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Dimension 1
SCIENTIFIC AND ENGINEERING PRACTICES

From its inception, one of the principal goals of science education has been to cultivate students’ scientific habits of mind, develop their capability to engage in scientific inquiry, and teach them how to reason in a scientific context [1, 2]. There has always been a tension, however, between the emphasis that should be placed on developing knowledge of the content of science and the emphasis placed on scientific practices. A narrow focus on content alone has the unfortunate consequence of leaving students with naive conceptions of the nature of scientific inquiry [3] and the impression that science is simply a body of isolated facts [4].

This chapter stresses the importance of developing students’ knowledge of how science and engineering achieve their ends while also strengthening their competency with related practices. As previously noted, we use the term “practices,” instead of a term such as “skills,” to stress that engaging in scientific inquiry requires coordination both of knowledge and skill simultaneously.

In the chapter’s three major sections, we first articulate why the learning of science and engineering practices is important for K-12 students and why these practices should reflect those of professional scientists and engineers. Second, we describe in detail eight practices we consider essential for learning science and engineering in grades K-12 (see Box 3-1). Finally, we conclude that acquiring skills in these practices supports a better understanding of how scientific knowledge is produced and how engineering solutions are developed. Such understanding will help students become more critical consumers of scientific information.



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3 Dimension 1 SCIENTIFIC AND ENGINEERING PRACTICES F rom its inception, one of the principal goals of science education has been to cultivate students’ scientific habits of mind, develop their capability to engage in scientific inquiry, and teach them how to reason in a scientific context [1, 2]. There has always been a tension, however, between the emphasis that should be placed on developing knowledge of the content of science and the emphasis placed on scientific practices. A narrow focus on content alone has the unfortunate consequence of leaving students with naive conceptions of the nature of scientific inquiry [3] and the impression that science is simply a body of isolated facts [4]. This chapter stresses the importance of developing students’ knowledge of how science and engineering achieve their ends while also strengthening their com- petency with related practices. As previously noted, we use the term “practices,” instead of a term such as “skills,” to stress that engaging in scientific inquiry requires coordination both of knowledge and skill simultaneously. In the chapter’s three major sections, we first articulate why the learning of science and engineering practices is important for K-12 students and why these practices should reflect those of professional scientists and engineers. Second, we describe in detail eight practices we consider essential for learning science and engineering in grades K-12 (see Box 3-1). Finally, we conclude that acquiring skills in these practices supports a better understanding of how scientific knowledge is produced and how engineering solutions are developed. Such understanding will help students become more critical consumers of scientific information. 41

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BOX 3-1 PRACTICES FOR K-12 SCIENCE CLASSROOMS 1. Asking questions (for science) and defining problems (for engineering) 2. Developing and using models 3. Planning and carrying out investigations 4. Analyzing and interpreting data 5. Using mathematics and computational thinking 6. Constructing explanations (for science) and designing solutions (for engineering) 7. Engaging in argument from evidence 8. Obtaining, evaluating, and communicating information Throughout the discussion, we consider practices both of science and engi- neering. In many cases, the practices in the two fields are similar enough that they can be discussed together. In other cases, however, they are considered separately. WHY PRACTICES? Engaging in the practices of science helps students understand how scientific knowledge develops; such direct involvement gives them an appreciation of the wide range of approaches that are used to investigate, model, and explain the world. Engaging in the practices of engineering likewise helps students under- stand the work of engineers, as well as the links between engineering and science. Participation in these practices also helps students form an understanding of the crosscutting concepts and disciplinary ideas of science and engineering; moreover, it makes students’ knowledge more meaningful and embeds it more deeply into their worldview. The actual doing of science or engineering can also pique students’ curios- ity, capture their interest, and motivate their continued study; the insights thus gained help them recognize that the work of scientists and engineers is a creative A Framework for K-12 Science Education 42

