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Multivoicedness and univocality inclassroom discourse: an examplefrom theory of matterEduardo Fleury Mortimer aa Faculdade de Educação , Universidade Federal de MinasGerais , Belo Horizonte ‐ MG, BrazilPublished online: 24 Feb 2007.

To cite this article: Eduardo Fleury Mortimer (1998) Multivoicedness and univocality inclassroom discourse: an example from theory of matter, International Journal of ScienceEducation, 20:1, 67-82, DOI: 10.1080/0950069980200105

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INT. J. sci. EDUC., 1998, VOL. 20, NO. 1, 67-82

Multivoicedness and univocality in classroomdiscourse: an example from theory of matter

Eduardo Fleury Mortimer, Faculdade de Educação, Universidade Federal deMinas Gerais, Belo Horizonte - MG, Brazil

The analyses of talk amongst students in three episodes, video recorded from a teaching sequence on theparticle model for Brazilian students (age 14-15) is presented. The analysis has two dimensions: thediscoursive dimension is an attempt to understand how meanings are constructed in the classroom as aresult of discoursive interactions; the conceptual dimension comprises the description of the patterns ofevolution of ideas of matter based on the notion of a conceptual profile of matter, in which conceptualand historical features of the atom concept are profiled with pupils' and adolescents' ideas on atomism.From the students talk we can hear the interaction among different 'voices', representing different zonesof a conceptual profile of matter. In this interaction, the students resort to both 'authoritative' and'internally persuasive' discourses. The analysis emphasizes the role of these two types of discourse andof epistemological and ontological obstacles in the construction of scientific meanings in the classroom.

Introduction

The investigation of classroom talk, mainly in the area of social psychology andlinguistics, has generated results which have implications for science education.Some authors, drawing on Vygostky (1978), consider that discourse is at the heartof the study of teaching and learning, as language is, at the same time, both apsychological and a communicative tool (Mercer 1996). According to these authorswe use language not only to communicate and to share meaning but also to makesense of our experience, to constitute our thoughts.

Empirical studies of classroom talk have shown the implicit rules working onclassroom talk, the particular features of this kind of discourse (as, for example, theI-R-F sequence), and how teachers use the discourse to guide and to evaluate thelearning process (e.g. Edwards and Mercer 1987, Newman et al. 1989, Lemke1990, Mercer 1995). These studies have indicated that the analysis of classroomtalk should take into account the content of the discourse and how the context ofschooling frames the content and shape of this discourse.

Several authors have attempted to study the discourse of science and of scienceclassrooms (Lemke 1990, Sutton 1992, Halliday and Martin 1993, Scott 1996,1997, Ogborn et al. 1996, Mortimer 1997). Scientific language, according toHalliday (1993), has its own grammar, in which the functions of verbs andnouns are different from those of everyday language. The processes of science,which would require an entire phrase to be expressed in everyday language, arenominalized in scientific language. The verbs function as a causal link betweenthese nouns/processes in a phrase. Through this grammatical metaphor (Halliday1993) processes are put into a relationship in the construction of a scientific argu-

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ment. The language of science is, therefore, a way of talking about the world that isdifferent from everyday language, even in its grammar. Studies of science class-rooms demonstrate that they are populated by abstract entities (electrons, mol-ecules and so on) whose meanings are constructed as much as through talk asthrough experiments or practical activities. Scott (1996, 1997), for instance, refersto a 'teaching narrative', a sequence of talk, and activities mediated by talk, thatenact the transformation of knowledge in the intermental plane of the classroom.These studies also suggest 'that the way in which the teacher "talks around" theevidence or activity is at least as important as the evidence or activity itself (Scott1997:127).

The study presented here aims at relating the discoursive analysis of scienceclassrooms with conceptual profiling - a personal and conceptual analysis of thedevelopment of students' ideas through which the content of the classroom dis-course can be highlighted. Conceptual profiling (Mortimer 1995) is a way todescribe the evolution of students' ideas of matter that is based on the conceptualand historical features of the atom concept (Gregory 1931, van Melsen 1952,Knight 1968) and in studies on children's ideas of atomism (e.g. Piaget andInhelder 1941, Novick and Nussbaum 1978, Driver 1985). This article examinesthe ways through which classroom discoursive practices frame the development ofstudents' ideas of a particular concept - the concept of matter. How different'voices', representing different zones of conceptual profile of matter, frame theinteractions among students in three episodes, and what the roles of differenttypes of discourse are in overcoming epistemological and ontological obstacles inthe construction of scientific meanings, are the two rnain issues addressed. Theconsequence of this analysis for constructivism theory is briefly discussed.

