Development of pre-service teachers’ pedagogical content knowledge and the factors affecting that development: a longitudinal study

Abstract

The purpose of this longitudinal study was to explore the development of pre-service chemistry teachers’ pedagogical content knowledge regarding the effect of temperature on reaction rate topic as they took pedagogical content knowledge courses throughout the teacher education program. Pre-service teachers’ pedagogical content knowledge was examined under five components: Orientations toward science teaching, Knowledge of curriculum, Knowledge of instructional strategies, Knowledge of learners, and Knowledge of assessment. Two pre-service chemistry teachers participated in the study. Data were collected through a vignette and semi-structured interviews over two years. Analysis of data revealed that both participants’ pedagogical content knowledge components showed development. However, there was an uneven development of components of pedagogical content knowledge. Moreover, the degree and pattern of development were different for some components of pedagogical content knowledge for each participant. The present study has some implications for teacher educators and teacher education programs.

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Introduction

Since Shulman's epochal initiatives (1986, 1987), pedagogical content knowledge (PCK) has become a well-known framework for what teachers know and how they practice their knowledge (Abell, 2007). He defined PCK as a “special amalgam of content and pedagogy that is uniquely the province of teachers” (Shulman, 1987, p. 8). PCK requires teachers to transform their knowledge of content and pedagogy into a form of knowledge of teaching. That special knowledge makes science topics more comprehensible to learners (Shulman, 1986).

Researchers have conducted PCK studies in science education with various purposes since the introduction of the PCK construct. Chan and Hume (2019) determined five main research lines, namely investigating the nature of PCK (e.g.Demirdöğen, 2016; Akın and Uzuntiryaki-Kondakci, 2018; Belge-Can, 2021), the development of PCK (e.g.Henze et al., 2008; Chan and Yung, 2017), factors related to PCK (e.g.Rollnick, 2017; Uzuntiryaki-Kondakci et al., 2017), the effect of an intervention on PCK change (e.g.Aydin et al., 2013, 2015; Boz and Belge-Can, 2020), and development of tools for measuring PCK (e.g.Park et al., 2018). These lines of research can be augmented by inserting sub-themes to those of majors: studies searching for integration among PCK components (e.g.Park and Chen, 2012; Aydin and Boz, 2013) and the development of a PCK model (e.g.Magnusson et al., 1999; Park and Oliver, 2008; Gess-Newsome, 2015; Carlson and Daehler, 2019). As well as subject-specific PCK, the literature contains various studies investigating domain-specific PCK as well: For instance, PCK for nature of science (NOS) (e.g.Demirdöğen et al., 2016; Hanuscin et al., 2011), PCK for argument-based inquiry approach (e.g.Suh and Park, 2017), and PCK for science-technology-engineering-mathematics (STEM) (e.g.Aydin-Gunbatar et al., 2020), etc.

To date, PCK development has taken researchers’ attention, and even become the dominant focus of science PCK with the introduction of recent PCK models. Nowadays, research studies widely investigate how PCK develops over time instead of what it is (Park, 2019). In this respect, teacher education has been acknowledged as crucial for effective science teaching (Friedrichsen et al., 2009). Insights of PCK development cannot be fully understood unless the pathways pre-service teachers move through within teacher education programs and the period they experience that development is searched profoundly. Certain tools, including explicit PCK instruction with Content Representations (CoRes) and/or Pedagogical and Professional-experience Repertoires (PaP-eRs) (Loughran et al., 2006), reflections on teaching experience (Nilsson, 2008; Park and Oliver, 2008), and mentoring (Barnett and Friedrichsen, 2015) were utilized in the related literature to develop PCK. Park (2019) viewed PCK development as “continual change across a broad span of time, rather than as a series of discrete changes resulting from particular training experiences or critical classroom incidents” (p. 125). To be able to support teachers’ PCK growth, science PCK literature needs longitudinal studies that explore (pre-service) teachers’ PCK development and the factors affecting that development.

Literature background

The framed model of pedagogical content knowledge (PCK)

The PCK model of Magnusson et al. (1999) informed this study. PCK was conceptualized by Magnusson et al. (1999) as “the transformation [italics in original] of several types of knowledge for teaching (including subject matter knowledge), and that as such it represents a unique domain of teacher knowledge” (p. 95). This model consists of five PCK components, namely science teaching orientations, knowledge of curriculum, knowledge of students’ understanding of science, knowledge of instructional strategies, and knowledge of assessment.

Of these components, science teaching orientations are the one on which PCK researchers cannot reach a consensus about what orientations entail as they refer to messy, complex, and unstraightforward teacher beliefs (Friedrichsen et al., 2011). In fact, consensus models (Gess-Newsome, 2015; Carlson and Daehler, 2019) addressed science teaching orientations as filters or amplifiers of PCK instead of a component of PCK. Although Magnusson et al. (1999) defined them with regard to science teaching only, Friedrichsen et al. (2011) proposed a set of teacher beliefs while describing science teaching orientations, which are beliefs about the goals or purposes of science teaching, beliefs about the nature of science, and beliefs about science teaching and learning.

Science PCK researchers may adopt distinct combinations regarding PCK components. Ignoring science teaching orientations, for instance, is a common tendency (Friedrichsen et al., 2011; Chan and Hume, 2019). In their study, Henze and Barendsen (2019) preferred not to use science teaching orientations by considering those to be less specific to content than the other four PCK components. Aydin-Gunbatar et al. (2020), for instance, preferred including all PCK components except science teaching orientations while investigating PCK for integrated STEM development. They justified their decision due to challenges associated with science teaching orientations’ definition and measurement. Taking only knowledge of students’ understanding of science and knowledge of instructional strategies as components of PCK is another research tendency in science PCK (Chan and Hume, 2019). Park et al. (2011), as an example, developed a PCK rubric to measure teachers' PCK levels based on these two PCK components. Demirdöğen et al. (2016), on the other hand, investigated the nature and development of pre-service chemistry teachers’ PCK for NOS through excluding knowledge of the curriculum. Researchers reported the reason for this choice as the related curriculum did not involve NOS objectives at the time their study was performed.

As the original PCK model of Magnusson et al. (1999) all of the five PCK components are under investigation in this research with slight modifications. Specifics of modifications are as follows; science teaching orientations are conceptualized as a belief set as suggested by Friedrichsen et al. (2011) except beliefs about the nature of science, which is out of the scope of this study, and knowledge of curriculum is conceptualized as to include not only knowledge of objectives (Magnusson et al., 1999) but also links to other topics and disciplines as offered by Grossman (1990). The resulting framework was used by other researchers as well (e.g.Ekiz-Kiran, Boz and Oztay, 2021). As seen in Table 1, lastly the term “science” was changed to “chemistry” as this study focuses on chemistry.

