Introduction

Achieving scientific literacy for all has been emphasized in a host of reform documents in the USA (American Association for the Advancement of Science [AAAS], 1993; National Research Council [NRC] 2011) as well as in Turkey, Britain, Netherlands, North America, Canada, Australia, and South Africa (Dillon 2009). In order for students to become scientifically literate, they should develop an understanding not only of science concepts but also an understanding of the enterprise of science and the nature of scientific knowledge (NOS). In terms of scientific literacy, understanding NOS is necessary to make sense of scientific information encountered in everyday life, understand socioscientific issues, and participate in the decision-making process (Driver et al. 1996).

Research identifies teachers as the most influential factor in classroom learning (Lumpe 2007; Miller 2001), so it is no surprise that students’ failure to grasp NOS has focused researchers’ attention on teachers. While research has been effective in identifying ways to address gaps in preservice and in-service teachers’ understanding of NOS (Akerson et al. 2000; Lin and Chen 2002; McDonald 2010), research on teachers’ classroom practice indicates that knowledge of NOS is a necessary, but not sufficient, condition for effective NOS instruction (Abd-El-Khalick et al. 1998; Akerson and Abd-El-Khalick 2003; Akerson and Volrich 2006; Lederman et al. 2001). As such, a recent focus of NOS researchers has been the knowledge teachers need in order to translate their views of NOS into forms accessible to learners, or their pedagogical content knowledge for NOS (PCK) (Hanuscin et al. 2011).

Developing PCK for NOS is more complex than merely acquiring a repertoire of NOS lessons (Abd-El-Khalick 2013; Hanuscin 2013; Schwartz and Lederman 2002). Rather, PCK is the integration of several different knowledge bases (Magnusson et al. 1999). These include knowledge of curriculum, learners, instruction, and assessment, as well as teachers’ orientations toward science teaching. Research suggests that teachers need opportunities to examine subject matter (such as NOS) from a teaching perspective (van Driel et al. 1998) and be “…offered meaningful ways of defining, assessing and explicitly developing PCK” (Nilsson and Loughran 2012, p. 700).

Taking this into account, we developed instructional materials and activities to support the development of teachers’ PCK for NOS in the context of a chemistry teacher education program. We acknowledge that preservice teachers have relatively undeveloped PCK (van Driel et al. 1998) and that preservice teachers’ PCK may more appropriately be considered their “PCK readiness” (Davis 2003; Smithey 2003). Through case study, we examined the nature of preservice chemistry teachers’ PCK for NOS in order to answer the overarching question, “How does instruction that uses PCK as an organizing framework influence the development of preservice teachers’ PCK for NOS?” In seeking answers to this question, we also considered:

  • To what extent does the nature of preservice teachers’ individual component knowledge bases for PCK for NOS indicate their “PCK readiness”?

  • How and to what degree are preservice teachers prepared to integrate the individual component knowledge bases of their PCK for NOS in their instructional planning?

Literature Review

The design of our teacher education program and the study we conducted draws upon research literature related to both NOS and PCK.

The Nature of Science

The “nature of science” (NOS) is a commonly used phrase by science educators to indicate ideas about science—issues of what science is and is not, how science and scientists work, the ontological and epistemological foundations of science, and how science and society impact one another (Clough 2006; McComas et al. 1998). However, the specific definition of NOS and what level of NOS understanding should be communicated to students has been a debate both among philosophers of science and science educators (e.g., Abd-El-Khalick 2013; Alters 1997; Irzık and Nola 2010; Smith et al. 1997).

As science educators, we cannot expect teachers or students to delve into the complexities of science from a philosophical stance that even scientists themselves do not need when doing science (Smith and Scharmann 1999). As Taber (2008) emphasizes, any account of NOS presented in school science is necessarily a simplification; the aim of introducing NOS is to provide students “a more complex understanding of science, not a total or even a very complex understanding” (Matthews 1998, p. 168). This more complex understanding should progress beyond what is currently emphasized in science textbooks (Abd-El-Khalick et al. 2008), taught by majority of science teachers (Abd-El-Khalick and BouJaoude 1997), and understood by students (Dogan and Abd-El-Khalick 2008).

In this study, we framed NOS using a set of characteristics of science common to reform documents and believed to be relevant and accessible to K-12 students (i.e., from kindergarten to 12th grade) (see Table 1) (Abd-El-Khalick et al. 1998; Lederman and Abd-El-Khalick 1998; McComas and Olson 1998; Osborne et al. 2003; Smith and Scharmann 1999). Although these aspects could be misinterpreted as merely declarative statements about science that students should memorize, our aim was to ensure that students can contextualize these aspects by analyzing contemporary and historic examples from science, and explain how these aspects relate to one another in terms of the practice of science (Ozgelen et al. 2013).

Table 1 Aspects that constituted NOS understanding in this study
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In our chemistry teacher education course, our instruction about NOS was explicit-reflective, in that we intentionally planned for, taught, and assessed ideas about NOS. Explicit does not mean to teach NOS directly or didactically. Rather, this approach requires identifying desired NOS learning outcomes. The reflective part of NOS instruction involves providing structured opportunities for learners to examine their experiences from an epistemological perspective, that is, thinking about the questions of development, validation, and the characteristics of scientific knowledge. The specific conceptual tools we utilized to enable students to think about and reflect on the activities in which they are engaged will be elaborated in detail in the methodology.

Pedagogical Content Knowledge for Nature of Science

PCK is the specialized knowledge that differentiates a science teacher from a scientist (NRC 1996). Shulman first conceptualized PCK as the knowledge “which goes beyond knowledge of subject matter per se to the dimension of subject-matter knowledge for teaching” and he continues…

…the most regularly taught topics in one’s subject area, the most useful forms of representation of those ideas, the most powerful analogies, illustrations, examples, explanations, and demonstrations—in a word, the ways of representing and formulating the subject that make it comprehensible to others. (1986, p. 9).

Since Shulman’s initial proposition, much effort has been focused on the nature and development of PCK and subcomponents of PCK (Cochran et al. 1991, 1993; Grossman 1990; Magnusson et al. 1999; Shulman 1986, 1987; Tamir 1988) and teachers’ PCK for different topics (De Jong et al. 2005; Friedrichsen et al. 2009; Henze et al. 2008); however, it is only recently that PCK has been used as a framework for researching teaching about the nature of science (Faikhamta 2013; Hanuscin 2013; Hanuscin et al. 2011).

Prior to any investigation of teachers’ PCK for NOS, various PCK for NOS models were proposed by researchers. In 2000, Abd-El-Khalick and Lederman posited that PCK for NOS would include:

… an adequate understanding of various aspects of NOS, knowledge of a wide range of related examples, activities, illustrations, explanations, demonstrations, and historical episodes. These components would enable the teacher to organize, represent, and present the topic for instruction in a manner that makes target aspects of NOS accessible to precollege students. Moreover, knowledge of alternative ways of representing aspects of NOS would enable the teacher to adapt those aspects to the diverse interests and abilities of learners (p. 692).

Since then, some researchers have developed their own NOS-specific PCK models (Abd-El-Khalick 2013; Jenny 2011; Kim et al. 2005; Schwartz and Lederman 2002) or utilized existing PCK models for investigating teachers’ PCK for NOS (Faikhamta 2013; Hanuscin 2013; Hanuscin et al. 2011). Other studies have focused on teachers’ PCK for NOS without an explicit PCK framework (e.g., Pongsanon et al. 2011). When examined more closely, however, these different conceptualizations of PCK for NOS have all shared elements of the PCK model proposed by Magnusson et al. (1999) (see Table 2).