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❚ The actual doing of science or engineering can pique students’ ❚ curiosity, capture their interest, and motivate their continued study. endeavor [5, 6]—one that has deeply affected the world they live in. Students may then recognize that science and engineering can contribute to meeting many of the major challenges that confront society today, such as generating sufficient energy, preventing and treating disease, maintaining supplies of fresh water and food, and addressing climate change. Any education that focuses predominantly on the detailed products of scientific labor—the facts of science—without develop- ing an understanding of how those facts were established or that ignores the many important applications of science in the world misrepresents science and marginal- izes the importance of engineering. Understanding How Scientists Work The idea of science as a set of practices has emerged from the work of historians, philosophers, psychologists, and sociologists over the past 60 years. This work illuminates how science is actually done, both in the short term (e.g., studies of activity in a particular laboratory or program) and historically (studies of labora- tory notebooks, published texts, eyewitness accounts) [7-9]. Seeing science as a set of practices shows that theory development, reasoning, and testing are compo- nents of a larger ensemble of activities that includes networks of participants and institutions [10, 11], specialized ways of talking and writing [12], the development of models to represent systems or phenomena [13-15], the making of predictive inferences, construction of appropriate instrumentation, and testing of hypotheses by experiment or observation [16]. Our view is that this perspective is an improvement over previous approaches in several ways. First, it minimizes the tendency to reduce scientific practice to a single set of procedures, such as identifying and controlling variables, classifying entities, and identifying sources of error. This tendency overemphasizes experimental investigation at the expense of other practices, such as modeling, critique, and communication. In addition, when such procedures are taught in iso- lation from science content, they become the aims of instruction in and of them- selves rather than a means of developing a deeper understanding of the concepts and purposes of science [17]. 43 Dimension 1: Scientific and Engineering Practices

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Second, a focus on practices (in the plural) avoids the mistaken impression that there is one distinctive approach common to all science—a single “scientific method”—or that uncertainty is a universal attribute of science. In reality, practicing scientists employ a broad spectrum of methods, and although science involves many areas of uncertainty as knowledge is developed, there are now many aspects of sci- entific knowledge that are so well established as to be unquestioned foundations of the culture and its technologies. It is only through engagement in the practices that students can recognize how such knowledge comes about and why some parts of scientific theory are more firmly established than others. Third, attempts to develop the idea that science should be taught through a process of inquiry have been hampered by the lack of a commonly accepted definition of its constituent elements. Such ambiguity results in widely divergent pedagogic objectives [18]—an outcome that is counterproductive to the goal of common standards. The focus here is on important practices, such as modeling, developing explanations, and engaging in critique and evaluation (argumentation), that have too often been underemphasized in the context of science education. In particular, we stress that critique is an essential element both for building new knowledge in general and for the learning of science in particular [19, 20]. Traditionally, K-12 science education has paid little attention to the role of critique in science. However, as all ideas in science are evaluated against alternative explanations and compared with evidence, acceptance of an explanation is ultimately an assess- ment of what data are reliable and relevant and a decision about which explana- tion is the most satisfactory. Thus knowing why the wrong answer is wrong can help secure a deeper and stronger understanding of why the right answer is right. Engaging in argumentation from evidence about an explanation supports students’ understanding of the reasons and empirical evidence for that explanation, demon- strating that science is a body of knowledge rooted in evidence. How the Practices Are Integrated into Both Inquiry and Design One helpful way of understanding the practices of scientists and engineers is to frame them as work that is done in three spheres of activity, as shown in Figure 3-1. In one sphere, the dominant activity is investigation and empirical inquiry. In the second, the essence of work is the construction of explanations or designs using reasoning, creative thinking, and models. And in the third sphere, the ideas, such as the fit of models and explanations to evidence or the appropriateness of product designs, are analyzed, debated, and evaluated [21-23]. In all three spheres A Framework for K-12 Science Education 44