Table 1 Adopted PCK framework

a Friedrichsen et al. (2011). b Grossman (1990).
Science teaching orientations (STOs)	• Beliefs about the purposes of chemistry teaching^a
	• Beliefs about chemistry teaching and learning
	• Beliefs about the role of students and teachers^a
Knowledge of curriculum (KC)	• Knowledge of objectives
	• Links to other topics and disciplines^b
Knowledge of students’ understanding of science (KSU)	• Pre-requisite knowledge
	• Areas of student difficulties
	• Misconceptions
Knowledge of instructional strategies (KIS)	• Knowledge of subject-specific strategies
	• Knowledge of topic-specific strategies
	• Representations
	• Activities
Knowledge of assessment (KA)	• Knowledge of what to assess
	• Knowledge of how to assess

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Research on the development of PCK components

Similar to the trend of PCK research in general, most of the studies searching for science PCK development are qualitative (Chan and Hume, 2019). This line of research indicates uneven development in terms of individual PCK components. Henze et al. (2008) explored the development of experienced science teachers' PCK regarding the models of the solar system and the universe for three years. The analysis of data revealed two distinct types of PCK, type A and type B. The former was defined as having model content orientation, and the latter was identified as having model production and thinking regarding the nature of model orientation in addition to the model content orientation. Concerning both types of PCK development, knowledge of goals and objectives did not show a significant change throughout the three years. In type A, knowledge of instructional strategies, consistent with knowledge of curriculum and students’ understanding of science, showed more development compared to the other PCK components. On the other hand, knowledge of assessment did not change substantially. In contrast to PCK development in type A, in which interaction among components of PCK was labeled as static, interaction among components of PCK was typified as dynamic in type B PCK development. Likewise, as in type A, the development of knowledge of instructional strategies was consistent with the knowledge of curriculum and knowledge of learner in type B. Moreover, the development of knowledge of learner was related to the knowledge of instructional strategies and assessment. Development of knowledge of learner and instructional strategy influenced the development of knowledge of assessment. In a two-year-long longitudinal study, Melo et al. (2017) searched for PCK characterization, the emotions, and the relationship between PCK and emotions of two physics teachers regarding the electric field before and after their attendance in an innovation project. All PCK components of Magnusson et al. (1999) were involved in the research except science teaching orientations. Participants' PCK development was analysed by a rubric indicating three categories across PCK components, namely traditional, intermediate, and innovative. These categories were defined as they are orientations to teaching electric fields. Case-based results showed that the teacher, whose entry tendency was traditional, developed the most knowledge of curriculum, and instructional strategies. On the other hand, the other teacher, whose starting tendency was intermediate, indicated resistance to change mostly in the knowledge of instructional strategies. With the same methodology, Melo et al. (2020) investigated a physics teacher's PCK development after participating in an intervention, based on reflections about teaching the electric field. In contrast to knowledge of assessment, results revealed development in the knowledge of curriculum and instructional strategies.

In another study, Brown et al. (2013) concluded that pre-service biology teachers’ science teaching orientations were stable over a year-long teacher education course, and based mainly on their personal previous experiences. With more teaching experience, their knowledge of students' difficulties is enhanced. Moreover, their knowledge of instructional strategies increased throughout the course. Their science teaching orientations influenced their knowledge of learner and instructional strategies. Moreover, Adadan and Oner (2014) investigated two pre-service teachers' PCK development over the chemistry teaching methods course on the gases topic. Results revealed that neither of the participants showed signs for all PCK components at the beginning of the course (PCK1). Science teaching orientations in one case and knowledge of assessment in the other case were deficient initially. On the contrary, all of the five PCK components were valid at the end of the course (PCK2). However, their development of PCK components was not the same, and they were not developed evenly. In another study, Sickel and Friedrichsen (2018), furthermore, concluded that three beginning biology teachers’ teaching and learning beliefs were stable over two consecutive years. Two of them held a constructivist orientation while the other participants had a didactic orientation. The participants with constructivist orientations expanded more PCK components and more PCK connections than the participant with didactic orientation. All participants' knowledge of assessment was enhanced in the second year. Moreover, uneven and idiosyncratic knowledge expansions were detected in this study. Similarly, Ekiz-Kiran et al. (2021) concluded on five PCK components of the model of Magnusson et al. (1999) as being developed in varying qualities as a result of the enriched school experience course. Although pre-service chemistry teachers’ science teaching orientations were stable, their knowledge of curriculum and assessment developed for some, and their knowledge of students’ understanding of science and instructional strategies developed for all. Reynolds (2020), moreover, explored the features of PCK development for pre-service science teachers by focusing on the integration of PCK components. Participants’ PCK was found as limited in general. The central relationship to PCK belonged to the knowledge of students’ understanding of science, and knowledge of instructional strategies. Participants' knowledge of students' understanding of science, and knowledge of assessment were weak. Their science teaching orientations were not dynamic, and scarcely influenced pre-service science teachers’ PCK.

Research on the factors affecting PCK development

Besides the development of individual PCK components, it is also crucial for effective science teaching to search for factors affecting that development (Henze and Barendsen, 2019; Park, 2019; Wilson et al. (2019)). In this respect, teacher education has been acknowledged as crucial (Friedrichsen et al., 2009). Researchers have searched the pathways pre-service teachers move through within teacher education programs to be able to understand insights into PCK development. Correspondingly, factors related mostly to teacher knowledge and practice have been reported as influential to PCK development (Park, 2019), including explicit PCK instruction with CoRes and/or PaP-eRs (Loughran et al., 2006), teaching experience (Aydin et al., 2013; Ekiz-Kiran et al., 2021), reflections on teaching experience (Nilsson, 2008; Park and Oliver, 2008; Nilsson and Karlsson, 2019), mentoring (Hanuscin and Hian, 2009; Aydin et al., 2013; Barnett and Friedrichsen, 2015), and observation (Grossman, 1990; van Driel et al., 2002; Barendsen and Henze, 2019).

These factors were used to design educational courses, as they are significant to PCK development. For instance, Aydın et al. (2013) prepared a research-informed practicum course, which was made up of mainly CoRes as a lesson planning tool, explicit PCK instruction, and educative mentoring, to develop pre-service chemistry teachers’ PCK. After a 14 week exposition to this course, pre-service teachers stated that not only the aspects of this course but also teaching experience and peer observation contribute to their PCK development. Likewise, Ekiz-Kiran et al. (2021) devised a school experience course including the use of CoRes as lesson planning tools, observations of the mentors’ teaching and discussions on these observations, and reflections on their teaching to enhance pre-service chemistry teachers’ PCK. It was found that the use of CoRes and observing mentors' instruction employing observation form based on PCK components and discussions of these observations were beneficial to improve pre-service teachers' PCK. Moreover, teaching experience and reflection on this helped to enhance pre-service teachers’ knowledge of instructional strategy.

Some researchers, on the other hand, have searched for other factors in PCK development. Most of these studies framed the Refined Consensus Model (RCM) of PCK (Carlson and Daehler, 2019) since this model emphasized the importance of contextual factors deeper than previous PCK models. Henze and Barendsen (2019), for example, found efficacy, emotion, and micro-politics as the personal factors influencing pre-service chemistry teachers' personal PCK development, a type of PCK postulated by the RCM of PCK. Moreover, Mavhunga (2019) concluded that pre-service chemistry teachers’ personal PCK development at the topic level differed as a result of some factors, namely personal beliefs, the ability to see connections and disconnections, and the interactive use of representations with other topic-specific PCK components.

Significance of the study

The RCM of PCK, a consensus PCK model proposed by the contribution of well-known science PCK researchers, introduced three realms: enacted PCK, personal PCK, and collective PCK (Carlson and Daehler, 2019). Although the PCK model of Magnusson et al. (1999) informed this study, it is important to situate the type of PCK investigated in this research by taking the most recent model of PCK into consideration. Since this study examined two pre-service chemistry teachers’ PCK development as they took PCK courses throughout the teacher education program, it can be readily stated that it is the personal PCK that is “developed, shaped, and refined over time through formal education, teaching experiences, and professional sharing” (Carlson and Daehler, 2019, p. 86). The reasons for using the PCK model of Magnusson et al. (1999) are it being the most cited PCK model in science PCK research and it making PCK components apparent. Another reason why this model was preferred pertains to researchers’ view of PCK conceptualization which correlates directly with the transformative stance of Magnusson et al. (1999). In short, PCK was viewed as a distinct knowledge category involving STOs, KC, KSU, KIS, and KA. We hope to make valuable contributions to science PCK literature by taking all five PCK components into account as in the original PCK model of Magnusson et al. (1999).

