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421 10 Teaching to Promote the Development of Scientific Knowledge and Reasoning About Light at the Elementary School Level Shirley J. Magnusson and Annemarie Sullivan Palincsar Children at play outside or with unfamiliar materials look as though they might be answering such questions as: What does this do? How does this work? What does this feel like? What can I do with it? Why did that happen? This natural curiosity and exploration of the world around them have led some people to refer to children as "natural" scientists. Certainly these are the very types of questions that scientists pursue. Yet children are not scien- tists. Curiosity about how the world works makes engaging children in sci- ence relatively easy, and their proclivity to observe and reason (see Chapter 1, Box 1-1) is a powerful tool that children bring to the science classroom. But there is a great deal of difference between the casual observation and reasoning children engage in and the more disciplined efforts of scientists. How do we help students develop scientific ideas and ways of know- ing?' Introducing children to the culture of science its types of reasoning, tools of observation and measurement, and standards of evidence, as well as the values and beliefs underlying the production of scientific knowledge—is a major instructional challenge. Yet our work and that of others suggest that children are able to take on these learning challenges successfully even in the earliest elementary grades.2

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422 HOW STUDENTS LEARN: SC ENCE N THE C ASSFOOM mE STUDY OF AGE Unlike madhematics, in which topics such as whole-number arithmetic are foundational for The study of rational nurnber, and bodh are foundational for The study of functions, There is currendy little agreement on The selection and sequencing of specific topics in science, particularly at the elementary levels What clearly is foundational for later science study, however, is learn- ing what it means to engage in scientific inquiry—learning The difference between casual and scientific investigations. That learning can be accom- plished in The context of many different specific topics. In dais chapter, we choose light as our topic of focus because it affords several benefits. The first is practical: The topic involves relatively simple concepts that children can undo stand from investigating widh relatively simple matenals. For example, our bodies and The sun make shadows dhat can be studied, and similar studies can occur with common flashlights and class- room materials Pencil and paper, and perhaps some means of measuring distance, are all that is needed for data collection. Children can also study light using simple light boxes (Elementary Science Study's Optics unit ) in which light bulbs are placed in cardboard boxes containing openings cov- ered widh construction paper masks that control The amount of light emanat- ing from The box. Thin slits in The masks make the dlin beams of light necessary for studies of redection and refraction. Multiple wider openings covered widh different colored cellophane filters enable investigations mix- ing colors of light. And again, pencil and paper are all that are needed for data collection showing The padhs of light. In addition, developing scientific knowledge of light challenges us to conceptualize aspects of The world that we do not directly experience—a critical element of much scientific study. For example, light travels, yet we do not see it do so; we infer its travel when we turn on a flashlight in The dark and see a lighted spot across the room, t)eveloping scientific knowledge often requires conceptual changes in which we come to view The physical world in new ways 6 Students must learn dhat things are not always what They seem—itself a major conceptual leap. The study of light gives children an accessible opportunity to see The world differently and to challenge their existing conceptions. We see the world around us because light redects from objects to our eyes, and yet we do not sense dhat what we see is The result of reflected light. Some children, moreover, view shadows as objects instead of under- standing dhat shadows are created when light is blocked. Conceptual devel- opment is required if they are to understand The relationship among a light source, an ob ect, and The shadow cast by that object. Working widh dash- lights can provide children an opportunity to challenge directly everyday conceptions about shadows, providing them with a powerful early expen-

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TEACH NG ABOUT SC ENCE AND L GHT N EEEMENTAFY GRADES 423 ence of scientific ways of knowing. Because casual observation of The be- havior of light can be misleading, but a relatively accessible investigation of light can be illuminating, the study of light demonstrates the contrast between casual observation and expenmentation. For all these reasons, Then, The study of light supports children's understanding dhat relationships in The physical world are not self-evident and that constructing scientific knowledge from observation of The world is different from their everyday reason ng. Three major instructional challenges parallel The principles of How People Learn as They apply to The study of light: (1) providing students widh oppor- tunities to develop deep conceptual understanding of targeted aspects of light, and of standards and norms in science for investigating and drawing conclusions (bodh about light and more generally); (2) supporting students in building or bridging from prior knowledge and experience to scientific concepts; and (3) encouraging children to engage in the kind of metacognitive questioning of Their own thinking dhat is requisite to scientific practice. Conceptual Understanding How People Learn suggests that learning for understanding requires the organization of knowledge around core concepts. Thus while light can be studied with tools dhat are easy to use and opportunities to observe the behavior of light abound, if The classroom activity described in This chapter were simply a set of experiences and observations, it would leave students widh little deep knowledge Experiencing many individual activities (e.g., seeing dhat light reflects from wood as well as mirrors) does not ensure dhat students understand The overarching concepts about light outlined below that allow Them to predict how light will behave in a wide variety of circum- stances. As a result, a major focus in This chapter is on The role of The teacher in guiding students' observations, reasoning, and understanding so dhat core concepts are grasped. What conceptual understandings do we consider to be core? As sug- gested above, grasping the differences between everyday observations and reasoning and those of science is not only core in our approach to teaching about light, but also paramount in providing a foundation for further science study. Salient concepts include The following: . Standards of The scientific community for understanding and commu- nicating ideas and explanations about how The world works are different from everyday standards. Science requires careful observations dhat are re- corded accurately and precisely, and organized so dhat patterns can be ob- served in the data. · Patterns in observations are stated as knowledge claims.