Categories for a conceptual profile of matter

The categories to trace the evolution of students' atomistic ideas and to determinethe obstacles to the learning of scientific ideas were developed from an analysis ofthe conceptual profile of the concept of matter (Mortimer 1995). This notionshares with Bachelard's epistemological profile (Bachelard 1968) the idea that anunique form of thought is not enough to explain a single concept. Nevertheless,each zone of a conceptual profile, besides its own characteristic epistemology, hasalso an ontological component. An important feature of the idea of a conceptualprofile is that its 'pre-scientific' divisions are constrained by the epistemologicaland ontological commitments of individuals. As these individual characteristics arestrongly influenced by culture, it is possible to define a conceptual profile as a'superindividual system of forms of thought' (Marton 1981) that can be assigned toany individual within the same culture. Despite the differences between individualprofiles, the categories by which each conceptual profile is drawn are the same. Anindividual conceptual profile is strongly rooted in the individual's distinctive back-ground, and is content-dependent, since it refers to a particular concept. At thesame time its categories are context-independent, as within a culture we have thesame categories by which the zones of a specific profile are determined. In ourWestern, industrial civilization, the scientific divisions of the profile of a scientificconcept can be defined by the history of scientific ideas. The pre-scientific zonesfor many concepts can also be defined, as a consequence of the last two decades of

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intensive research on students' alternative ideas, that has identified the same sortof conceptions related to the same scientific concept in different parts of world.

In this article, the categories of the conceptual profile of matter (Mortimer1995) will be used to analyse the content of the students' discourse. The first zoneof a conceptual profile of matter is called 'sensible', which means appealing to thesenses, and it is characterized by the absence of any discontinuous notion of mat-ter. A student who only has this notion of matter represents it as continuous,without any reference to particles. Its main obstacle is the negation of the possi-bility of the existence of empty space between the particles. Related to this conceptof matter there is a notion of the physical states of matter being closely linked withexternal appearances and physical features of materials, which states, for example,that a solid is hard and a liquid is soft (Stavy and Stachel 1985, Stavy 1988, 1990).

The second zone of the profile is called 'substantialist atomism'. The notion ofsubstantialism leads to the conclusion that, despite using particles in their repre-sentations, the students think of such particles as grains of matter than can dilate,contract, change state, and so forth. Students, thus, make an analogy between thebehaviour of the particles that they draw and that of the substance. They are notreferring to the atom as a scientific concept, but to grains of matter that showmacroscopic properties. This analogy between the macroscopic and the micro-scopic worlds is the main epistemological obstacle to further progress for studentswhose concepts can be classified in this region. Moreover, the fact that they useparticles in their representations of matter is no guarantee that they believe in theexistence of the vacuum between them. This is particularly important in the sensethat someone in this zone has not necessarily overcome the obstacle of the previouszone.

The kind of ideas that characterize these two first zones of the profile ofmatter, i.e. matter as continuous and 'substantialist atomism', are described inalmost all articles about students' ideas related to the concept of matter (e.g.Piaget and Inhelder 1941, Doran 1972, Novick and Nussbaum 1978, 1981,Nussbaum 1985, Griffiths and Preston 1992, Garnett and Hackling 1995).Although it is not possible to relate all the students' ideas about matter to thesetwo zones, the notion of a conceptual profile of matter provides a theoretical back-ground that can highlight the main characteristics of such ideas and its mainobstacles to the construction of scientific ideas about matter in the classroom. Inthe previous descriptions there was no reference, for example, to the idea that amolecule is 'macro' in size (Griffiths and Preston 1992). However, if studentsthink about atoms and molecules as grains of matter that show macroscopic beha-viour such as dilating, melting and so forth, they should think of these grains as'macro' in size as well.

The third zone of the profile of matter corresponds to a classic notion of theatom as the basic unit of matter, which is conserved during chemical transforma-tions. The atom is a material particle and its behaviour is governed by mechanicallaws, like any other body. Substances are made up of molecules that result fromthe combination of atoms. Atoms of the same type have the same atomic number.