The results of this research hope to provide invaluable perspectives to PCK development research due to its' longitudinal approach, which is one of the research gaps reported in science PCK literature. In Chan and Hume's (2019) review of individual science teachers’ PCK, researchers identified that “longitudinal studies of PCK development are lacking in the science education field” (p. 54). Furthermore, Park (2019), Sorge et al. (2019) and many other researchers stated a need for longitudinal studies through which contexts for gradual PCK development can be designed. By this two-year long study, new insights could be anticipated about the development of pre-service chemistry teachers’ PCK such as how to design research-based PCK courses in the teacher education program, and prepare professional development projects that support pre-service chemistry teachers’ gradual PCK development as they move along from junior to senior. These perspectives are thought to make this study valuable not only for teacher educators but also for experts and leaders making instructional decisions. In the framework for upcoming science PCK research, Wilson et al. (2019) pointed out a need for studies examining PCK development. They further divided this theme of research into longitudinal, intervention, and contextual studies. This holistic framework made it visible that it is crucial to search for factors influencing the development of PCK. Park (2019) stated that if the effects of some factors on PCK development are known, professional development programs and interventions can be styled in a manner to serve more readily the purpose of effective science teaching. Henze and Barendsen (2019) viewed the investigation of factors affecting PCK development as significant as well. Then, results on factors affecting PCK development are another expected contribution of this research to the science PCK.

Collectively, this study explores the development of pre-service chemistry teachers’ PCK components and factors affecting that growth in the effect of temperature on reaction rate topic as they take PCK courses during the teacher education program. Research questions are as follows;

(1) How did pre-service chemistry teachers’ PCK components develop regarding the effect of temperature on reaction rate topic as they took pedagogical content knowledge courses throughout the teacher education program?

(2) Which factors influenced the development of pre-service chemistry teachers’ PCK components in the effect of temperature on reaction rate topic?

Methodology

Research design

A qualitative research design was used in the present study. As Fraenkel and Wallen (2006) state, qualitative research focuses on the process as well as the product and words rather than numbers. We employed a qualitative research design since it fit with the aims and research questions of the study. In the present study, we aimed to get in-depth information about the development of pre-service teachers’ PCK as well as the factors influencing its development during the teacher education program. Qualitative research design includes five types of methodologies, narrative qualitative study, ethnography, phenomenology, grounded theory, and case study (Creswell, 1998). Among these, we chose the case study. Bogdan and Biklen (1998, p. 54) described a case study as “a detailed examination of one setting, or a single subject, a single depository of documents, or one particular event”. In the present study, two pre-service chemistry teachers enrolled in a chemistry teacher education program constituted the case.

Sample

After getting permission from the ethics committee of the university, we explained the purpose of our research to the pre-service chemistry teachers and asked for volunteers. We also told them that they could withdraw from the study at any time they want. Initially, five pre-service chemistry teachers volunteered to take part in the study. However, three of them left the study in the process of time. Pseudonyms were used instead of real names to provide confidentiality. Two pre-service chemistry teachers (Barbara and Deborah) were the participants in the study. Both of them were female. They were enrolled in a five-year chemistry education program. Barbara's cumulative grade point average (CGPA) was 2.39 out of 4.00 at the beginning of the study while Deborah's CGPA was 2.97. When they completed all the pedagogical content knowledge courses, Barbara's and Deborah's CGPAs were 2.58 and 3.07, respectively. When we compare the grades of Barbara and Deborah regarding pedagogical content knowledge courses, Deborah's grades were better. However, both of the participants were eager to learn in the courses they took. They always participated in class discussions. Before taking any pedagogical content knowledge courses, they both believed in the importance of chemistry teaching in terms of explaining daily life events. Differently, Deborah also mentioned that chemistry teaching enhances scientific thinking, which is important in people's life such as relationship with family, people's world view as well as understanding other disciplines such as mathematics and social sciences. They were also placed at the same high schools for the practicum courses. For the school experience course, they were placed at a private high school while they completed their practice teaching at a state high school.

Instruments

Vignettes and semi-structured interviews were used in the collection of data.

Vignette

The use of vignettes has been suggested in the related literature to evaluate teachers' pedagogical content knowledge (Veal, 2004; Kind, 2009). The vignette in the present study describes a description of the class, the problematic situation, and questions regarding the components of pedagogical content knowledge.

Mrs Smith is a chemistry teacher in a high school. She plans to teach the topic of the effect of temperature on reaction rate to a class of 11th-grade students. The class has medium-ability students. However, she can't decide how to teach. Therefore, she needs some help. Could you please help Mrs Smith to answer the following questions?

(a) What are the objectives regarding the effect of temperature on reaction rate in the curriculum?

(b) Do you think that Mrs Smith needs to follow the curriculum strictly or does she need to make changes if necessary? Why?

(c) What are the previous topics that form the base for teaching temperature effect on reaction rate? What are the following topics that the effect of temperature on reaction rate forms the base of?

(d) How can Mrs Smith relate this topic with the topics in other disciplines such as physics, biology, mathematics, etc.?

(e) Which pre-requisite knowledge do students need to have to learn the topic?

(f) What are the difficulties students encounter while learning this topic?

(g) What are the misconceptions students may have regarding this topic?

(h) Which teaching strategies and activities can Mrs Smith use to teach this topic? And how can she employ these strategies and activities? Please explain in detail.

(i) Which assessment strategies and techniques can Mrs Smith use to assess students regarding this topic? How, when, and why does Mrs Smith intend to use these strategies? What does Mrs Smith aim to measure by using these strategies and techniques?

Participants completed the vignette at different times, a total of four times. Time 1 refers to the time that participants did not take any pedagogical content knowledge courses. Time 2 describes the time that participants completed three pedagogical content knowledge courses, which are “curriculum development in science education”, “methods of science teaching I” and “laboratory experiments in science education” courses. At time 3, pre-service chemistry teachers completed four more pedagogical content knowledge courses; “measurement and evaluation in science education”, “methods of science teaching II”, “instructional technology and material development” and “school experience in science education”. Time 4 refers to the time they completed all the pedagogical content knowledge courses. The below figure shows the pedagogical content knowledge courses the pre-service teachers took at different times (Fig. 1).

Fig. 1 Pedagogical content knowledge courses concerning times.

Semi-structured interviews

Likewise, after the participants completed the vignettes, semi-structured interviews were conducted with participants four times throughout their teacher education program. The elapsed time between the vignettes and interviews was approximately a week. The interviews aimed to understand participants' reasonings about the responses given in the vignettes and clarify unclear responses in the vignette to obtain in-depth information about participants' PCK. Therefore, after examining each participant's vignette, some questions were prepared in advance. However, some additional questions were also asked according to participants' responses during the interview. Each interview lasted about 45 minutes to one hour. Each interview was tape-recorded after receiving the permission of the pre-service teachers. Some sample interview questions were: “Why did you use simulation to teach the effect of temperature on reaction rate?”, “In the vignette, you mentioned the link of this topic with mathematics. Could you please give more details regarding this link?” etc. Another aim of the semi-structured interviews was to reveal pre-service teachers’ science teaching orientations and factors that influence the development of PCK. Therefore, questions regarding pre-service chemistry teachers’ science teaching orientation and questions with respect to the factors influencing the participants’ PCK development were also asked during the interviews. Examples of these questions were: “What is the purpose of chemistry teaching in high schools?”, “Why do we teach chemistry in high schools?”, “What is the role of the teacher during chemistry teaching?”, “Which factors influenced the development on your knowledge of instructional strategy?”