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424 HOW STUDENTS LEARN: SC ENCE N THE C ASSFOOM · Claims are judged on the quality of the evidence supporting or disconf~rming them. · Hypotheses take on the status of claims only after they have been tested. · Claims are subject to challenge and not considered new sciellTiflc knowledge until the scientific community accepts them. These understandings are foundational for all future study of science. There are also core concepts regarding the topic of light that we want students to master. These will vary somewhat, however, according to the grade level and the amount of time that will be devoted to the topic. These concepts include the following: . All objects (expenenced in our everyday lives) reflea and absorb light, and some objects also transmit light. - Dark or black objects mainly absorb light; light or white objects mainly reflect light. - There is an inverse relationship between light reflected Tom and absorbed by an object: more reflected light means less absorbed light. · Light reflects from objects in a particular way: the angle of incoming light equals the angle of reflected light. · What we see is light reflected from objects. - There must be a source of light for us to see an object. - Sources of illumination can produce light (e.g., the sun) or reflect light (e.g., the moon). · When an object blocks a source of light, a shadow is formed. Shad- ows are dark because there is no light reaching them to be reflected to our eyes. The distance of an object from a source of light it blocks detemmines the size of the object's shadow. The shape of an object's shadow depends on the angle of the object to the light, so the shadow of an object may have more than one shape. . The color of an object is the color of light reflected from the object. - The colors of light come from white light, which can be separated into many colors. - The color of an object depends on the extent to which particular colors of light in white light are reflected and absorbed. Other concepts such as the nature of light as both a wave and a par- ticle—are beyond what elementary students need to understand. But teach- ers need to know these core concepts to deal effectively with questions that may arise, as we discuss later in this chapter

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TEACH NG ABOUT SC ENCE AND L GHT N EEEMENTAFY GRADES 425 Prior Knowledge Students bring many prior conceptions about light to The classroom. Some of These are influenced relatively easily. For example, some students believe a shadow is an object, but This conception is not deeply held, and simple experiments with light can provide convincing evidence to The con- trary. Other scientifically inaccurate conceptions are not so easily changed by simple expenments. A very common belief is dhat light reflects only from shiny objects, such as a mirror or shiny metals. This is hardly surpnsing; reflections from shiny objects are strikingly obvious, while observing reflection from objects widh no apparent shine requires a tool (e.g., a simple device such as a piece of paper strategically placed to show redected light, or a more sophisticated device such as an electronic meter dhat measures light energy). In fact, The nature of light has puzzled scientists for centunes.7 Part of The challenge to our understanding is that the behaviors and effects of light are not easily determined by our senses. Light travels too fast for us to see it traveling, and our observation of light that has traveled great distances, such as light fi om The sun and odher stars, provides no direct evidence of The time it has taken to reach us. Scientists have determined dhat light exerts pressure, but this is not something we can feel. We see because light is reflected to our eyes, but we have no way of experiencing dhat dilectly. We commonly Think of color as an intrinsic characteristic of an object because we do not experience what actually occurs: dhat The color we see is the color of light reflected from the object. Furthermore, grasping This notion requires understanding that white light is made up of colors of light Slat are differentially absorbed and re- flected by objects. If none are reflected, we see black, and if all are reflected, we see white, and This is counter to our experience with colored pigments that make a dark color when mixed togedher Finally, perhaps The strongest testimony to The complex nature of light is The fact that scientists use two very different models to characterize light: a particle and a wave. Because daily experience reinforces ideas that may be quite different from scientific understanding, fostering conceptual change requires supporting students in paying close attention to how they reason from what They ob- serve. For this reason, The approach to teaching we suggest in this chapter provides students with a great many opportunities to make and test knowl- edge claims, and to examine The adequacy of Their own and adhere reason- ing in doing so. Once again, however, The role of the teacher is critical. As we will see, The prior conceptions widh which students work may lead Them to simply not notice, quickly dismiss, or not believe what They do not expect to see.