This article does not deal with the atom as a system of electrical particles norwith the quantum mechanical zones of the profile of matter. Nevertheless, it isimportant to realize that classical atomism still has some 'substantialist' character-istics as a legacy of its mechanistic origins. Despite the epistemological differencebetween classical atomism and the other two areas of the profile, all these concep-

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tions consider the atom as a kind of material thing, a basic block from whichsubstances are built. In this sense, all these 'atoms' belong to the same ontologicalcategory. The main difference is that, in a classical view, we cannot attribute allmaterial behaviour to atoms, just because some forms of behaviour (such as melt-ing, boiling, dilating) are a consequence of the motion of atoms, molecules or ionsin a vacuum and of the interaction between them, which can vary as the energy ofthe system is modified. Consequently, an individual atom does not show propertieslike boiling or melting points; these are interpreted as resulting from aggregatingthe behaviour of a great number of them in macroscopic amounts. Nevertheless, aclassical atom shows some other material properties like mass, volume, radius, etc.;it is a material thing, that belongs to the ontological category of substance. Matteris only changed to another ontological category with quantum mechanics, whereparticles of matter are seen as quantum objects described by mathematical equa-tions. The 'reality' of those particles is the subject of a polemic that began with theEinstein-Bohr debate (Bohr 1935, Einstein et al. 1935) and is still far from reach-ing an agreement.

Teaching theory of matter for a conceptual profile change

There are some implications for establishing a strategy for teaching elementaryatomism that follow from the categories of the conceptual profile of matter. Assuggested in previous work (Mortimer 1995), the instructional approach and itssteps depend on the specific epistemological and ontological features of the zone ofthe conceptual profile to be taught. In addition we should consider two distinctparts in the learning process, as a consequence of using the conceptual profilenotion. The first corresponds to the acquisition of the concept in a specific profilezone, and the second relates to the pupils achieving consciousness of their ownprofile, allowing comparison between different zones of the profile, as well as anevaluation of their relative power. In this process, students become conscious ofthe limitations of their alternative conceptions without necessarily giving them up.

Another implication for teaching elementary atomism that follows from thecategories of the conceptual profile of matter is how to elicit the students' views ofphenomena in order to access their profile before teaching. To achieve this it isconvenient to choose phenomena in which matter is in the process of transforma-tion, such as dilation, compression, change in physical state and so on (Appendix),which might somehow be experienced by the students themselves, in the labora-tory or in their everyday life. If students are asked to draw models for a systembefore and after any sort of transformation they might use an intuitive atomism(Piaget and Inhelder 1941, Bachelard 1975) which is an alternative to the scientificatomism (Novick and Nussbaum 1978, Driver 1985) and has some obstacles to theconstruction of the scientific concept that have to be addressed during the teachingprocess.

Moreover, consideration of the conceptual profile of matter suggests that itwould be more sensitive to students' thinking to ask them to represent modelsrather than draw what they imagine might be happening 'inside the material', or todraw the material as if it were 'seen' through very powerful magnifying glasses.These last questions might lead students to an answer based on external features ofthe materials, since the approach suggested (seeing) would not be adequate fordealing with constructed models.

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MULTIVOICEDNESS AND UNIVOCALITY IN THE CLASSROOM 71

The classroom as a social setting

The transfer of categories of the conceptual profile used to analyse evolution ofindividual understanding to the social setting of the classroom presented severalproblems. It is impossible to analyse classroom talk by looking for the ideas ofindividuals and the way those ideas evolve. Evolution of ideas in the classroomhappens in a social space, as a result of the contribution of several individuals.Newman et al. (1989) offer some insight into this sort of problem by suggestingthat the individual is not the most useful unit of analysis to deal with cognitivechange. Instead, they propose the 'analysis of social events involving negotiationbetween participants with different understandings or analyses of the situation'(P-62).

The analysis of the social and linguistic features of the classroom has incor-porated some aspects of research on classroom talk. Studies of the development ofunderstanding in the classroom have generated several works in recent years andsome of them have a direct relationship with the sociocultural approach and thesemiotic analysis of Vygotsky.

Drawing on the work of Vygotsky, Bakhtin and Lotman, Wertsch (1991)offers an insightful way to look at the generation of meaning in social settingsthat can be used to analyse the construction of shared knowledge in the classroomand that complements the approach based on conceptual profile outlined here. Ifwe look at the classroom as a space where at least two different languages - thescientific and the everyday - are put in contact to generate new meaning, thendialogicality and multivoicedness offer fundamental categories to analyse thisprocess. According to Voloshinov, any true understanding is dialogic in nature:

To understand another person's utterance means to orient oneself with respect to it, tofind the proper place for it in the corresponding context. For each word of theutterance that we are in process of understanding, we, as it were, lay down a set ofour own answering words. The greater their number and weight, the deeper and moresubstantial our understanding will be (Voloshinov 1973:102, cited by Wertsch1991:54)

In this way, an utterance involves not only the voice producing it, but also thevoices to which it is addressed. This is a consequence of the multivoicedness thatcharacterizes the process of understanding.

