J Sci Educ Technol (2010) 19:580–601 DOI 10.1007/s10956-010-9225-8 Elementary Students’ Learning of Materials Science Practices Through Instruction Based on Engineering Design Tasks Kristen Bethke Wendell • Hee-Sun Lee Published online: 14 May 2010 Springer Science+Business Media, LLC 2010 Abstract Materials science, which entails the practices of selecting, testing, and characterizing materials, is an important discipline within the study of matter. This paper examines how third grade students’ materials science performance changes over the course of instruction based on an engineering design challenge. We conducted a case study of nine students who participated in engineering design-based science instruction with the goal of constructing a stable, quiet, thermally comfortable model house. The learning outcome of materials science practices was assessed by clinical interviews conducted before and after the instruction, and the learning process was assessed by students’ workbooks completed during the instruction. The interviews included two materials selection tasks for designing a sturdy stepstool and an insulated pet habitat. Results indicate that: (1) students significantly improved on both materials selection tasks, (2) their gains were significantly positively associated with the degree of completion of their workbooks, and (3) students who were highly engaged with the workbook’s reflective record-keeping tasks showed the greatest improvement on the interviews. These findings suggest the important role workbooks can play in facilitating elementary students’ learning of science through authentic activity such as engineering design. K. B. Wendell (&) Department of Education and Center for Engineering Education and Outreach, Tufts University, Curtis Hall Lower Level, 474 Boston Ave., Medford, MA 02155, USA e-mail: [email protected] H.-S. Lee Department of Education, Tufts University, Medford, MA, USA 123 Keywords Design-based science Elementary science Design decisions Science workbooks Clinical interviews Properties of materials Objects, materials, and their physical properties are one of the school science topics with which students have the most firsthand, everyday experience (Spelke 1991). Beginning in infancy, children continually attempt to make sense of the objects and materials in the world around them (Piaget 1930). By the time children reach the primary grades, they already have a rich set of conceptual resources and concrete experiences with which to reason about objects, materials, and matter (Duschl et al. 2007). Within the physical sciences, the study of matter constitutes a major conceptual field (American Association for the Advancement of Science 1993; National Research Council [NRC] 1996; Smith et al. 2006). For professional scientists and engineers, the practice of specifying objects and materials by measurable physical properties has led to the creation of the discipline known as materials science (Callister 2007). Expert materials scientists have deep knowledge about the structure and composition of natural and synthetic materials, and they are skilled at conducting tests of materials, selecting appropriate materials, and describing materials’ invariant, intensive properties. This testing and characterization of materials is an important subspecialty within the scientific study of matter, and materials science may also play an important role in young students’ physical science learning. However, our knowledge of how to help students develop materials science proficiency is limited. Many studies on students’ conceptions of matter take the form of clinical interviews in which they sort objects or material samples into groups of similar samples (e.g., Dickinson J Sci Educ Technol (2010) 19:580–601 1987; Inhelder and Piaget 1964; Krnel et al. 1998). Researchers often probe for specific modes of classification, such as sorting by constituent material, state of matter, intensive properties like density or texture, or extensive properties like weight or shape (e.g., Krnel et al. 2003). They also explore how children differentiate object from material kind (e.g., Dickinson 1987; Smith et al. 1985). Although these studies have generated much knowledge about how children think about objects and materials, they have not addressed whether or how children apply that thinking to select objects and materials for practical tasks. For example, if a child can sort materials by their hardness, does that mean she can select an appropriate material for a table top? Research on students’ developing understanding of material properties through the use of materials, rather than on the classification and study of them, has been limited. Existing research studies also provided limited analysis of student work related to materials science during instruction. Research that measures performance at only one or two points in time is unable to capture fully the ‘‘instructional dynamic’’ (Ball and Forzani 2007) of a learning experience, which consists of constant interactions between teacher, students, and curriculum materials. The purpose of this article is to report on our investigation of what third-grade students learn about the practices of materials science through an engineeringdesign-based curriculum module. Engineering design can provide an authentic activity context for science learning; authentic activities are those that ‘‘require students to apply scientific knowledge and reasoning to situations similar to those they will encounter in the world outside the classroom, as well as to situations that approximate how scientists do their work’’ (NRC 1996, p. 75). For our research, we developed a materials science curriculum module where elementary students learn to apply knowledge about the properties of materials and objects to the engineering design problem of constructing a stable, quiet, thermally comfortable model house. The curriculum module uses LEGOTM construction elements and electronic sensors as tools for engineering design tasks. In designing our study, we were guided by three research questions: (a) What approaches do students use in selecting, testing, and describing the materials for practical engineering tasks before instruction? (b) How do their approaches change after instruction? and (c) How can the changes be traced to students’ engagement with the related learning tasks during the instruction? To answer these questions, we conducted a case study of nine-third-grade students who represented varying degrees of academic abilities and engagement with the learning tasks offered during instruction. The first and second research questions were answered using clinical interviews conducted before and after the instruction, and the third research question 581 was answered using students’ workbooks completed during instruction. The clinical interviews were situated in two engineering design tasks: choosing the materials for a sturdy stepstool and a warm pet habitat. In the workbooks, we analyzed student work related to strength and thermal insulation, which were critical concepts in the clinical interviews. In the first section of this paper, we characterize the discipline of materials science and review previous research related to children’s materials science learning. Next, we outline the instructional intervention used in this study and describe our research design, including subjects, data sources, and data collection and analysis procedures. We then present and discuss results by comparing them to previous work and summarizing their contributions and limitations. Literature Review Materials Science: The Study and Application of Material and Object Properties The major practical skills of materials scientists include analyzing existing materials for their constituent parts and structure, specifying materials by intensive properties that are invariant to amount, identifying the properties needed for particular tasks, and selecting existing materials and creating new materials with desired properties (Ashby et al. 2007; Dowling 1998). The primary content knowledge of materials scientists deals with how particular properties relate to particular technological challenges, how materials are composed and structured, and how macroscopic properties are determined by a material’s structure and composition (Allen and Thomas 1999; Schaffer et al. 1999). Among the properties considered most important by materials scientists are the mechanical qualities of compressive strength, elastic modulus, and density, and the thermal qualities of heat capacity, thermal conductivity, and expansion coefficient. These properties are crucial to the success of any physical technology that is subject to mechanical and thermal stress (Ashby and Jones 2005). The National Science Education Standards (NRC 1996) state that by the upper elementary grades, students should be able to describe and measure the observable properties of materials and objects. In their proposed learning progression, Smith et al. (2006) similarly assert that by the end of fifth grade, most students should be able to measure, classify, and describe materials according to their properties, which include directly observable properties like color and hardness as well as less obvious properties like density, flammability, and conductivity. Smith et al. do not include choosing materials and justifying material choices in their 123 582 J Sci Educ Technol (2010) 19:580–601 Table 1 Key practices and content knowledge of expert and introductory materials science Key scientific practices Key scientific content knowledge Expert materials science Materials science suitable for elementary school students a) Analyzing existing materials for their constituent parts and physical properties a) Testing materials for particular properties b) Identifying the properties needed for particular tasks and devices b) Identifying the material properties important to a given task c) Selecting materials with those properties c) Selecting materials with those properties d) Uniquely specifying materials by intensive properties that are invariant to the amount of material d) Describing materials specifically via intensive and extensive properties e) Creating new materials with desired properties e) Proposing combinations of materials that would accomplish a task a) How particular properties relate to particular technological challenges a) A few of the properties important for very common mechanical tasks b) How materials are composed and structured b) How objects are different from their constituent materials c) How macroscopic properties generally relate to materials’ structure and composition d) How specific macroscopic properties are particularly determined by a material’s structure and composition learning progression, but the NSES do elaborate that upper elementary students should be able to choose suitable materials for a particular task and justify their choice of materials. Incorporating the NSES (1996) and Smith et al. (2006), we summarzie our own ideal, full set of introductory materials science learning goals for elementary school students in Table 1. Our set of materials science learning goals is more comprehensive than existing lists of ‘‘properties of materials’’ standards because we have added the goals of recognizing important properties for practical tasks and articulating the reasons behind their importance. and Samarapungavan 1999) such as ‘‘wood is harder than water,’’ ‘‘wood is heavier than water,’’ or ‘‘wire is denser than wood.’’ Students were more likely to explain fluidity and malleability by discussing the sample’s hardness, weight, strength, or density, than by proposing explanations related to material composition or particulate structure. Very few students used mechanistic explanations such as, ‘‘water is free to move because its molecules are spread out,’’ or ‘‘wire is more flexible than wood because it has a different atomic structure’’ (Nakhleh and Samarapungavan 1999). Previous Findings on Students’ Materials Science Learning Strength Although previous studies of student achievement related to materials science have not focused on selecting and testing materials for everyday tasks, they have identified numerous challenges involved in developing a scientific perspective on the properties of materials and objects. Here we describe the conceptual and practical challenges relevant to this study. Explaining Properties Elementary and middle school students often have difficulty providing a mechanistic cause for a macroscopic property (Lee et al. 1993; Nakhleh and Samarapungavan 1999; Parkinson 2001; Snir et al. 2003). In one study, when asked to explain water’s fluidity and wire’s malleability (compared to wood’s fluidity and malleability), most students simply invoked macroscopic characteristics (Nakhleh 123 Studies of elementary grade students’ ideas about how to construct stable towers and bridges suggest that many students model strength as directly varying with weight (Gustafson et al. 1999; Parkinson 2001). For example, in one study (Gustafson et al. 1999), most students’ proposals for designing a tower that would not ‘‘tip over’’ related to the weight of the tower materials. Some students suggested adding weight to its base, support posts, or top, while others proposed increasing the weight of the entire tower. This inclination to associate weight with design improvement may be related to children’s tendency to attend to the property of weight moreso than to other properties (Krnel et al. 1998; Smith et al. 1985). A related investigation of students’ ideas about how to predict the strength of bridge designs found that students need explicit instruction on strategies for comparing the strength of multiple products (Gustafson et al. 2000). In that study, some students suggested simply that each J Sci Educ Technol (2010) 19:580–601 designed bridge should be built and tested. Other students described a specific action, such as adding weights or shaking the bridges, but did not discuss how to compare one bridge to another. A third group of students suggested comparing the two bridges but did not specify any conditions to be held constant for both bridges. Very few responses were both explicit about equivalent conditions and specific about how to quantify the bridge’s strength, such as counting how many weights could be added before collapse. These findings suggest the need to distinguish between two different barriers to student achievement in materials science: limited experience with experimental design (e.g., control of variables) and limited understanding of the physical phenomena related to particular material properties. 583 and cotton) are good at keeping things hot (Lewis and Linn 1994). Though the concepts of thermal conductivity and strength are challenging for elementary students, our decision to include these properties in this study was purposeful. If we task students with testing and selecting only for simple perceptual properties like weight and color, we cannot make strong arguments about their learning of materials science practices. There are many correct commonsense ways to test and select for simple properties. By asking students instead to test and select for complex properties, we can differentiate more precisely among levels of performance at these practices. A more novel discovery can be made by asking students to test and select for non-perceptually accessible properties such as strength and insulation. Thermal Insulation One of the major conceptual challenges related to thermal phenomena is the distinction between the concepts of temperature and heat. The scientific understandings are that heat is exchanged energy, and temperature is average molecular kinetic energy (Wiser and Amin 2001). Many preschool and early primary grade students, however, conceive of heat as a gas or vapor (Paik et al. 2007), and they tend to conflate heat with its effects, such as burning and melting (Shayer and Wylam 1981). Most upper elementary students conceive of heat as perceived hotness, so their concept of heat remains undifferentiated from their concept of temperature (Wiser and Amin 2001). One way to explore students’ understandings of heat and temperature is to ask them to discuss the perceived temperature of different objects within an environment of known ambient temperature (e.g., Clark 2006; Lewis and Linn 1994; Paik et al. 2007). A scientifically normative response would explain that all the objects are at the same temperature, but they feel different to your hand because they conduct heat at different rates. Children’s responses, in contrast, typically indicate that the temperature of a substance depends on its constituent material, size, or thickness, and they do not differentiate between a substance’s speed of heat transfer and its temperature (Clark 2006; Erickson 1979). A second major conceptual challenge related to thermal phenomena is the equivalence between insulation that maintains cold temperatures and insulation that maintains hot temperatures. Children instead believe that materials that can insulate ‘‘hotness’’ are fundamentally different from materials that can insulate ‘‘coldness’’ (Lewis and Linn 1994; Paik et al. 2007). They tend to think that materials that feel cool to the touch at room temperature (such as metal and glass) are good at keeping objects cold, while materials that feel warm to the touch (such as wool Curriculum Context Based on a situative, social constructivist framework (Driver et al. 1994; Greeno 1998), we characterize science learning as both social enculturation into practices and personal construction of ideas. Consistent with this framework, we suggest that students can effectively learn about object and material properties while engaged in solving authentic problems through actual materials science practices. This involves writing with, talking with, and physically using the cultural tools and symbolic resources of materials science. Engineering design is one kind of authentic activity that requires the use of both practices and content knowledge related to materials science. We consider design as the activity of creating or proposing plans for a product that will solve an open-ended and ill-structured problem (Dym 1994; Simon 1996). Engineering design is a particular domain of design. For this study, we define engineering design as the organized development and testing, through the use of mathematical and scientific knowledge and models, of artifacts that perform a desired function without violating known constraints (Davis and Gibbin 2002; Dym and Little 2004). We developed a curriculum module called Design a Model House: The Properties of Objects and Materials for upper elementary grade students. The module situates materials science learning within the activity of engineering design. It is an example of a design-based science curriculum module (Fortus et al. 2005; Kolodner 2006; Roth 1996). In design-based science, students are typically challenged to design and construct a physical prototype that meets a set of requirements while adhering to constraints. The design challenge is carefully structured so that both science knowledge and practices are important to 123 584 success. Students conduct scientific investigations to deepen their understanding of the design problem’s requirements or constraints, and as they generate and implement solutions to the design problem, they increase their understanding of science concepts and practices. Our approach to incorporating engineering design problems into primary-level science is similar to the Learning by DesignTM approach to middle-school science instruction (Kolodner 2006). In the opening lesson of the Design a Model House module, students learn that their engineering design challenge is to create a miniature model house that is stable, soundproof, and thermally insulated. Over the next six lessons, guided by their teacher and their science workbooks (called Engineer’s Journals), the students conduct a series of engineering tests to identify materials to meet these design requirements. They use weights, sound sensors, and temperature sensors for their tests and craft materials and LEGOTM construction elements for their house surfaces and frames. As the students test materials and begin prototyping, they are asked to make scientific arguments about the best materials for each portion of the house. They are encouraged to consider the material and object properties of stability, strength, soundproofing, reflectivity, and thermal insulation. To facilitate their efforts throughout the module, science workbooks are used to prompt students to reflect on experiments and observations. In the module’s two concluding lessons, the students employ their new understanding of object and material properties to complete the design and building of their miniature model houses. The nine-lesson module is intended