Context of the study

The chemistry teacher education program, a five-year program, was the context of the study. Pre-service chemistry teachers enrolled in this program take various content courses (general chemistry, analytical chemistry, physical chemistry, organic chemistry, and inorganic chemistry). They also complete some pedagogical courses (e.g. introduction to education, educational psychology, classroom management, and guidance). Besides these, pre-service teachers take some pedagogical content knowledge courses (curriculum development in science education, methods of science teaching, laboratory experiments in science education, measurement and evaluation in science education, instructional technology, and material development). They have also two teaching practicum courses (school experience in science education and teaching practice in science education) as pedagogical content knowledge courses. The pedagogical content knowledge courses aimed to enable pre-service chemistry teachers to learn about chemistry curriculum, methods, and teaching strategies to teach chemistry concepts, assessment, and evaluation techniques for chemistry topics. Table 2 gives brief information about each pedagogical content course.

Table 2 Description of pedagogical content knowledge courses

Course name	Description of the course
Curriculum development in science education	Theoretical information about curriculum, components of curriculum and curriculum development process
	Instructional objectives (how to evaluate the instructional objectives according to Bloom's taxonomy and write instructional objectives for different chemistry topics)
	Evaluation of national chemistry curriculum
Measurement and evaluation in science education	Critical evaluation of the existing assessment instruments and development of new assessment instruments for chemistry topics. Psychometric evaluations of instruments
Laboratory experiments in science education	High school chemistry experiments (content part of the experiment, carrying out the experiments, interpretations of the experiment results, students’ difficulties and misconceptions related to chemistry concepts, daily life applications of chemistry concepts)
Methods of science teaching I & II	Theoretical aspects of teaching methods and strategies and practical applications of these for chemistry topics employing microteaching after the preparation of lesson plans
Instructional technology and material development	Selection, modification and design of instructional technology and materials to teach chemistry (e.g. simulations, animations, worksheets, etc.)
School experience in science education	Comprehension of the school and classroom environment by observing and evaluating chemistry teachers' instruction in terms of PCK components (knowledge of curriculum, learner, instructional strategy, and assessment) and classroom management skills
Practice teaching in science education	Practice teaching chemistry in high schools (preparation of CoRes before instruction, microteaching in the university, and teaching various chemistry topics in the high schools)

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Data analysis

The responses to the vignettes and semi-structured interviews were the data sources. To find out the development of pre-service chemistry teachers' PCK as they take pedagogical content knowledge courses in the teacher education program, data were analyzed deductively based on the components and sub-components of the Magnusson et al. (1999) model (Table 1). Pre-service teachers’ responses to vignettes and interviews were read carefully and responses were categorized considering components and sub-components of Magnusson's (1999) model. For example, responses of pre-service teachers regarding the pre-requisite knowledge that learners need to have were put under the sub-component of prerequisite knowledge under the knowledge of learner component.

To reveal the factors influencing the development of pre-service teachers’ PCK, the inductive approach was used. Responses given to the semi-structured interviews mainly constituted the raw data for the factors that affect the pre-service teachers’ PCK development. Raw data was read and categories were formed based on it. For reliability, data were analyzed independently by two researchers. Afterward, their analysis was compared. In most of the cases, there was a match between the categories. In case of conflicts, the researchers came together and discussed until a consensus was reached.

Results

Science teaching orientations (STOs)

Both participants’ beliefs about the purposes of chemistry teaching showed slight changes during the chemistry teacher education program. For both participants, common belief about the purpose of chemistry teaching was to explain daily life events. Both Barbara and Deborah had this belief throughout their program. However, Barbara also added that chemistry teaching was important in terms of understanding physics, biology, and other disciplines easily after completing all the pedagogical content knowledge courses. On the other hand, Deborah had two purposes for chemistry teaching before taking any pedagogical content knowledge courses. One of them was to explain daily life events. The other was to increase scientific thinking that is necessary to be successful in personal life and understand other disciplines such as mathematics and social sciences. She gave the below explanations: “I think teaching chemistry increases students' scientific thinking. Scientific thinking affects other areas in people's life. For example, relationship with family, people's world view, mathematics, social sciences.” However, after completing all the pedagogical content knowledge courses, the belief regarding the purposes of chemistry teaching as the increase in scientific thinking was not present. Instead, Deborah mentioned the affective dimension of chemistry teaching and stated one of the purposes of chemistry teaching as increasing interest in chemistry.

Beliefs about the role of students and teachers were investigated under the participants' beliefs about chemistry teaching and learning parameter of STOs. Both participants' beliefs about the role of students and teachers also showed changes as they took pedagogical content knowledge courses. To illustrate, in the beginning, Barbara stated that both students and the teacher should have an active role in the teaching and learning process. However, after completing all the pedagogical content knowledge courses, she believed that the teacher's role may change as being passive or active depending on the nature of the topic:

Students cannot understand abstract concepts easily, so, for abstract concepts, teachers should make explanations to students. In this respect, teacher-centered instruction is necessary. But in some cases, student-centered instruction is required. Students need to make experiments and make inferences from the experiment or they need to make discussions.

However, for Deborah, as she took more pedagogical content knowledge courses, the role of the teacher changed from being more information provider to a facilitator and guide. This was the same for the role of the student. She believed that the teacher should have a facilitator role and students should be active in their learning process after completing all the pedagogical content knowledge courses.

Knowledge of curriculum (KC)

Both participants’ knowledge of objectives enhanced gradually as they took pedagogical content knowledge courses. To illustrate, both Barbara and Deborah did not consider the curriculum while writing the objectives before taking any pedagogical content knowledge courses. Barbara gave the following explanations: “I wrote the objectives myself by thinking about the content of the topic. I did not consult the curriculum.” However, after they took the curriculum development course, they stated that they checked the curriculum and wrote the objectives directly from there. Deborah also stated that she found the objectives in the curriculum satisfactory regarding the reaction rate topic: “Before the examination of the curriculum, I thought it was terrible. But when I examined it, I could not find so much trouble with the curriculum, maybe slight issues.” However, after completing both methods of chemistry teaching and school experience courses, both of the participants found the curriculum too superficial and criticized the objectives in the curriculum for the effect of temperature on reaction rate topic. For example, Deborah gave the following explanations:

Before, I used to think that teachers need to follow the curriculum strictly. But objectives in the rate of reaction topic are too superficial, nearly nothing written. We should not only stick to the objectives in the curriculum. We need to write our objectives related to the topic as well.

After taking the teaching practice course and completing all the pedagogical content knowledge courses, Barbara criticized the curriculum for this topic, and at this time, her critiques involved more specific explanations and these were mainly related to the level of the objectives: “There was only one objective regarding the effect of temperature on the reaction rate and it was a low-level objective in the comprehension level. The curriculum should involve more objectives in the higher level like application, analysis.”