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426 HOW STUDENTS LEARN: SC ENCE N THE C ASSFOOM Recognition Young children, and indeed many adults, assume that things are as they appear, and no further questioning is required. That light redects off objects only if they are shiny may appear to be true and in no need of further questioning. Science, however, is about questioning—even when somedhing seems obvious because explanation is at the heart of scientific activity. Thus The search for an explanation for why shiny objects redect light must include an answer to The question of why nonshiny objects do not. Such a search, of course, would lead to evidence refuting The notion that only shiny objects redect light Engaging children in science, Then, means engaging Them in a whole new approach to questioning. Indeed, it means asking Them to question in ways most of us do not in daily life. It means question- ing The typical assurance we feel from evidence dhat confirms our prior beliefs, and asking in what ways The evidence is incomplete and may be countered by additional evidence. To develop thinking in this way is a major instructional challenge for science teaching. THE STUDY OF LIGHT THROUGH INQUIRY Widh the above principles in mind, we turn now to The learning of science Through investigative activity in The classroom, or inquiry-based in- struction.8 Investigations in which students directly observe phenomena, we believe, serve several critical functions. First, when students experiment with light and observe phenomena they do not expect, These discrepant experi- ences can directly challenge Their inaccurate or partially developed concep- tions. Students will need many opportunities to observe and discuss The behavior of light that behaves in unexpected ways if They are to develop scientific conceptions of light. Inquiry dhat is designed to occur over weeks and allows students to work widh many different materials can provide dhat experience. The opportunity for repeated cycles of investigation allows stu- dents to ask the same questions in new contexts and new questions in increasingly understood contexts as they work to bring Their understanding of The world in line widh what scientists Think Equally important, participa- tion in well-designed guided-inquiry instruction provides students with a first-hand experience of the nomms of conducting scientific investigation. But inquiry is a time- and resource-intensive activity, and student inves- tigations do not always lead to observations and experiences That support The targeted knowledge. Therefore, we combine first-hand investigations with second-hand investigations in which students work with The notebook of a fictitious scientist to see where her inquiry, supported by more sophis- ticated tools, led. This second-hand inquiry provides a common investiga- tive experience that allows The teacher to direct attention to steps in The

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TEACH NG ABOUT SC ENCE AND L GHT N EEEMENTAFY GRADES 427 reasoning process pursued by the scientist that led to the development of core concepts. Moreover, it allows students to see that while scientists en- gage in a similar type of inquiry, more sophisticated tools, more control over conditions, and larger sample sizes are critical to drawing conclusions that can be generalized with some confidence. A Heuristic for Teaching and Learning Science Through Guided Inquiry To aid our discussion of the unfolding of instruction, we present a heu- nstic—a thinking tool—to support planning, enacting, and evaluating guided- inquiry instruction with elementary school teachers.9 This heuristic (see Fig- ure 10-1'°), which shares many features with other researched-based approaches to teaching elementary science through investigation," repre- sents instruction in terms of cycles with phases. The words in all capital letters in Figure 10-1 indicate the phases, and the lines with arrows show the progression from one phase to the next. Reposing is a key phase in this conception of instruction; it is the occasion when groups of students report the results of their investigations to their classmates. Students are expected to report on knowledge claims they feel cone dent in making and providing evidence for those claims from the data they collected during investigation, This expectation lends accountability to students' investigative activity that is often absent when they are simply expected to observe phenomena, To make a claim, students will need precise and accurate data, and to have a _;~ / m/atipmship / / axptanatipms 9! ~ Iheor es) ENGAGE PREPARE to q~estbn I NV ANTI GATE m thodi~J ted mmbr~ t 9 Magnussttn ZOO 1 REPORTING CisssnKtm + Small Getup Community Public Shanng ~ Fvdudlon \ Maims and \e thence thmntes, \ Pn~ddipms, \ osmium ms I PREPARE to REPORT _ INVESTIGATE ~ obmwv ton mad Em mmmtbton FIGURE 1 0 1 A cycle of inveshgahon in guided inqui y science t

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428 HOW STUDENTS LEARN: SC ENCE N THE C ASSFOOM claim that is meaningful to the class, they will need to understand the rela- tionship between the question that prompted investigation and the way in which their investigation has enabled them to come up with an answer Multiple lines leading from one phase to another indicate the two basic emphases of investigative activity in science: generating knowledge that describes how the world works (outer loop), and generating and testing theories to explain those relationships (inner loop). The reporting phase always marks the end of a cycle of inquiry, at which point a decision is made about whether to engage in another cycle with the same question and inves- tigative context, or to re-engage with a novel investigative context or a new question. Cycles focused on developing knowledge claims about empirical relationships generally precede cycles in the same topic area focused on developing explanations for those relationships. Thinking and discussing explanations may occur in other cycles, but the focus of the cycle repre- sented by the inner loop is on testing explanations. Each phase in the heuristic presents different learning opportunities and teaching challenges Each also provides opportunities to focus on ideas de- scnbing the physical world (concepts and theories or content) as well as the means by which we systematically explore the nature of the physical world (methods and reasoning or process). Each phase requires different types of thinking and activity on the part of the students and the teacher; hence, each has a unique role to play in supporting the development of scientific knowledge and ways of knowing, The following illustrations of teacher and student activity in each phase of instruction are drawn from our work in elementary school classrooms.' The Engage Phase Descriptions Each unit of study begins with an engagement phase, which onents thinking and learning in a particular direction. In the elementary classroom, a version of the classic KWL (i.e., what do I Know, what do I Want to learn, what have I Learned) can be a fine way to initiate engage- ment. In contrast to the typical use of KWL in the language arts, however, to maximize the value of having students identify what they know, teachers should invite students to identify how they have come to know the topic area doing so can develop students' awareness that "knowing" can mean different things Does their knowledge anse from something they actually observed? If so, where and when did that occur, and under what circum- stances? Or did others observe it and report it to them? If so, how confident were they in what was reported and why? If a student reports knowledge from something written in a book, what other information was provided? Were any data provided to substantiate the claim ? How extensive was the information provided regarding what the student reports knowing? This dis-