for 8- to 9-year-old students and requires approximately 12 h of instructional time. Multiple solutions exist to the model house design challenge. Several different combinations of materials enable the house to meet the criteria of being stable (it does not collapse under pressure from a student’s palm), quiet (a sound sensor in the house measures fewer decibels than one adjacent to the outer wall), and thermally insulated (a temperature sensor inside the house indicates slower temperature change than one exposed directly to a hot or cold stimulus). Students are told that they will be evaluated on how well their material choices can be justified with evidence from their investigations, rather than on the correctness of their choices. The primary instructional goal of this curriculum module is to enable students to carry out three main introductory materials science practices: (1) describing objects and materials by their extensive and intensive properties, (2) conducting tests to determine whether materials exhibit desired properties, and (3) selecting materials with the properties that are most important for accomplishing a specific design task. Therefore, we focus on students’ 123 J Sci Educ Technol (2010) 19:580–601 learning of materials science through the practices of describing, testing, and selecting. These encompass the first four introductory materials science practices listed in Table 1. The practices from Table 1 of identifying important material properties and selecting materials with those properties are now collapsed into a single practice termed ‘‘selecting.’’ Therefore selecting includes both choosing a material and justifying that choice with scientific knowledge. Throughout the module, the following resources are used to engage students in the practices of materials science: a) physical tests demonstrated by the teacher and conducted by the students (compressive test of strength, tap test for stability, insulation test with heat stimulus and temperature sensor, sound absorption test with decibel sensor), b) graphical representations in the students’ science workbooks (charts for recording test results, designated areas for sketching plans to use materials), c) scientific language spoken by the teacher and written in the workbook (material, property, test, pass, fail, result, select, strong, stable, insulating, absorbing), and d) physical processes of using materials to build and rebuild components of the model houses, as demonstrated by the teacher and conducted by the students. We consider these resources to be the main affordances of this module (Greeno 1998) because they enable children to pick up the discourse, practices, and representations— the cultural tools—of materials science. Thus, for this study, we hypothesized that in students’ post-interviews, they would more frequently refer to intensive physical properties to explain their selection of materials, and more frequently propose material tests based on quantified measures and fair comparisons. We also expected that students’ performances on the interview design scenarios would be traced to their engagement with the relevant design tasks in the workbooks throughout the curriculum module. Previous teaching sequences related to materials science have focused on determining and explaining material properties (e.g., National Science Resources Center 2005; Smith 2007), witnessing and explaining material transformations (e.g., Acher et al. 2007; Johnson 2000), and conducting scientific argumentation about material properties and changes (e.g., Education Development Center 2003; Lawrence Hall of Science 2005). These existing interventions do not emphasize the use of material samples in the design, construction, and testing of artifacts that serve authentic purposes. By including an engineering design component, our instructional approach expands upon previously implemented approaches. J Sci Educ Technol (2010) 19:580–601 Method We carried out an exploratory, descriptive case study of a relatively small number of students. Our case was comprised of a group of nine students of varying academic abilities from one third-grade classroom. In investigating our case, we utilized both quantitative and qualitative evidence (Yin 2003). A mixed-evidence case study approach was chosen for several reasons. For one, the phenomenon of interest, students’ science learning within a single classroom, is best explored via multiple sources of evidence, and this is a hallmark of case study methodology. Second, the phenomenon was naturally ‘‘bounded’’ and thus appropriately explored through case study research (Merriam 1998). Indications of the ‘‘boundedness’’ of the phenomenon were the finite number of students that could be sampled (the nine consenting students) and the fixed duration of the instruction (the nine lessons in the curriculum). Third, case study methods are particularly suitable for capturing process and development over time (Yin 2003), and our research questions called for attending to changes in students’ science practices over time. Quantifying some of the qualitative data, such as workbook responses, helped to characterize major patterns of change as well as identify students for in-depth descriptions of learning. Qualitative evidence, such as interview transcripts, highlighted the differences among individual students’ learning using their own accounts. Setting and Participants This case study took place in an urban K-8 public school in the northeastern United States. The student body in the school is 15% African American, 10% Asian, 40% Latino, 33% White, and 2% multiracial non-Latino. Of the student population, 79% are eligible for free or reduced-price lunch, and 60% learned English as a second language. The third-grade classroom in which this study was conducted was led by a teacher who volunteered to attend a summer training workshop and implement the Design a Model House science curriculum module. In the workshop, she completed every writing prompt, drawing task, and designand-build challenge that students are asked to complete in the module. She had no prior experience teaching engineering or using LEGO in her classroom, but she had previously taught about material properties during a unit on rocks and minerals. This teacher was the primary implementer of the curriculum. The first author of this paper was present for half of the instructional sessions, provided technical assistance with the LEGO electronics and construction materials, and conducted the interviews with students. 585 The teacher initiated each lesson by explaining the model house criteria to be investigated that day, and then students wrote and drew in their workbooks for 5 min to respond to an introductory ‘‘exploration’’ prompt related to those criteria. Students then worked in pairs to complete the day’s model house investigation. The teacher concluded each lesson by guiding the students through reflective prompts (Davis and Linn 2000) in their workbooks. Eighteen students participated in the curriculum module over a period of 4 weeks. Among them, two boys and seven girls returned permission forms. These nine students were included in this study. As shown in Table 2, these participants represented a broad range of academic abilities. All nine students were present for all nine lessons of the module. Data Sources To track students’ changes related to selecting, testing, and describing materials, we conducted clinical interviews and collected student workbooks. The interviews were conducted before and after the instruction, and the workbooks were embedded assessments used during the instruction. Clinical Interviews The semi-structured clinical interview (Ginsburg 1997; Piaget 1929) consisted of two material selection design tasks. To begin each task, the interviewer stated a design goal, displayed a design schematic, and gave the student two material samples. The interviewer then asked the student to select, justify the selection of, propose testing techniques for, and describe the material that would best accomplish the goal. For the first design task, students selected either bamboo pole or polyvinyl chloride (PVC) plastic pipe for the legs of a stepstool that ‘‘wouldn’t collapse.’’ This sturdy stepstool task elicited their ideas about the property of strength in addition to probing for their abilities to select, test, and describe materials. For the second task, students selected either aluminum sheeting or foam sheeting for the walls of a pet habitat that ‘‘would stay warm.’’ This warm habitat task was designed to focus students’ thinking on the property of insulation as they again were asked to select, test, and describe a material. Both strength and insulation were properties also addressed during instruction; they were required characteristics of the model houses. Each interview lasted approximately 20 min. The preinterviews took place the week before the students began working on the curriculum module. The post-interviews took place over the two-week period after they completed their model houses. The pre- and post-interview protocols 123 586 Table 2 Profiles of the student participants J Sci Educ Technol (2010) 19:580–601 Name Sex Typical written science test achievement Currently designated as english language learner? Ava Female Middle (third quartile) No Brandon Male Middle (third quartile) No Chinelle Female Low (fourth quartile) No Elisa Female Low (fourth quartile) No Julia Female Low (fourth quartile) Yes Katie Female Middle (second quartile) No Macon Male Middle (second quartile) No Stella Female Low (fourth quartile) No Viola Female High (first quartile) No were identical. A summary of the protocol is presented in the ‘‘Appendix’’. Workbooks Student workbooks were analyzed to investigate how the changes in interview performance connected to students’ engagement with materials science practices throughout the curriculum module. The paper and pencil workbooks were structured to provide students with introductory questions, investigation instructions, data recording prompts, and reflective prompts for each of the nine instructional activities of the module. The 21-page workbooks included six pages with writing and drawing tasks related to the property of strength, five pages with tasks related to the property of insulation, and three pages with tasks related to both strength and insulation. Data Analysis Interview Scoring Interviews were transcribed in their entirety. Each transcript was then separated into six segments: the select, test, and describe sub-tasks within the sturdy stepstool design task, and the select, test, and describe sub-tasks within the warm habitat design task. Each of the six segments was assigned a set of descriptive codes (Glaser and Strauss 1967; Miles and Huberman 1994) as well as a numerical score. The coding details are discussed below. Overall, Table 3 presents how the coding and scoring scheme was designed to probe high and low levels of student ability related to materials science practices. All interview responses were coded and scored by two independent raters. The interrater reliability for the numerical scores was 0.87 (Pearson correlation coefficient). We created a coding scheme that emphasizes just three aspect of the students’ responses: their selection rationales, proposed tests, and 123 descriptions of materials. Students did not earn or lose points for choosing one or the other material. For the select sub-tasks, students stated their rationales for choosing a certain material. Each rationale was coded for three factors: (a) relevance to design goal (Fortus et al. 2005), (b) accuracy for selected material sample (Minogue 2008), and (c) type, including intensive property, extensive property (Smith 2007), material kind (Dickinson 1987), or irrelevant to design goal. Responses earned 2 points for each rationale that considered a relevant property with scientifically accurate justification, such as ‘‘I chose the PVC because hard plastic is stronger than hollow wood.’’ Responses earned 1 point for each rationale that considered a relevant property but used scientifically inaccurate justification, such as, ‘‘I picked the hollow bamboo because it is harder to push down than the PVC.’’ (This rationale is scientifically inaccurate because bamboo is more compressible than PVC. However, compressibility is a relevant property to consider in designing a stepstool). By assigning partial points to rationales built on consideration of relevant properties, we were able to credit a student’s ability to note the properties most important for a task even when she could not accurately identify a material characterized by those properties. Zero points were earned by responses in which all rationales were both irrelevant and scientifically inaccurate. For the test sub-tasks, students proposed techniques for testing a given property (strength for the stepstool, insulation for the habitat). Each proposed technique was coded for three factors: (a) relevancy to design goal (Fortus et al. 2005), (b) productivity for determining property (Smith et al. 2006), and c) requirement for full prototyping, such as building an entire stepstool or pet habitat (Dym and Little 2004). Responses earned 2 points for each relevant, productive test that did not require prototyping, such as ‘‘I would put a heavy weight on the PVC pipe and see if it broke.’’ Responses earned 1 point for each suggestion to build and test a full prototype, such as, ‘‘I would get more J Sci Educ Technol (2010) 19:580–601 587 Table 3 Construct analysis with examples of introductory materials science practices Science Practices Related to Material and Object Properties STUDENTS: The student has… Highly proficient abilities related to material and object properties SELECTING: To select a material for a specific task, the response… TESTING: To discuss how to test for a material property, the response… DESCRIBING: To describe a specific material sample, the response… Names an appropriate material and provides a rationale that is both relevant to the task and accurate for the material. Proposes and justifies an effective method that does not require full prototyping. Accurately uses multiple intensive and extensive properties. e.g., I choose foam for the bath toy because it has very low density and is buoyant in water. e.g., That cube of wood is lightweight and about 2 inches long on each side. It is brown and buoyant in water. Proposes and justifies an effective method, but it requires full prototyping. Primarily describes surface features and extensive properties. e.g., Test for the strength of that plastic by building a bed out of it and seeing if the bed collapses. e.g., That cube of wood has rough spots on it. It could give splinters. It feels heavy. Provides no information relevant to selecting materials for the task. Provides no information relevant to measuring the property. Provides no information relevant to the material. e.g., I would choose wood for the bath toy because it’s the best choice. e.g., I know that plastic has a lot of strength. e.g., I like how that cube of wood feels. Names a material and provides a rationale that is either relevant to the task or accurate for the material, but not both. e.g., I choose clay for the bath toy because clay can float. Very limited abilities related to material and object properties e.g., Test for the strength of that plastic by measuring its compression distance under a 1-kg weight. PVC, build a stepstool, and stand on it.’’ Responses earned 0 points if all proposed tests were both irrelevant to the goal and unproductive for determining the property. For the describe sub-tasks, students described the material samples in as much detail as possible. Each descriptor was coded as intensive property, extensive property (Smith 2007), surface appearance (Smith et al. 1985), material kind (Dickinson 1987), function (Dickinson 1987), simile or metaphor (e.g., it looks like a log), or inaccurate. Responses earned 1 point for the first intensive property descriptor and 1 point for the first extensive property descriptor. A score of 0 points represents a description that included neither intensive nor extensive properties. We incorporated science content knowledge into the materials science practices coding. First, for a selection rationale to be coded as ‘‘scientifically accurate,’’ the student needed to have at least some content understanding of the material that she chose. Second, for a material test to be coded as ‘‘productive,’’ the student needed to have understanding of the property for which he was proposing a test. After coding and scoring each individual student’s responses, we computed summary statistics for the entire participant group, and we tabulated the frequency with which each code was applied. We also computed the total number of distinct (i.e., unique) ideas elicited from the group of students for each selecting, testing, and describing sub-task. Counting the number of unique ideas elicited by a task is important because it indicates the generativity of the task as well as the expertise of the students. Students are not always able to generate relevant ideas in novel situations, and the ability to generate multiple relevant ideas is an important characteristic of experts (Linn and Eylon 2006). 123 588 Workbook Scoring Each workbook page on strength or insulation was assigned an activity completeness score that indicated how fully the student attempted the tasks (Baxter et al. 2000). A response earned 1 point if between one-third and two-thirds of the page had been completed, and 2 points if two-thirds or more of the page had been completed. Each workbook page was also scored for performance on the science practice it featured. As shown in the sample scored workbook page in Fig. 1, each page consisted of multiple prompts for written or drawn responses. If the student accurately selected, tested, or described materials in all of the responses on a page, that page was rated as showing full accuracy. If only some of the responses showed accurate work, the page was rated as showing partial accuracy. For each workbook page, a specific scoring rubric described what could be considered partial or full accuracy at its key science practice. For example, for the page shown in Fig. 1, the key science practice is selecting materials, and full accuracy requires choosing column materials that are consistent Fig. 1 Sample scoring of a workbook page featuring the property of strength and the science practice of selecting materials 123 J Sci Educ Technol (2010) 19:580–601 with the recorded data as well as referencing strength in the rationale for the choice. Two raters scored each workbook response for both completeness and science practice. Interrater reliability for the workbook scores was 0.86. Results The case study of nine students is reported in three steps. First, we provide a summary of students’ responses to the stepstool and habitat scenarios. Second, we utilize quantitative evidence to highlight the changes in interview performance from preinstruction to postinstruction. Finally, we describe connections between students’ interview gains and their engagement with workbook tasks during the module. Based on the patterns observed across all nine students, we use four students to illustrate how students’ materials science practices changed and how these changes can be traced to workbook efforts. When presenting these four prototypical students, we identify the other students who showed similar characteristics. J Sci Educ Technol (2010) 19:580–601 589 Selecting, Testing, and Describing Materials for Sturdy Stepstools and Warm Habitats Justifying Material Selections As shown in Table 4, in selecting materials, students responded with fewer relevant and accurate rationales for their material selection for the warm habitat task than for the sturdy stepstool task. However, both before and after instruction, the students offered a greater total number of selection rationales for habitat materials than for stepstool Table 4 Material selection rationales offered by all students materials. This result means that while students were able to engage in the practice of selecting materials for both design tasks, they had greater conceptual understanding of the phenonomena related to sturdiness than to temperature maintenance. Though they offered an abundance of rationales for their habitat material choices (a sign of science practice ability), the rationales for their stepstool material choices were more relevant and accurate (a sign of conceptual understanding). For example, Brandon stated only two reasons for choosing PVC for the stepstool, but both reasons were Rationales for material selection List of all rationales No. of distinct rationales Percentage relevant and accurate Relevant and accurate Irrelevant or inaccurate 8 3/8 (38%) Stronga Heavy Sturdy Stable Holds a lot of weight Metal Stepstool task Pre-interview Wooden Paintable Post-interview 12 5/12 (42%) Strong Heavy Sturdy Stable Holds a lot of weight Plastic Hard Splinter-free Tear-resistant Layered Attachable Thick Habitat task Pre-interview 10 2/10 (20%) Retains heat Blocks coldness Heavy Strong Unbreakable Hard Thick Cut-able Lightweight Feels warm Post-interview 15 2/15 (13%) Retains heat Heavy Proven as insulator Strong Unbreakable Hard Thick a Rationale statements made by multiple students are counted and listed only once. Synonymous statements have been collapsed into one entry; e.g., the statements ‘‘unbreakable,’’ ‘‘not breakable,’’ and ‘‘can’t be broken easily’’ are collapsed into the entry ‘‘unbreakable.’’ Cut-able Feels warm Heats up quickly Shiny Metal Soft Melt-proof Sound-proof 123 590 directly related to the goal of a collapse-proof stepstool: PVC is ‘‘strong’’ and ‘‘sturdy.’’ In contrast, when Brandon chose metal for the pet habitat, he gave three reasons, and none of them was directly related to the goal of an insulated habitat wall. He explained that he chose metal because it is ‘‘hard,’’ ‘‘heavy,’’ and ‘‘the mouse can’t bite through it.’’ Although Brandon’s rationales for his chosen habitat material were not relevant to the explicit design goal of insulation, we do note that his response shows awareness of other important design features. Proposing Material Tests Table 5 illustrates that the students more frequently proposed scientifically productive tests for determining strength than they did for determining insulation. However, both preand postinstruction, the students offered a greater number of distinct proposals for testing insulation than they did for testing strength. Taken together, these results indicate that students’ conceptual understanding of strength enabled them to conduct the practice of testing materials more productively for the stepstool task than for the habitat task. For example, Julia suggested three appropriate, productive tests for determining PVC’s strength: ‘‘use a hammer to bang it and see if it doesn’t break,’’ ‘‘put a rock on it and see if it breaks,’’ and ‘‘try dropping it on the floor.’’ In contrast, within the habitat task, Julia’s list of tests was more extensive, but fewer of the tests were relevant and productive to testing for insulation. She said that to test for insulation, she would ‘‘touch [the metal] and see if it feels hot,’’ ‘‘use a rock or a hammer,’’ ‘‘put something heavy in the middle and see if it breaks,’’ ‘‘try to bend it,’’ ‘‘build a house and try it,’’ and ‘‘make a little door to let air in and out.’’ This difference in performance between the stepstool and habitat tasks also suggests that the design goal of an insulated pet habitat was not well understood by all the students; it was not a goal that fit easily into their conceptions of habitats. Even when the interviewer moved on from the term ‘‘insulation’’ and reiterated the design goal as choosing a wall material that would ‘‘keep a warm temperature inside the habitat,’’ the students chose to select materials for and propose tests for other attributes of pet habitats. In contrast, for the stepstool task, they remained focused on the attribute of strength. The goal of a sturdy stepstool made sense to the students, but the notion that insulation (i.e., maintenance of a particular temperature) is an important design goal did not resonate with their conceptions of adequate pet habitats. Thus, to complete the habitat task, they drew from a variety of their personal, everyday experiences with pets. In contrast, to complete the stepstool task, they drew more from their school-science experiences with strength and stability and generated a narrower range of responses. 123 J Sci Educ Technol (2010) 19:580–601 To explore the results of the selecting and testing subtasks further, we examined students’ postinstruction responses to interview questions about the definitions of strength and insulation. In the post-instruction interview, students were asked what it meant for something to be strong and what it meant for something to be insulating, before they were asked to propose tests for those properties. Students who were not able to define a term were provided with its definition before being prompted with the next interview question. At postinstruction, all nine students produced accurate definitions of ‘‘strong.’’ However, only two students, Chinelle and Macon, produced an accurate definition of ‘‘insulating,’’ which they described as ‘‘keeping something at the temperature you want.’’ Despite being able to define insulation, these two students showed below-average performance on selecting and testing materials for the habitat in their postinstruction interviews. In contrast, five of the students who could not accurately define the term insulating showed above-average performance on selecting and testing materials for the habitat (after they were reminded of the definition of insulating). The remaining two students, Stella and Brian, could neither define insulating nor competently perform the materials science practices for the habitat task, but they excelled at the materials science practices when asked to apply them to the sturdy stepstool task. These data highlight the distinction between having vocabulary knowledge and applying that knowledge to practical tasks. Although vocabulary knowledge is no doubt crucial to long-term science achievement, in this study it was neither necessary nor sufficient for students’ success with materials science practices. In other words, the data show no consistent relationship between vocabulary knowledge and science practice abilities. However, what did emerge from the data was the importance of specific conceptual understanding for students’ materials science success. Students’ materials science practices did not generalize across material properties. For example, although Stella and Brian were excellent at justifying selections and proposing tests for a strong material, they were not able to select and test for an insulating material. Whether or not they had mastered the vocabulary term ‘‘insulating,’’ students were only able to select and test for insulating materials if they had some understanding of thermal phenomena. More important than the definition of insulation were awareness of the situations when it is important and of the variables that allow it to be observed. Although the sophistication of the term ‘‘insulating’’ contributed to the difficulty of the habitat task, the conceptual challenges related to heat and temperature played a larger role in limiting students’ success in selecting and testing materials for an insulated habitat. J Sci Educ Technol (2010) 19:580–601 591 Table 5 Material property tests proposed by the overall group of students Tests of material properties List of all proposed tests Number of distinct ideas Percentage relevant and productive Relevant and productive Irrelevant or unproductive 8 (7/8) 88% Build prototype and step on ita Weigh on scale Stepstool task Pre-interview Build prototype and put rocks on it Drop test Bend until break Tap until break Impact with rock Apply body weight Post-interview 12 (10/12) 83% Build prototype and step on it Weigh on scale Build prototype and do compression test Drop test Measure thickness Squeeze test Impact with rock Apply body weight Apply test weight Impact with hammer Impact with golf ball Flick test Habitat task Pre-interview 11 (2/11) 18% Build and measure air temp over time Expose to heat and measure temp [looking for warmth] Build prototype and test with mouse Build and check for breathing holes Measure height Measure thickness Measure length Weigh on scale Check for melting Impact with hammer Try to poke holes Post-interview 18 (4/18) 22% Build and measure air temp over time Feel for warmth Build and test with mouse Expose to heat and measure temp [looking for warmth] Expose to light and measure temp on each side over time Put on overhead projector Form into cylinder and expose to light and measure temp Build and check for breathing holes Weigh on scale Try to break Drop test Impact with hammer Apply test weight Expose to light and check for light transmission Push test 123 592 J Sci Educ Technol (2010) 19:580–601 Table 5 continued Tests of material properties List of all proposed tests Number of distinct ideas Relevant and productive Percentage relevant and productive Irrelevant or unproductive Expose to light and feel for warmth Add door to house Add tape to house a Tests proposed by multiple students are counted and listed only once. Synonymous tests have been collapsed into one entry; e.g., the proposals to ‘‘add a test weight,’’ ‘‘put weight on top,’’ and ‘‘see if it can hold a weight,’’ are collapsed into the entry ‘‘apply test weight.’’ Describing Material Properties In describing materials for both the stepstool and habitat tasks, students expressed accurate and prolific ideas. Before instruction, 29% out of a total of 116 distinct material descriptors were intensive properties, like ‘‘weak,’’ ‘‘white,’’ and ‘‘hard,’’ while 31% were extensive properties, like ‘‘skinny,’’ ‘‘rectangular,’’ and ‘‘heavy.’’ Only two of the descriptors were inaccurate: Katie described the foam sheeting by saying ‘‘warm air goes through it,’’ and ‘‘it won’t burn down.’’ After instruction, 25% of the 114 distinct descriptors were intensive properties, and 30% were extensive properties. Only one of the descriptors was inaccurate: a description of metal sheeting as being ‘‘easy to melt.’’ Changes in Materials Science Practices from Preinstruction to Postinstruction For each interview performance, we computed three types of scores: a total score, a score for each of the two design tasks, and a score for each of the three materials science practices of selecting, testing, and describing. For all six of these measures, the postinstruction means were higher than the preinstruction means (Table 6). However, out of the three individual science practices, only the pre-post increase for the testing sub-task was statistically significant (p \ .05, 2-tailed Wilcoxon test). This means that after instruction, the students improved most in proposing methods to test for material properties. The students exhibited greater understanding of the use of engineering tests to determine a material’s appropriateness for a design goal, and this resulted in overall improvement on the stepstool and habitat tasks. Connecting Pre-Post Changes to Science Workbook Performance Workbook scores varied greatly across the nine students and across tasks. As shown in Fig. 2, students’ interview scores were positively correlated with their workbook scores. Greater gains on the individual stepstool and habitat interview tasks, respectively, were associated with higher completion of and accuracy on the corresponding strength and insulation workbook tasks (q = 0.478, p \ 0.05). Throughout the instructional module, all students conducted the same number of engineering tests on house materials and constructed the same number of house components. Thus, they did the same amount of ‘‘handson’’ work. The difference among students was the amount of information they recorded in the workbooks. Those who recorded more in their workbooks learned more. When we analyzed the students’ workbook performances using only Table 6 Average scores on design-task interviews (n = 9) Measure Pre-instruction mean (SD) Post-instruction mean (SD) Average paired gain, pre-post (SD) Effect sizea, cohen’s d Total interview (out of possible 36) 8.8 (3.4) 13.8 (3.9) 5.0* (3.7) 1.34 Stepstool task (out of 18) 6.2 (2.4) 10.0 (3.8) 3.8* (3.6) 1.27 Habitat task (out of 18) 2.6 (1.5) 3.8 (1.8) 1.2* (1.1) 1.27 ‘‘Select’’ sub-tasks (out of 16) 2.7 (2.8) 4.3 (2.3) 1.7 (3.0) 0.56 ‘‘Test’’ sub-tasks (out of 16) 2.6 (1.4) 5.6 (2.4) 3.0* (1.7) 1.73 ‘‘Describe’’ sub-tasks (out of 4) 3.6 (0.7) 3.9 (0.3) .33 (.87) 0.38 a Effect size is calculated according to the Cohen’s d statistic, where d = (average of paired differences)/(standard deviation of paired differences) * p \ .05; 2-tailed Wilcoxon test 123 J Sci Educ Technol (2010) 19:580–601 593 lowest total post-interview score. Both before and after instruction, his responses comprised a narrow set of ideas focused on weight. For the sturdy stepstool task, he selected PVC because it felt heavier. At both interview times he proposed weighing the PVC on a scale to test for its strength: M I M I M I Fig. 2 Students’ gains on the interview design tasks plotted against their scores on the corresponding workbook exercises (Spearman correlation = 0.48, p \ 0.05, n = 18); letters adjacent to the markers identify individual students their completeness scores, we found that greater gains on the stepstool and habitat interview tasks were also significantly correlated with the completeness of the corresponding strength and insulation workbook exercises (q = 0.473, p \ 0.05). Even if their recordings were inaccurate, the students who recorded more in their workbooks improved more on the interviews. This indicates that the importance of both task engagement and record keeping for design-based science learning. If students ably experiment and design, but do not keep records, then they gain less from their experimentation and design activities. Four Student Cases We now use the work of four prototypical students to illustrate qualitatively the nature of the connections between the interviews and workbooks. Four representative examples are those of Macon, who improved the least on both interview tasks, Stella, who improved the most on the stepstool interview task, Julia, who improved the most on the habitat interview task, and Chinelle, who received the highest total workbook score. M I M I M For the warm habitat task, Macon again focused on weight as a priority in establishing the property of a material. At both interview times, he chose aluminum because it felt heavier, and he suggested weighing the aluminum to determine its insulation ability. To Macon, the property of weight could be used to determine both strength and insulation: M I M I M I Macon: No Improvement on Interview Tasks Macon is the representative case for students who earned low workbook scores and showed little or average gain on the interview. Brian and Elisa also displayed these characteristics. Macon’s scores did not increase on either the stepstool task or the habitat task, and he received the [Chooses PVC pipe for as better material for stepstool leg.] Okay. Why do you think that would be the better material for the stool? Because it’s metal [incorrectly identifying PVC plastic as metal] Okay, because it’s metal. Why would that make it better? Because metal’s stronger than wood [3-s pause] Can you tell me more about that? [5-s pause; M shrugs shoulders] What, why is metal stronger than wood? Because it’s heavier. And heavier stuff is stronger …Okay. What is something you could do to measure exactly how strong this material is? So that you could tell You could weigh it?….Um, you can put it on, like, one of those weigh things that people stand on And then what would that tell you about how strong it is? It would, it would, because heavier stuff makes it stronger so, if it’s heavy, if it’s heavier than this [picks up bamboo], then it [PVC] would be stronger M I M I This one [points to metal tray] Why do you think this would be the better material for Cuz it’s heavy and stronger And why would heavier and stronger make it better? Because, if it’s thicker, then it might be heavy and strong, and if it’s heavy and strong it makes stuff warm Okay, why do you think that something heavy and strong makes stuff warm? Because it’s thick And what does the thickness do with the warmth? It traps it all inside of something …So you picked this metal, the other engineers want to know exactly how good it is at insulating. …It means how good it is at keeping the temperature the 123 594 M I M J Sci Educ Technol (2010) 19:580–601 same… inside the house. How could you measure how insulating this material is? You could weigh it on a scale And if it weighed more, what would that mean about how insulating it is? It would mean that it would be warmer Macon’s workbook performance aligned with his lack of improvement on the interview tasks. His workbook score, 18 out of 60, was the lowest of all nine students’ scores. Although Macon and his partner did complete all of the hands-on construction and testing activities with the rest of their class, Macon responded to very few of the exploration or follow-up prompts, and his workbook contains very few complete phrases or drawings. It also contains very little data from the class’s tests of material properties, with one major exception: Macon recorded all the results from the sound absorption test and responded to the follow-up prompt about soundproof materials. As a result, the one new idea posed by Macon at postinstruction involved sound absorption. Despite several reminders that the design goal for the second task was a habitat that would stay warm, Macon based his initial material selection for that task on the samples’ soundproofing qualities. He declared that the mouse should not be bothered by outside noises, and foam was the best material because its sound absorption ability had been proved in class. Stella: Greatest Improvement on Stepstool Task Stella illustrates the case of showing a very high gain for one interview task while showing a below-average gain for the other interview task. Stella is a unique case, as no other students fit this profile. Of all nine interviewed students, Stella showed the greatest pre-post improvement on the stepstool task. Both before and after the module, she expressed many ideas for both design tasks, but only on the stepstool task did her responses substantially improve in their level of sophistication. At preinstruction, Stella chose bamboo for the stepstool simply because of its material kind: ‘‘because it’s wooden.’’ To test for the bamboo’s strength, she proposed standing on it and trying to break it in half. To describe the bamboo, she offered only four descriptive terms, and none of them were extensive properties. I S I I want to know which you think would be the better material to use to make the stepstool This [bamboo] one because it wouldn’t break… because this [bamboo] one’s wooden… This [PVC] one would break because… it’s not wooden …Yeah, okay, so what could you do to tell the engineers exactly how strong this [bamboo] is? How could you measure its strength? 123 S I S I S You can stand on it And what would that tell you about how strong it is? Uh, um, tell you if its sturdy or not sturdy, and it’s like, uh, if it’s like, uh, not sturdy to stand on it, and it like, start standing on it and you’ll fall Okay, any other tests you could do to find out how strong it is? Like if you can break it in half and see if you can stand on it and it won’t break apart At postinstruction, Stella switched to choosing PVC for the stepstool, and she based her choice on its intensive properties: it was ‘‘strong,’’ ‘‘sturdy,’’ and ‘‘hard.’’ To test for strength, she suggested a number of useful tests, including hitting it with a golf ball, compressing it, building a prototype stepstool, and once again, standing on the PVC. She described the bamboo in 10 different ways, which included both intensive and extensive properties. S I S I S I S I S I S This one [PVC] Okay, why would that be better? Because, um this [bamboo] one like is wood, and this [PVC] one um, is like stronger, cuz when you stand on it, you’re um, you won’t fall… Why do you think this one [PVC] is stronger? Because, um, it has, um, good materials, and it’s sturdy… Like, um, it’s hard, and um …What could you do to measure exactly how strong this material is? You can, um [3-s pause], put it like, um, on something, and, um make sure it doesn’t break with anything… You can try to stand on it …Are there any other tests that you could do with this material, to see how strong it is? You can um, make something out of it, and then you can like um, like do it with, that thing we did for a golf ball, you can… We hit it with a ball What did you do in that, is there anything you did in that project where you tested for strength, that you could use to test for the strength of this? Um, you can like um, we pressed it down. [Holds PVC upright, pushes on top] You can um, you can uh [6-s pause] you can [12-s pause] you can make it out a stepstool, and then you can try it Like Macon’s workbook, Stella’s workbook aligned well with her interview performance. On the tasks related to strength, she earned the second highest score. With the exception of the tasks for the second lesson, Stella’s responses to prompts about strength are complete, and they show proficiency at materials science practices. Her written and pictorial inscriptions indicate that she was attempting to connect materials’ characteristics to their appropriateness for certain tasks. In response to a prompt about useful J Sci Educ Technol (2010) 19:580–601 materials for support columns, she listed, ‘‘brick, wood, metal, gold, stone, silver, and cement,’’ because these materials are ‘‘sturdy, strong, stable, able to support weight.’’ Stella’s much improved stepstool task performance and her high level of workbook engagement indicate that she learned a great deal about the property of strength, and that the opportunity to write and draw about strength in several different contexts enabled her to construct and explore new ideas. However, her much more moderate improvement on the habitat interview task suggests that students’ learning about materials science practices does not generalize to all material properties. Stella was able to apply her classroom experiences to a novel interview task involving the property of strength, but not to a novel task focused on insulation. Julia: Greatest Improvement on Habitat Task Julia represents the case of improving on both interview tasks and earning workbook scores that were consistent with both interview gain scores. Ava and Katie also showed these characteristics. Julia’s gain on the habitat task was the highest among all nine students. She also improved substantially on the stepstool task, and she was one of only three students who improved on all three subtasks: selecting, testing, and describing materials. Julia, an English language learner, shifted from providing just a few vague ideas in her pre-interview to offering many wellarticulated ideas at post-interview. Before instruction, she chose metal for the habitat walls because it ‘‘can’t break,’’ and she proposed testing the metal with a hammer to see if it was strong. Neither her selection rationale nor her proposed test was relevant to the design goal of insulation. Further, in describing materials, she generated only three descriptors for the metal. Below, she explains her choice for the habitat: I J I J I J I J Why would you pick that [metal] one as the better material? Because this [metal] one, it can’t break and this [foam] one is kind, could break, if you let it, do it like this Mm, this [foam] white one could break Yes What if you had to think mostly about the job of keeping the mouse house warm, would you still pick this [metal] one, or would you pick this [foam] one? Still pick this [metal] one Okay, tell me about that Because [3-s pause], um, if you like, made it with, you could like, maybe you could like make a door with it? At post-interview, Julia still cited metal’s strength as part of her selection rationale for the habitat material, but 595 she also introduced new rationales and tests that did relate to insulation. She reasoned in a relevant (though inaccurate) manner that metal ‘‘won’t let the cold in,’’ and she suggested testing the metal by touching it to see if it felt hot and by building a prototype house to test its insulation abilities. She also described the metal in seven different ways. I J I J I J I J I J So why would you pick this one [metal] as the better material for keeping the temperature warm? Because, um, when you put it in a house, this one [metal] will make it hot, and this [foam] will not, because it will like, cover the hotness and somehow it’s gonna go in, the cold …So how could you measure exactly how good this material [metal] is at keeping the temperature the same?… Um, I would…I would like put it on, and touch it, and if it’s cold, and maybe when you build it, it will make it hot because it lets in the – So when you touch it, it feels kind of cold Yeah But when you use it to build something – Yeah, inside It would keep it warm? Yeah. For the mouse Like Macon and Stella, Julia engaged with her workbook tasks in a manner that aligned with her pre-post interview changes. Her workbook earned the second highest total score and the second highest score for insulation tasks. In the workbook, Julia engaged in each lesson’s beginning exploration question, which gave her many opportunities to practice reasoning about material and object selections. For example, as shown in Fig. 3, she reasoned that a winter jacket keeps you warm because ‘‘it is thick and [it] keep[s] your body heated by sorta stick onto you.’’ Julia also completely and accurately recorded results in her workbook for both tests related to insulation (for the model house wall and roof materials). Her computations of temperature changes were correct, and her conclusions about the most insulating materials were consistent with the data. Metal was not a material used during the instructional module. Although Julia’s workbook answers were correct, she was not considering metal as a potential insulating material when she composed those answers. Chinelle: Highest Workbook Score In the previous three examples, each student’s workbook scores were aligned with his or her interview performance. Chinelle’s example is less straightforward. She earned the highest total workbook score, 51 out of 60 points. If her 123 596 J Sci Educ Technol (2010) 19:580–601 Fig. 3 Pages from the workbooks of Macon, Julia, and Chinelle; left-hand samples are exploration questions about insulation from the middle of the module; right-hand samples are from the concluding workbook page results followed the pattern of Macon and Julia, the quality of her workbook would predict a great improvement on her interview responses. But instead, Chinelle’s 4-point interview gain was below average. Because her pre-interview score of 6 points was among the lowest, this small pre-post gain was not due to a ceiling effect. We use Chinelle to represent the case of earning workbook scores that would predict much higher interview gains than were actually achieved. Viola is the other student whose work followed this pattern. One potential explanation for Chinelle’s lack of pre-post improvement is that she somehow failed to engage in a critical instructional activity. Indeed, one-third of Chinelle’s missing workbook points were on the very last workbook page, which prompted the students to review 123 how they had treated a given property during their model house design. The prompts were, ‘‘How did you test for the property of ____?’’ and ‘‘Why is the property of ___ important to your house?’’ Each individual student was assigned a different property by the teacher. Chinelle was assigned the property of insulation, but as shown in Fig. 3, her page was only partially complete; she wrote only, ‘‘The white is a good insulator.’’ This work gave no indication of accurate science practices and earned only 1 out of 4 possible points. In contrast, Julia and Stella earned 4 and 3 points, respectively, on their work for this page. Stella wrote that to test for strength, ‘‘you have to push down and see if it pushes,’’ and that strength is important for a house because you have ‘‘to keep it up.’’ Julia recalled that for her reflectivity test, she had ‘‘got foam, [and] J Sci Educ Technol (2010) 19:580–601 cardboard of the color black or white,’’ and that reflectivity is important because one needs to ‘‘let the heat out not in the house.’’ Julia used her final workbook page to write about temperature regulation for the model house, and she performed well on the habitat task in her post-interview. Likewise, Stella concluded her workbook by writing accurately about the property of strength, and she expressed sophisticated ideas about strength in her post-interview. Chinelle, on the other hand, did not take advantage of the last workbook task, and her subsequent post-interview performance showed relatively little improvement from pre-interview. Macon, similarly, earned 0 points on his last workbook page, and he showed no improvement between the two interviews. Besides Macon and Chinelle, one other student earned less than 2 of the closing activity’s points, and his interview gain was just above the class average. Though additional investigation is needed, these patterns suggest that the closing instructional activity, which tasked students with reflecting on the actions and reasoning that led to their model house design decisions, may have been a critical factor in helping students attain their newly learned materials science practices. Discussion This case study focused on third-grade students’ learning of materials science practices. During both the curriculum module and the interviews, students had multiple opportunities to select, test, and describe materials. The model house, sturdy stepstool, and warm habitat design scenarios provided authentic contexts (Brown et al. 1989; Roth 1996) for materials science practices and for reasoning about properties of materials and objects. Several intriguing patterns emerged from the workbook performances and interview responses elicited by these design scenarios. Third-Graders’ Approaches to Materials Science The students relied on perceptually accessible properties (Smith 2007), including thickness, texture, felt weight, and felt temperature, as they constructed their rationales for material selection. They also preferred perceptually accessible properties as they proposed methods for testing strength and insulation, two properties that are not immediately observable. This preference for perceptual accessibility is consistent with findings in other studies (Gustafson et al. 1999; Lewis and Linn 1994), and it can help to explain why, despite the substantial gains between pre- and post-interviews, the highest post-interview scores were still less than 60% of the maximum score. The properties that the children were asked to consider were 597 complex physical properties determined by underlying molecular structure, bonding, and manufacturing methods. Primary grade students lack knowledge about these invisible determinants of complex properties (Nakhleh and Samarapungavan 1999). As a result, when the students tried to select and propose tests for materials, they relied on immediate perception and based their ideas on directly observable properties, rather than on underlying intensive properties. Changes in the Third-Graders’ Approaches to Materials Science Despite their preference for perceptually accessible properties, all the students included at least one intensive property in their post-interview rationales for material selection, and all but one student proposed at least one useful material test for an intensive property. These results indicate that elementary students can learn to recognize and test intensive properties, even