After completing all pedagogical content knowledge courses, though Deborah was aware of the objectives regarding this topic in the curriculum she stated that it is not always possible to implement the curriculum in reality:

There are some problems with the curriculum. Objectives are low level. However, it is not even possible to fulfill these objectives in class with some groups of students. In the teaching practice course, in some classes I observed, some students do not even know how to write correctly. Their levels are very low.

Concerning the previous topics that form the base for temperature effect on reaction rate topic, Barbara's knowledge showed sharp progress after completing all the pedagogical content knowledge courses. Before taking any pedagogical content knowledge courses, Barbara stated that the topics that form the base for the topic of temperature effect on reaction rate were the definition of reaction and how reactions occur. At time 2, she still stated these concepts that form the base for the topic of temperature effect on reaction rate. At time 3, Barbara added single-step reactions and the average reaction rate to the concepts she previously mentioned. After completing all the pedagogical content knowledge courses, she mentioned the microscopic view of chemistry and stated collision theory, effective collisions, activation energy, and threshold energy as important concepts mentioned in the curriculum that provide the basis for the effect of temperature on reaction rate topic. Compared to Barbara, Deborah's knowledge developed gradually as she took more pedagogical content knowledge courses. As the prior topics in the curriculum, before taking any pedagogical content knowledge courses, Deborah stated the structure of the matter only without giving any further details. At time 2, Deborah gave detailed explanations:

The particulate nature of matter and how reactions occur should be the prior concepts that form the base for temperature effect on reaction rate. The matter has a particulate nature and it is composed of particles. There are spaces among particles. Particles collide with each other and form reactions.

The completion of methods and school experience courses did not cause any change in Deborah's knowledge of the curriculum regarding the prior topics that provide the base for the temperature effect on reaction rate. After she finished all the pedagogical content knowledge courses, in addition to the particulate nature of matter, she stated that potential and kinetic energy concepts form a base for the temperature effect on reaction rate topic: “Until three months ago, I could not define potential energy. It is a hard concept to understand.”

However, both Deborah's and Barbara's views regarding the subsequent topic did not change throughout the program. They mentioned chemical equilibrium as the subsequent topic all the time.

For the link of the effect of temperature on reaction rate topic with other disciplines (e.g. physics, mathematics, and biology), Barbara's view showed only slight development throughout the program. While she could not relate the topic with biology at any time, she interrelated the topic with mathematics for the equation of reaction rate all the time. However, the link of the topic with physics gradually enhanced as she took more pedagogical content knowledge courses. At times 1 and 2, she associated the particulate nature of matter with physics. However, she could not give detailed explanations. However, after completing school experience and methods courses (time 3), she explained the relationship between the particulate nature of matter with physics: “With an increase in temperature, the kinetic energy of particles increases. This can be linked with physics”. After taking all the pedagogical content knowledge courses, she both associated threshold energy with kinetic energy and activation energy with potential energy, which are the concepts that are taught in physics: “When students do not understand activation energy, we could give the example of potential energy. We can also explain threshold energy based on kinetic energy.”

On the other hand, Deborah's knowledge for the link of the temperature effect on reaction rate topic with physics and mathematics did not change at all. However, Deborah showed very slight progress for the link of the topic with biology. At times 1 and 2, she just stated that biological reactions could be linked with the effect of temperature on reaction rate. However, she gave more detailed explanations at times 3 and 4.

We could mention the rate of biological reactions to link temperature effect on reaction rate. For example, we could explain the spoiling of food as temperature increases. Moreover, the effect of temperature on the rising of dough can be explained.

Knowledge of students’ understanding of science (KSU)

Barbara's KSU concerning the pre-requisite knowledge required for the effect of temperature on reaction rate topic did not show any development between the time she did not take any pedagogical content knowledge (time 1) and the time she completed most of the pedagogical content knowledge courses (e.g. curriculum development, methods, school experience courses). However, she showed sharp progress after completing the teaching practice course at time 4. At times 1, 2, and 3, she stated that the definition of reaction, how reactions occur, and the interaction between the reactants and products were the pre-requisite knowledge learners should have. However, she mentioned collision theory as well after completing the teaching practice course:

Students need to understand the definition of reaction and how reactions occur. To understand the effect of temperature, students need to know collision theory, what effective collision means, and how effective collisions occur. Moreover, students need to know the effect of a factor on reaction rate. What it means to increase and slow the reaction. Moreover, students need to know single-step and multi-step reactions and the slowest step determines the reaction rate.

Differently, Deborah's KSU regarding the pre-requisite knowledge showed gradual progress as she took more pedagogical content knowledge courses. At time 1, she stated that the particulate nature of matter was the pre-requisite knowledge students should have. At time 2, she again stated the particulate nature of matter as the pre-requisite knowledge but at this time her explanations were more detailed: “Students need to know the particulate nature of matter. Matter is composed of particles. Particles move, vibrate and they have velocity”. However, Deborah added the concept of reaction rate as pre-requisite knowledge in addition to the particulate nature of matter after she completed methods courses and the school experience course (time 3):

Both the concept of rate of reaction and particulate nature of matter are the pre-requisite knowledge students should have. Before the effect of temperature on reaction rate, students should know what the rate of a reaction means. Average reaction rate, they also need to know. The reaction rate is determined according to the slow reaction. Homogenous and heterogeneous phase reactions, students also need to know these. Another concept students need to know is that matter is composed of particles and these particles move, there is space among particles and particles collide with each other.

After taking all the pedagogical content knowledge courses (time 4), Deborah made more scientific explanations for the pre-requisite knowledge required for the effect of temperature on reaction rate topic. She mentioned collision theory:

Students need to know what the rate of a reaction means. They need to know that matter is composed of particles and particles move. They need to know collision theory and the conditions of collision theory, like enough kinetic energy and collision in the correct orientation They also need to know activation energy and the need to exceed the activation energy for a reaction to occur.

In terms of areas of student difficulties about the effect of temperature on reaction rate topic, both Barbara's and Deborah's knowledge was the same at time 1 and time 2. To illustrate, Barbara mentioned that students had difficulty understanding abstract concepts in the formation of reactions. This was a general statement and did not involve any detailed explanations. Similarly, Deborah stated that students would have difficulty understanding abstract concepts without making further explanations. However, both Barbara's and Deborah's progress about learner's difficulties was noticeable after they completed all the methods courses and the school experience course (time 3). Barbara stated that the concept of successful collision may be difficult for students to understand:

Successful collision may be hard for students to understand. This was also hard for me to understand when I was a student. Students may think that each collision is successful. However, it is not like that. Each collision may not be the right collision. We increase the temperature; the kinetic energy of particles increases and they move faster. When they become faster, there are more collisions among them. However, for a successful collision, particles should collide at the right angle. Students may have difficulty understanding that.

Similarly, Deborah's explanations were detailed:

Students may state that the rate of a reaction increases with an increase in temperature. However, they may have difficulty explaining the reasons behind it. They may find collision theory hard to understand since it is at the microscopic level. They may have difficulty understanding the increase in the motion of particles and the probability of collisions with the increase in temperature.

On the other hand, after completing all the pedagogical content knowledge courses, in addition to the above view at time 3, Barbara added the concepts of activation energy and threshold energy as difficult concepts to understand while Deborah's knowledge of learner's difficulties did not show any change with the view she mentioned at time 3.