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TEACH NG ABOUT SC ENCE AND L GHT N EEEMENTAFY GRADES 429 cussion can provide the grist for later camper sons of ways of knowing in everyday life versus in science, history, or the language arts. It also affords teachers an opportunity to draw out and learn about students' prior knowl- edge, metacognitive awareness, and reasoning abilities. For example, in a class beginning to investigate how light interacts with matter, one student stated that he already knew the answer because he knew that objects were opaque, transparent, or translucent. This statement indicated to the teacher that the student might assume light interacts with an object in only one way, which could limit what he observed. Knowing of this possibility, the teacher would want to monitor for it, and possibly raise questions about the thor- oughness of students' observations. The scientific community defines for itself what knowing in particular ways means. For example, in each discipline (e.g., physics, chemistry, biol- ogy), the community defines what are acceptable methods for data collec- tion and what constitutes precise and accurate observation. The community also dictates what constitutes a valuable contribution to the knowledge base. The relative value of a contribution is a function of the extent to which it extends, refines, or challenges particular theories of how the world works. In our everyday world, we do not have a community detemmining the valid- ity of our thinking or expenences. Thus, the initial conversation when be- ginning a new area of study provides an important opportunity for the teacher to ascertain children's awareness of the roots of their knowledge, as well as the expectations of the scientific community. For example, when students describe knowing something about the physical world but indicate that their knowledge did not arise from observation or direct expenence, the teacher might ask them to think about what they have observed that might be the kind of evidence scientists would expect to have. When students do provide evidence, the teacher might ask them questions about that evidence such as those above, reflecting the norm that systematic study under controlled con- ditions is a hallmark of the practice of science, and that evidence not ob- tained under those conditions would lead scientific thinkers to be skeptical about the knowledge claim. The next step in engagement is to begin to focus the conversation about the topic of study in ways that are likely to support the learning goals. For example, showing students the kinds of materials and equipment available for investigating can lead to a productive conversation about phenomena they can explore. Focusing on ideas that were generated during the KWL activity, the children can be encouraged to suggest ways they might investi- gate to determine whether those ideas are scientifically accurate (meaning that the claims can be backed by evidence from investigation). Students can also be encouraged to identify what cannot easily be studied within the classroom (because of the nature of the phenomenon or a lack of resources or time) and might be better studied in a second-hand way (i.e., through

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430 HOW STUDENTS LEARN: SC ENCE N THE C ASSFOOM reading or hearing about what others have studied and concluded from first- hand investigation). For example, we observed a group of third graders studying light who had numerous questions about black holes, the speed of light, and light sources on different planets, all of which they decided were best pursued through second-hand investigation At the end of engagement, the students should have a sense of a general question they are trying to answer (e.g., How does light interact with mat- ter7), and should have identified a particular question or questions to be the focus of the first cycle of investigation. To this end, a teacher might (1) focus the class on a particular phenomenon to study and have them suggest spe- cific questions, (2) draw upon conflicting ideas that were identified in the KWL activity and have the class frame a question for study that can infomm the conflict, or (3) draw on a question that was identified during the discus- sion that is a profitable beginning for investigation, ilustratiOrL What does this kind of beginning look like in a classroom? In a kindergarten classroom,'3 after a brief opportunity for the children to state what they thought they knew about light and how it behaved, the teacher, Ms. Kingsley, ar anged for pairs of students to take turns using flashlights in an area of the classroom that had been darkened. This activity provided children an opportunity to become familiar with investigative materials and phenomena that Ms. Kingsley knew would be the focus of later investiga- tion. The children responded to this activity in a variety of ways, from ini- tially becoming focused on finding spiders to dwelling later on the effects they could create with flashlights. For example, one student commented on the colors she saw as she shone the flashlight on the wall in the darkened area: "There's color When it shines on a color, then it's the color, green, or white, or red, or black. And then you put the light on the ceiling, it's gone." In the following interaction, the children "discover" reflection: IAnisha walks forward under the loft, holding the flashlight with her left hand at an angle to the mi rror that she holds flat in front of her I Oh Deanna, look, I can bounce the light. [Deanna holds the mirror so light is bouncing directly behind her I Deanna Excitedly If you look back, maybe you can see the light. A third student focused on what he saw while holding ob ects in the beam of light. The following interchange occurred when the students explored with large cardboard cutouts of letters of the alphabet.

