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Organizing Science Education Around Core Concepts

In order to develop a deep understanding of scientific explanations of the natural world, students need sustained opportunities to work with and build on the concepts that support these explanations and to understand the connections between concepts. Yet many science curricula consist of disconnected topics, with each given equal priority. Too little attention is paid to how students’ understanding of a concept can be built on from grade to grade. While students are continually introduced to new concepts, unless those concepts connect to other related ideas, they will not build conceptual understanding in a meaningful way.

Research strongly suggests that a more effective approach to science learning and teaching is to teach and build on core concepts of science over a period of years rather than weeks or months. These core concepts offer an organizational structure for the learning of new facts, practices, and explanations, and they prepare students for deeper levels of scientific investigation and understanding in high school, college, and beyond.

Other ways have been proposed to organize science curriculum and instruction over extended periods of time, and it is important to distinguish between these other proposals and the teaching and building of core concepts. For example, the American Association for the Advancement of Science has proposed a set of themes—constancy and change, models, systems, and scale—that would extend across science curricula. These themes are much broader in scope than the core ideas, and they are not clearly rooted in science. The core concepts are science ideas that have been well tested and validated and are central to the disciplines. Examples of core concepts in science are the atomic-molecular theory of matter, evolutionary theory, cell theory, and Newtonian laws of force and motion—all of which are considered foundational ideas in science. Each integrates many different findings and is the source of coherence for many key



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concepts, principles, and even other theories in the discipline. Each guides new research and can be understood in progressively more complicated ways. Each enables creative links to be made between disciplines. For example, atomic- molecular analyses are important in physics, chemistry, biology, and geology. Biologists work with DNA molecules to understand patterns in genetic code and unravel the interrelations of species. Chemists seek to articulate the laws that govern interactions between molecules that result in newly formed or broken chemical bonds. And Examples of Core Science Concepts teams of multidisciplinary experts—including • Atomic-molecular theory of matter chemists and biologists—draw heavily on molecu- lar science to develop drugs that attack unhealthy • Evolutionary theory molecules (or cells) and leave others undisturbed. • Cell theory The proposed use of core concepts and learning progressions still requires significant • Newtonian laws of force and motion additional research and development on the part of science educators, scientists, and education researchers. The science education community will need to identify core ideas, and specific learning progressions will need to be developed and tested exten- sively in classrooms. Here we define learning progressions and offer an example of how learning progressions might be structured over the course of the K-8 school years. This is a dramatic departure from current classroom practice. Many educators and school systems are not in a position to pursue an immediate wholesale change to their science curricula. Accordingly, later in the chapter we reflect on the incremental steps that can be made right away at the classroom and the school levels. Building on Core Concepts Over Time Organizing science education around core concepts that provide a specific context for learning is a significant departure from typical classroom practice. Science edu- cators must work cooperatively to define long-term goals for students that take into account the reality that students need opportunities to learn over multiple years to deepen their understanding of scientific concepts. Much thought will need to be given to how specific experiences along the K-8 grade span will accu- mulate and contribute to student learning and how to provide the kinds of sup- port that teachers will need to accomplish this. 60 Ready, Set, SCIENCE!

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The core concepts used in this practice would be dramatically fewer in number than those currently focused on or included in standards and cur- riculum documents. This would allow teachers and teacher educators to focus on building and deepening their own knowledge of a smaller number of criti- cal science concepts. At the same time, a grade-level teacher would need to be concerned not only with the relevant “slice” of a given core idea taught in her particular grade, but also with the longer continuum of learning that K-8 stu- dents experience. Thus, teachers and science teacher educators (at the district, school, and college levels) would need to build structures and social processes to support the exchange of knowledge and information related to core concepts across grade levels. Because core ideas are bound up in the practices of science, teachers would also need a solid foundation in science and excellent classroom skills to guide and extend students’ experiences. Again, a network of science educators would need to work together to ensure that the complex instructional practices described here are supported with systematic, sustained professional learning throughout teach- ers’ careers. An excellent curriculum built on core ideas is but one of many major shifts required. At the same time that science teachers are identifying and promoting long- term goals and connections related to core concepts, they must also define shorter term goals for students that involve more immediate understanding. At each grade level, teachers will need to aim for teaching specific intermediate ideas, with an eye to how these will connect with and inform the more sophisticated concepts that students are building toward understanding. For example, later in this chap- ter we describe a K-2 level intermediate understanding of atomic-molecular theory that does not employ the language of “atoms,” “molecules,” or “theory.” Instead, it builds essential conceptual bases for students to learn atomic-molecular theory in progressively more complex ways over the years. Although most schools and school systems maintain control over the science curriculum, in the short term, individuals and small groups of science educators may find that they have opportunities to organize instruction in their own class- rooms in a way that will build students’ understanding of core ideas across the year. Gradually, as this approach is implemented in schools and districts, science curricula can be organized around a limited number of key scientific concepts that are linked over successive grades. 61 Organizing Science Education Around Core Concepts