In terms of learner's misconceptions, Deborah's knowledge showed progress as she took more pedagogical content knowledge courses. In the beginning, she could not mention any particular misconception but just stated that students may have misconceptions about abstract concepts in the topic. However, at time 2, she mentioned that students may have the misconception of “solids do not have a reaction rate since there are no spaces among the particles of a solid and therefore no collision among particles occur”. After completing all methods courses and school experience courses (time 3), Deborah's knowledge did not change, it was the same. However, after taking all the pedagogical content knowledge courses, Deborah stated that students may have the misconception of the “Reaction rate of exothermic reactions decreases with an increase in temperature”. She gave the below explanations for the reason for this misconception:

Exothermic reactions give heat out. Therefore, they do not like heat. Therefore, when temperature increases, their reaction rate decreases. But this is wrong. In both exothermic and endothermic reactions, the reaction rate increases with an increase in temperature. We can explain it by collision theory.

Similarly, Barbara's knowledge regarding misconceptions showed progress. In the beginning, Barbara, herself, had the misconception and stated that reaction rates of both exothermic and endothermic reactions increase with an increase in temperature as a possible misconception that may be mentioned by students. However, at time 2, she corrected her misconception and she stated that the reaction rate of endothermic and exothermic reactions differs as possible misconceptions of students. This view was the same at time 3 after she finished methods courses and school experience courses. But after completing all pedagogical content knowledge courses, she mentioned a different misconception that students may have regarding the topic of temperature effect on reaction rate: “When we say rates of reactions increase with an increase in temperature in all reactions, we may cause a misconception. Students may think the solubility of gases increases with an increase in temperature. However, this is not correct”.

Knowledge of instructional strategies (KIS)

Both Barbara's and Deborah's knowledge of subject-specific strategies developed as they took more pedagogical content knowledge courses. In particular, methods courses were effective in this development. At the beginning (time 1) and at time 2, both Barbara and Deborah could not indicate any subject-specific strategies. However, after completing the methods courses (time 3), both of them stated that they would prefer to use the 5E learning cycle model to teach the topic. At time 4, Barbara preferred to use the 5E learning cycle model, however, Deborah preferred a mixture of the 5E learning cycle model and conceptual change strategies and explained the reasons for her choice:

At first, I used to say I always use 5E, but later, I thought that using 5E restricts me. For example, I find the first two steps of 5E, the engage and explore steps, very useful. However, for the other steps, I may use other strategies. I do not want to restrict myself by including all steps of 5E. Since the topic involves misconceptions, I can use conceptual change strategies as well.

In terms of topic-specific strategies, Barbara's knowledge showed gradual progress as she took pedagogical content knowledge courses. In the beginning, she stated that she would use experiments, video, and simulation. However, she could not explain the content of the experiment and video. She stated that she would use simulation to make the topic more visual:

Researcher (R): you said you would use simulation. What would the simulation involve?

Barbara (B): We will increase the temperature and students will see an increase in reaction rate. Since it is more visual, students would remember better. The topic is abstract. But when students see it, they will learn better

In time 2, in addition to the use of video, experiment, and simulation, she mentioned that the use of daily life examples would help students learn the topic better. However, she could not give a specific daily life example. She also gave more detailed explanations about the content of the experiment at this time:

I may use vitamin tablets and I put one tablet in cold water and another tablet in hot water. I want students to measure the time by the chronometer until tablets are dissolved in water. Then, I want students to compare the time and they can see that tablets dissolve faster in hot water.

Moreover, Barbara stated that she would use a simulation to remedy the misconception “Reaction rates of endothermic and exothermic reactions differ” by showing the effect of temperature on the particles and successful collisions, however, she still could not state a specific simulation:

I do not have a simulation example in my mind. But I show the movement of particles, their interaction with each other by increasing temperature. They would see an increase in successful collisions with an increase in temperature that would help to increase the reaction rate.

After completing all methods courses (time 3), Barbara stated that she would use the 5E learning cycle model and would begin the instruction with a daily life case involving a daily life question. However, she could not state the example of the case. Similar to her previous view, she mentioned that she would use an experiment that would involve the dissolving of anti-acid tablets in cold and hot water. Different from her previous view, she mentioned the use of an activity that would involve the discussion based on the misconception “Reaction rates of endothermic and exothermic reactions differ”:

I would say that there are students in a class. Some of the students think that reaction rates decrease in exothermic reactions with an increase in temperature. Some students do not think like that. I can ask a question what do you think about rates of exothermic and endothermic reactions with an increase in temperature. I can divide the students into groups and want them to discuss reaction rates of endothermic and exothermic reactions. They can produce a claim and discuss the reasons for their claims.

Moreover, similar to her previous view, she stated that she would use a simulation that would help students see the interaction among particles with an increase in temperature.

After completing all pedagogical content knowledge courses, she did not consider the misconceptions of students in her instruction at this time. Similar to her previous view, she stated that she would begin with a daily life case involving a daily life question. She mentioned the use of an experiment involving the dissolving of anti-acid tablets in cold and hot water. Differently, instead of the experiment, she stated the use of demonstration with the same content of the experiment with the predict-observe-explain technique: “I can show the experiment. First, I want students to predict what would happen to the rate of reaction with an increase in temperature. Then, they would observe the experiment and then explain the reasonings.”

Moreover, though she still could not state the specific simulation example before, she gave more detailed explanations of what the simulation would involve at this time:

The simulation would show collision theory. It would involve interaction among particles, activation energy and would show the number of particles exceeding the activation energy. When we increase the temperature, students should see the increase in the movement of particles and the probability of successful collisions and the number of particles exceeding the activation energy.

Similar to Barbara, Deborah's knowledge of topic-specific strategies showed gradual progress throughout the teacher education program. At first, Deborah stated the use of daily life examples and experiments to teach the topic: “As a daily life example, I can ask why the food in the refrigerator does not spoil fast compared to the food kept outside. Since students link the topic with daily life, they can learn better.”

She also stated that she could use this daily life example in the design of an experiment: “As an experiment, we could keep some food in a refrigerator and keep some food outside and discuss which one spoiled faster. Though this experiment requires some time, I think it is a good experiment.”

She stated she would use direct instruction while teaching:

I just know direct instruction therefore I explain the concepts. For example, I tell that temperature increases reaction rate. I also explain the reason for it by stating that an increase in temperature increases the movement of particles and number of collisions.

At time 2, Deborah preferred the use of more student-centered instruction and stated the use of a case, experiment, and simulation to teach the topic.

I can begin with a case, a story related to daily life. I can say there are some people on an island and they want to keep their food fresh. What can they do? Students discuss it and they become more active.

She also explained the content of an experiment: “It may be related to the dissolving of some substance in hot and cold water. Students can record the time of dissolving and compare their time.”

Deborah also mentioned the use of a simulation without giving detailed explanations:

I can use a simulation but I do not have a specific simulation example. But our instructor showed us a website for chemistry simulations. I can search from that website. The simulation may show the relationship between temperature and movement of particles.

After taking methods courses (time 3), Deborah's knowledge regarding topic-specific strategies was enhanced. She stated the use of questions, experiments, and simulation. At this time, she gave importance to eliciting students' misconceptions through the use of questions. She stated that she would use the simulation to explain collision theory and remedy students' difficulties and her explanation of the content of the simulation was more detailed at this time:

This simulation showed the collisions among particles. Two reactions are occurring at 30 °C and 60 °C. As temperature increases, particles collide more. All the collisions are not successful. The reaction at 60 °C ends faster. One of my friends used this simulation in class. I liked it very much. Since students have difficulty understanding the microscopic view, this simulation helps them.