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TEACH NG ABOUT SC ENCE AND L GHT N EEEMENTAFY GRADES 431 Jeremy Hazel Working with a letterl Ooo. this makes a shadow. A different shadow Ithan the one he just sawl. IHe picks up the letter G and hands it to his partner I See if the G makes a shadow. It does make a shadow. See, look at th is. When the children described their observations to the class, Ms. Kingsley was able to use those observations to elicit the children's current ideas about light and shadows and how they might investigate those ideas. In a fourth-grade classroom,'4 the teacher, Ms. Lacey, introduced her students to the study of light by asking them what they wondered about light. The children identified over 100 "wondenngs," including questions about how we see, why we see rainbows of color from some glass objects or jewelry, what makes light from the plastic sticks you bend to make them "glow" in the dark, what are black holes, and how fast is the speed of light. The next day, students were given a written assessment about light, pre- sented as an opportunity for them to identify their current thinking about the nature and behavior of light. After reviewing students' responses, Ms. Lacey wrote statements on the board (see Table 10-1) indicating the vanety of ideas the class held about light. The variation in views of light exhibited by the students provided a reason to investigate to determine the accuracy of the ideas and the relationships among them. TABLE 10-1 Fourth Graders' Initial Ideas About Light Light travels. Light travels in a curved path. Light travels in a straight line. Light travels in all directions. Light can be blocked by materials. Light can shine through materials. Light can go into materials. Light can bounce off of materials. Later in the unit on light, Ms. Lacey turned to other wonderings the students had about color and light. In the following excerpt, she ascertains whether students' questions came from what they had been told, read, or observed, and she prompted one student to hypothesize about color from what had previously been learned about the behavior of light. Ms. Lacey I know you guys had a few questions about color, so I'm wondering what you know or would like to know about colors What is it you think you want to learnt Levon7 When I said that my shirt's a light blue, you said how do we know its And you said we might be able to tell. Levon

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464 HO W STUDENTS LEARN: SC ENCE N THE C ASSFOOM Derek Yes, because some were really see-th rough and reflection together, but we had to decide which one to put it in. Ms. Lacey Do you think you might have another claim here7 Light can do two things with one object. Kevin Widh The introduction of the idea that light can interact with matter in more than one way, the students embarked upon a second cycle of investi- gation widh The same matenals, with The intent of determining which if any objects exhibited The behavior claimed by Kevin and Derek. From this sec- ond round of investigation, all groups determined That multiple behaviors can occur with some objects, but the e was uncertainty about whedher These interactions occur with some types of materials and not odhers (see Figure 10-5). Nevertheless, the significance of tills day's findings is That they repre- sent a different conceptual organization from That of The first cycle (see Figure 10-4) to the extent that light is not confined to behaving in only one way. At The same time, The possibilities for The behavior of light have in- creased significantly, and only The case of four types of interaction has been ruled out in discussion by the community (following interaction comparing what different groups meant by "blocked" versus "absorbed"). LIGHT ~— E~3 INTERACTa WITH — E~E~a MATERIALa ~ Evil l `~ | block=A | FIGURE 105 Community knowledge from ibe second c cle of inveshgcfion thrsfhondl. R = refle i; T = ironsmii; A = absorb.

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TEACH NG ABOUT SC ENCE AND L GHT N EEEMENTAFY GRADES 465 in addition, some students expressed puzzlement about how light could interact with a material in more than one way. In response to this question, one group introduced the idea that there was a quantitative relationship among the multiple behaviors observed when light interacted with an object: Miles Co rey Co rey If you said that light can reflect, transmit, and absorb, absorb means to block. How can it be blocked . . . and still go th roughs If just a little bit came th rough, then most of it was blocked. Ms. Lacey Would you draw him a picture, p at se ? I Corey and Andy draw setup.l Here's the light, a little being blocked inside, and a little of it comes out . . Some of it's reflecting. An dy Turing the third cycle of investigation, in which the students and the teacher interactively read a Lesley Park notebook text about light using re- ciprocal teaching strategies, :4 the students encountered more evidence that light can interact with matter in multiple ways (see Figure 10-6). This led to conversation concerning how general a claim might be made about the behavior of light: An dy Tommy An dy Can all objects reflect, absorb, and transmits Tommy7 Most of them. Co rey7 LIGHT ~ INTERACTS WITH _ ceil tAAnERIAL5 i_ —33 FIGURE 10~ Community knowledge from ibe third c cle of inveshgahon Isecond hondl