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Core Concepts in Relation to Standards and Benchmarks In the 1990s, the K-12 subject matter communities, comprised of education researchers, curriculum developers, scientists, teacher educators, and teach- ers, developed frameworks to guide state and local authorities with curriculum development. These became the National Science Education Standards (NSES)1 and the Benchmarks for Science Literacy.2 In turn, local and state authorities developed standards, curricula, and assessments that were meant to align with the national standards. The development of standards and benchmarks was an important step toward building and expressing shared values for K-12 science education. These standards succeeded in building common frameworks. While standards were mar- ginally rooted in research on children’s learning and analyses of scientific practice, we now have a richer research base to inform science education and a better sense of the critical role this research should play. Current national, state, and district standards do not provide an adequate basis for designing effective curriculum sequences, for several reasons. First, they contain too many topics. When the NSES were compared with curricula in countries that participated in the Third International Mathematics and Science Study, the NSES were found to call for much broader coverage of topics than those in high-achieving countries.3 Second, the NSES and benchmarks do not identify the most important top- ics in science learning. Comparisons of the NSES with curricula in other coun- tries show that they provide comparatively little guidance for sequencing across grades. As we pursue a course of organizing curricula around core ideas, we need to ask ourselves questions that were not central to the development of the current standards. What areas of study are critical for students’ future learning? Which of these critical areas of scientific study can students explore in meaningful and increasingly complex ways across the K-8 grade span and beyond? Which areas of science can safely be deferred until high school or college? These are not easy questions, and answering them will require collective, sustained attention and focus among a number of stakeholders. Finally, the NSES and benchmarks provide limited insight into how stu- dents’ participation in science practices can be integrated with their learning about scientific concepts; that is, they do not describe how an understanding of scientific concepts needs to be grounded in scientific practice. In addition, although the 62 Ready, Set, SCIENCE!

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NSES and benchmarks recognize the importance of the first three strands of sci- ence learning, each strand is described separately, so the crucial issue of how the strands are interwoven and how they support each other is not addressed. Although there is a solid research base that supports the premises of orga- nizing science around core concepts, one should be mindful that few studies have examined children’s learning of core concepts over multiple years. So questions about what the optimal set of core concepts are, how they should be distributed and organized over the grades, and how to link together instruction across the grades are as yet unanswered. It is, however, very clear that future revisions to the national science standards—and the subsequent interpretation of those standards at the state and local levels and by curriculum developers—should dramatically reduce the number of topics of study and provide clear explanations of the knowl- edge and practices that can be developed from kindergarten through eighth grade. Using Core Concepts to Build Learning Progressions Research indicates that one of the best ways for students to learn the core con- cepts of science is to learn successively more sophisticated ways of thinking about these ideas over multiple years. These are known as “learning progres- sions.” Learning progressions can extend all the way from preschool to twelfth grade and beyond—indeed, people can continue learning about core science concepts their whole lives. If mastery of a core concept in science is the ultimate educational destination, learning progressions are the routes that can be taken to reach that destination. Learning progressions for K-8 science are anchored at one end by the con- cepts and reasoning abilities that young children bring with them to school and at the other end by what eighth graders are expected to know about science. The most effective and appropriate concepts on which to build learning progressions are those that are central to a discipline of science, that are accessible to students in some form starting in kindergarten, and that have potential for sustained explo- ration across grades K-8. A well-designed learning progression will include the essential underlying ideas and principles necessary to understand a core science concept. Because learning progressions extend over multiple years, they prompt educators to think about how topics are presented at each grade level so that they build on and support each other. 63 Organizing Science Education Around Core Concepts

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Learning progressions have many other potential benefits. They can draw on research about children’s learning in determining the scope and sequence of a curriculum. They can incorporate all four strands of scientific proficiency. Since they are organized around core concepts, they engage students with meaningful questions and investi- gations of the natural world. They Some Benefits of Learning Progressions suggest the most appropriate ages for introduction of core concepts. • They require serious thinking about the underlying con- And they can suggest the most cepts that need to be developed before a student can important tools and practices to master a particular area of science. assess understanding. • They prompt educators to think about how topics are In this chapter, we’ll be presented at each grade level so that they build on and examining a learning progression support each other. based on the atomic-molecular theory of matter. The idea that • They can draw on research about children’s learning in determining the scope and sequence of a curriculum. all matter is composed of atoms and molecules is a core scientific • They can incorporate all four strands of scientific concept that all students should proficiency. master. It allows for the integra- • They engage students with meaningful questions and tion of many different scientific investigations of the natural world. findings and explains otherwise • puzzling aspects of the physi- They suggest the most appropriate ages for introduction of core concepts. cal world. It allows for links to be made between various scien- • They can suggest the most important tools and tific disciplines, including physics, practices to assess understanding. chemistry, biology, and geology. We explore this learning progres- sion to illustrate the intermediate levels of understanding achieved at various points throughout the K-8 curriculum and how this understanding is rooted in science and learning research. We intend for this to serve as an example that can be further elaborated, tested, and emulated in the service of developing learning progressions in other areas of study. The learning progression in this chapter is divided into three grade bands— grades K-2, grades 3-5, and grades 6-84—with a case study at each grade band that focuses on one or more of the concepts covered as part of atomic-molecular theory. This learning progression was designed so that students can give progres- sively more sophisticated answers to the following questions: 64 Ready, Set, SCIENCE!

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1. What are things made of, and how can we explain their properties? 2. What changes, and what remains the same, when things are transformed? 3. How do we know? A well-designed learning progression on atomic-molecular theory won’t mention atoms and molecules in the earliest grades. The notion of atoms, chemical substances, and chemical change are complex ideas that take time to develop, test, expand, and revise. These ideas are too advanced for most young children, although some may have heard about atoms and molecules and may use these terms or ask questions about them. The point is to emphasize the goal of understanding concepts, which is very different than merely memoriz- ing vocabulary or definitions. By not emphasizing technical terms in the early grades, the teacher avoids sending the counterproductive message to students that science is about memorizing terms and definitions for phenomena that they fundamentally don’t understand. Even in the later years of elementary school, students may not be ready for the idea that all matter is composed of atoms and molecules. They first need to develop a sound macroscopic understanding of matter. In general, one of the most difficult transitions children must make during the K-8 years is linking macro-level processes with micro-level phenomena. For example, elementary school students may think that, at a molecular level, wood will look like tiny pieces of wood, rather than consisting of molecules. It takes several years for students to work out the subtleties of understanding the basic constituents of matter (atoms and mol- ecules) and how they combine to create larger units. It is important to keep in mind that a learning progression is not a lock- step sequence. Different classrooms, and even different students within the same classroom, can follow different pathways in coming to understand core science concepts. There are many ways to learn that all matter is composed of atoms and molecules. The following case study involves a classroom of kindergartners who are investigating the idea that different objects are made out of different materials, that there is a difference between what an object is used for (its function) and what it is made of (its material kind), and that these different materials have prop- erties that can be discussed, examined, and described. 65 Organizing Science Education Around Core Concepts