Bakhtin's (1981) notion of voice refers to more than an auditory signal. Itinvolves the much more general phenomenon of the speaking subject's perspectivewhich is related to his/her world view. Related to the issues of dialogicality andmultivoicedness, Lotman's account of the functional dualism of texts in a culturalsystem is very useful for analysing classroom talk. According to Lotman, the twobasic functions that texts fulfil are 'to convey meanings adequately, and to generatenew meanings' (Lotman 198: 34, cited by Wertsch 191:73). The first function -called by Wertsch the univocal function of text — 'is fulfilled best when the codes ofthe speaker and the listener most completely coincide and, consequently, when thetext has the maximum degree of univocality' (Lotman 1988:34). The secondfunction of a text — called by Wertsch the dialogic function — is to generate newmeanings.

In this respect a text ceases to be a passive link in conveying some constant informa-tion between input (sender) and output (receiver). Whereas in the first case a differ-ence between the message at the input and that at the output of an information circuit

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can occur only as a result of a defect in the communication channel... in the secondcase such a difference is the very essence of a text's function as a 'thinking device'.What from the first standpoint is a defect, from the second is a norm, and vice versa(Lotman 1988: 36-37, cited by Wertsch 1991:74).

Bakhtin's distinction between 'authoritative' and 'internally persuasive' dis-course is clearly related to the univocal and dialogic functions of text. According toBakhtin (1981), in an authoritative discourse the utterances and their meanings arepresupposed to be fixed, not modifiable as they come into contact with new voices.

It is not a free appropriation and assimilation of the world itself that authoritativediscourse seeks to elicit from us; rather, it demands our unconditonal allegiance.(Bakhtin 1981:343)

In contrast, the internally persuasive discourse seeks for the 'counter words', it is'half-ours and half-someone else's', allowing dialogic interanimation.

The semantic structure of an internally persuasive discourse is not finite, it is open; ineach of the new contexts that dialogize it, this discourse is able to reveal ever new waysto mean. (Bakhtin 1981: 346; emphasis in original).

According to Wertsch, for any text there is a tension between its univocal anddialogic functions. Any discourse has authoritative and internally persuasive char-acteristics. We can look to classroom talk searching for the context where one oranother feature predominates. The construction of a new meaning within a pre-dominantly 'internally persuasive' discourse can be followed by recapitulationswhere the 'authoritative' prevails. The use — or not — of the appropriate discoursefor each context can help us to explain the matching and mismatching betweenteacher and student undertandings.

Analysing the classroom discourse

In this section, analyses of three episodes from a Brazilian Year 8 classroom (age14—15), where the atomic model was taught in connection with the physical statesof matter, are presented. The data were collected by video recording both one ofthe students' groups and the whole class. The episodes to be analysed belong to asequence of 12 lessons that lasted three weeks. The camera was introduced into theclassroom two months before this sequence began, so the students were able toignore its presence when the lessons began. All the classroom talk produced duringthe 12 lessons was transcribed. From the whole transcription, 14 episodes of thestudents' group discussion were selected for analysis such that they should repre-sent all the students' ideas which arose in the teaching process. In this article theanalyses of three of these episodes are presented.

The lessons were based on group discussion alternated with whole class dis-cussion. In the lessons the students had to discuss and then choose one of the'models' they suggested in a pre-test, for the following phenomena: compression ofair in a plugged syringe; expansion of air heated in a test tube with a balloon overits neck; the release of a vacuum in a flask connected to a large syringe; the diffu-sion of gas odour in the kitchen as it escapes from its container; dilation, by meansof heating with the hand, of the alcohol (or mercury) column of a thermometer;melting and vaporization of naphthalene heated in a test tube. The activities andlessons that were planned for teaching atomism as a model to explain the physicalstates of matter are summarized in the Appendix. This set of activities was planned

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MULTIVOICEDNESS AND UNIVOCALITY IN THE CLASSROOM 73

' " > • w

(b)

- So'/.cfc>

(c)

Figure 1. Examples of students' representations for matter undergoingchange (a) discontinuous representations, (b) mixed representations,(c) sensible representations.

to fit a minimum of 10 lessons of 50 minutes each, and a maximum of 14 lessons,depending on the individual classroom.

It is important to notice that the task of drawing models for matter undergoingchange might not be understood in the same sense by all of the students. Theexamination of some of their drawings [figure l(c)] suggests that some of themactually drew sensible representations of matter, which is an indication that theydo not understand the word 'model' in the same sense as the teacher does. Thisdistinction is important because when a student represents matter undergoingchange by means of drawings, even when his/her model does not coincide withthe scientific one, it can be considered a model if it goes beyond the sensibleaspects of the material, relating macroscopic aspects of the transformation to some-thing that is imagined. Nevertheless, a second student whose representation does

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not relate something imagined to the phenomenon but, instead, simply makes adrawing of the situation [figure l(c)], cannot be considered as having the sameunderstanding of the word model as the first student.