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466 HO W STUDENTS LEARN: SC ENCE N THE C ASSFOOM Co rey Alan Yes, because it says right in here, "Light can be reflected, absorbed and transmitted by the same object." Ms. Lacey I think we need to clarify something, because you said one thing, Corey, and Miles said something else. Andy's question was "Can all objects reflect, absorb, and transmit lights" No. It just says light can be reflected, ab- sorbed, and transmitted by the same object. It doesn't say anything about every object. Ms. Lacey So you say not all can. Do we have any data in our reading that tells us that not all things absorb, reflect, and transmits Tommy We have evidence that all objects reflect and absorb I referring to a table in the notebook textl. The concept map representing the community's understanding about light up to this point shows greater specification of the prevalence of rela- tionships ("always" versus "sometimes") and a narrowing of the possible relationships that can occur when light interacts with matter: light always reflects and is absorbed. Lesley's quantitative data about the amount of reflection and transmis- sion of light from an object as measured by a light meter supported addi- tional conversation about the issue of quantitative relationships raised by one group in the previous cycle. However, students did not yet add those ideas to their class claims chart. In the fourth cycle of investigation, students returned to a first-hand investigation and were now quite comfortable with the idea that light can simultaneously interact with matter in multiple ways. In addition, despite not having tools to compare the brightness of the light, they qualitatively compared the amount of light behaving in particular ways. This is repre- sented in the map in Figure 10-7. t)o all students have the understanding represented in Figure 10-7? The excerpt below suggests that this is unlikely. In this excerpt, a student reveals that he and his partner did not think light would reflect from an object even after the class had established in the previous cycle that light always reflects: Kenny Ms. Lacey When you saw the blue felt, is that the claim you first thoughts Yeah, we learned that this blue felt can do three—reflect, transmit, and absorb—at one, at this one object. And it did. It reflected a little, and transmitted some and it absorbed some.

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TEACH NG ABOUT SC ENCE AND L GHT N EEEMENTAFY GRADES 467 / 3 LIGHT ~ if a lot R. lltile A INTERACTS WITH Em_ 2 THINGS _~ MATERIALS ~ —~ if a lot A, little R if a lot R. \ If a lot T. llille RtA FIGURE 1 07 Community knowledge from he fourth c cle of inveshgahon thrsthond} Kenny Ms. Lacey And when you started out, what did you think was going to happens That it was only going to transmit and absorb. We didn't think it would reflect. Ms. Lacey What do we know about materials and reflect- ing7 They always reflect and absorb. Class We see the teacher checking on the student's understanding, which is scientif cally accurate. But we know that for such a clarm—that light reflects off all materials—many experiences may be needed for that knowledge to be robust Relationships such as this for which we have no direa experience or that are countenntuitive (we see reflected light from objects, not the objects themselves) take time and attention, as well as recursive tacking to knowledge-building processes and the conceptual framework that is emerg- ing from those processes. Conceptual frameworks that represent the physi- cal world in ways we have not experienced (e.g., the electromagnetic spec- trum) or are counterintuitive (light is a particle and a wave) pose even greater challenges to the development of scientific knowledge. THE ROLE OF SUBJfECT-SPEC~FIC KNOWLEDGE IN EFFECTWE SCIENCE INSTRUCTION At the core of teacher decision making featured in this chapter is the need to mediate the learning of individual students. To do this in a way that leads to targeted scientific knowledge and ways of knowing, teachers must be confident about their knowledge of the learning goals. That is, teachers

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468 HO W STUDENTS LEARN: SC ENCE N THE C ASSFOOM must have sufficient subject matter knowledge, including aspects of the cul- ture of science that guide knowledge production, to fully understand the nature of the learning goals. When students say that light "disappears" into paper but reflects off of mirrors, a teacher's uncertainty about whether that claim is accurate will hamper effective decision making. When students claim an object is opaque and the question at hand is how light interacts with matter, the teacher needs to recognize that the word "opaque" describes the object and not light, and that an opaque object can reflect and absorb light and even transmit some light in certain cases (e.g., a piece of cardboard). At the same time, having accurate subject matter knowledge is not suf- ficient for effective teaching. When students claim that light is a gas, it is not sufficient for the teacher to know that light is energy, not a state of matter The teacher also needs to know what observations of light might convince students that it is not a gas, which in turn is informed by knowing how students think of gases, what their experiences of gas and light have likely been, and what it is possible to observe within a classroom context. This knowledge is part of specialized knowledge for teaching called pedagogical content knowledge because it is derived from content knowledge that is specifically employed to facilitate learning. It is the knowledge that teachers have about how to make particular subject matter comprehensible to par- ticular students 4s Pedagogical content knowledge includes knowledge of the concepts that students find most difficult, as well as ways to support their understand- ing of those concepts. For example, it is difficult for students to understand that the color of objects is the color of light reflected from them because we are not aware of the reflection. Having students use a white screen to exam- ine the color of light reflected from colored objects can reveal this phenom- enon in a way that is convincing to them Pedagogical content knowledge also includes knowledge of curriculum materials that are particularly effec- tive for teaching particular topics. A still valuable resource for the study of light in the elementary grades is the Optics kit mentioned earlier that is part of Elementary Science Study curriculum materials developed in the 1960s. A teacher's knowledge of these materials and how they can be used to support knowledge building is key to employing them effectively in mediating stu- dent learning, Finally, pedagogical content knowledge includes ways to assess student knowledge. A classic item to determine students' understanding of how we see is a diagram with the sun, a tree, and a person looking at the tree.4 Students are asked to draw lines with arrows in the diagram to show how the person sees the tree. Arrows should be drawn from the sun to the tree to the person, but it is not uncommon for students to draw arrows from the sun to the person and the person to the tree. Use of this item at the beginning of a unit of study can provide a teacher with a wealth of information on current