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Science Class THE MYSTERY BOX (GRADES K-2)5 “Are you ready to run a Mystery Box investigation FiguRE 4-1 The Mystery Box. with me?” Shawna Winter asked as her 22 kin- dergartners gathered around her. The classroom FiguRE 4-2 erupted into cheers. “Look at all these different eat- Eating utensils used ing utensils I’ve brought from home.” She pointed with the Mystery Box. to two identical sets of spoons and forks made of three different materials. Each set was lined up in a row in front of a wooden chest a little bigger than a toaster. The box was latched shut with a heavy lock, and next to the box was a key tied to a long ribbon (see Figures 4-1 and 4-2). “One set of these utensils is going to be mine, and the other set is going to be yours,” Ms. Winter said. She quickly established with the children the names of each of the utensils and the material it was made of. “So,” she summed up, “we have a plastic spoon, a wooden spoon, and a metal spoon, as well as a plastic fork, a wooden fork, a metal fork.” game. “If you ask me a question about what’s inside “Now I’m going to take my whole set away,” the Mystery Box, I will tell you the truth.” she said, scooping up one row of the spoons and “I know,” said Maya. “Is it the plastic spoon?” forks and tossing them into a bag. “Then I’m “That is a very good question, Maya. Do you going to take one item—just one—from my set know why it’s a good question? It’s a good question and put it into the Mystery Box. Close your eyes. because . . . it’s not the plastic spoon.” Several kids No peeking!” All 22 kindergartners gleefully cov- giggled; a few sighed with disappointment. ered their eyes. “So Maya’s question has taught us something Ms. Winter turned her back to the kids, unlocked important,” Ms. Winter said. “Whatever is inside the Mystery Box, selected an item from her bag of the box, it is not a plastic spoon. So that means we utensils, and locked it inside the box with the key. don’t need this one here anymore.” She picked up The students’ set of six items—forks and spoons— the plastic spoon from the students’ set of utensils remained lined up in front of the Mystery Box. and put it on the table, out of sight. “Now open your eyes,” she said. “Inside the Ms. Winter reached into a cup of Popsicle sticks Mystery Box is one thing taken from my set of that had all of the children’s names written on them, objects, which is just like your set. And here’s the which she used to ensure that each child had an amazing thing. You’re going to figure out what equal chance of getting a turn. The stick she pulled is inside the Mystery Box just by asking me ques- from the cup had “Carlos” written on it. tions.” Then, very dramatically, Ms. Winter uttered “Carlos, what question do you want to ask?” the words she always used to start the Mystery Box Carlos was new to the classroom, having moved to 66 Ready, Set, SCIENCE!

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the United States from Central America just a few “Wow! Did anyone hear what Kelly said?” weeks before. Carlos said nothing for several sec- Lots of hands went up. onds. Ms. Winter and the children waited. Then “Does anyone think they can put what Kelly said Carlos said, “Tenedor, um, fork!” in their own words? Yes, James?” Marisa, who was sitting next to Carlos, piped up. “She said Carlos asked his question about all the “He’s supposed to ask it as a question, right?” forks. Maya asked about only one spoon—the plas- “Marisa’s right,” said Ms. Winter. “You’re ask- tic spoon. It’s like we got three answers with one ing if there’s a fork inside our Mystery Box, Carlos, question.” is that right?” Carlos nodded. “Can you say it as a “Is that what you were saying, Kelly?” question?” Kelly nodded. “Is it a fork?” Carlos asked. “Wow, you guys are really thinking today. I can “Is it a fork?, Carlos wants to know,” said Ms. see smoke coming out of your ears. Let’s see who’s Winter. “That’s another good question, because next. Lassandra?” what is in the Mystery “It has to be a Box . . . is not a fork.” spoon,” several chil- The children laughed dren called out. and clapped. “And “Ah, but which because it’s not a spoon? What is the fork, what have we spoon made of?” learned?” Ms. Winter Ms. Winter asked. picked up the plastic “Lassandra?” fork, the wooden fork, “Is it the wooden and the metal fork. spoon?” “We don’t need “That’s a very them,” two children good question. Do said. you know why? “Right. Because we know it’s not a fork in our Because, I’m telling you the truth, it is the wooden box, we can get rid of every single fork. It can’t be spoon.” The kids squealed with delight. Ms. Winter one of these.” Ms. Winter put the three forks out of reached for the key. “So you think there’s going to sight. be a wooden spoon in there? How certain are you?” “Hey, I just noticed something interesting,” said “A billion percent,” called out Jason. Slowly Ms. Winter. “With Maya’s question we got rid of and dramatically Ms. Winter removed the lock one thing, the plastic spoon. With Carlos’s question, and opened the doors of the Mystery Box, reveal- we got rid of three things, all three forks. Can any- ing—“Ta dah!”—the wooden spoon inside. one figure out why that is?” No one said anything. “Congratulations,” Ms. Winter said. “Just by asking Ms. Winter waited. questions, without being able to see inside, you’ve Finally, Kelly, who tended not to talk much in the discovered what’s in the Mystery Box.” Ms. Winter’s large group, raised her hand. “Carlos asked about all 22 kindergartners broke into applause. of the forks, and Maya just asked about the plastic one, just the plastic spoon.” 67 Organizing Science Education Around Core Concepts

