual situated learning events. The design of dual situated learning events should fulfil both requirements: creating dissonance and providing new mental sets to help students construct a more scientific view of the physical concepts.
According to the results, to instruct students whose ontological view of spe-cific science concepts lacks two mental sets, two dual situated learning events are needed for conceptual change to occur. This implies that the number of dual situated learning events required would depend on the number of mental sets the students lack for constructing a more scientific view of the concepts. This finding can provide an alternative explanation why some of the concepts are more difficult to change than others. These relatively more difficult concepts are usually those that subsume more underlying concepts, they are concepts of higher hierarchical level. Previous studies have shown that the mismatch of ontological categories of the science concepts would be the major reason accounting for why some concepts are harder to change than others (Carey 1991, Thagard 1992, Chi et
al. 1994). Other studies report that students have great difficulty explaining the nature of substances and observable changes of substances (Osborne and Cosgrove 1982, Stavy and Stachel 1985, Stavy 1988, Bar 1989). The hierarchical level of the concept is another crucial factor influencing the relative ease or difficulty students experienced in understanding physical concepts.
This study also sheds light on the process of conceptual change among students. There are two advantages of employing the Dual Situated Learning Model. First, it does provide students with the essential mental sets with concrete understanding of the concepts in addition to creating dissonance with their onto-logical view concerning air pressure and buoyancy. Second, the events help students understand both the dynamic process and content of the physical con-cepts. In fact, any other resources can be used as dual situated learning events as long as they achieve the purpose of creating dissonance among students, providing new schemas, as well as helping them to visualize observable changes of substances and understand both the process and matter of physical concepts.
Recent studies have argued that conceptual change in learning is often an incremental process (Duschl and Gitmoer 1991) that may be driven by a range of hot, irrational, social, and motivational forces (Pintrich et al. 1993). According to the Dual Situated Learning Model proposed by She (2001), students are moti-vated to learn science out of curiosity aroused by the events that create dissonance and present a new schema for them.
The limitation of this study is that the Dual Situated Learning Model is employed through individualized interview-about-instance instruction. It would be of interest to put the model into real classroom teaching for further observation.
Solomon (1987) claimed that social factors have significant influence on classroom learning and knowledge construction. In addition, progress in reforming children’s intuitive conceptions appears to be most successful when the social milieu of the classroom becomes a platform of the construction of the desired science concepts (Hennessey 1993). It is believed that putting this model into actual classroom teaching, taking into consideration the social factors suggested by Solomon, would result in more successful promotion of knowledge construction among students.
Acknowledgements
This research was funded by the National Science Council (NSC 89-2511-S-009-004).
References
Bar, V. (1989) Children’s views about the water cycle. Science Education, 73, 481–500. Brook, A., Briggs, H. and Driver, R. (1984) Aspects of Secondary Students’ Understanding
of the Particulate Nature of Matter, Leeds: Children’s learning in science project
(Centre for Studies in Science and Mathematics Education, University of Leeds). Brown, D. E. (1993) Refocusing core intuitions: a concretizing role for analogy in
concep-tual change, 30, 1273–1290.
Carey, S. (1985) Conceptual Change in Childhood (Cambridge, MA: MIT Press).
Carey, S. (1986) Cognitive science and science education. American Psychologist, 1, 1123– 1130.
Carey, S. (1991) Knowledge acquisition: enrichment or conceptual change? In S. Carey and R. Gelman (eds) The Epigenesis of Mind: Essays on Biology and Cognition (Hillsdale, NJ: Erlbaum), pp. 257–291.
Chi, M. T. H., Slotta, J. D. and deLeeuw, N. (1994) From things to processes: a theory of conceptual change for learning science concepts. Learning and Instruction, 4, 27–43. Demastes, S., Good, R. and Peebles, P. (1995) Students’ conceptual ecologies and the
process of conceptual change in evolution. Science Education, 79, 637–666.
DiSessa, A. (1993) Ontologies in pieces: response to Chi and Slotta. Cognition and
Instruction, 10, 273–280.
Driver, R. (1989) Students’ conceptions and the learning of science. International Journal of
Science Education, 11, 481–490.
Duit, R. (1995) Conceptual Change Approaches in Science Education. Paper presented at the Symposium on conceptual change, Friedrich-Schiller University, Jena, Germany. Duschl, R. A. and Gitomer, D. H. (1991) Epistemological perspectives on conceptual
change: implications for educational practice. Journal of Research in Science
Teaching, 28, 839–858.
Duschl, R., Smith, M., Kesdou, S., Gitomer, D. and Schauble, L. (1992) Assessing
Student Explanations for Criteria to Format Conceptual Change Learning Environments. Paper presented at American Educational Research Association, San
Francisco, CA.
Gabel, D. L., Samuel, K. V. and Hunn, D. (1987) Understanding the particulate nature of matter. Journal of Chemical Education, 64, 695–697.