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THEORIES THE REAL WORLD AND MODELS Imagine Ask Questions ARGUE Reason Observe CRITIQUE Calculate Experiment ANALYZE Predict Measure COLLECT DATA FORMULATE HYPOTHESES TEST SOLUTIONS PROPOSE SOLUTIONS Developing Explanations Investigating and Solutions Evaluating FIGURE 3-1 The three spheres of activity for scientists and engineers. of activity, scientists and engineers try to use the best available tools to support the task at hand, which today means that modern computational technology is integral to virtually all aspects of their work. At the left of the figure are activities related to empirical investigation. In this sphere of activity, scientists determine what needs to be measured; observe phenomena; plan experiments, programs of observation, and methods of data collection; build instruments; engage in disciplined fieldwork; and identify sourc- es of uncertainty. For their part, engineers engage in testing that will contribute data for informing proposed designs. A civil engineer, for example, cannot design a new highway without measuring the terrain and collecting data about the nature of the soil and water flows. The activities related to developing explanations and solutions are shown at the right of the figure. For scientists, their work in this sphere of activity is to draw from established theories and models and to propose extensions to theory or create new models. Often, they develop a model or hypothesis that leads to new questions to investigate or alternative explanations to consider. For engineers, the major practice is the production of designs. Design development also involves constructing models, for example, computer simulations of new structures or pro- cesses that may be used to test a design under a range of simulated conditions or, 45 Dimension 1: Scientific and Engineering Practices

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at a later stage, to test a physical prototype. Both scientists and engineers use their models—including sketches, diagrams, mathematical relationships, simulations, and physical models—to make predictions about the likely behavior of a system, and they then collect data to evaluate the predictions and possibly revise the mod- els as a result. Between and within these two spheres of activity is the practice of evalua- tion, represented by the middle space. Here is an iterative process that repeats at every step of the work. Critical thinking is required, whether in developing and refining an idea (an explanation or a design) or in conducting an investigation. The dominant activities in this sphere are argumentation and critique, which often lead to further experiments and observations or to changes in proposed models, explanations, or designs. Scientists and engineers use evidence-based argumenta- tion to make the case for their ideas, whether involving new theories or designs, novel ways of collecting data, or interpretations of evidence. They and their peers then attempt to identify weaknesses and limitations in the argument, with the ulti- mate goal of refining and improving the explanation or design. In reality, scientists and engineers move, fluidly and iteratively, back and forth among these three spheres of activity, and they conduct activities that might involve two or even all three of the modes at once. The function of Figure 3-1 is therefore solely to offer a scheme that helps identify the function, significance, range, and diversity of practices embedded in the work of scientists and engineers. Although admittedly a simplification, the figure does identify three overarching categories of practices and shows how they interact. How Engineering and Science Differ Engineering and science are similar in that both involve creative processes, and neither uses just one method. And just as scientific investigation has been defined in different ways, engineering design has been described in various ways. However, there is widespread agreement on the broad outlines of the engineering design process [24, 25]. Like scientific investigations, engineering design is both iterative and sys- tematic. It is iterative in that each new version of the design is tested and then modified, based on what has been learned up to that point. It is systematic in that a number of characteristic steps must be undertaken. One step is identifying the problem and defining specifications and constraints. Another step is generat- ing ideas for how to solve the problem; engineers often use research and group A Framework for K-12 Science Education 46

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sessions (e.g., “brainstorming”) to come up with a range of solutions and design alternatives for further development. Yet another step is the testing of potential solutions through the building and testing of physical or mathematical models and prototypes, all of which provide valuable data that cannot be obtained in any other way. With data in hand, the engineer can analyze how well the various solutions meet the given specifications and constraints and then evaluate what is needed to improve the leading design or devise a better one. In contrast, scientific studies may or may not be driven by any immedi- ate practical application. On one hand, certain kinds of scientific research, such as that which led to Pasteur’s fundamental contributions to the germ theory of disease, were undertaken for practical purposes and resulted in important new technologies, including vaccination for anthrax and rabies and the pasteurization of milk to prevent spoilage. On the other hand, many scientific studies, such as the search for the planets orbiting distant stars, are driven by curiosity and under- taken with the aim of answering a question about the world or understanding an ❚ Students’ opportunities to immerse themselves in these practices and to explore why they are central to science and engineering are critical to ❚ appreciating the skill of the expert and the nature of his or her enterprise. 47 Dimension 1: Scientific and Engineering Practices