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TEACH NG ABOUT SC ENCE AND L GHT N EEEMENTAFY GRADES 469 student thinking about how we see, as well as stimulate students to wonder about such questions. The more teachers know and understand about how their students think about particular concepts or topics of study, how that thinking might de- velop and unfold during systematic study of the topic, and how they might ascertain what students' understanding of the topic is at any point in time, the better they are able to optimize knowledge building from students' var- ied experiences and support students in developing desired scientific knowl- edge and ways of knowing. When and how to employ particular strategies in the service of supporting such knowledge building is a different issue, but the topic-specific knowledge for teaching that is identified as pedagogical content knowledge is a necessary element if students are to achieve the standards we have set. CONCLUSION Science instruction provides a rich context for applying what we know about how people team. A successful teacher in this context is aware that he or she is supporting students in activating prior knowledge and in building upon and continuing to organize this knowledge so it can be used flexibly to make sense of and appreciate the world around them. To do this well, the teacher must be knowledgeable about the nature of science, including both the products the powerful ideas of science—and the values, beliefs, and practices of the scientific community that guide the generation and evalua- tion of these powerful ideas. Fur he neon e, teachers must be knowledgeable about children and the processes of engaging them in knowledge building, reflecting upon their thinking and learning new ways of thinking. We have proposed and illustrated a heuristic for conceptualizing in- struction relative to the opportunities and challenges of different aspects of inquiry-based instruction, which we have found useful in supporting teach- ers in effective decision making and evaluation of instruction. We have ar- gued that the development of scientific knowledge and reasoning can be supported through both first- and second-hand investigations. Furthermore, we have proposed that the teacher draws upon a broad repertoire of prac- tices for the purposes of establishing and maintaining the classroom as a learning community, and assessing, supporting, and extending the knowl- edge building of each member of that community. All of these elements are necessary for effective teaching in the twenty-first century, when our stan- dards for learning are not just about the application of scientific knowledge, but also its evaluation and generation.

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470 HOW STUDENTS LEARN: SC ENCE N THE C ASSFOOM NOTES 1. Schwab, 1964. 2. Hapgood et al., in press; Leh¢r et al., 2001; Magmusson et al., 1997; Metz, 2004. 3. National Research Counci, 2003. 4. These materials, onginally developed in the 1960s, can be purchased from Delta Education: http://www. delta-education. com/. Whereas some view conceptual change as referring to a change from existing ideas to new ones, we suggest that new ideas are often developed in parallel with existing ones. The new ideas am rooted in different va ues and beliefs those of the scientific community rather than those guidmg our dai y lives. Chi, 1992. Gall i and Hazan, 2000. Our decision to focus on irst Action in which investigation is central ref ects the national standard that Cal s for science irst Action to be inqui y based. 9. We use the temm "guided" inquiry to sigmal that the teacher plays a prominent role in shaping the inqui y expenence, guiding student thinking and activity to enable desired student learning from investigation. 10. Magmusson and Palincsar, 1995. 11. Bames, 1976; Bybee et a ., 1989; Karplus, 1964; Osborne and Freyberg, 1985; Lehrer and Schauble, 2000. 12. A of the lost Action featured in this chapter was conducted by teachers who we¢ a part of GlsML Community of Practice. a mu uyear professional devel- opment effort aimed at identifying effective practice for inquiry-based science teaching. 13. This discussion draws on a study focused on children's self-regulation during science lost Action, which took place in a school in a relatively small distdct (about 4,600 students) that includes a state university. Approximately 45 per- cent of the students in this district pass the state standardized tests, and 52 percent are economically disadvantaged. 14. This class is in a school in a relatively small district (about 3,000 students) near a major industdal plant in a town with a state university. Approximately 38 percent of the students in this district pass the state standardized tests, and 63 percent are economically disadvantaged. 15. Whi e we are featuring contexts in which there is a sing e question, teachers could choose to have a context in which children am investigating different questions related to the same phenomenon. However, it is impo tant to ecog- nize the substantially greater cognitive and procedural demands this app oach places on the teacher, so it is not something we recommend if a teacher is inexperienced in conducting inqui y-based irst Action. 16. A though it can be motivating and conceptually beneficial for students to be placed in the mle of generating questions for investigation, the teacher needs to be mindful of the consequences of taking time to investigate questions that may be trivial or peripheral to the unity of study. The teacher may judge the time to be useful as students can sti l learn a gnat deal about investigation, but