if they cannot generate mechanistic explanations for those properties. Smith et al. (1985) conducted a study in which most 6- to 9-year-olds simply invoked material kind to explain why a clay ball is heavier than a wax ball; they said one ball was heavier because it was made of different ‘‘stuff’’ than the other ball. This finding suggests that the students in our study would simplistically invoke material kind and state that the bamboo was weaker just because it was made of wood, and that the aluminum was less insulating just because it was made of metal. However, after instruction, very few of the students appealed to material kind to explain why one sample was weaker or less insulating than the other. Rather, they made serious attempts to construct a causal relationship between immediately accessible material and object properties and the less accessible properties of strength and insulation. Another pattern in the data was the emergence of synthetic models in the postinstruction responses to the warm habitat task. When instruction causes a student to find incoherencies in her commonsense theory for making meaning of something, then she might be inclined to create what Vosniadou (2002) calls a synthetic model. This happens when ‘‘information received through instruction seems to become assimilated to the initial explanatory framework creating synthetic or internally inconsistent models’’ (Vosniadou 2002, p. 62). We identified two examples of synthetic models. The first was Katie’s idea that a material’s ability to block light transmission determines its ability to block heat transfer. In both her workbook and postinstruction interview, Katie suggested that if she held a material up to a light and saw light passing through, she would know the material was a poor insulator. This model of equating transparency with 123 598 thermal conductivity could have been based on the curricular activity in which a lamp provides the heat for an insulation test. Katie possibly viewed the lamp’s primary function as a light source rather than a heat source. The second synthetic model was the idea, put forth by both Stella and Julia, that air flow into a space is equivalent to heat input into the space. At postinstruction, both of these students proposed methods for insuring that adequate air could enter the pet habitat. Stella wanted to make holes in the habitat walls, and Julia wanted to create an open door. They reasoned that if the air could flow into the habitat, then the habitat would be warm. This model for warmth maintenance could be based on home experiences of opening doors and windows to regulate the indoor temperature, and it is consistent with nonnormative ideas uncovered by previous research (Clark 2006; Erickson 1979; Paik et al. 2007). Connecting the Third-Graders’ Interview Approaches to Their Workbook Performances When studying an instructional intervention with the aim of improving student learning outcomes, it is important to examine the ‘‘black box,’’ or ‘‘instructional dynamic’’ (Ball and Forzani 2007), of the interactions between students, teacher, and curriculum materials. In this study, we focused on analyzing the students’ interactions with the curriculum materials—the science workbooks. Overall, the workbooks served as a tool that enabled the students to track the tests they conducted on potential materials as well as the selection decisions they made based on the test results. In this way, the workbooks may have eased the cognitive effort required to connect test results back to experimental procedures, and to link test results forward to decisions about courses of action (Shepardson and Britsch 2001). This means that students who take great advantage of opportunities to record their observations and reasoning (like Julia and Stella) are likely to show the greatest change in their approaches to the selection and testing of materials. This is consistent with the finding by Olson (1996) that writing about abstract notions, rather than only speaking about them, has helped humans to advance new ideas and concepts. However, because most third-grade students have not yet developed differentiated concepts of heat and temperature, third-grade student performance on the habitat interview task might not improve even with tireless effort on writing and drawing exercises related to insulation. Even after hours spent writing and drawing about thermally comfortable model houses, there may be a conceptual cap on children’s ability to select, test, and describe materials in the context of designing an insulated structure. 123 J Sci Educ Technol (2010) 19:580–601 Moreover, there are also specific kinds of writing and drawing tasks that may do more to foster the building of proficiency at materials selection, testing, and description. The closing workbook activity used in this study prompted the student to reflect on the scientific reasoning behind design decisions—e.g., to explain how and why particular properties were tested and particular materials were chosen. This kind of reflection activity appears to be a critical exercise for learning materials science practices. As shown in Chinelle’s example, if students engage in almost all learning tasks but do not respond to reflective prompts (Davis and Linn 2000), they may miss a key chance to consolidate newly constructed ideas with newly learned practices. Study Limitations Several factors limit the generalizability of this study’s findings. First, since the interviews used particular material samples and posed particular design scenarios, they did not comprise an exhaustive assessment of introductory materials science. We did not collect information on the students’ initial commonsense theories of matter. This information can help to examine whether a student’s existing theory of matter, including the presence or absence of material/object differentiation, is predictive of ability to select, test, and describe materials. Second, although nine students can be an appropriate number for a descriptive, exploratory case study, the small sample size prohibited the use of statistical analyses to generalize from patterns observed in the target student group. Finally, our analysis of the relationship between workbook and interview performance was intended to explore the role of instructional experiences in student learning, but workbook tasks are a single element of the multifaceted instructional environment. Other indicators such as discourse patterns among students and between students and teacher can be used to further examine the instructional dynamic of the classroom. Conclusions In this paper, we described a case study of elementary students who developed materials science practices within a science learning environment focused on the use of materials, rather than on the classification and study of them. The results of this study showed that elementary students are capable of learning the practices of materials science, even though it is a discipline typically limited to college-level engineering students. The results also showed that the act of recording materials science decisions during instruction is associated with improved J Sci Educ Technol (2010) 19:580–601 ability to make and explain materials science decisions during interviews. Thus, engagement not just with prototype building and testing, but also with reflecting upon and inscribing decisions about that prototype, is critical for learning. Using science workbooks, we were able to connect individual variations in learning gains directly to students’ varying completion of record-keeping tasks. Finally, this study demonstrated that while design-based instruction can improve students’ abilities to make and test materials selection decisions, students’ full achievement is hindered by limitations in their conceptual understanding of particular material properties. Thus, even when applied to the elementary school level, designbased instruction in the physical sciences needs to pay as 599 much attention to conceptual supports as it does to practical experiences. Acknowledgements This study was funded by National Science Foundation Grant DRL-0633952 but does not necessarily represent the policies or positions of the NSF. We would like to thank the readers and reviewers who have offered helpful comments on earlier drafts of this paper. We also wish to thank the students who took part in the study and their teacher, who generously devoted time and energy to the project and enthusiastically taught two new science units in her classroom in 1 year. Appendix See Table 7. Table 7 Summary of the clinical interview protocol Property Practice Scenario and props presented to students Examples of additional spoken prompts Strength Selecting materials and objects for a particular task Your job is to pick the material for this stepstool design. The stepstool shouldn’t collapse when someone steps on it. Imagine you have to choose between these two materials: Which material would you pick as the better material for the stepstool? (Compressive yield strength) Why do you think this is better for the stepstool? 12’’ length of PVC, 1.5’’ in diameter 12’’ length of bamboo, 1.5’’ in diameter Testing for a particular property Insulation (Inverse of thermal conductivity) Now the other engineers want to know exactly how strong these two materials were. What does it mean for something to be strong? (Provide definition if student does not know.) Tell me how you would measure how strong the materials are. And are there any other tests you would do to figure out how strong the materials are? Describing objects and materials Now the other engineers need to find the material that you picked in a big supply room. Describe the strong material to me with as many details as you can think of. Selecting materials and objects for a particular task Now imagine you have a new engineering job. Your job is to pick the material for the walls of this mouse habitat. The walls should keep the inside of the habitat warm. Imagine you have to choose between these two materials. Which material do you think you would pick as the better material for the mouse house walls? Why do you think this is better for the walls? 6’’ 9 9’’ Styrofoam tray 6’’ 9 9’’ aluminum tray Testing for a particular property Describing objects and materials Now imagine the other engineers want to know exactly how insulating these two materials are. 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