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observed pattern. For science, developing such an explanation constitutes success in and of itself, regardless of whether it has an immediate practical application; the goal of science is to develop a set of coherent and mutually consistent theoreti- cal descriptions of the world that can provide explanations over a wide range of phenomena, For engineering, however, success is measured by the extent to which a human need or want has been addressed. Both scientists and engineers engage in argumentation, but they do so with different goals. In engineering, the goal of argumentation is to evaluate prospec- tive designs and then produce the most effective design for meeting the specifi- cations and constraints. This optimization process typically involves trade-offs between competing goals, with the consequence that there is never just one “cor- rect” solution to a design challenge. Instead, there are a number of possible solu- tions, and choosing among them inevitably involves personal as well as technical and cost considerations. Moreover, the continual arrival of new technologies enables new solutions. In contrast, theories in science must meet a very different set of criteria, such as parsimony (a preference for simpler solutions) and explanatory coherence (essentially how well any new theory provides explanations of phenomena that fit with observations and allow predictions or inferences about the past to be made). Moreover, the aim of science is to find a single coherent and comprehensive theory for a range of related phenomena. Multiple competing explanations are regarded as unsatisfactory and, if possible, the contradictions they contain must be resolved through more data, which enable either the selection of the best available expla- nation or the development of a new and more comprehensive theory for the phe- nomena in question. Although we do not expect K-12 students to be able to develop new scien- tific theories, we do expect that they can develop theory-based models and argue using them, in conjunction with evidence from observations, to develop explana- tions. Indeed, developing evidence-based models, arguments, and explanations is key to both developing and demonstrating understanding of an accepted scien- tific viewpoint. ❚ A focus on practices (in the plural) avoids the mistaken impression that there is one distinctive approach common to all science—a single ❚ “scientific method.” A Framework for K-12 Science Education 48

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PRACTICES FOR K-12 CLASSROOMS The K-12 practices described in this chapter are derived from those that scientists and engineers actually engage in as part of their work. We recognize that students cannot reach the level of competence of professional scientists and engineers, any more than a novice violinist is expected to attain the abilities of a virtuoso. Yet students’ opportunities to immerse themselves in these practices and to explore why they are central to science and engineering are critical to appreciating the skill of the expert and the nature of his or her enterprise. We consider eight practices to be essential elements of the K-12 science and engineering curriculum: 1. Asking questions (for science) and defining problems (for engineering) 2. Developing and using models 3. Planning and carrying out investigations 4. Analyzing and interpreting data 5. Using mathematics and computational thinking 6. Constructing explanations (for science) and designing solutions (for engineering) 7. Engaging in argument from evidence 8. Obtaining, evaluating, and communicating information In the eight subsections that follow, we address in turn each of these eight practices in some depth. Each discussion describes the practice, articulates the major competencies that students should have by the end of 12th grade (“Goals”), and sketches how their competence levels might progress across the preceding grades (“Progression”). These sketches are based on the committee’s judgment, as there is very little research evidence as yet on the developmental trajectory of each of these practices. The overall objective is that students develop both the facil- ity and the inclination to call on these practices, separately or in combination, as needed to support their learning and to demonstrate their understanding of science and engineering. Box 3-2 briefly contrasts the role of each practice’s manifestation in science with its counterpart in engineering. In doing science or engineering, the practices are used iteratively and in combination; they should not be seen as a lin- ear sequence of steps to be taken in the order presented. 49 Dimension 1: Scientific and Engineering Practices