Table 2 PCK for NOS frameworks in literature with their components
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Magnusson et al. (1999) viewed PCK as a transformation of subject matter knowledge, pedagogical knowledge, and knowledge of context. They conceptualized PCK as consisting of five components: (a) orientations toward science teaching (teachers’ knowledge and beliefs about the purposes and goals for teaching science at a particular grade level), (b) knowledge and beliefs about science curriculum (goals and objectives/curriculum and materials), (c) knowledge and beliefs about students’ understanding of specific science topics (requirements for learning specific science concepts and areas of science that students find difficult including misconceptions), (d) knowledge and beliefs about assessment in science (knowledge of the dimensions of science learning that are important to assess and knowledge of the methods by which learning can be assessed), and (e) knowledge and beliefs about instructional strategies for teaching science (topic-specific activities and subject-specific strategies).

As aforementioned, several studies have applied the model of Magnusson et al. (1999) as a lens for research on PCK for NOS and have provided strong evidence for the utility of this model as a lens for research on NOS teaching (Faikhamta 2013; Hanuscin 2013; Hanuscin et al. 2011). Hanuscin (2013) examined critical incidents in the development of a prospective teacher’s PCK for NOS and found that although the prospective teacher developed her knowledge of instructional strategies for teaching NOS in her methods’ coursework, she did not develop the requisite knowledge of learners that would facilitate her successful NOS instruction. The researchers emphasized that teacher education and professional development efforts could be made more effective through a more comprehensive approach addressing all PCK subcomponents, rather than targeting only instructional strategies for NOS (e.g., explicit and reflective instruction) as has been common. They also highlighted a need for further research on interplay among PCK subcomponents in supported effective teaching about NOS.

Another recent study (Faikhamta 2013) investigated in-service science teachers’ NOS understanding and orientation within a PCK-based NOS course. This course was framed using the PCK for NOS model that Hanuscin et al. (2011) adapted from the model of Magnusson et al. (1999). Throughout the course, teachers’ NOS understanding was explicitly addressed, using reflective approaches embedded in both content-generic (e.g., mystery cube) and content-embedded activities (e.g., collision theories). Moreover, the course included instruction targeting each of the subcomponents of PCK (orientations, learners, instructional strategies, assessment, and curriculum). Analysis of the results showed that although in-service teachers had naive and partially informed ideas about several NOS aspects (e.g., laws and theories, and tentativeness) before the course, they improved these understandings. In the study, Faikhamta (2013) primarily considered orientations in relation to PCK. While the most prevalent orientations among teachers were initially project-based science, process, and guided inquiry, following the course, there were decreases in the frequency of those orientations and a shift was observed toward an inquiry orientation. The researcher did not consider other subcomponent knowledge bases of PCK nor the interaction of these.

Given that research has shown that the development of teachers’ PCK may be uneven and that teachers may have more developed PCK for some components than others (Magnusson et al. 1999; Hanuscin et al. 2011), we focused our attention on each of the individual component knowledge bases of PCK. Nonetheless, we recognize that Magnusson et al. (1999) did not see their model just as a collection of the proposed components; rather, they emphasized that a teacher’s level of PCK highly depends on the degree to which the components are integrated and coherent (see also Friedrichsen et al. 2009; Park and Oliver 2008). Therefore, in the present study, we were also concerned with the degree to which prospective teachers drew upon and made connections between these various components in their instructional planning.

Within the model of Magnusson et al. (1999), knowledge of curriculum refers to teachers’ knowledge on mandated goals and objectives and specific curricular programs and materials related to the topic they teach. For example, this entails an awareness of specific curriculum materials and how these can be used to address NOS, as well as the various NOS objectives students are expected to achieve in particular grade levels. In Turkey, there is a national curriculum in which the same textbooks are used in all public schools. Within these textbooks, there is not an explicit and purposeful emphasis on NOS. Furthermore, we know of no supplemental curricular materials that are available in teachers’ native language (the language in which they teach). This, combined with the fact that there were no specific NOS objectives in the secondary chemistry curriculum standards at the time our study was conducted, led us to omit teachers’ knowledge of curriculum from our study. Rather, we utilized content-embedded and content-generic instructional strategies as a means to introduce supplementary curricular materials to teachers so that they might be able to teach NOS. While these have the potential to inform teachers’ knowledge of curriculum, this was not a major focus of our work within the given context.

While past research has been successful in identifying ways to support teachers in developing an understanding of NOS, they have been less successful in terms of helping teachers develop PCK for NOS. Our study extends beyond previous research (Akerson and Abd-El-Khalick 2003; Akerson and Volrich 2006; Faikhamta 2013; Schwartz and Lederman 2002) by examining the development of prospective teachers’ PCK for NOS at a critical juncture in their preparation (Abell 2008) and thorough examination of a comprehensive intervention framed through PCK (Hanuscin 2013).

Research Design

Method of Inquiry

The purpose of this study is to investigate the development and nature of preservice chemistry teachers’ PCK for NOS using the model for PCK of Magnusson et al. (1999). Following recommendations by researchers in the recent literature, we focused on the degree of integration and coherence among the components of PCK (Abell 2008; Friedrichsen et al. 2009; Park and Oliver 2008). In this manner, we hoped to understand how instruction that uses PCK as an organizing framework influenced the development of preservice teachers’ PCK for NOS and how that was expressed in their instructional plans. We chose to conduct a qualitative case study (Creswell 2003) to gain in-depth information about an innovative system (pedagogical instruction framed by PCK for NOS instruction) and little known phenomena (development PCK for NOS) (Marshall and Rossman 2011). We explored the development of PCK for NOS (an issue) in a bounded system (during PCK for NOS instruction period of an elective course) through multiple data collection sources including observations, interviews, audiovisual material, documents, and reports.

Context: Research in Chemistry Education Course

The study took place within a teacher education program at a public university in Turkey that certifies undergraduates as chemistry teachers for grades 9–12. During their 5-year program, chemistry education majors take chemistry (e.g., general chemistry, analytical chemistry, organic chemistry, industrial chemistry), general pedagogical courses (e.g., introduction to education, instructional planning and evaluation), and subject-specific pedagogical courses (e.g., methods of science teaching, laboratory experiments in science education). In addition to these required courses, preservice chemistry teachers take elective courses on chemistry and chemistry education. A two-semester elective course, “Research in Chemistry Education” was the focus of our study. All the participants had completed chemistry, general pedagogical, and subject-specific pedagogical courses before this elective course. This two-semester elective course was offered to preservice chemistry teachers during their final year in the program. The course was scheduled as 3-h-long instructional sessions per week and all the sessions were done consecutively on a single day. The catalog description of the course did not specifically include a lab session. However, the course was designed as it includes lectures and labs depending on the topic covered each week. The classes were conducted in chemistry laboratory since students worked in groups and some activities required laboratory materials. The course formed the context for the second year of a 3-year government-funded project aiming to help both pre- and in-service teachers develop their understanding of NOS and ability to teach NOS (for more information about the project, see Köseoğlu et al. 2010). The content of this particular course was new for students, since they had not received explicit NOS instruction in their previous courses. The course included two instructional parts: the first was devoted to learning about NOS and the second was devoted to pedagogical instruction related to NOS. This latter part was framed by PCK for NOS.