Episodes 1 and 2 are based on classroom discourse that took place at thebeginning of the teaching sequence, during the discussion of the first two phenom-ena (compression of air in a plugged syringe; expansion of air heated in a test tubewith a balloon over its neck). Two types of obstacles, belonging to the first twozones of the conceptual profile of matter, were addressed in these episodes: thenegation of the empty space between particles and substantialism. Episode 3belongs to the end of the teaching sequence and the analysis attempts to showhow the students use features of a classical view of matter — the third zone of theprofile - that they have acquired through teaching.

Episodes 1-3 show a pattern of evolution of the students' ideas as they dealtwith the obstacles to the construction of an atomistic model of matter. In EpisodeI, the students discussed and chose a model for the compression of air, addressinga question that the teacher had asked about the nature of space between particles.This was the strategy used by the teacher to make these obstacles explicit in thestudents' thinking.

Episode 1: What is this empty space?

1. Car: Which do you think is the best?2. Edw: That one with the dots (Edw is referring to the dots into the drawing).3. Car: I think that the most scientific is the one with the dots.5. Raq: But, that one with the dots . . . What is that empty space there? In fact,

the air is all around, and not only in the dots. Then, we could colour allaround, this is what I think. Did you hear what he said? [referring to theteacher] We should think about the space...

6. Car: But then it is not that with dots . . . It is that one [she points to anotherdrawing].

7. Raq: I think we could colour it, in this way: you make this first one verylight... then, when you compress it, it would be darker because it ismore concentrated. In this way there won't be space and there won't beany doubt.

8. Car: But what happens is that air is not continuous like that... air is formedby several particles.

9. Raq: [Ask Edw] What do you think?!10. Edw: . . . The air... is as she said, air has particles.II . Raq: But, between the particles, is there a vacuum?12. Car: No, but . . . here we don't have only air particles, we have other

particles . . . Nitrogen, pollution, dust, all sorts of things.13. Raq: Hum.. .

There are at least two different conceptions of matter represented in the dis-cussion which characterize two distinct zones of the conceptual profile of matter.Car and Edw have chosen the atomistic model (utterances 2 and 3), as 'the mostscientific'. Raq was not convinced that air has particles, which is consistent withthe ideas that she had revealed in the pre-test — that matter is something contin-uous. She made her view explicit in utterances 5 and 7. If the teacher did not refer

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to the space between particles as something to be addressed, the students might nottake this as a problem. When Raq referred to the space between particles, at theend of utterance 5, it was not her 'voice' that was speaking, but the teacher's, whichbegan to frame the student's negotiation of meaning. Raq would prefer to use acontinuous model because in this model 'there won't be space and there won't beany doubt' (utterance 7). Although her view of matter was not accepted, herquestion had to be addressed by her classmates.

The presence of the teacher's voice in the students' dialogue is an example ofthe dialogicality that characterizes the generation of new meanings. In this text,each utterance involves not only the voice producing it, but also the voices towhich it is addressed (Voloshinov 1973). The model that emerges at the end ofthe episode (utterance 12) also reflects its predominately internally persuasivenature. According to Bakhtin, 'the semantic structure of an internally persuasivediscourse is not finite, it is open; in each of the new contexts that dialogize it, thisdiscourse is able to reveal ever new ways to mean' (Bakhtin 1981: 346; emphasisoriginal). To counter Raq's objection ('But, between the particles, is there avacuum?') Car had to re-build her argument. Understanding the difficulty ofthe idea of 'nothing' between the particles, she filled the empty space with particlesof things other than air ('we have other particles... nitrogen, pollution, dust, allsorts of things').

Substantialism and atomism

Episode 2 offers an example of the presence of a substantialist view - the secondzone of the matter's profile - in the students' discourse. The students were dealingwith the second task of the teaching sequence (Appendix), drawing a model of airbefore and after expanding as a consequence of being heated in a test tube with aballoon over its neck.

Episode 2 took place after a long class discussion about the first phenomenon(the compression of air in a plugged syringe), in which the teacher tried to dealwith the 'nature abhors a vacuum' obstacle. In doing so, he also argued that itwould be better to have a model which does not depend upon the nature of theparticle. In the teacher's words,

I can use that model [he is referring to the atomistic model] without having to talkabout the exact nature of the particle: I don't need to say whether the particle is a ballor a square, whether it is elastic or non-elastic. It would be better to work with amodel which doesn't specify the nature of the particle, as I cannot observe it.