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BOX 3-2 DISTINGUISHING PRACTICES IN SCIENCE FROM THOSE IN ENGINEERING 1. Asking Questions and Defining Problems Science begins with a question about a phe- Engineering begins with a problem, need, or desire nomenon, such as “Why is the sky blue?” or that suggests an engineering problem that needs to “What causes cancer?,” and seeks to develop be solved. A societal problem such as reducing the theories that can provide explanatory answers to nation’s dependence on fossil fuels may engender a such questions. A basic practice of the scientist variety of engineering problems, such as designing is formulating empirically answerable questions more efficient transportation systems, or alternative about phenomena, establishing what is already power generation devices such as improved solar known, and determining what questions have cells. Engineers ask questions to define the engineer- yet to be satisfactorily answered. ing problem, determine criteria for a successful solu- tion, and identify constraints. 2. Developing and Using Models Science often involves the construction and use Engineering makes use of models and simulations of a wide variety of models and simulations to to analyze existing systems so as to see where flaws help develop explanations about natural phe- might occur or to test possible solutions to a new nomena. Models make it possible to go beyond problem. Engineers also call on models of various observables and imagine a world not yet seen. sorts to test proposed systems and to recognize the Models enable predictions of the form “if . . . strengths and limitations of their designs. then . . . therefore” to be made in order to test hypothetical explanations. 3. Planning and Carrying Out Investigations Scientific investigation may be conducted Engineers use investigation both to gain data in the field or the laboratory. A major practice of essential for specifying design criteria or parameters scientists is planning and carrying out a system- and to test their designs. Like scientists, engineers atic investigation, which requires the identifica- must identify relevant variables, decide how they tion of what is to be recorded and, if applicable, will be measured, and collect data for analysis. Their what are to be treated as the dependent and investigations help them to identify how effective, independent variables (control of variables). efficient, and durable their designs may be under a Observations and data collected from such work range of conditions. are used to test existing theories and explana- tions or to revise and develop new ones. A Framework for K-12 Science Education 50

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4. Analyzing and Interpreting Data Scientific investigations produce data that Engineers analyze data collected in the tests of must be analyzed in order to derive meaning. their designs and investigations; this allows them Because data usually do not speak for them- to compare different solutions and determine how selves, scientists use a range of tools—including well each one meets specific design criteria—that tabulation, graphical interpretation, visualization, is, which design best solves the problem within the and statistical analysis—to identify the signifi- given constraints. Like scientists, engineers require cant features and patterns in the data. Sources a range of tools to identify the major patterns and of error are identified and the degree of certainty interpret the results. calculated. Modern technology makes the collec- tion of large data sets much easier, thus provid- ing many secondary sources for analysis. 5. Using Mathematics and Computational Thinking In science, mathematics and computation In engineering, mathematical and computa- are fundamental tools for representing physi- tional representations of established relationships cal variables and their relationships. They are and principles are an integral part of design. For used for a range of tasks, such as constructing example, structural engineers create mathematically simulations, statistically analyzing data, and rec- based analyses of designs to calculate whether they ognizing, expressing, and applying quantitative can stand up to the expected stresses of use and if relationships. Mathematical and computational they can be completed within acceptable budgets. approaches enable predictions of the behavior of Moreover, simulations of designs provide an effective physical systems, along with the testing of such test bed for the development of designs and their predictions. Moreover, statistical techniques are improvement. invaluable for assessing the significance of pat- terns or correlations. 51 Dimension 1: Scientific and Engineering Practices

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In engineering, reasoning and argument are essential to finding the best possible solution to a problem. At an early design stage, competing ideas must be compared (and possibly combined) to achieve an initial design, and the choices are made through argumentation about the merits of the various ideas pertinent to the design goals. At a later stage in the design process, engineers test their potential solution, collect data, and modify their design in an itera- tive manner. The results of such efforts are often presented as evidence to argue about the strengths and weaknesses of a particular design. Although the forms of argumentation are similar, the criteria employed in engineering are often quite different from those of science. For example, engineers might use cost-benefit analysis, an analysis of risk, an appeal to aesthetics, or predictions about market reception to justify why one design is better than another—or why an entirely different course of action should be followed. GOALS By grade 12, students should be able to Construct a scientific argument showing how data support a claim. • Identify possible weaknesses in scientific arguments, appropriate to the stu- • dents’ level of knowledge, and discuss them using reasoning and evidence. A Framework for K-12 Science Education 72