Nature of Science Instruction

Keeping in mind that understanding NOS is prerequisite to teaching NOS, participants first learned about NOS. In line with the literature, we used both content-generic and subject-specific activities to address NOS. Content-generic activities included The New Society (Cavallo 2008) and The Tube (Lederman and Abd-El-Khalick 1998) among others. We revised several content-embedded activities to address NOS, including Competing Theories: Lamarck and Darwin (National Academy of Sciences 1998), Why did the water rise? (Lawson 2002), and others. Additional activities were designed by the first author and the research project group to address agreed-upon common aspects of NOS and common myths about NOS (see Table 3). Using explicit-reflective NOS instruction (Abd-El-Khalick and Lederman 2000), we provided opportunities for participants to reflect on their experiences that they gained through engaging in the activity from the perspective of NOS. For example, in the activity “Science and Technology: In the Pursuit of Seharap—Designs are Competing,” participants engaged in the technological design process. Participants were presented the problem: “Design a vehicle which makes the transportation easier and safer for the farmers who have to climb high mountains to collect Seharap (i.e., a plant)”. The participants worked in groups of four or five to design a solution. After completion of design phase, the groups built models of their designs, tested their models, and revised it if needed. At the end of the activity, the instructor/s facilitated a whole class discussion on the nature of science and technology and relationship between them. Students were asked to consider the practices they engaged in and whether they considered these to be related to science or technology, and to consider the similarities and differences between science and technology in terms of their purpose, process, and product.

Table 3 How did each explicit-reflective NOS activity address various NOS aspects focused in this study?
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Pedagogical Instruction Framed by PCK for NOS

During the course, we utilized activities (summarized in Table 4) to enhance the various component knowledge bases that would inform the development of preservice teachers’ PCK for NOS. These activities were planned by the first author and reviewed by faculty with expertise in teaching and learning about NOS. We relied on the model of Magnusson et al. (1999) for PCK to design instruction that would enhance prospective teachers’ science teaching orientations (STO), knowledge of learners (KoL), knowledge of instructional strategies (KoIS), and knowledge of assessment (KoA), except knowledge of curriculum (KoC). The teaching module spanned 4 weeks (corresponding to 12 in-class hours). Each class session began with students answering a series of open-ended questions to elicit their ideas about the targeted component of PCK for NOS. Next, students engaged in argumentative discussions within small groups and presented their ideas to the class. The instructor facilitated the discussions and wrapped up the session with a presentation related to the session’s focus. Students ended the session by writing a reflection on their learning. For example, in one session about STO, the purpose of this class was to reveal participants’ orientations toward teaching chemistry and encourage them to reflect on the value of NOS teaching. Students were first asked to consider the goals of science and chemistry education and the kinds of instruction necessary to achieve those goals. Preservice chemistry teachers then watched a video of a mother who is trying to decide whether or not she should get her baby vaccinated for swine flu (socioscientific decision making). Then, the participants were presented with two different science teachers’ arguments about the types of scientific knowledge the mother would need to make an informed decision. One argument claims that it is enough to know biology and related science concepts, while the other advocates that, in addition to science concepts, further knowledge (i.e., NOS) is needed to make an informed decision about getting the baby vaccinated. The participants were asked to select one of the arguments by providing evidence and warrants. During this process, preservice chemistry teachers worked in groups of five or six and then presented their ideas to the class. During these presentations, the instructor facilitated the discussions and then closed the session with a presentation about scientific literacy and the importance of NOS. Following this, the participants wrote a reflection paper about their ideas. We use “PCK for NOS instruction” hereafter, but do not intend this to mean we explicitly introduced the PCK construct to students. Rather, we used framing questions aligned with this construct for each session (e.g., “Why are you teaching science?” for science teaching orientations and “What kind of instructional strategies do you use for teaching NOS?” for knowledge of instructional strategies).

Table 4 Activities designed to enhance different components of PCK for NOS
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Participants

Participants included 30 preservice chemistry teachers (8 males and 22 females). All started an undergraduate teacher education program in 2005 and their ages ranged between 22 and 24 with an average of 23. All were in their senior year and in a position to graduate at the end of the year in which the study was conducted. Each had similar background in terms of coursework, including chemistry courses (e.g., organic chemistry), pedagogical courses (e.g., classroom management), and subject-specific pedagogical courses (e.g., science teaching method). The participants were typical in the sense that they took similar courses during their teacher education program compared to other chemistry education majors in other universities in Turkey.

Data Collection Sources

This study relied on qualitative data sources to gain in-depth information about the phenomenon being investigated, as summarized in Fig. 1. Data sources included responses given to open-ended instruments, interviews, observations, and documents such as lesson plans and reflection papers. We used the Views on Nature of Science Questionnaire Form C (VNOS-C, Lederman et al. 2002) in conjunction with follow-up interviews before and after the NOS instruction. To investigate the development of preservice chemistry teachers’ PCK for NOS, we utilized interviews, reflection papers, responses to open-ended instruments, observational records including videos, and lesson plans. Figure 1 shows how data collection occurred within the various course activities.

Fig. 1
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Flowchart of data collection within the various course activities

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Views on Nature of Science Questionnaire Form C

The VNOS-C and associated follow-up interviews formed the main data source in identifying how preservice chemistry teachers’ NOS views changed. Although there were 10 activities in NOS instruction, some activities lasted more than three course hours that correspond to at least 2 weeks. Therefore, the implementation of 10 activities spanned one and one-half semesters. The VNOS-C was administered two times: before NOS instruction (at the beginning of the first semester) and finally after NOS instruction (in the mid of the second semester). Therefore, in this study, the change in preservice chemistry teachers’ NOS understanding will be elaborated in terms of how they were used to understand NOS before NOS instruction and what kind of NOS views they had after NOS instruction.

Open-Ended Questions

We used two types of open-ended questions. The first type was used to understand whether learning the NOS part influenced participants’ views on chemistry teaching and to make a comparison between their views on chemistry teaching before and after PCK for NOS instruction. For example: What is the goal of science and especially chemistry education? What kind of instruction do you design to achieve the goals you mentioned in previous questions? What are the difficulties that you may encounter when you are teaching what you want to teach? The second type of open-ended question is related to the focus component of PCK (Table 5) and served as a comparison point to responses obtained at the end of the class through reflection papers.

Table 5 Prequestions asked before each PCK for NOS instruction class
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Reflection Papers

To clarify each session’s effect on preservice chemistry teachers’ knowledge of the related PCK component, students were asked to write reflection papers following each PCK for NOS session. The questions in reflection papers were as follows: What is the message of this lesson? What did you learn about chemistry/science education? How did this lesson change your perspective on chemistry/science education? How do the things you learned in this lesson affect your ideas about chemistry/science teaching?

Lesson Plans

Two lesson plans were collected: the first after students learned about NOS but before instruction targeting their PCK and the second at the end of the course (Fig. 1). The first lesson plan was helpful for providing supporting or counter evidence for the view that even if teachers have informed understanding of NOS consistent with reforms, they generally do not explicitly teach NOS (Schwartz and Lederman 2002). Several possible chemistry topics (e.g., particulate nature of matter, atom, solutions, and mole) were assigned to the participants. The participants were free to select the concepts on which they wanted to focus within these topics and they were not explicitly instructed to integrate NOS into their instruction. A lesson plan format including several parts such as general and specific objectives, teaching strategy, detailed explanation of their instruction, and assessment was given to preservice chemistry teachers. Lesson 2 was collected after PCK for NOS instruction, in which preservice chemistry teachers were asked to revise their earlier lesson plan 1. Lesson plan 2 was used to determine whether and how our instruction assisted preservice chemistry teachers in translating their NOS understanding into their lesson plans.