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The Mystery Box activity may seem a long way from the kinds of scientific investigations children will do in later grades relating to the atomic-molecular structure of matter, but it actually has some important similarities. Students are using their reasoning abilities to draw inferences about something they can’t see. They are thinking about how to ask questions and how to learn from other peo- ple’s questions. They are learning that different kinds of questions can produce different amounts of information. Perhaps most importantly, they are learning that getting the right answer isn’t the only thing that matters in a scientific investi- gation. Negative evidence can be very useful. While the Mystery Box activity doesn’t directly address the atomic structure of matter, it enables Ms. Winter’s kindergartners to practice making a distinction that will be essential in their understanding of matter. They are separating the use or type of an object (spoon or fork) from what it’s made of, or its “material kind” (plastic, wood, or metal). This may seem to be a simple task—indeed, it’s something that children generally master before they begin school. But they have to make this distinction clearly before they can learn about the detailed proper- ties and micro- scopic composition of matter. Science learn- ing can be very effective when it is grounded in a task that supports multiple predic- tions, explanations, or positions. In such a setting, chil- dren have reasons to “argue” (to agree and disagree) and to back up their positions with evidence. These rich tasks involve the students in actual scientific investigations but require support and guidance from the teacher. For example, the Mystery Box activity is a focused, teacher-guided activ- ity, but the children are playing active roles, reasoning and theorizing. They are listening hard to one another and building on one another’s ideas. Ms. Winter is also actively involved, pressing them to clarify and explain their ideas to one another. The activity involves a whole-group discussion in which everyone takes 68 Ready, Set, SCIENCE!

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part and has equal access to everyone else’s thinking, with help from Ms. Winter to keep the discussion on track. In addition, the Mystery Box activity can be played in many different ways and can be used to classify many different kinds of objects over the course of the school year. This activity can help students become thoughtful and logical questioners and data analysts. The Mystery Box is an activity that supports logical or deductive reason- ing practices. The implicit reasoning of the students as they play is as follows: We know that what’s in the Mystery Box is not a plastic spoon. We also know it’s not the plastic fork, the metal fork, or the wooden fork. Therefore, we have figured out that what’s in the Mystery Box must be a metal spoon or a wooden spoon, because they’re the only choices left. In contrast, the proposed measurement activity in Ms. Martinez’s kindergar- ten class (Chapter 1) would be considered an “empirical investigation.” In that case, the students tested a prediction: “Measuring with shoes on would make a difference in measurement.” They would need to examine evidence to suggest a pattern and then interpret the pattern to decide if their prediction was correct or not. They would thus be arranging the world (selecting, lining up, and measur- ing shoes) in order to learn something about it. They would have to collect measurement data, organize the data in some way, and then decide, based on their evidence, whether wearing shoes made a difference or not. The data might prove difficult to interpret (most shoes are the same but a few are dif- ferent), and the students might never be as certain of the right answer as they are with the Mystery Box activity. Generalizations about the empirical world are never certain. You cannot “prove” generalized conclusions via observation. Moderating uncertainty is central to scien- tific thinking. Unlike proof in mathematics, there is no absolute certainty in science. The skills the students are learning in the Mystery Box activity—making sense of, categorizing, and reasoning with available information—are key to asking good questions and formulating good hypotheses. And of course the students are also learning to participate in discussions with peers. That is, they are learning the norms of participation in science and how to handle uncertainty together. 69 Organizing Science Education Around Core Concepts

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Extending Scientific Discussion This chapter emphasizes the importance of building on learning progressions as they unfold over the course of several school years. Learning progressions can also take place in the short term as the ideas and concepts related to specific sci- ence activities are extended and deepened. For example, in Ms. Winter’s classroom, the Mystery Box activity eventually led to an investigation of the different objects in the classroom that were made of wood, plastic, or metal. The students, working in pairs, focused on each type of material and attempted to catalog, using pictures or words, all of the objects they could identify that were made of that material. When two or more of the same objects were identified, such as chairs, the students counted and recorded the total number of those objects. At group meeting time, for a period of several days, the students reported on their findings. Questions arose that led to further investigation. Had each student pair identified the same items? Was there agreement or disagreement about some items? What did all of the wooden items have in common, and in what ways did they differ? How could the students tell, for sure, if something was made of wood? The students requested magnifying glasses in order to see the grain of cer- tain items better, and Ms. Winter introduced a set of “density blocks,” which were same-sized cubes and triangular prisms made out of different materials (wood, plastic, metal). This led to several weighing and measuring activities that involved using a pan balance and a water displacement cup (sometimes called a “Eureka can”). This allowed the students to begin the transition away from reliance on sensory observations (felt weight) and to see the need for standard measurement—critical developments that are frequently overlooked or underes- timated in science curricula and instruction. The students explored weight versus volume, and they made predictions about whether the weight of the triangular prisms would match the rank ordering of weight of the cubes—that is, whether the metal triangular prism would be heavier than both the wooden and plastic ones, and why that might be. This is an example of just one of many ways the Mystery Box activity could be extended to allow students more time to work with complex ideas across dif- ferent contexts—an integral and essential part of learning progressions. Students themselves might generate questions about the materials that would be worthy of investigation. The teacher might engage the students in a discussion about the 70 Ready, Set, SCIENCE!