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Identify flaws in their own arguments and modify and improve them in • response to criticism. Recognize that the major features of scientific arguments are claims, data, • and reasons and distinguish these elements in examples. Explain the nature of the controversy in the development of a given scientific • idea, describe the debate that surrounded its inception, and indicate why one particular theory succeeded. Explain how claims to knowledge are judged by the scientific community • today and articulate the merits and limitations of peer review and the need for independent replication of critical investigations. Read media reports of science or technology in a critical manner so as to • identify their strengths and weaknesses. PROGRESSION The study of science and engineering should produce a sense of the process of argument necessary for advancing and defending a new idea or an explanation of a phenomenon and the norms for conducting such arguments. In that spirit, students should argue for the explanations they construct, defend their inter- pretations of the associated data, and advocate for the designs they propose. Meanwhile, they should learn how to evaluate critically the scientific arguments of others and present counterarguments. Learning to argue scientifically offers students not only an opportunity to use their scientific knowledge in justifying an explanation and in identifying the weaknesses in others’ arguments but also to build their own knowledge and understanding. Constructing and critiquing argu- ments are both a core process of science and one that supports science education, as research suggests that interaction with others is the most cognitively effective way of learning [31-33]. Young students can begin by constructing an argument for their own interpretation of the phenomena they observe and of any data they collect. They need instructional support to go beyond simply making claims—that is, to include reasons or references to evidence and to begin to distinguish evidence from opinion. As they grow in their ability to construct scientific arguments, students can draw on a wider range of reasons or evidence, so that their argu- ments become more sophisticated. In addition, they should be expected to dis- cern what aspects of the evidence are potentially significant for supporting or refuting a particular argument. 73 Dimension 1: Scientific and Engineering Practices

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Students should begin learning to critique by asking questions about their own findings and those of others. Later, they should be expected to identify pos- sible weaknesses in either data or an argument and explain why their criticism is justified. As they become more adept at arguing and critiquing, they should be introduced to the language needed to talk about argument, such as claim, reason, data, etc. Exploration of historical episodes in science can provide opportunities for students to identify the ideas, evidence, and arguments of professional scien- tists. In so doing, they should be encouraged to recognize the criteria used to judge claims for new knowledge and the formal means by which scientific ideas are evaluated today. In particular, they should see how the practice of peer review and independent verification of claimed experimental results help to maintain objectiv- ity and trust in science. Obtaining, Evaluating, and Communicating Information Practice 8 Being literate in science and engineering requires the ability to read and under- stand their literatures [34]. Science and engineering are ways of knowing that are represented and communicated by words, diagrams, charts, graphs, images, symbols, and mathematics [35]. Reading, interpreting, and producing text* are fundamental practices of science in particular, and they constitute at least half of engineers’ and scientists’ total working time [36]. Even when students have developed grade-level-appropriate reading skills, reading in science is often challenging to students for three reasons. First, the jargon of science texts is essentially unfamiliar; together with their often exten- sive use of, for example, the passive voice and complex sentence structure, many find these texts inaccessible [37]. Second, science texts must be read so as to extract information accurately. Because the precise meaning of each word or clause may be important, such texts require a mode of reading that is quite dif- ferent from reading a novel or even a newspaper. Third, science texts are multi- modal [38], using a mix of words, diagrams, charts, symbols, and mathematics to communicate. Thus understanding science texts requires much more than sim- ply knowing the meanings of technical terms. Communicating in written or spoken form is another fundamental practice of science; it requires scientists to describe observations precisely, clarify their thinking, and justify their arguments. Because writing is one of the primary means of com- *The term “text” is used here to refer to any form of communication, from printed text to video productions. A Framework for K-12 Science Education 74

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municating in the scientific community, learning how to produce scientific texts is as essential to developing an understanding of science as learning how to draw is to appreciating the skill of the visual artist. Indeed, the new Common Core State Standards for English Language Arts & Literacy in History/Social Studies, Science, and Technical Subjects [39] recognize that reading and writing skills are essential to science; the formal inclusion in this framework of this science practice reinforces and expands on that view. Science simply cannot advance if scientists are unable to com- municate their findings clearly and persuasively. Communication occurs in a variety of formal venues, including peer-reviewed journals, books, conference presenta- tions, and carefully constructed websites; it occurs as well through informal means, such as discussions, email messages, phone calls, and blogs. New technologies have extended communicative practices, enabling multidisciplinary collaborations across the globe that place even more emphasis on reading and writing. Increasingly, too, scientists are required to engage in dialogues with lay audiences about their work, which requires especially good communication skills. Being a critical consumer of science and the products of engineering, whether as a lay citizen or a practicing scientist or an engineer, also requires the ability to read or view reports about science in the press or on the Internet and to recognize the salient science, identify sources of error and methodological flaws, and distinguish observa- tions from inferences, arguments from explanations, and claims from evidence. All of these are constructs learned from engaging in a critical discourse around texts. Engineering proceeds in a similar manner because engineers need to communi- cate ideas and find and exchange information—for example, about new techniques or new uses of existing tools and materials. As in science, engineering communica- tion involves not just written and spoken language; many engineering ideas are best communicated through sketches, diagrams, graphs, models, and products. Also in wide use are handbooks, specific to particular engineering fields, that provide detailed information, often in tabular form, on how best to formulate design solu- tions to commonly encountered engineering tasks. Knowing how to seek and use such informational resources is an important part of the engineer’s skill set. GOALS By grade 12, students should be able to Use words, tables, diagrams, and graphs (whether in hard copy or electroni- • cally), as well as mathematical expressions, to communicate their under- standing or to ask questions about a system under study. 75 Dimension 1: Scientific and Engineering Practices