We intentionally omitted explicit instructions to integrate NOS in order to assess whether students were likely to do this on their own (versus simply doing so to fulfill the assignment). Given flexibility in choice of topic/concept, we did not expect that all participants would integrate the same NOS aspect or aspects. Rather, we focused on (1) whether they identified a specific NOS learning outcome, (2) whether that aspect was appropriate to the choice of topic/concept, and (3) how they proposed to teach and/or assess that NOS learning outcome. For instance, two participants who opted to teach factors affecting the rate of reactions both used the 5E learning cycle method. One of them integrated the empirical basis for scientific claims and the use of creativity in science, while the other focused on the role of creativity and the myth of scientific method. Similarly, two participants who integrated the inferential NOS prepared their lesson plans on different chemistry topics (i.e., particulate nature of matter versus electrochemistry).

Interviews

Two types of semistructured interviews were conducted in this study. The first one was conducted with nine participants in order to understand the meanings they ascribed to NOS aspects. During those interviews, respondents were provided their questionnaires and asked to explain and justify their responses. The second type of interview was conducted after PCK for NOS instruction with nine participants in order to gain an in-depth understanding of their PCK development and how PCK for NOS instruction contributed to this development. Several examples for the interview questions are as follows:

  • Was there any change in your views about what you expect students to learn about chemistry before NOS instruction, after NOS instruction, and after PCK for NOS instruction? If yes, how?

  • Do you think that your students should learn NOS? Was there any change in your views about this before NOS instruction, after NOS instruction, and after PCK for NOS instruction? If yes, how?

  • What kind of instructional strategies would you use or did you use to teach NOS? How did learning NOS part and PCK for NOS part contribute to your knowledge of instructional strategies? Which instructional strategies are more effective than others? Please, explain why.

Participant Observation

Eleven researchers (of whom two are the authors of this paper) were part of the project that funded the Research in Chemistry Education course, and each had a share in instructional responsibilities for the project. Thus, while some team members were engaged in teaching, the other team members served as participant observers to capture data. As a secondary data source, information gathered as the participant observers facilitated small group discussions helped enhance the credibility of our interpretations of students’ reflection papers. In each class, the research group of two or three was the leader in conducting all the course activities. However, the other researchers in the project were also responsible during the guidance provided to small group discussions. All class sessions were videotaped as well, to enable us to document our PCK for NOS instruction (Flick 1996).

Data Analysis

Two main analyses were conducted to determine how the preservice chemistry teachers’ NOS understanding and their PCK for NOS changed throughout PCK for NOS instruction.

Analysis of NOS Views

In order to identify participants’ NOS views before and after NOS instruction, data obtained from VNOS-C and follow-up interviews were analyzed deductively. An already existing categorization proposed by Khishfe and Abd-El-Khalick (2002) was used for identifying participants’ NOS views. Khishfe and Abd-El-Khalick (2002) advocated that there is a continual change in students’ understanding about NOS. Considering this continuum, preservice chemistry teachers’ NOS understandings were categorized as naive, transitional, and informed. Each NOS aspect addressed in this study was evidenced itself in more than one data source (interview and VNOS-C) and, moreover, in more than one item in VNOS-C. A participant’s view on a particular aspect was categorized as informed if s/he had provided evidence of meaningful understanding related to that aspect in all contexts. If a participant had not exhibited any meaningful understanding with respect to a particular aspect in all contexts, his/her view of the related aspect was categorized as naive. If a participant had demonstrated meaningful understanding of a particular aspect in some contexts but not the others, his/her view in that aspect was categorized as transitional.

Analysis of Participants’ PCK for NOS

Analysis of participants’ PCK for NOS focused on lesson plans 1 and 2, reflection papers, responses to open-ended questions, and interviews. This analysis involved both deductive and inductive analysis (Patton 2002). In the deductive phase, we conducted in-depth analysis of explicit PCK (Park and Chen 2012; Park and Oliver 2008), and in the inductive phase, we used the constant comparative method (Glaser and Strauss 1967).

In-Depth Analysis of Explicit PCK

In order to determine the PCK for NOS components developed by participants and the degree of integration of these components, a modified version of in-depth analysis of explicit PCK (Park and Chen 2012; Park and Oliver 2008) was employed during the deductive phase of qualitative analysis. This method mainly relies on construction of a PCK profile for each participant as defined by the model of Magnusson et al. (1999). Although preservice chemistry teachers were asked to prepare lesson plan 1 right after the NOS instruction, they did not integrate any NOS aspects explicitly in their lesson plans. When asked whether they attempted to teach NOS in the lesson, only two participants claimed to teach NOS by engaging students in an inquiry-based learning setting (i.e., and implicit approach). Therefore, while the PCK profiles were created, mainly lesson plan 2, reflection papers written at the end of each PCK for NOS class, responses to open-ended questions given at the beginning of each PCK for NOS class and after PCK for NOS instruction, and interviews conducted with nine participants were used as suggested in literature to assess and capture the complexity of PCK (Baxter and Lederman 1999). The PCK profile consisted of several components including (see Appendix) (a) chemistry topic on which the lesson plan was prepared, (b) objectives including science process skills and NOS aimed to be achieved, (c) synopsis of the lesson plan prepared after PCK for NOS instruction, (d) evidence for the components of PCK for NOS and connections among them, (e) a description of where the PCK for NOS components was evident throughout data collection, and (f) postintervention PCK for NOS map representing which components and connections or consistencies are present. The final PCK for NOS map included only four components of the model of Magnusson et al. (1999), namely, STO, KoL, KoIS, and KoA since KoC was not a focus in PCK for NOS instruction. Different types of lines were used to show connections and consistencies among the PCK for NOS components which were evident in different data sources:

  • Bold lines for the connections and consistencies that exist in lesson plans

  • Solid lines for the connections and consistencies that exist in reflection papers

  • Dashed lines for the connections and consistencies that does not exist in any of the data sources

It was obvious that the strength of one connection or consistency between two components might be different from another and it was. Although we assumed the same strength for each connection or consistency for convenience (Park and Chen 2012) when drawing the PCK for NOS map for each participant, we considered the differences in power of consistencies and connections when presenting the results. In order to decide whether a connection or consistency was evident in any of the data source, a coding scheme was formed (see Table 6). This coding scheme described the instances of PCK components and integration of components in preservice chemistry teachers’ PCK. During the formation of the coding scheme, we relied on the data and literature using in-depth analysis of explicit PCK (Park and Chen 2012; Park and Oliver 2008). Based on the data and the literature, we defined every possible instance which can be counted as an evidence for any PCK component and consistencies or connections among them. Formation of the coding scheme was accomplished by a researcher who is an expert on both PCK and PCK for NOS by discussing and negotiating any incongruities. For deciding whether the integration between any two PCK components addressed in this study was an indication of consistency or connection, we utilized the PCK literature during the formation of our coding scheme. With the recognition of the way in which STO shapes KoL, KoIS, and KoA (Magnusson et al. 1999), any integration between STO-KoL, STO-KoIS, and STO-KoA was coded as consistency. On the other hand, any integration which was observed for any two components of KoL, KoIS, and KoA was coded as connection since each has the capacity to inform other (Abell 2008) (e.g., KoL might inform KoIS and KoA might inform KoL).