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These are not simply facts to be memorized. These are complex concepts that students need to develop through engagement with the natural world, through drawing on their previous experiences and existing knowledge, and through the use of models and representations as thinking tools. Students should practice using these ideas in cycles of building and testing models in a wide range of specific situations. At this grade band, students can begin to ask the questions: What is the nature of matter and the properties of matter on a very small scale? Is there some fundamental set of materials from which other materials are composed? How can the macroscopically observable properties of objects and materials be explained in terms of these assumptions? In addition, armed with new insight provided by their knowledge of the existence of atoms and molecules, they can conceptually distinguish between ele- ments (substances composed of just one kind of atom) and compounds (substanc- es composed of clusters of different atoms bonded together in molecules). They can also begin to imagine more possibilities that need to be considered in tracking the identity of materials over time, including the possibility of chemical change. Students have to be able to grasp the concept that if matter were repeat- edly divided in half until it was too small to see, some matter would still exist—it wouldn’t cease to exist simply because it was no longer visible. Research has shown that as students move from thinking about matter in terms of common- sense perceptual properties (something one can see, feel, or touch) to defining it as something that takes up space and has weight, they are increasingly comfortable making these kinds of assumptions. This is one example of the ways in which the framework that students developed in the earlier primary and elementary grades prepares them for more advanced theorizing at the middle school level. Middle school science students must conjecture about and represent what matter is like at a level that they can't see, make inferences about what follows from different assumptions, and evaluate the conjecture based on how well it fits with a pattern of results. Research has shown that middle school students are able to discuss these issues with enthusiasm, especially when different models for puzzling phenom- ena are implemented on a computer and they must judge which models embody the facts. This approach led students who had relevant macroscopic understand- ing of matter to see the discretely spaced particle model as a better explanation than alternatives (e.g., continuous models and tightly packed particle models). Class discussions allowed students to establish more explicit rules for evaluating 77 Organizing Science Education Around Core Concepts

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models: models were evaluated on the basis of their consistency with an entire pattern of results and their capacity to explain how the results occurred, rather than on the basis of a match with surface appearance. In this way, discussions of these simulations were used to help them build important metacognitive under- standing of an explanatory model. Describing and explaining the behavior of air or other gases provide still more fertile ground for demonstrating the concept that matter is fundamentally particulate rather than continuous. Of course, these investigations are effective only if students understand that gases are material, an idea that the proposed learning progression recommends they begin to investigate at the grades 3-5 level. At the same time, coming to understand the behavior of gases in particulate terms should help consolidate student understanding that gas is matter and enable them to visualize the unseen behavior of gases. In other words, developing macro- scopic and atomic-molecular conceptions can be mutually supportive. Direct sup- port for this assumption was provided in a large-scale teaching study with urban sixth-grade students that compared the effectiveness of two curriculum units.9 One unit focused more exclusively on teaching core elements of the atomic-molecular theory, without addressing student misconceptions about matter at a macroscopic level. The other included more direct teaching of relevant macroscopic and micro- scopic concepts and talked more thoroughly about how properties of invisible molecules are associated with properties of observable substances and physical changes. The latter unit led to a much greater change in understanding phenomena at both macroscopic and molecular levels. Thus, sequencing instructional goals to reflect findings on student learning has important implications for how children make sense of science instruction. Instruction that is focused on building core ideas is especially effective when students are regularly involved in classroom debates and discussion about essential ideas and alternative theories. Classroom debate and discussion make scientific experiments more meaningful and informative. Thus, building an understanding of atomic-molecular theory must also involve engaging students in cycles of mod- eling, testing, and revising models that describe a wide range of situations, such as explaining the different properties of solids, liquids, and gases, the thermal expan- sion of solids, liquids, or gases, changes of state, dissolving, and the transmission of smells. Students engage in these types of discussions and investigations in the fol- lowing case study. 78 Ready, Set, SCIENCE!

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Science Class THE NATuRE OF gASES (GRADES 6-8) Over the past 10 years, the Investigators Club (I-Club) has sought to bridge what students already know about science and what they learn about science in school. The I-Club has been used in a variety of after-school and in-school settings. In its original design, the I-Club is an after-school program, meeting three times a week with students from a wide range of cultural and linguistic backgrounds, predominantly students from low-income fami- lies who are struggling or failing in school. It has since been expanded to include an in-school program in middle schools, as well as a prekindergarten curriculum. The following case involves 25 seventh- and eighth-grade students participating in an I-Club after-school program. Richard Sohmer directs the Investigators Club pro- It was at this point in their investigation that gram, which meets for 15 weeks each school term. Mr. Sohmer introduced the students to a number There are no special tests or grade requirements for of demonstrations, all of which involved everyday participating in the program, but students in the materials that the students were familiar with and program have to commit to attending regularly, which they could take home and share with their be respectful of one another, and work hard “to families. With each demonstration, the students discover, practice, and acquire the skills of scientific predicted what would happen or attempted to investigation.” explain what had caused the demonstration to work Mr. Sohmer’s students were investigating air the way it did. pressure and the nature of gases and were about Over the years, he had found it difficult to dis- midway through their investigation. Prior to this abuse his students of the notion of suction and vacu- time, the students had begun learning about bal- ums as useful explanatory devices. Even though his anced and unbalanced forces. students knew that air molecules don’t stick togeth- In order to demonstrate concepts related to bal- er and can’t hook onto anything and therefore can’t anced and unbalanced forces, Mr. Sohmer had had pull anything, they routinely invoked the idea of suc- two students stand on either side of him and push tion. To help his students adjust their view of how him hard but with equal force. Despite their efforts, air pressure worked, Mr. Sohmer came up with an he hadn’t moved. He had then instructed the stu- analogy, a narrative form of the ideal gas law, that dent on his left, at the count of three, to take a step he called the “Air Puppies” story. back, while the student on his right kept pushing. Mr. Sohmer drew a large rectangle on the black- The result was that Mr. Sohmer had stumbled to the board. He told his students to pretend that they left, nearly falling down. were looking down at a large room. The demonstration had generated a discussion “In this room is a special wall that divides the about how objects that were stationary had forces room into two parts. The wall is on roller blades, acting on them, but that these were balanced forc- the kind with really good wheels, so it’s practically es. The students had also explored the difference frictionless.” among the three phases of matter: solid, liquid, and Mr. Sohmer drew a line down the middle and gas. They had investigated how phases of matter showed the roller blades in red. He said: “The wall stem from the interaction of molecular speed and can move easily, to the right or left, if something intermolecular attraction. touches it. So if I were standing on the left side of 79 Organizing Science Education Around Core Concepts