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Read scientific and engineering text, including tables, diagrams, and graphs, • commensurate with their scientific knowledge and explain the key ideas being communicated. Recognize the major features of scientific and engineering writing and speak- • ing and be able to produce written and illustrated text or oral presentations that communicate their own ideas and accomplishments. Engage in a critical reading of primary scientific literature (adapted for class- • room use) or of media reports of science and discuss the validity and reliabil- ity of the data, hypotheses, and conclusions. PROGRESSION Any education in science and engineering needs to develop students’ ability to read and produce domain-specific text. As such, every science or engineering lesson is in part a language lesson, particularly reading and producing the genres of texts that are intrinsic to science and engineering. Students need sustained practice and support to develop the ability to extract the meaning of scientific text from books, media reports, and other forms of scientific communication because the form of this text is initially unfamiliar— expository rather than narrative, often linguistically dense, and reliant on precise logical flows. Students should be able to interpret meaning from text, to produce text in which written language and diagrams are used to express scientific ideas, and to engage in extended discussion about those ideas. From the very start of their science education, students should be asked to engage in the communication of science, especially regarding the investigations they are conducting and the observations they are making. Careful description of obser- vations and clear statement of ideas, with the ability to both refine a statement in response to questions and to ask questions of others to achieve clarification of what is being said begin at the earliest grades. Beginning in upper elementary and middle school, the ability to interpret written materials becomes more important. Early work on reading science texts should also include explicit instruction and practice in interpreting tables, diagrams, and charts and coordinating information conveyed by them with information in written text. Throughout their science education, stu- dents are continually introduced to new terms, and the meanings of those terms can be learned only through opportunities to use and apply them in their specific con- texts. Not only must students learn technical terms but also more general academic language, such as “analyze” or “correlation,” which are not part of most students’ everyday vocabulary and thus need specific elaboration if they are to make sense of A Framework for K-12 Science Education 76

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❚ From the very start of their science education, students should be asked to engage in the communication of science, especially regarding the ❚ investigations they are conducting and the observations they are making. scientific text. It follows that to master the reading of scientific material, students need opportunities to engage with such text and to identify its major features; they cannot be expected simply to apply reading skills learned elsewhere to master this unfamiliar genre effectively. Students should write accounts of their work, using journals to record observations, thoughts, ideas, and models. They should be encouraged to create diagrams and to represent data and observations with plots and tables, as well as with written text, in these journals. They should also begin to produce reports or posters that present their work to others. As students begin to read and write more texts, the particular genres of scientific text—a report of an investigation, an explanation with supporting argumentation, an experimental procedure—will need to be introduced and their purpose explored. Furthermore, students should have opportunities to engage in discussion about observations and explanations and to make oral presentations of their results and conclusions as well as to engage in appropriate discourse with other students by asking questions and dis- cussing issues raised in such presentations. Because the spoken language of such discussions and presentations is as far from their everyday language as scientific text is from a novel, the development both of written and spoken scientific expla- nation/argumentation needs to proceed in parallel. In high school, these practices should be further developed by providing students with more complex texts and a wider range of text materials, such as technical reports or scientific literature on the Internet. Moreover, students need opportunities to read and discuss general media reports with a critical eye and to read appropriate samples of adapted primary literature [40] to begin seeing how science is communicated by science practitioners. In engineering, students likewise need opportunities to communicate ideas using appropriate combinations of sketches, models, and language. They should also create drawings to test concepts and communicate detailed plans; explain and critique models of various sorts, including scale models and prototypes; and pres- ent the results of simulations, not only regarding the planning and development stages but also to make compelling presentations of their ultimate solutions. 77 Dimension 1: Scientific and Engineering Practices