Gilbert, J., Osborne, R. and Fensham, P. (1982) Children’s science and its consequences for teaching. Science Education, 66, 623–633.
Goetz, J. and Lecompte, M. (1984) Ethnography and Qualitative Design in Educational
Research (New York: Academic Press).
Hennessey, M. G. (1993) Students’ Ideas About Their Conceptualization: Their Elicitation
Through Instruction. Paper presented at the annual meeting of the American
Educational Research Association, Atlanta, GA.
Jung, W. (1993) Uses of cognitive science to science education. Science and Education, 2, 31–56.
Kuhn, T. S. (1970) The Structure of Scientific Revolutions, second edition (Chicago, IL: University of Chicago Press).
Linder, C. (1993) A challenge to conceptual change. Science Education, 77, 293–300. Marton, F. (1993) Commentary: our experience of the physical world. Cognition and
Instruction, 10, 227–237.
Murray, T., Schultz, K., Brown, D. and Clement, J. (1990) An analogy-based computer tutor for remediating physics misconceptions. Interactive Learning Environments, 1, 79–101.
Osborne, R. and Freyberg, P. (1985) Learning in Science: The Implication of Children’s
Science (Auckland: Heinemann).
Osborne, R. and Gilbert, J. (1980) A method for investigating concept understanding in science. European Journal of Science Education, 2, 311–321.
Osborne, R. and Cosgrove, M. M. (1983) Children’s conceptions of the changes of state of water. Journal of Research in Science Teaching, 20, 825–838.
Piaget, J. (1974) Understanding Causality (New York, NY: W.W. Norton).
Pintrich, P. R., Marx, R. W. and Boyle, R. A. (1993) Beyond cold conceptual change: The role of motivational beliefs and classroom contextual factors in the process of con-ceptual change. Review of Educational Research, 63, 167–200.
Posner, G. J., Strike, K. A., Hewson, P. W. and Gertzog, W. A. (1982) Accommodation of a scientific conception: Toward a theory of conceptual change. Science Education, 66, 211–227.
Rea Ramirez, M. A. and Clement, J. (1998) In Search of Dissonance: The Evolution of
Dissonance in Conceptual Change Theory. Paper presented at the annual meeting of
National Association of Research in Science Teaching, San Diego, CA.
She, H. C. (2001) Dual Situated Learning Model: An Instrumental Approach Toward
Scientific Conceptual Change. Proceedings of 2001 Sino-Japanese Symposium on
Science Education (Taipei, Taiwan, ROC: National Science Council).
Solomon, J. (1987) Social influences on the construction of pupils’ understanding of science. Studies in Science Education, 14, 63–82.
Stavy, R. (1988) Children’s conception of gas. International Journal of Science Education, 10, 553–560.
Stavy, R. and Stachel, D. (1985) Children’s ideas about ‘solid’ and ‘liquid’. European
Journal of Science Education, 7, 407–421.
Steinberg, M. and Clement, J. (1997) Constructive model evolution in the study of electric circuits. In R. Abrams (ed.) Proceeding, The Fourth International Seminar on
Misconceptions Research (Santa Cruz, CA: The Meaningful Learning Research
Group).
Sternberg, R. J. and Frensch, P. A. (1996) Mechanisms of transfer. In D. K. Detterman and R. J. Sternberg (eds) Transfer on Trial: Intelligence, Cognition, and Instruction (Norwood, NJ: Ablex Publishing), pp. 25–38.
Strike, K. and Posner, G. (1992) A revisionist theory of conceptual change. In R. Duschl and R. Hamilton (eds) Philosophy of Science, Cognition Psychology, and Educational
Theory and Practice (Albany, NY: State University of New York), pp. 147–176.
Thagard, P. (1992) Conceptual Revolutions (Princeton, NJ: Princeton University Press). Toulmin, S. (1972) Human Understanding (Princeton, NJ: Princeton University Press). Tytler, R. (1998) The nature of students’ informal science conceptions. International
Journal of Science Education, 20, 901–927.
Vosniadou and Brewer (1987) Theories of knowledge restructuring in development. Review
of Educational Research, 57, 51–67.
Appendix 1
Dual situated learning events for instruction on air pressure
(1) First dual situated learning event for air pressure
Ask students what would happen if we push the plunger of the syringe? Why?
(2) Second dual situated learning event for air pressure
Ask students what would happen to the foam rubber if we push the plunger of the syringe? Why?
Appendix 2
Dual situated learning events for instruction on buoyancy
(1) First dual situated learning event for buoyancy
Ask students which object would float? Why? (Both the solid and boat-shaped objects are made of the same amount of clay.)
(2) Second dual situated learning event for buoyancy
Ask students what would happen if we put the empty can into the 2% salt water and 22% salt water? Why?
(3) Third dual situated learning event for buoyancy
Ask students which object would displace more water? Why? What has buoyancy to do with it?
Appendix 3
Challenging situated learning event
Ask students what would happen to the floating dropper if we push the bottle on both sides? Why?
2% salt water 22% salt water