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students understand how scientific knowledge is constructed and how central models are in the construction of that knowledge. The Air Puppies are the bumbling (mindless) agents in a modifiable drama with a particular setting (always includ- ing two rooms separated by a moveable wall-on- wheels). The necessary result of the Air Puppies’ incessant, unintentional bumbling is a completely understandable, completely predictable, and thor- oughly lawful effect—that is, the wall moves as it FiguRE 4-5 must, given the Air Puppies’ opposing impacts on Mr. Sohmer’s wall-on-wheels. both sides. Mr. Sohmer continued the Air Puppies story. In the wall, and—by accident—I leaned against it, what fig 4-6 his first version, the two rooms on either side of the would happen to the wall?” (See Figure 4-5.) wall-on-wheels each contain an equal number of “It’ll move over there—it’s gonna move to the the line in the middle represents a wall-on-wheels identical Air Puppies mindlessly bumbling around right!” and bumping into the walls and each other. The “True. And it’s going to keep on moving to wall-on-wheels moves whenever a puppy bumps into the right until—remember, these are frictionless it (see Figure 4-6). wheels—until it bounces off the end of the room, and comes back the other way.” Then Mr. Sohmer told the story of the Air Puppies. “Imagine that Air Puppies represent air mol- ecules. Think about how newborn puppies bumble around constantly, mindlessly, with no intentions at all. They move around constantly, in every direction, like air molecules, without thinking, wanting, plan- ning, or choosing to do anything.” “Do Air Puppies breathe air like real puppies?” one of the students asked. FiguRE 4-6 Mr. Sohmer responded by introducing a discus- The view from above at the beginning of the Air Puppies sion about models and how they are never exactly story showing an equal number and kind of Air Puppies on each side of the wall. the same as the thing they represent. Students vol- unteered examples: Model airplanes don’t fly. Maps “So what will happen to the wall?” don’t include the potholes that are on some roads. 4-7 “It’ll stay in the same place,” a number of stu- A menu doesn’t taste like the food it describes. dents called out. With the aid of a QuickTime movie “Different models highlight different things,” he of an interactive physics animation, Mr. Sohmer dem- explained. “They’re useful in different ways. They onstrated how the scenario in Figure 4-7 was set in make some things visible and other things invisible.” motion. The wall stayed in approximately the same This kind of discussion about the advantages place, oscillating about the centerline (Figure 4-7). and limitations of different models helped the 80 Ready, Set, SCIENCE!

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“Great! You’re starting to see how this model works!” Mr. Sohmer said. “As the 10 puppies on the right get more and more squished into less and less space, they’re going to get bounced more, and move faster and faster, and hit the wall more and more times. At the same time, the 25 puppies on the other side will still be bumbling around—but as their room expands each of the 25 puppies has, on aver- age, farther to go before running into and bouncing off something. There will be more and more time FiguRE 4-7 between hits against the wall—they’ll be hitting the With an equal number and kind of Air Puppies on each side, the wall-on-wheels is continually bumped from side wall less often. The wall will move pretty far over to side. to the right, then get pushed back some, to the left, Mr. Sohmer continued with a variation on this and so on, ending up by shimmying back and forth 4-8 basic story: around a point well to the right of the original cen- “What will happen to the wall if we have 25 Air terline.” Puppies on the left side and 10 represent oscillation of wall on wheelsSohmer had another QuickTime video that vertical lines Air Puppies on the Mr. due to equal number of air puppies on each side right side?” Mr. Sohmer asked. He drew a diagram showed exactly what would happen in this 25-to-10 on the board (Figure 4-8). situation. When he projected it from his computer “Point which way the wall will go.” onto the wall, the students watched the wall be Everyone pointed to the right. “But it wouldn’t driven to the right until a new equilibrium of puppy go all the way over,” Jennifer noted. “It would go hits was established. about three-quarters of the way and then the pup- “Let me ask you one more thing,” said Mr. pies on the other side would be getting squished.” Sohmer. “When the wall moved over to the right, “Wouldn’t the wall keep moving back and forth, how did that happen? Was it due to suction?” just a bit, because the puppies on the right side would A chorus of voices called out, “No, the puppies still be moving and hitting the wall?” Raul asked. on the other side pushed it over!” Mr. Sohmer continued the discussion with anoth- er variation. “What if we start out with the same number of Air Puppies on both sides of the wall, but the pup- pies on the left, the red puppies, are more active. They are excited and running fast, fast, fast, while the puppies on the right, the blue puppies, are just moving around at a normal, unexcited pace. What do you think is going to happen to the wall?” “The fast puppies are gonna bump into the wall faster and more times and harder, so it’s gonna be FiguRE 4-8 pushed away, towards the slow puppies,” Sandra Divided room with 25 Air Puppies on the left side and 10 answered. on the right side. 81 4-9 Organizing Science Education Around Core Concepts