Table 6 Coding scheme describing instances of PCK components and integration among them
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The Constant Comparative Method

After completion of profiles for each participant and accompanying postintervention PCK for NOS maps, we focused on the identification of patterns or regularities among the maps, resulting in two-dimensional categorizations for participants’ PCK. One dimension shows the degree to which the components are integrated. Since there were four components focused in this study (STO, KoL, KoIS, and KoA), the maximum number of connections among the components of PCK is six and the degree of integration ranged between highly integrated (number of connections/consistencies is 5 and 6), somewhat integrated (number of connections/consistencies is 3 and 4), and nonintegrated (number of connections/consistencies is 1 and 2). The other dimension represents the degree to which preservice teachers can translate their PCK to their practice, and it ranged between knowledge (map includes one bold line and the rest is solid), knowledge-application (map includes a mixture of bold and solid lines), and application level (map only includes bold lines). We developed categories based on the maps using an interactive process of constant comparison (Glaser and Strauss 1967).

Credibility Issues of the Study

In this study, triangulation and prolonged engagement were used to ensure credibility. We used multiple data sources to triangulate our findings in the current study as well as analyst/investigator triangulation using multiple observers, interviewers, and analysts. Throughout all data collection process, at least three researchers who are familiar with NOS and PCK were present during course instruction. During the analysis stage, two analysts, among those researchers, independently coded the data for NOS and PCK for NOS after forming a rubric for NOS and a coding scheme for PCK for NOS. Moreover, four researchers who were studying PCK individually compared participants’ PCK for NOS maps and then reached a consensus on categories inductively derived from the data. The rubric for NOS directly came from NOS literature (Khishfe and Abd-El-Khalick 2002), and the coding scheme used for creating PCK for NOS profiles including participants’ maps was formed by two authors, one of whom is an expert on both PCK and PCK for NOS, by discussing and negotiating any incongruities. After formation of the rubric and coding scheme, two independent researchers coded the data for NOS and PCK for NOS. The incongruities between researchers were resolved by negotiation and discussion. Interrater reliabilities were calculated at 95 % for NOS and 90 % for PCK for NOS. The inconsistencies between coders were resolved by negotiating and discussing.

Prolonged engagement is achieved by being present in the research site for an extended period of time. Two of the researchers spent a whole year, including two semesters, within this research setting and with these participants. Most of the time, two authors were among the leading instructor of the class and had a chance to observe and talk with participants in and out of the class settings.

We note that data were collected and analyzed in the participants’ native language (Turkish), and then findings were translated into English. The first and third authors, who are competent in English speaking, writing, and reading translated the findings into English. Those findings were back-translated to Turkish by an outside science educator. Inconsistencies between translators were resolved to ensure accurate translation. Finally, all English translations were reviewed for clarity by a native English speaker.

Ethical Issues of the Study

All study activities were conducted in alignment with the Institutional Review Board (IRB). All participants voluntarily participated in the study through written consent form. During class sessions, students were aware of the role of participant observers (who also had teaching roles). As such, an external gatekeeper (Department Chair) served as a point of contact for participants to voice any concerns. Through this, issues regarding ethics in research, such as protection of the participants from harm, and confidentiality were assured (Fraenkel and Wallen 2006).

Findings

Developing teachers’ PCK for NOS is a challenge for science teacher educators. Therefore, we developed a specialized course to enhance both preservice chemistry teachers’ NOS understanding and their PCK for NOS. To investigate how preservice teachers’ NOS teaching practices developed throughout the course, we collected multiple data sources including lesson plans, responses to open-ended questions, reflection papers, and interviews. Analysis of data revealed four major themes related to the nature of preservice chemistry teachers’ NOS teaching practices and their PCK for NOS. The findings will be presented according to those themes, which focus on (1) prerequisite knowledge and beliefs necessary to teach NOS, (2) developmental progressions in PCK for NOS, (3) relationship between subject matter knowledge and PCK for NOS, and (4) interaction and integration of components of PCK for NOS.

Prerequisite Knowledge and Beliefs Necessary to Teach NOS

Analysis of data revealed that both adequate NOS understanding and beliefs in the importance of learning NOS are necessary for ensuring that teachers attempt to teach NOS, either implicit or explicit. Even after learning NOS, and indicating a reasonable progress in NOS understanding, only one preservice teacher integrated NOS into her planning; however, she used an implicit approach without stating her NOS-related objectives explicitly. In her postinterview, she stated that she assumed students could learn NOS through experiencing the science itself. No other preservice teachers indicated intent to teach NOS in their first lesson plan. This supports earlier research that showed understanding of NOS is necessary but not sufficient to teach NOS and emphasized the importance of teachers’ intentions to teach NOS (Schwartz and Lederman 2002); however, our study provides empirical evidence that an approach framed by PCK is productive in helping shift teachers’ orientations in ways that support their intention to teach NOS.

Learning about NOS content (the first part of the course) had little impact on pre-service teachers’ beliefs about the goals and purposes of teaching chemistry, as GreyFootnote 1, one of the pre-service chemistry teachers participated to the study, explained in her interview:

In the first part where we learned about nature of science, I did not think that nature of science is something that I should teach to my students. In the second part where we learned how to teach nature of science, I realized the importance of nature of science for scientific literacy and decided to integrate into my teaching. Moreover, while I was learning about nature of science, [I realized that] I used to think that nature of science can be learned implicitly…. (Grey, post PCK for NOS interview)

On the other hand, we noted substantial changes in preservice teachers’ orientations after our PCK for NOS instruction; 93 % (28 out of 30) of preservice teachers believed in the importance of learning NOS for their students during their chemistry teaching. This transition was evident both in their reflections on their teaching and learning and in their lesson plans. The majority of preservice teachers designed a lesson to teach at least one aspect of NOS. For instance, Margaret designed an inquiry-based lesson for teaching metallic activity. More importantly, she used explicit-reflective and content-embedded approach to teach three major ideas about NOS: (a) nature and role of experiments in science, (b) the role of creativity and imagination in science, and (c) the subjectivity in science. Margaret explicated how she changed her orientation as follows:

Before the [first session of pedagogical instruction about NOS], I was thinking that I should just teach chemistry to my students. Then, I realized the importance of communicating nature of science to my students… (Reflection paper 3)

Developmental Progression of PCK

The analysis of 30 preservice chemistry teachers’ postintervention PCK for NOS maps showed that all participants developed PCK for NOS (at least some components) and integrated this knowledge to some extent. The differences in the levels of integration suggest a developmental progression in participants’ PCK from knowledge about how to teach NOS (knowledge level) to translation of that knowledge in their lesson design (application level). This seemed to increase as components of participants’ PCK became more integrated. As shown in Table 7, those with more highly integrated PCK were more likely to include NOS teaching in their lessons.

Table 7 Number and percentage of participants in each PCK category
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In the sections that follow, we highlight the cases of three participants, Nancy, Irving, and Howard, to illustrate the variation in their PCK integration and degree of translation (Fig. 2).

Fig. 2
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a–c Three preservice teachers’ PCK for NOS maps from different levels of translation

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For example, Nancy had highly integrated PCK and her lesson demonstrated application of this in her lesson plan (see Fig. 2a). She was oriented to teach NOS and included NOS objectives in her lesson plan (i.e., tentativeness, subjectivity, and creativity and imagination in science) as well as chemistry-related ones. Nancy planned her lesson considering students’ difficulties and misconceptions about NOS. She administered 10 questions in true-false format as a preassessment. In other words, she successfully aligned her instructional strategy, learner, and assessment with her teaching orientation (i.e., NOS) in her lesson plan. Three of the questions were directly related to NOS which are as follows:

  • Definitions about the phases of matter is absolute.

  • Scientists produce unchangeable knowledge since they do numerous tests.