This is predominately authoritative utterance, and he used it when he was trying toclose the discussion. The mismatch between this authoritative teacher's discourseand the understanding of the students in Episode 2 is evident, as they chose asubstantialist model, where the particles expanded themselves.

Episode 2: Expanding the particles

1. Car: What happened is that the particles got bigger.2. Raq: Then the particles expanded . . .3. Car: Expanded...

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4. Raq: That is model three (she is referring to the number of the model thatthey have on the sheet distributed by the teacher).

5. Car: What do you think, Gla?6. Gla: Nothing. . . I don't know.7. Car: Hey! We have to answer here . . . We observed that the balloon filled up,

didn't we? But we have no answer: explain...8. Raq: We have to explain: Air, when heated, expands.9. Car: Expands. The air particles expand when heated because there is empty

space between the particles.10. Edw: It is the air that expands.11. Car: It isn't the air that expands, it is the particles that expand.12. Car: Ah, now we have to draw here . . . the model that we've chosen... (They

draw.)13. Car: Here, see: we have to write the characteristics. What is the character-

istics of the first (tube)?14. Edw: Normal.15. Car: Normal. The particles have their normal size. . . now, in the second

(tube), they've got bigger, expanded, filling a bigger volume, haven't they?16. Edw: Yes.

Episode 2 shows that Raq and Car had, at the outset of the episode, a consensusabout attributing the macroscopic property of expanding to the particles(utterances 1 and 2). As Gla and Edw did not challenge their views, the textbecame predominantly authoritative in nature. In contrast to Episode 1, where'counter-words' had an important role in building a common understanding,Episode 2 shows no space for voices other than the substantialist one. Car'semphatic statement in utterance 11 in answering Edw's objection (utterance 10)shows that she was not trying to negotiate her view any more, but only to find thebest way to express it, which was achieved in utterance 15.

Another characteristic of this episode is that the teacher's voice was not repre-sented as in Episode 1. The students were not addressing a teacher's question nor didthey take any of his arguments against substantialism into account. The idea of emptyspace between particles seems not to be a problem any more, and Car referred to itin utterance 9 as an 'explanation' for the idea that particles could expand themselves.

The third zone of the conceptual profile of matter: theclassical atomism

Episode 3 occurred at the tenth lesson, near the end of the teaching sequence. Itshows how the students addressed a question which belongs to an activity aimed toreview and summarize the characteristics of the atomistic model (Appendix). Theepisode shows the students using several characteristics of a classical atomisticmodel which they have learned in these three weeks, since they did not use anyof these characteristics - motion, energy, arrangement - in their pre-tests nor inthe first two episodes.

Episode 3: Using the characteristics of an atomistic model

1. Raq: Then, how is energy related to the particles' motion?

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2. Ale: We only have to take into account... as a gas has more motion, it hasmore energy. Now. . . , the problem is how to explain gas.

3. Edw: It is this . . .4. Raq: In the gaseous state the particles have more energy and their motion is

greater . . . wait a minute . . .5. Ale: Please, you are driving us crazy . . .6. Raq: Yes . . . I am crazy too.7. Car: If we were talking about solids, how much energy is associated with the

motion of these particles... Because it is solid and they vibrate, Imean. . . then . . . If we chose the liquid it means that they move them-selves in groups, but if we chose the gaseous they move with morefreedom.

8. Raq: But it has to be logical.9. Ale: Yes, you can't say it is because it is, it is because it i s . . .

10. Car: But it is because it is . . .11. Gla: The gaseous.. . , when a gas is heated, its volume increases and its

motion increases as well.12. Edw: But you can't say that a gas has motion only when it is heated.13. Car: Good god! It is related to the particles . . .14. Raq: Why is its motion greater than that of solids and liquids? Because the

particles move individually.15. Edw: Because they can be considered as individual particles.16. Car: Then! . . .17. Raq: Then they can move faster.18. Edw: Yes! Move faster.19. Raq: Then we have to explain it this way. Then we can say that because they

move themselves . . . , no, they move themselves because of what? Whatis this?

20. Edw: Because they are individual, the particles are individual... it is that . . .21. Ale: The problem is the quantity of...22. Edw: Wait a minute . . .

[They stop and become thoughtful.]

23. Ale: I'd say that they are independent and move more quickly, then . . .24. Raq: Yes, it is necessary to say that they move more quickly because . . .25. Ale: How is energy related to motion? How is the amount of energy related

to motion? The greater the energy, the faster the motion. And that is all.