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Mr. Sohmer showed another QuickTime video, door (see Figure 4-9). The students reasoned that with the red Air Puppies moving much faster than as Air Puppies escaped from the open door on the the blue Air Puppies. right, the wall would move to the right, resulting in “This is a nifty picture definition of what heat the room on the right getting smaller and the room is. The red Air Puppies are pounding on everything on the left getting bigger. much more than the blue Air Puppies are—so we “What if you close the door after a lot of Air could say they are hot, and the blue puppies are Puppies have already escaped from the right side?” cold. But as long as the blue puppies are moving Gina asked. “There’s going to be lots of space, and at all—and they always will be—they will have heat lots of puppies, on the left side, and then the wall energy. Even ice has heat!” between them, and then only a little teeny space Mr. Sohmer added another variation to the story. over on the right side with hardly any puppies. But “How about if we had our regular situation, with can the wall just destroy the puppies on the right?” 100 puppies on one side and 100 puppies on the “No, they won’t be destroyed,” Mr. Sohmer said. other, the same amount of excitement activity on “They’ll still be there, still be bumbling and bounc- both sides, but we make the room on the right big- ing around.” ger. What would happen to the wall then?” “Then it seems like at some point, after a long “The wall’s going to move to the right,” Pedro time, the wall is going to come to some kind of bal- said. ance point. It’s going to be somewhere way over on “Why do you think that?” asked Mr. Sohmer. the right side, but it’s gonna eventually stop.” “What’s making the wall move? Is it getting sucked “If the wall stops moving, does that mean there’s over?” no more pressure, no more puppy hits per area?” “No, it’s getting pushed. There’s more space on asked Mr. Sohmer. the right, so the puppies bop around the same, but “No,” Gina said. “I think I get it. If the wall’s they don’t hit the wall as often.” not moving, it just means that there’s the same num- Mr. Sohmer then added another aspect to the ber of hits on both sides, or equal pushes, or equal problem by asking students to imagine what would forces. Like when you had two guys pushing you happen when each room had an equal number of the same on both sides and you didn’t move. So I Air Puppies, but the room on the right had an open guess you were like the wall!” Time FiguRE 4-9 As Air Puppies in the right room bumble randomly out the open door, there are fewer and fewer Air Puppy impacts on the wall from the right. Increasingly unopposed Air Puppy impacts from the left push the wall to the right. 4-10 82 Ready, Set, SCIENCE!

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“Truth!” Mr. Sohmer declaimed. Laughter and a students also published a bimonthly Investigators buzz of speculation ensued about the other air pres- Club newsletter, detailing their work and describ- sure demonstrations the class had done. ing interesting physics demonstrations that could be “Okay all, so that’s the Air Puppies story,” Mr. done at home. Discussions of the demonstrations Sohmer said. “With that story, you can see into a were written up in an issue. I-Club students devel- ton of interesting phenomena, explain to your par- oped teaching texts that were used to teach younger ents how vacuum cleaners really work! But in order students and archived in the school library. They to know that you really understand the story, you presented their work to adults in the community and have to be able to explain it to someone else. So I’d participated in science fairs. like you all to go home and explain it to someone Many of the I-Club students were reluctant, there—a brother, a sister, a parent, a grandparent struggling writers in school, and most read far below whoever is at home. And also explain one of the grade level. Nonetheless, every one of them decided demos we did in class.” that they wanted to prepare teaching texts. Of the Mr. Sohmer reminded the class that the Air 25 students, 23 voluntarily entered their school sci- Puppies story was a new tool, and that it was often ence fair, most of them doing physics projects that difficult at first to use any new tool. He had his revolved around the power of air pressure. And 13 students each choose one of the air pressure demon- students were among their school winners and went strations they had done and explain it to the group. on to the citywide competition. The goal, Mr. Sohmer said, was to explain things In spite of the fact that they said they “hated to clearly enough so that even a person who could write in school,” the I-Club kids put an enormous only hear and not see them presenting could still effort into preparing science fair or teaching texts, understand what they were saying. The students in writing as “experts” rather than as students. They the audience listened to the explanations and made worked in teams of four, adding elaborate photo- suggestions for how they could be explained more graphs and diagrams, formatting their texts on the clearly or completely. Each presenter had as many computer, soliciting comments from other groups, chances as needed to revise their presentation, until and drafting and revising. everyone in the group was satisfied. These tasks motivated the students to take their After a few weeks of practice in small groups thinking and their presentation of their ideas (in using the Air Puppies model in many different situ- writing and orally) to a higher level. Sandra, one of ations, each group selected a demonstration and the I-Club students, put it well when she said, “In worked hard to develop a thorough, compelling, and school, they just give you a book. It’s boring. But in cogent explanation of all the causal forces at work. the I-Club, we really get to explain things, down to These were eventually put on posters and presented the very core of the problem. That’s why we did so in a schoolwide after-school celebration. The I-Club well in the science fair.” 83 Organizing Science Education Around Core Concepts