  • Scientists claim that previous knowledge in the discipline is wrong since they do not like each other. (Nancy, lesson plan 2)

Nancy stated that “The purpose of administering this test is to elicit students’ misconceptions and design instruction considering students’ misconceptions”. That is her knowledge of learner informed her assessment which in turn linked to her instructional strategy. She used 5E learning cycle to teach NOS aspects in an explicit-reflective and content-embedded way. Moreover, Nancy assessed students’ understanding of NOS at the beginning, throughout, and/or at the end of the lesson. While there can certainly be improvements made to Nancy’s specific assessments, what is critical here is the degree of alignment between the component knowledge bases of her PCK evident in her approach.

In contrast to Nancy, Irving (see Fig. 2b) had somewhat-integrated PCK. His lesson indicated application of some PCK components in the plan whereas other components stayed at the knowledge level. In other words, his PCK stayed at the knowledge-application level. Considering that an increase in the degree of translation level is associated with an increase in the degree of integration of PCK components, Irving had somewhat-integrated PCK in knowledge-application category as opposed to Nancy whose PCK is highly integrated in application category. Irving was able to translate orientation, instructional strategy, and assessment components of his PCK into his planning, but not his knowledge of learners. He focused on empirical-based and subjective NOS elements using an explicit-reflective and content-embedded approach in his planning. Irving designed a 5E learning cycle lesson on the topic of saturated, unsaturated, and supersaturated solutions. He stated that he would informally assess students’ NOS understanding about targeted NOS aspects. However, he did not provide any evidence for his knowledge of learner related to the NOS aspects (e.g., scientists are particularly objective) in his lesson plan although he explained what he could do for not causing a misconception as follows:

I realized that students may have various misconceptions about the nature of science. Teachers and instruction are two of the sources of these misconceptions. I will be careful about the language I use during my teaching. Since, my language may lead students to have some misconceptions such as hierarchical relationship between theory and law. (Irving, Reflection paper 2)

Lastly, Howard (see Fig. 2c) had somewhat-integrated PCK and his lesson did not indicate application of this. Instead, the majority of Howard’s components and connections were at the knowledge level. Only his orientation and instructional strategy components were evident in his lesson plan. On the other hand, his knowledge of learner and assessment components stayed at the awareness level. Howard explicitly and reflectively integrated tentativeness of science in his lesson plan on acid–base theories. He used a history of science approach to teach acid–base concepts and NOS aspects. However, Howard did not consider students’ difficulties and misconceptions about tentativeness. Nor did he assess what students learned about scientific knowledge throughout his lesson plan. Nonetheless, he emphasized the importance of considering misconceptions and mentioned about strategies to assess NOS in his postinterview as follows:

When I saw the concept cartoons [second session of pedagogical instruction about NOS], I realized that there are some students who have various kinds of misconceptions about the nature of science… I thought that I should elicit students’ misconceptions first. If we ignore the existence of misconceptions, students will not learn targeted nature of science aspects and will continue to keep their misconceptions…I can use concept maps, KWL charts, true-false items, or cases to assess students’ understanding about nature of science.

Relationship Between Subject Matter Knowledge and PCK

While previous studies have examined the relationship between content knowledge of NOS and teachers’ instructional practices, this study provides a more holistic picture of teachers’ practices through the lens of PCK. In order to reveal the relationship between preservice chemistry teachers’ NOS understanding and their PCK for NOS, how each participant changed his/her NOS views is considered first (see Table 8).

Table 8 The change in participants’ NOS views and their PCK for NOS
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Analysis of VNOS-C administered before NOS instruction indicated that preservice chemistry teachers had various misconceptions about NOS (e.g., hypotheses become theories that turn into laws, scientists are particularly objective). When all NOS aspects addressed in the NOS instruction were considered, the percentage of naive (33 %) and transitional (28 %) views was 61 %, whereas the percentage of informed views was 26 % (13 % of the views were missing). While the vast majority of the participants (80 %) had naive views about theory-law aspect of NOS, interestingly, no participant had naive views about creative and imaginative NOS aspect. However, in terms of the creative NOS, 43 % of the participants had transitional views. Analysis of data from the VNOS-C administered after the NOS instruction revealed that participants’ NOS views changed in the desired way. When all NOS aspects addressed in the NOS instruction were considered, the average percentage of transitional (21 %) and naive (5 %) views decreased substantially, whereas the percentage of informed views rose to 73 %. In spite of the increase in informed NOS views, preservice chemistry teachers still had difficulty in understanding empirical-based (7 %) and social- and cultural-embedded NOS (7 %) as well as the difference between theory and law (13 %) and observation and inference (10 %).

Various comparisons made among the participants from various groups (i.e., participants in three categories of degree of integration and participants in three categories of degree of translation) to clarify how NOS understanding contributes to the nature of PCK for NOS revealed that there was no clear pattern or relationship between those two (e.g., the more the number of informed views a participant has about NOS, the more integrated PCK for NOS s/he has).

For a closer look at the relationship between NOS understanding and NOS teaching practices, we attended to participants’ choice of which aspects of NOS to emphasize in their lessons in relation to their understanding of NOS, whereas other studies have examined teacher’s understanding of NOS in relation to whether or not they explicitly taught NOS. Our data suggest that some comfort in preservice chemistry teachers’ own understanding of NOS is prerequisite to teaching NOS. The vast majority of preservice chemistry teachers (70 %) chose to include NOS aspects about which they had informed views. Others who integrated NOS aspects that were not addressed in VNOS-C (17 %) or who included aspects about which they had transitional views (13 %) relied on their informed views throughout their planning.

Interaction and Integration of Components of PCK

Although preservice teachers classified into the application subcategory were enabled to translate their PCK for NOS into their lesson plans, they were different from each other in terms of how successfully their lessons communicated NOS aspects. Preservice teachers whose PCK for NOS was well-developed and well-integrated were better able to create lessons to teach NOS. In the sections that follow, we highlight the cases of three participants, Grey, Florrie, and Fletcher, to illustrate the variation in their PCK integration and in the effectiveness of their lesson plans (Fig. 3).

Fig. 3
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a–c Three participants’ maps from different degrees of integration subcategories in application level

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Grey (see Fig. 3a) was oriented to teach NOS and included NOS objectives (i.e., nature of theory, law, and hypothesis) in her lesson plan in addition to chemistry-related objectives (i.e., polarity in covalent bonds). She provided evidence for consistency of her knowledge of learner, assessment, and instructional strategies with her NOS teaching orientation in her lesson plan. Those consistencies are indicated by bold lines in her map. Grey planned her lesson by considering students’ difficulties and misconceptions about theory and law. In her lesson plan, she asked students to investigate valence theory as proposed by Gilbert Newton Lewis before the class session in which she teaches about polarity in covalent bonds. For this investigation, Grey gave students some questions to consider during their investigation, such as What is the role of valence theory in explaining bonding? Why did Lewis call it as theory not the law? Can valance theory be a law? At the beginning of the class, she had students share what they found. She explained that students’ sharing their findings and ideas framed around these questions would help her understand difficulties and misconceptions that students have about theory and law. This part of the lesson plan is an indication of how Grey’s knowledge of assessment informed her knowledge of learners (indicated by bold arrow pointing from assessment toward learner in Grey’s map). After the sharing session, Grey conducted an explicit-reflective discussion considering expected students’ misconceptions as follows:

Grey (G): Why do we call it Lewis’s theory although it sheds light modern chemistry? [aiming to elicit students’ misconception, which is theory is not proved and not accepted by the scientific community therefore stays as theory, not become a law and does not play important role in science] and Can there be a Lewis Law?