We notice here that the students did not have a full understanding of the question -how is energy related with the particles' motion - when they began to deal with it.At the outset Ale seemed to have understood the question, as he tried to relatemotion to energy in the gaseous state (utterance 2), but he was not convinced thathis statement could be the answer. The dialogue that follows shows how thestudents try to construct this understanding by building an argument aroundthe notions of energy, motion and arrangement. In doing so they review severalcharacteristics of an atomistic model for solids, liquids and gases: which kind ofmotion predominates in each state (utterance 7); how heat can affect the volumeand the particles' motion in a gas (utterance 11); that the particles have an intrinsicmotion, as 'y°u can't say that a gas has motion only when it is heated' (utterance

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12); that the particles in a gas are far apart and therefore 'they can be considered asindividual particles' (utterances 15 and 20); and that being individual they movemore quickly (utterances 17, 18 and 23).

Some of these statements are not completely true. For example, the particles ofa gas do not necessarily move faster than the particles of a liquid, as kinetic energy -and consequently motion - depends on the temperature and not on the particles'condition of being individual or not. Nevertheless, the students in this episode areframing a question with much more appropriate variables — motion, energy andarrangement - than they framed the questions in Episodes 1 and 2. The teacher'svoice is present throughout the episode, but in a way that is different from Episode1, where it was only referred to. In Episode 3 the teacher's voice becomes thestudents' voices. Therefore, we have an appropriation of the teacher's voice by thestudents and not only the teacher's voice speaking through the students. Theclassical atomistic view of matter appeared initially on the intermental plane andthe students had several difficulties in using it, as shown in Episodes 1 and 2. Asthis view of matter became internalized it moved from the intermental to theintramental plane and the students became able to use it as their own view(Vygotsky 1978, Wertsch 1991).

The discourse of Episode 3 has an internally persuasive nature as the studentsare trying to build a suitable answer to the teacher's question. It also has anauthoritative nature, as the students' statements throughout the episode are notin negotiation. The students used them as true statements to build a new argument -how energy is related to the particles' motion. They use logical prompts to assurethe continuity of thinking through discourse (utterances 16 and 18) which is anindication they they are building new thoughts in the intermental plane throughthis discoursive interaction.

How did the students grasp this atomistic model? To answer this question wewould need to analyse other types of episodes, mainly teacher-students dialogue,which is beyond the scope of this article. What could be suggested - although thisis based on data not analysed in this article - is that the alternation of internallypersuasive and authoritative discourse that characterized the students' talk wasalso present in the teacher-students dialogue. In several of these dialogues theteacher considered each student's argument and tried to build a counter argument.Even when this strategy led to a model that was different from what he had inmind he did not avoid the arguments or refuse the model suggested. In contrast tothis more persuasive discourse, the teacher resorted several times to assertivestatements and to univocal questions, that demand a unique and 'true' answer.The alternation of these two types of discourse seems to be a very pervasivecharacteristic of classrooms, one that contributes to the process of negotiationand elaboration of meaning.

Conclusions

The analysis presented in this article articulates two dimensions of the scienceclassroom - the discoursive and the conceptual. In describing the evolution ofstudents' ideas in terms of a conceptual profile of matter, the obstacles to theconstruction of a scientific idea and the difficulties students face when trying toexplain some phenomena with their own ideas could be highlighted. However, if

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the analysis had had only this conceptual dimension, we could not say anythingabout the way the new ideas emerged in the classroom talk.

The analyses of the episodes demonstrated that the students resorted to threedifferent zones of a conceptual profile of matter in different parts of a teachingsequence, and showed the different kinds of discourse they used in building theirarguments. We might expect not to find an authoritative discourse when analysingthe students' talk. Nevertheless, the analysis of these episodes indicates that dis-course in the classroom can be authoritative or internally persuasive independentlyof being enunciated by the students or by the teacher. Both types of discourse werepresent in the students' dialogues. An alternation between these two types ofdiscourse seems to be an important feature of the classroom talk. The phenomenonof multivoicedness associated with this alternation enables an encounter betweentwo different voices in the classroom to take place: the scientific one, representedby the teacher's discourse, and the everyday voice, represented by the students'talk. When the students begin to share meaning with the teacher, we can observe ashift in their discourse as they begin to use the teacher's voice as their own dis-course.

The alternation between 'internally persuasive' and 'authoritative' discoursesseems to be part of the rhetorical design of the classroom talk. While the 'internallypersuasive' discourse allows alternative explanations and contradictory versions tobe considered through argumentation and justifications, the 'authoritative' dis-course stresses the shared knowledge already constructed. In rhetorical psychology(e.g. Billig 1987, Kuhn 1992), argumentation is not only a general feature of dis-course, but of thinking as well. In this sense, the alternation of 'internally pre-suasive' and 'authoritative' discourse in the intermental plane of the classroom isimportant for developing conceptual thinking in the intramental plane.