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The Benefits of Focusing on Core Concepts and Learning Progressions As the cases in this chapter suggest, it takes considerable time and effort to intro- duce students to ideas about atomic-molecular theory in a meaningful manner. It is important to take that time at the middle school level for several reasons. First, understanding atomic-molecular theory opens up many productive new avenues for investigating matter. For example, it introduces the concept of chemical change, which research suggests is not really accessible to students with only macroscopic criteria for identifying substances. Understanding atomic-molecular theory also helps students more clearly understand what substances stay the same and what substances change during the water cycle. In addition, many important topics across the sciences—osmosis and diffusion, photosynthesis, digestion, decay, ecological matter cycling, the water cycle, the rock cycle—depend on an understanding of atomic-molecular theory. Finally, atomic-molecular theory gives students an opportunity to begin developing an understanding of and respect for the intellectual work and experi- mentation needed to formulate successful scientific theories. In current practice, atomic-molecular theory is often presented to students without careful attention to how their ideas develop through instruction or how to help them link science with their emergent ideas and relevant everyday experi- ences. As a result, as research makes clear, the majority of students fail to inter- nalize the core assumptions of atomic-molecular theory, and they are unable to understand such important ideas as chemical change. Perhaps more importantly, students are not given the opportunity to recognize the standards that a scientific theory is built on, how it is formed, and why it cannot be challenged by other theories that do not meet the same rigorous epistemological standards. Without an understanding of those epistemological standards, students will not know the grounds on which they should test and believe scientific arguments. i Learning progressions are a promising way to design and organize science learning. Recognizing this, teams of educators and researchers are actively devel- oping learning progressions with support from the National Science Foundation and other sponsors. For now, fully developed, well-tested learning progressions that are ready for broad application will have to wait. But that does not mean 84 Ready, Set, SCIENCE!

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that science educators can’t use aspects of this work now. In fact, it is important for science educators to begin to consider how learning progressions might be used in their own schools and classrooms and how learning progressions might affect their current teaching practices. The effectiveness of learning progressions is dependent on committed and capable implementation, and they will benefit from the experience and feedback of early adopters who can also play an active role in refining the practice. In order for productive science learning to take place, students and teachers need to have a clear idea of major conceptual goals. We’ve proposed a frame for thinking about K-8 goals, but shorter term goals can also be set for a four- to six- week unit or over a year of instruction. Science educators can begin to reflect on their curricular goals, identifying and focusing on those that are most scientifically powerful and fundamental. Meaningful science learning takes time, and learners need repeated, varied opportunities to encounter and grapple with ideas. Identifying core ideas means making hard decisions about “coverage” and will require that a curriculum be pared down and significantly focused. For this reason, it is advisable to begin on a small scale. A group of teachers at a given grade level, for example, might begin with a single unit of study, one that they feel comfortable with; perhaps the unit they feel is the strongest at their grade. They will need to give themselves ample time to identify meaningful problems, figure out how best to sequence the unit, and plan lessons that will provide students with the skills they need to do the sci- ence involved. Beginning this effort a year in advance of trying to enact changes to the curriculum should allow time for adequate teacher learning and planning. Whether at the state, district, school, or individual classroom level, as educa- tors take up learning progressions, it is important to treat them as a research and development initiative. As such, educators will require support in order to break from current practice and embrace new ideas. They will require feedback on the quality of the changes they enact as well as student learning outcomes. 85 Organizing Science Education Around Core Concepts

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For Further Reading Lehrer, R., Catley, K., and Reiser, B. (2004). Tracing a trajectory for developing under- standing of evolution. Invited paper for the National Research Council Committee on Test Design for K-12 Science Achievement. Available: http://www7.nationalacademies. org/bota/Evolution.pdf. National Research Council. (2007). Learning progressions. Chapter 8 in Committee on Science Learning, Kindergarten Through Eighth Grade, Taking science to school: Learning and teaching science in grades K-8 (pp. 211-250). R.A. Duschl, H.A. Schweingruber, and A.W. Shouse (Eds.). Center for Education, Division of Behavioral and Social Sciences and Education. Washington, DC: The National Academies Press. Schmidt, W., Wang, H., and McKnight, C. (2005). Curriculum coherence: An examination of U.S. mathematics and science content standards from an international perspective. Journal of Curriculum Studies, 37, 525-559. Smith, C., Wiser, M., Anderson, C.A., Krajick, J., and Coppola, B. (2004). Implications of research on children’s learning for assessment: Matter and atomic molecular theory. Paper commissioned by the National Academies Committee on Test Design for K-12 Science Achievement. Available: http://www7.nationalacademies.org/bota/ Big%20Idea%20Team_%20AMT.pdf. 86 Ready, Set, SCIENCE!

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5 Making Thinking Visible: Talk and Argument As we noted in Chapter 1, science requires careful communication and representa- tion of ideas. Scientists frequently share formulas, theories, laboratory techniques, and scientific instruments, and require effective means by which to understand and disseminate these types of information. They share their ideas and observa- tions in myriad ways, including the use of text, drawings, diagrams, formulas, and photographs. They communicate via PowerPoint slides, e-mail exchanges, peer- reviewed research articles, books, lectures, and TV programs or documentaries. They participate in research groups, academic departments, scientific societies, and interdisciplinary collaborations. Often, scientific collaboration takes the form of disagreement and argument about evidence. In this way, communities of scientists challenge and validate one another’s ideas in order to advance knowledge. These practices have analogues in science classrooms.1 Effective science teaching can employ some of the same methods of communication and representa- tion that are used by scientists in the real world. This chapter and the subsequent one focus, respectively, on the ways in which students can use language and argu- ment, as well as other forms of representation, to communicate and further devel- op their ideas. As the case studies in previous chapters make clear, science teaching and learning involve more than just conducting interesting demonstrations in the hope that students will somehow, on their own, discover the underlying concepts behind the outcomes. Effective science teaching and learning must also include communication and collaboration, which require both spoken and written repre- sentations of the world. In this chapter, we explore how talk and argument work in science and the role they play in good science teaching. We focus on language, both oral and writ- ten, as the primary tool for communication in science and the primary mechanism 87