As she stated previously, the content of the experiment was about the dissolving of tablets in hot and cold water. However, she had doubts about the experiment she prefers:

I may want students to dissolve one tablet in hot water and one tablet in cold water. Then they can compare the time. It is related to the effect of temperature on solubility but still, it is a reaction. I am not sure this is the right experiment. Maybe, I can search for other experiments.

Her view about the use of experiments also changed:

Previously, I used to think experiments are not that necessary. I thought that students can observe from daily life and there is no necessity to make an experiment again. For example, when I ask students why the food kept outside spoils faster, students can say that insects spoil the food. But in an experiment, you keep everything constant but only change the temperature, students cannot say anything else but they can only state that temperature increases the reaction rate.

After completing all pedagogical content knowledge courses (time 4), her knowledge of topic-specific strategies was enhanced. She mentioned the use of daily life examples, experiments, simulations, graphs, and analogies to teach the topic. Her view about the content of the experiment changed. At this time, she stated that she would use an exothermic reaction for the experiment to remedy students' misconceptions as well: “I can use calcium chloride and water. I can give students a thermometer, chronometer, a beaker of cold water, and a beaker of hot water and want them to design their experiments”.

Moreover, she preferred to use graphs to explain the effect of temperature on reaction rate. The graph showed that the fraction of collisions that exceed the activation energy increases with an increase in temperature. She also used an analogy with the use of this graph to make it more understandable:

Think of a house and a room in that house. If the door of a room is wider, more people can enter together. It is also similar in the graph. When temperature increases, the number of collisions increases and this causes an increase in the number of molecules with enough energy that can exceed the activation energy.

Moreover, she preferred to use another simulation, which shows the relationship between temperature and collisions among particles. She described the simulation:

There is an option of a single collision and many collisions in the simulation. Moreover, students can select the reaction and change the temperature of the reaction and observe the particles in the simulation. In addition, there was also a reaction coordinate versus energy graph regarding the reaction in the simulation.

Knowledge of assessment (KA)

Deborah's knowledge of what to assess and how to assess it enhanced throughout the teacher education program though her knowledge was the same at time 1 and time 2. She stated that she would assess students' understanding of content with the help of questions throughout the class. However, at time 3, she also emphasized the importance of assessing students' science process skills, achievement of curriculum objectives, and teacher's instruction in addition to students' understanding of content. Similar to the previous view, she stated the use of continuous questioning throughout the class to assess students' understanding of content, and achievement of curriculum objectives. She also mentioned the necessity of assessing teacher's instruction:

I did not use to think that I needed to check the success of my instruction. But it is very important; for example, I showed a simulation but I need to ask questions to students to understand whether the simulation was effective or not or whether it caused misconceptions or not.

She also declared that she would use an assignment to measure students' science process skills, however, she could not give a specific example related to the temperature effect on reaction rate:

The assignment should be related to the design of an experiment or STEM-related activity. Students will observe, record, and measure. These are related to science process skills. For example, primary school students observe the phases of the moon. They need some time to do this which is not possible in class. I think this is a good activity.

After completing all pedagogical content knowledge courses (time 4), she declared that she would use both formative and summative assessments. Similar to her previous view, she mentioned the importance of questioning during the class. Differently, she stated the importance of grading and summative assessment:

At the end of the class, I make a quiz. This quiz would involve three to five questions related to my instruction. I think grading is also important since students give importance to grades and grading causes students to study harder. I was not thinking like this before but my view about grading changed.

Moreover, she mentioned that she would assess students' understanding of content, their misconceptions, difficulties, ability to interpret graphs as well as their science process skills. However, her explanations were more specific to the topic at this time:

I would assess students’ misconceptions, difficulties. I would also assess their interpretation of the graph, and their understanding of collision theory since the microscopic view regarding this topic is important. Moreover, I would assess their science process skills through the design of the experiment. I would give the materials to them but want them to design an experiment to evaluate the effect of temperature on reaction rate.

Similar to her previous view, she also gave importance to self-evaluation of teacher's instruction: “I can assess my instruction, and the effectiveness of it by understanding the students' responses given to my questions.”

On the other hand, when compared to Deborah, Barbara's knowledge regarding what to assess and how to assess it showed slight development. Barbara stated that she would ask questions at the beginning of the class to elicit students' prior knowledge. She also emphasized the importance of asking questions throughout the lesson to understand students' understanding of content. At the end of the class, she mentioned that she would make a quiz to understand students' comprehension of the content. She also stated the importance of asking questions to evaluate her instruction. At times 2 and 3, she mentioned similar issues. How to assess did not change at all. The only difference was that she thought assessing students' ability to apply their knowledge to daily life was important. After completing all pedagogical content knowledge courses (time 4), her knowledge of assessment improved in terms of what to assess and how to assess it. She stated that she would measure students' misconceptions, their understanding of the topic, and their ability to apply their knowledge to explain daily life events. Similarly, she mentioned the use of questions at the beginning to elicit students' prior knowledge. She also stated the importance of asking questions during the lesson. However, differently from the previous, she preferred a different assessment strategy, a concept map, at the end of the lesson: “I make a concept map with my students at the end of the lesson. I ask them questions and construct a concept map. There should also be a link with previous concepts in the concept map.”

She also stated that she would give homework to the students: “For example, as homework, I can ask them to find the reasons for the decrease in reaction rate with temperature regarding gases.”

Interactions among PCK components

When we investigated the data in terms of the interactions among the PCK components, interactions among PCK components also showed development. Although PCK components were fragmented and rarely connected with each other before taking any pedagogical content knowledge courses for both participants, the interactions were enhanced by the end of the teacher education program. Not only did the number of connections among PCK components increase, but also new connections among PCK components occurred. To illustrate this, Barbara's science teaching orientation influenced only her knowledge of instructional strategy initially. At time 2, Barbara stated that she would use daily life examples since they would help students link chemistry with daily life. However, at time 4, Barbara's science teaching orientation influenced her knowledge of assessment as well. She mentioned that she would assess students’ ability to apply their knowledge to explain daily life events since it is important that students should relate chemistry with daily life events. For Deborah, there was also an increase in the number of interactions and the occurrence of new interactions between PCK components as she took more pedagogical content knowledge courses. For example, the number of connections between her knowledge of instructional strategy and knowledge of learner increased indicating that her knowledge of learner shaped her instructional decisions more as she took more pedagogical content knowledge courses.

Factors influencing the development of PCK components

In the present study, we also investigated the factors that have an impact on the development of PCK components. Table 3 reveals the factors that influenced the development of pre-service teachers’ PCK.

Table 3 Factors influencing the development of PCK components

PCK components	Factors
STO	Observations in the teaching practicum courses
KC	Curriculum development courses
	Construction of lesson plans
KSU	Discussions of students’ possible misconceptions in the theoretical courses
	Preparation of lesson plans, CoRes
	Microteaching
	Observations in the teaching practicum courses
KIS	Methods courses
	Microteaching
	Teaching in high schools
	Observations of peers’ instruction
	Feedback from mentors, tutors and students
KA	Theoretical courses (e.g. methods courses)
	Observation of peers’ instruction
	Feedback from mentors, tutors and students
	Observations in the teaching practicum courses

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Science teaching orientations (STO)

In terms of the factors influencing the change in their STOs, we found that teaching practicum courses influenced the change. For Deborah, observations in the high school affected her belief about the role of the teacher and student as well as the purposes of chemistry teaching:

I think that it is important to enhance students’ interest in chemistry. We can achieve this by engaging students in experiments and activities, making them more active in class. The teacher should not have the role of information provider, instead they should help students’ learning by making them active in class. I observed it in my last teaching practicum course. Students make experiments in class. They felt as if they were scientists. They are active in class and this increases their interest in chemistry.