The development of ideas in the classroom seems to depend at least as muchon social constraints as on empirical results, discrepant events of crucial experi-ments. The same phenomena used to support the atomistic view can be interpretedby students, using a substancialist or continuous view of matter, as shown inEpisodes 1 and 2. The construction of knowledge in classrooms is, therefore, aguided process by which the teacher introduces students to the discourse of science(Mercer 1995), helping them to build new meanings that could not be acquiredonly through active participation in experimental activities and individual struggleto make sense of these experiments.

The data presented in this article suggest that a movement from multivoiced-ness to univocality characterizes the construction of meaning in science classrooms.A contradictory consequence of the 'social pressure' towards the univocal voice ofscientific knowledge in the classroom is that this kind of pressure can hide theepistemological and ontological obstacles that, despite being invisible, remainalive. They are hidden by the circumstances, but they are still alive. The obstaclesthat seemed to be overcome in classroom discussion, can reappear in group dis-cussion, where the social pressure to conform is less than in the whole class, or in atest, where the students are alone with their ideas.

The pressure towards univocality that characterizes the science classroom'sdiscourse suggests that knowledge is both constructed and transmitted in thissocial setting, as the limits of what can be 'constructed' are clearly established inthe curriculum, which frames the functions and forms that the discourse canassume. There seems to be no opposition or contradiction between transmission

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and construction of meanings in the classroom, as some constructivist approachesto science education have suggested. The teaching and learning process could bereferred to as a dialogue between scientific and everyday discourses where newmeanings are both constructed and transmitted.

The methodology of research presented in this article, articulating two dimen-sions — conceptual and discoursive — of science classrooms, provides a useful toolfor understanding the construction of scientific concepts in the classroom. Thealternation between internally persuasive and authoritative discourse is only oneamongst several rhetorical aspects of science classrooms that can be revealedthrough this type of research. The investigation of these aspects can provideresources for professional development of teachers which combines the designingof teaching strategies with rhetorical and reflexive tools.

Acknowledgements

This work was supported by grants from CNPq and CAPES (PADCT-SPEC).

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Appendix

Summary of the activities and lessons

(1) Classifying materials as solids, liquids and gases and identifying the criteria used inthe classification.

(2) Choosing, from the models presented in the pre-test and selected by the teacher,the best model to explain:2.1. Compression of air in a plugged syringe2.2. Dilation of air submitted to heating in a test tube with a balloon over its neck2.3. Vacuum in a flask connected to a large syringe2.4. Gas odour scattering in the kitchen as it escapes from its container

For each of these four phenomena three steps were planned (after the secondphenomenon, step 1 was omitted as it seemed to be redundant):

(a) Identification of the features of the model drawn by the students (class as awhole)

(b) Discussion in groups to choose the best model (groups of students)(c) Discussion with the whole class to choose the best model

(3) Summarizing the characteristics of a model for gases:3.1. How the model explains compression, dilation, vacuum and diffusion:(a) Group discussion(b) Class discussion3.2. Generalizing the model to explain temperature and pressure of gases

(teaching exposition and class discussion).

(4) Generalizing the atomistic model to liquids and gases by choosing, from the mod-els presented in the pre-test and selected by the teacher, the best one to explain:4.1. Dilatation, by means of heating with the hand, the alcohol (or mercury)

column of a thermometer4.2. Melting and vaporization of naphthalene heated in a test tube

For each of these two phenomena two steps were planned:(a) Discussion in groups to choose the best model (groups of students)(b) Discussion with the whole class to choose the best model

(5) Summarizing the atomistic model for solids, liquids and gases (group discussionfollowed by class discussion).

(6) Generalizing the atomistic model to new situations:6.1. Spontaneous dissolving of potassium manganate(VII) in water6.2. Dissolving of sugar and salt in water

For each of these two phenomena two steps were planned:(a) Discussion in groups to explain the phenomenon based on the atomistic

model(b) Discussion with the whole class to choose the best explanation

(7) Different conceptions of solids, liquids and gases:7.1. Analysing the criteria to classify solids, liquids and gases revealed in the first

activities, in the light of the new atomistic concept of solid, liquid and gas.How does the new concept explain the properties of solids, liquids and gasesidentified in the first activity?

7.2. Materials that 'resist' classification as solid, liquid or gas: glass, cloud, fog,etc. The conception of colloidal solution.For each of these two themes two steps were planned:

(a) Discussion in group to answer several questions related to the theme(b) Discussion with the whole class to choose the best answer to each question

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