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TEACH NG ABOUT SC ENCE AND L GHT N EEEMENTAFY GRADES 471 the teacher also may seek to ¢shape the question so it is not so conceptually distant as to sidetrack the focus relative to the desired content Boa s. 17. Hapgood et al., in puss; Lehrer et a ., 2001; Metz, 2004. 18. This person monitors the time the group is taking for the investigation to support the students in examining how efficient y they are working and decid- ing whether it is necessary to adjust the tempo of their activity to finish m the allotted time. 19. It is very reasonable for the teacher to d scuss these issues with the whole class dunng the preparing to mvestigate phase and to invite the class to specify procedures. . ~ddnessing these matters with the whole c ass gives the teacher opportunities to model thinkmg for the benefit of all. However, whi e this is enabling for students when they are quite new to investigating, it constrains students' development of the knowledge and skills needed to make these decisions independent y. Thus it is important for the teacher to give students an opportunity to make these types of decisions on their own during some investigations. 20. Herrenkoh et al., 1999. 21. The students inadvertent y interpreted the idea of categorizing to mean that light would behave in on y one way with each object. This led many students to stop observing an object as soon as they had identified one way light be- haved with it. 22. In both cases, the fact that we can see the object tel s us that light is ref ected. However, students had not yet established that relationship, so we Refer hem on y to the direct evidence of light. 23. Blumenfeld and Meece, 1988. 24. Magmusson et al., in press. 25. This class is in a moderately sized distdct (about 16,700) students) in a town with a major university. Approximately 70 percent of the students m this dis- tdct pass the state standardized tests, and 16 percent are economically disad- v mtaged. 26. Blown and Campione, 1994; Palincsar et al., 1993. 27. Campanario, 2002. 28. Osborne, 1983. 29. Magmusson et al., 1997. 30. C ement, 1993 31. We observed a group of children in a fou th-grade class working very ha d to determine if black felt ref ects light. They piled their matena s in the bathroom m the classroom, taped around the door to block out any light, and studied the black felt. They were quite proud to Report their evidence that it did indeed reflect light 32 Chi. 1992 33 Mouthed. 1995 34. Driver et al., 1994. 35. National Research Council, 1996. 36. Crawford et a., 1996. 37. Magmusson and Pa incur, m pness-b.

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472 HOW STUDENTS LEARN: SC ENCE N THE C ASSFOOM 38. See Magnusson and Palincsar (in press-a) for discussion of the theory and principles underlying the development of these texts; Pa incsar and Magmusson (2001), for a more complete description of Lesleys notebook and of research investigating the use of these notebook texts; and Magnusson and Pa incsar (in press-b) for a discussion of teaching from these notebook tests. 39. K ahr et al., 2001. 40. Magmusson et al., in press; Palincsar et al., 2001. 41. Newmann et a ., 1995. 42. Einstein, 1950. 43. Ford, 1999. 44. Pa inapt and Blown, 1984. 45. Magmusson et al., 1999; Wi son et al., 1988. 46. Eaton et al., 1984. REFERENCES Barnes, D. (1976). From communication to curriculum Hammondswo th, UK Pen- guin Books. Blumenfeld, P. C., and Meece, J.L. (1988). Task factors, teacher behavior, and stu- dents' involvement and use of learning strategies in science. Elementary 5< hool Journal, 88(3), 235-250. Brown, A.L., and Campione, J.C. (1994). Guided discovery in a community of leam- ers. In K. McCii Iy (Ed.), Classrooms lessons integrating cognitive theory and classroom practice (pp. 229-272). Cambndge, MA: MIT P¢ss. Bybee, R. W., Buchwald, C E., Cnssman, s., Hell, D R., Kuerbis, PJ., Matsumoto, C., and Mclnerney, J.D. (1989). Science and technology education for the elemen- tary years Frameuorksfor curriculum and instruction. Washington, DC: Na- tional Center for improving Science Education. Camp ma-do, J.M. (2002). The parallelism between scientists' and students' resistance to new scien~ifrc ideas. InternationalJournal of ScienceEducation, 24 10), 1095- 1110. Chi, M.TH. (1992). Conceptual change within and ac 055 ontological categories: Examples f om learning and discovery in science. In R Giere (Ed.), Cognitive models of science Minnesota studies in the philosophy of science (pp. 129 186). Minneapolis, MN: University of Minnesota P¢ss. Clement, J. (1993). Using bridging analogies and anchonng intuitions to deal with students' preconceptions in physics. Journal of Research in Science Teaching, 30, 1241-1257. C awfo d, s Y., Hu d, J.M., and Weller, A.C. (1996). From print to electronic The transformation of scientific communication. Medford, NJ: Infommation Today. Dnver, R. Asoko, H., Leach, J., Alortimer, E, and Scott, P. (1994). Const Acting scien- tific knowledge in the c asstoom. Educational Researcher, 23 7), 5-12. Eaton, J.F, Anderson, C.W., and Smith, E L. (1984). Students' misconceptions inter- fe¢ with science learning: Case studies of fifth-g ade students. Elementary Sckoo/ Journal, 84, 365-379. Einstein, A. (1950). Out of my lateryears. New York Phi osophical Library.

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