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REFLECTING ON THE PRACTICES Science has been enormously successful in extending humanity’s knowledge of the world and, indeed transforming it. Understanding how science has achieved this success and the techniques that it uses is an essential part of any science education. Although there is no universal agreement about teaching the nature of science, there is a strong consensus about characteristics of the scientific enterprise that should be understood by an educated citizen [41-43]. For example, the notion that there is a single scientific method of observation, hypothesis, deduction, and conclusion—a myth perpetuated to this day by many textbooks—is fundamentally wrong [44]. Scientists do use deductive reasoning, but they also search for patterns, classify different objects, make generalizations from repeated observations, and engage in a process of making inferences as to what might be the best explanation. Thus the picture of scientific reasoning is richer, more complex, and more diverse than the image of a linear and unitary scientific method would suggest [45]. What engages all scientists, however, is a process of critique and argumenta- tion. Because they examine each other’s ideas and look for flaws, controversy and debate among scientists are normal occurrences, neither exceptional nor extraor- dinary. Moreover, science has established a formal mechanism of peer review for establishing the credibility of any individual scientist’s work. The ideas that sur- vive this process of review and criticism are the ones that become well established in the scientific community. Our view is that the opportunity for students to learn the basic set of prac- tices outlined in this chapter is also an opportunity to have them stand back and reflect on how these practices contribute to the accumulation of scientific knowl- edge. For example, students need to see that the construction of models is a major means of acquiring new understanding; that these models identify key features and are akin to a map, rather than a literal representation of reality [13]; and that the great achievement of science is a core set of explanatory theories that have wide application [46]. Understanding how science functions requires a synthesis of content knowledge, procedural knowledge, and epistemic knowledge. Procedural knowl- edge refers to the methods that scientists use to ensure that their findings are valid and reliable. It includes an understanding of the importance and appropri- ate use of controls, double-blind trials, and other procedures (such as methods to reduce error) used by science. As such, much of it is specific to the domain A Framework for K-12 Science Education 78

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and can only be learned within science. Procedural knowledge has also been called “concepts of evidence” [47]. Epistemic knowledge is knowledge of the constructs and values that are intrinsic to science. Students need to understand what is meant, for example, by an observation, a hypothesis, an inference, a model, a theory, or a claim and be able to readily distinguish between them. An education in science should show that new scientific ideas are acts of imagination, commonly created these days through collaborative efforts of groups of scientists whose critiques and arguments are fundamental to establishing which ideas are worthy of pursuing further. Ideas often survive because they are coherent with what is already known, and they either explain the unexplained, explain more observations, or explain in a simpler and more elegant manner. Science is replete with ideas that once seemed promising but have not with- stood the test of time, such as the concept of the “ether” or the vis vitalis (the “vital force” of life). Thus any new idea is initially tentative, but over time, as it survives repeated testing, it can acquire the status of a fact—a piece of knowledge that is unquestioned and uncontested, such as the existence of atoms. Scientists use the resulting theories and the models that represent them to explain and pre- dict causal relationships. When the theory is well tested, its predictions are reli- able, permitting the application of science to technologies and a wide variety of policy decisions. In other words, science is not a miscellany of facts but a coherent body of knowledge that has been hard won and that serves as a powerful tool. Engagement in modeling and in critical and evidence-based argumentation invites and encourages students to reflect on the status of their own knowledge and their understanding of how science works. And as they involve themselves in the practices of science and come to appreciate its basic nature, their level of sophistication in understanding how any given practice contributes to the scientific enterprise can continue to develop across all grade levels. 79 Dimension 1: Scientific and Engineering Practices

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