ESAs: (1) Since the truth of Lewis’s theory is not proved, it is not called a law, (2) Since it is not directly observable, it remains a theory. For instance, evolution is a theory and it is not observable too, and (3) The Lewis theory is not accepted by all of scientific community and therefore remains a theory and does not become a law.

G: There is a difference between the way we use the word theory in our daily life and the way it is used in science (scientific theory). If the truth of theories was not proved or theories were not accepted by most of the scientific community, we would not teach and learn in our chemistry or science classes.

Moreover, she was aware of one of the sources of misconceptions about the hierarchical relationship between theory and law (e.g., daily life usage of the words). Grey clarified this for students, and then gave several examples (e.g., evolution theory, gas laws, kinetic molecular theory) to explain the nature of theories-laws and the difference between them. She purposefully used an instructional strategy, asked specific questions, and gave key examples to remedy students’ misconceptions about theory and law. This is an indication of how Grey’s knowledge of learner informed her choice of instructional strategy (indicated by bold arrow pointing from learner toward instructional strategy in Grey’s map). At the end of the class, she asked her students to investigate the concepts of scientific fact, theory, and law for the next class and be prepared to share. This is an indication of how Grey’s knowledge of learner informed her knowledge of assessment (indicated by bold arrow pointing from learner toward assessment in Grey’s map). By integrating her component knowledge bases of PCK, she was better-positioned to design a lesson that could address students’ misconceptions about scientific theories and laws.

Florrie, whose PCK is somewhat integrated (see Fig. 3b), was similar to Grey. First, she had also consistencies between their orientation and learner, assessment, and instructional strategy (indicated by bold lines in Florrie’s map). Florrie’s lesson plan was on teaching electrochemical cells. Second, she was oriented to teach NOS and integrated NOS objectives in her plan (i.e., observation, inference, and difference between them). Also, Florrie was aware about students’ difficulty in discriminating observation and inference. She planned guided-inquiry lesson to teach about NOS aspects in an explicit-reflective way and assessed her students’ understanding about targeted NOS aspects at the end. However, Florrie was different from Grey in the sense that the only integration among the components of her PCK was between knowledge of learners and knowledge of instructional strategies. In her plan, she asked her students to make an electrochemical cell, run it, and write their observations and inferences. Florrie thought that this electrochemical cell observation would be useful to teach students observation, inference, and the difference between them. After completion of cells, students were to present their cells together with their observations and inferences. Then, she planned to conduct an explicit-reflective discussion on observation, inference, and the difference between them by asking What are your observations? How did you observe? What are your inferences? and What is the difference between observation and inference? This is an indication of how her knowledge of learner informed her knowledge of instructional strategy (indicated by bold arrow pointing from learner toward instructional strategy in Florrie’s map). There was no evidence of integration between her knowledge of assessment and learners, however, nor assessment and instructional strategies. Florrie was not as successful as Grey, since she designed instruction to teach observation and inference without successfully aligning her NOS instruction and assessment with her knowledge of learners.

Fletcher, whose PCK is nonintegrated (see Fig. 3c), was similar to Grey and Florrie as he had a NOS teaching orientation, included NOS objectives (i.e., tentativeness and subjectivity) in his plans to teach acid–base theories, and used a history of science approach to teach NOS aspects in an explicit-reflective way. That is, his knowledge of instructional strategies was consistent with his orientation (indicated by bold lines in Fletcher’s map). Fletcher had his students play the roles of Arrhenius, Bronsted-Lowry, and Lewis. After this, he planned to use discussion as an explicit-reflective strategy by asking Why did acid–base theories change? Why did scientists need to develop different theories on the same phenomena? and Did scientists use their previous knowledge when developing their theories? Unlike Grey and Florrie, Fletcher did not develop learner and assessment components of his PCK for NOS (indicated by gray filling in Fletcher’s map), and consequently, he was not able to integrate those components with his orientation and instructional strategy. In his plan, he did not consider students’ difficulties understanding theory, nor did he plan to assess what students already knew and learned during the lesson.

Discussion

Currently, researchers have met with only limited success in supporting development of teachers’ PCK for NOS (Akerson and Abd-El-Khalick 2003; Akerson and Volrich 2006; Faikhamta 2013; Schwartz and Lederman 2002). Helping preservice teachers develop PCK for NOS is additionally challenging, given that preservice teachers generally lack robust PCK associated with classroom teaching experience (Loughran et al. 2004). A limitation of PCK research conducted in teacher education contexts is that data more likely indicate “PCK readiness” (Davis 2003; Smithey 2003), consistent with the view that PCK is a construct consisting of understanding and enactment dimensions (Park and Oliver 2008). Thus, our first research question focused on examining the nature of preservice teachers’ understanding in each of the component knowledge bases of PCK, and how these reflect their “PCK readiness.” When we analyzed all participants’ PCK for NOS map, we saw that knowledge of instructional strategies and science teaching orientation components were central to this integration. Furthermore, those PCK components were the only components that all participants could translate their knowledge into their lesson plans.

Our data clearly showed that pedagogical instruction framed by PCK for NOS tackled an important challenge—namely, helping preservice teachers internalize NOS as an important learning outcome and achievable by students (Abd-El-Khalick et al. 1998; Schwartz and Lederman 2002), and also this instruction fulfilled the lack of research on providing guidance for how to develop teachers’ valuing of NOS (Lederman 2007). During the first session of this instruction, preservice teachers’ orientations were elicited, in order that they become dissatisfied with these orientations as suggested by others (Aydin and Boz 2013; Brown et al. 2009). The intelligibility of new orientations that support NOS integration in classroom teaching practices was enhanced by developing an understanding of scientific literacy, the importance of it, and the role of NOS in achieving scientific literacy. The plausibility of new orientation was achieved by relating this orientation to teachers’ existing science teaching orientations (e.g., daily life and correct scientific explanation). New orientations became fruitful for preservice teachers when they realized the applicability of it to all grades from kindergarten to university. Satisfying these conditions for conceptual change in preservice teachers’ orientations may explain the change in their orientation to teach NOS and the reflection of that orientation in their planning.

Through participation in pedagogical instruction framed by PCK for NOS, all but three preservice chemistry teachers developed knowledge of instructional strategies effective for teaching NOS, and to a greater extent than any other components. This finding aligns with research indicating that teachers’ development of instructional strategies is more prevalent than the development of other PCK components (Abd-El-Khalick et al. 1998; Bell et al. 2000; Hanuscin 2013). However, in contrast to prior studies (Bell et al. 2000; Hanuscin 2013), most of the preservice chemistry teachers in this study (22 out of 30) specifically assessed students’ understanding of NOS, as evident in their lesson plans. Some researchers attribute teachers’ inability to assess NOS to lack of knowledge of strategies for assessing students’ NOS understanding (Hanuscin et al. 2011), while others view this as a discrepancy between teachers’ practice and their belief in the importance of teaching NOS (Abd-El-Khalick et al. 1998). In both circumstances, our pedagogical instruction helped student teachers to align their beliefs with their practice and to increase their knowledge of assessment in terms of both what and how to assess. Participants were more successful in translating their knowledge of assessment (22 out of 30) and instructional strategies (30 out of 30) into their lesson plans than they were in translating their knowledge of learners into their lessons (16 out of 30). Several studies have documented similar findings about teachers’ knowledge of learners. A study by De Jong and Van Driel (2001) reported that even in-service teachers did not have concerns for students’ learning. Other studies have shown that preservice teachers do not consider students’ ideas in their practice adequately (Park and Chen 2012; Tabachnick and Zeichner 1999). One factor influencing this study could be that participants did not have the chance to implement their lesson plans in real classrooms; therefore, they were not able to translate their knowledge of learners into their lesson plans as they do other PCK components. This is supported by research by Abell (2007) that emphasizes knowledge of learners improves with teaching experience.

The analysis of preservice chemistry teachers’ postintervention PCK for NOS maps revealed a developmental progression in participants’ PCK from knowledge about how to teach NOS (knowledge level) to translation of that knowledge in their lesson design (application level). That is, although participants developed particular knowledge components of PCK for NOS, not all were translated into lesson plans. Our findings lend further support to the view that PCK is a construct consisting of understanding and enactment dimensions (Park and Oliver 2008) and reflect earlier findings that “…increased knowledge in a single component may not be sufficient to stimulate change in practice.” (Park and Chen 2012, p. 939).

Another possible explanation for why preservice teachers were unable to translate PCK components into their planning may be related to their relatively low efficacy (Aydin and Boz 2013; Park and Oliver 2008). Since preservice teachers lack teaching experiences, they typically have relatively low efficacy, and therefore, inability to enact PCK components may be expected. Despite the differences in our preservice teachers’ PCK for NOS, pedagogical instruction framed by PCK for NOS was helpful to them in developing their professional practical knowledge for teaching NOS. This knowledge serves as the building blocks of their future PCK and can be thought of their PCK readiness (Davis 2003; Smithey 2003).

Our second research question examined the extent to which preservice teachers integrated their understanding within various subcomponents of PCK as they developed science lessons. Our findings demonstrate that pedagogical instruction framed by PCK for NOS enhanced preservice teachers’ PCK readiness (i.e., knowing and applying PCK components) and, to some extent, put these pieces together (i.e., integrate components of PCK), which are two steps toward developing rich and usable PCK (Smithey 2003). Interestingly, however, we found that having more informed views about NOS did not necessarily lead to having more integrated PCK for NOS. Yet, a closer look at the data showed that the vast majority of preservice chemistry teachers chose to include in their lesson plans the NOS aspects about which they had informed views. This indicates that some comfort in preservice chemistry teachers’ own understanding of NOS is prerequisite to teaching NOS. It is important to consider, however, how successfully preservice teachers designed a lesson plan to teach the specific NOS aspect they chose. We found preservice teachers whose PCK for NOS was well-developed and well-integrated were better able to create appropriate lessons to teach NOS. This finding is compatible with the idea that the integration among the various subcomponents is necessary for robust PCK, which is the key to successful teaching (Friedrichsen et al. 2009; Magnusson et al. 1999; Park and Chen 2012).

The lesson plans constructed by our participants prompt questions regarding the nature of PCK for NOS. PCK is generally viewed as being topic-specific (van Driel et al. 1998), and researchers have asserted that NOS is analogous to other topics a teacher may teach (Lederman 1998). It logically follows that teachers would then have topic-specific PCK for different topics, including NOS. Yet, cases in which participants planned to teach NOS embedded within science topics defy this characterization. For example, Howard prepared a lesson on atomic theories and Fletcher designed a lesson on acid–base theories. While they had different PCK for these different chemistry topics, both of them used explicit-reflective instructional approaches to teach about the nature of theories. That is, the two drew on different PCK specific to the topics of atomic theories and acid–base theories, but both drew on PCK for teaching the nature of theories. Nonetheless, it stands to reason that teaching about the nature of theories within these two contexts (acid–base theories and atomic theories) would differ. At this point, an argument proposed by Davis et al. (2008) provides a useful way for conceptualizing this intersection. Davis et al. (2008) advocated that “…[w]hile PCK is typically conceptualized as topic-specific, teachers also need discipline-specific knowledge about how a discipline works” (p. 6). Moreover, Davis and Krajcik (2005) defined PCK for disciplinary practices as “teachers must know how to help students understand the authentic activities of a discipline, the ways knowledge is developed in a particular field, and the beliefs that represent a sophisticated understanding of how the field works (p. 5). Davis et al. (2008) illustrated their argument by discussing how discipline-specific PCK for scientific modeling includes “…knowledge of instructional strategies that can promote students’ engagement in modeling practices and learning of metamodeling knowledge…[as well as] teacher’s knowledge of their students’ ideas and the challenges students face, again associated with modeling practices and metamodeling knowledge” (p. 6). Thus, teachers need to develop specific knowledge of modeling (PCK for scientific modeling) but might apply that within the context of teaching different topics. In this study, the discipline-specific PCK perspective helps explain preservice teachers’ NOS teaching practices across different science topics. While preservice teachers developed knowledge of various aspects of NOS and PCK for teaching those aspects of NOS, this PCK for NOS intersects teachers’ PCK for teaching other topics in the planning and implementation of instruction through topic-specific representations and activities that address both the targeted aspects of NOS and the focus science concepts.

Implications

In this study, we found that NOS instruction followed by pedagogical instruction framed by PCK for NOS was effective in stimulating preservice chemistry teachers to integrate NOS into their chemistry teaching. This suggests that deliberate and purposeful efforts to target specific elements of preservice teachers’ PCK may be more effective than approaches focused solely on how to teach NOS (i.e., teaching explicit-reflective instruction) that are commonly described in the literature. This also suggests value in providing coherence and connection across preservice teachers’ coursework in terms of NOS. To foster the development of PCK for NOS, teachers should be provided with the opportunities where they study NOS as learners (developing an understanding of NOS) but also from a teaching perspective. This can be realized by enacting an explicit PCK framework (e.g., Magnusson et al. 1999) in a course where NOS is taught. Moreover, our results indicate that individual PCK components should be revisited in a way such that teachers are able to see how those components connect with each other in the design of instruction. Teachers, especially preservice teachers, may have difficulty in seeing the relevance of PCK for NOS instruction to their teaching. Engaging in explicit-reflective discussions of PCK for NOS components (e.g., knowledge of learner, curriculum, and instructional strategy) and the way they connect these knowledge bases can address this. In addition to approaches used in our study, there are several examples of research using a PCK framework and tools for making PCK explicit such as CoRes and PaP-eRs (Hume and Berry 2010; Loughran et al. 2008). It stands to reason that utilizing CoRes and PaP-eRs on NOS, developed by experienced NOS teachers, could help novice teachers to develop PCK for NOS. However, further research is needed to substantiate the effectiveness of various approaches to supporting development of pre- and in-service teachers’ PCK for NOS.

As more studies are being conducted in regard to teachers’ PCK for NOS, further consideration should be given to the nature of PCK for NOS. Which level of specificity in conceptualizing PCK (e.g., topic-specific and disciplinary-specific) can best capture the way teachers enact their PCK for NOS? How does this differ within the context of content-generic and content-specific NOS instruction? Is topic-specific PCK (e.g., PCK for acid–base theories) a prerequisite for development PCK for NOS when teaching NOS embedded in content or vice versa? Studies that focus specifically on the interplay of teachers’ discipline-specific and topic-specific PCK are needed.

As educational standards emphasize NOS as a curriculum component, consideration should be given as to not only the knowledge of NOS teachers need to understand NOS, but also the complex knowledge required to teach NOS. Policy documents such as the US Next Generation Science Standards have advocated that NOS be taught integrated with disciplinary core ideas, cross-cutting concepts, and science and engineering practices. How NOS is related to these three fundamental areas and the possible ways to integrate NOS should be explored. In addition, there needs to be more explicit and clear portrayal of how this would look in actual classroom practice. That is, there needs to be support in terms of models for how teachers can achieve the vision of the reforms in terms of helping students develop an understanding of NOS.