However, Barbara's observations in the teaching practicum courses caused her to think that the role of the teacher should be both information provider and facilitator in class: “I observed students in the high school. They cannot learn abstract concepts in chemistry if the teacher does not explain them.”

Knowledge of curriculum (KC)

Concerning the factors influencing the development of pre-service teachers' knowledge of the curriculum in the effect of temperature on reaction rate topic, participants mentioned that constructing lesson plans and the curriculum development course were beneficial to enhance their curriculum knowledge: “As I wrote more lesson plans, my curriculum knowledge enhanced since you need to write objectives and to write them, you need to examine the curriculum.”

Barbara also mentioned the effect of the curriculum development course on her curriculum knowledge:

Previously, I used to think of objectives as the headings of the topic. But I learned that they were the statements that show the expected behavior of students. We can also determine their levels such as knowledge, comprehension, etc. When we evaluated the chemistry curriculum, I learned that it is important to include high-level objectives as well.

Knowledge of students’ understanding of science (KSU)

Concerning the factors affecting the development of pre-service teachers' KSU in the effect of temperature on reaction rate topic, participants mentioned the effect of discussions about students’ possible misconceptions in the theoretical courses in the university, preparation of lesson plans, observations of both students in high school and microteaching sessions made by their peers. For example, Barbara stated the effectiveness of the laboratory experiments course on her development of knowledge of learner: “In the laboratory experiments in science education course, we always discussed the possible misconceptions of students related with high school chemistry topics. We also realized that we also had similar misconceptions.”

She also mentioned the need to focus on students' misconceptions while preparing CoRes: “There is a misconception section in the CoRes that you need to write. Therefore, to find the possible misconceptions, I search articles, theses. I think this improved my knowledge of the learner.”

Similarly, Barbara stated the importance of observations of their peers’ microteaching sessions: “When I observed my friends’ instruction in the university, I became aware of students’ misconceptions regarding chemistry topics. It was useful to observe my friends’ instruction.”

Additionally, Deborah mentioned the effect of her observations at high schools on the improvement of her knowledge of learner:

I can realize students' misconceptions while I observe chemistry classes at high school. For example, when the teacher says the rate of reaction increases with temperature, students ask whether exothermic or endothermic. Some students state that the reaction rate of exothermic reactions does not increase with temperature.

Knowledge of instructional strategies (KIS)

When we examined the factors regarding the development of pre-service teachers’ knowledge of instructional strategies, we found that methods courses in the university, preparation of lesson plans and teaching at the university and high school, feedback from the tutors, mentors, and students, and observations of their peers' instruction were influential to enhance pre-service teachers' knowledge of instructional strategies. Both Barbara and Deborah mentioned the importance of methods courses. They also stated that both preparations of lesson plans and teaching enhanced their knowledge of instructional strategy. For example, Barbara gave the following explanations:

Teaching both in the university and high school was effective for me. To teach, you need to prepare a lesson plan and you need to consider the instructional strategy, activities, etc. before instructing and constructing a lesson plan. I thought about which instructional strategy, activity, simulation I could use. I searched different sources, the internet, books, articles, theses. This enhanced my knowledge about suitable activities and simulations specific to that topic.

Deborah also emphasized the importance of her peers’ instruction for the development of knowledge about instructional strategy: “We observe our friends’ instruction in the university, I can learn from them like, I can also use this simulation or that analogy was very good so I can use it.”

As another factor, Barbara mentioned that feedback from the tutors, mentors, and students enhanced her knowledge of instructional strategy:

After my instruction, my tutors in the university and my mentors at high schools evaluate the effectiveness of the instruction and they give suggestions such as you can use a simulation to teach it or you can use group work.

Barbara also stated that she mentioned the feedback from students in developing her instructional strategy: “I ask students, for example, was the experiment useful or is there anything that you did not understand in this simulation. Depending on their feedback and reactions, I can change my instructional strategy.”

Knowledge of assessment (KA)

In terms of factors affecting pre-service teachers’ KA, theoretical courses, observations of peers' instruction, observation of students, preparation of lesson plans, school experience course, teaching, and feedback given by instructors, mentors and students were stated. For example, Deborah mentioned the effectiveness of methods courses for her knowledge of assessment: “When I learned STEM in the methods course, I thought it would be useful to include STEM assignments to assess students' understanding.”

Deborah also mentioned that her observations of high school chemistry classes influenced her knowledge of assessment:

When I observed students in class in my school practicum, I realized that they give importance to grading. This affected my knowledge of assessment and I think that a quiz at the end of each class that will be graded will enhance students’ understanding.

Deborah also mentioned that she learned a lot in the school experience course since the questions were well prepared and assessed students' higher-order thinking skills. She also stated that she learned from the instruction of their peers: “When I observed my peers' instruction in the university, I observed different assessment methods and I sometimes thought I could use this as well.”

Both Barbara and Deborah stated the usefulness of preparing lesson plans to enhance their assessment knowledge: “You need to think about assessment and assessment techniques, before instruction when you prepare lesson plans.”

As another factor, Barbara mentioned the effectiveness of teaching and feedback given by instructors in the university and students:

When we teach, we get feedback from our instructors. They say, e.g. this question is not suitable, you can also ask this question. I also ask my students to evaluate the questions, for example, in the worksheet. I pay attention to their comments to prepare well-prepared questions.

Discussion

The present study investigated the development of pre-service chemistry teachers’ PCK and the factors affecting this development in the context of temperature effect on reaction rate topic as they took pedagogical content knowledge courses during the teacher education program. Results of this research revealed that pre-service chemistry teachers showed uneven development in terms of PCK components and certain factors affect that development with the context of the effect of temperature on reaction rate topic. Development in an individual component of PCK did not mean overall PCK development in this research context, as some other researchers mentioned (Magnusson et al., 1999; Henze et al., 2008; Brown et al., 2013; Adadan and Oner, 2014; Sickel and Friedrichsen, 2018; Reynolds, 2020; Ekiz-Kiran et al., 2021).

Regarding STOs, explaining daily life events was the participants’ constant belief about the purpose of chemistry teaching from time 1 to time 4. We could consider the belief of the importance of chemistry teaching to explain daily life events as core beliefs since they were stable and resistant to change, and that was also reflected in their plan of instruction (Haney and McArthur, 2002; Boz et al., 2019). Though this purpose was stable over two years, they extended and changed some of their views on why they teach chemistry as they took educational courses. Specifically, Deborah had a view of the importance of scientific thinking while teaching chemistry but she stated the place of affective dimensions in chemistry teaching instead of scientific thinking after completing all the pedagogical content knowledge courses. Furthermore, participants’ beliefs about teacher and student roles, an aspect of chemistry teaching and learning, showed changes as they took more pedagogical content knowledge courses. For example, Barbara modified her view of the active role of the teacher. After completing all the pedagogical content knowledge courses, she started to think that the role of the teacher may change depending on the nature of the topic. These results deserve consideration as they are not in keeping with the science PCK literature. Although the related literature reported that STOs are stable (Brown et al., 2013; Sickel and Friedrichsen, 2018; Reynolds, 2020; Ekiz-Kiran et al., 2021), there may be some pathways for those to be improved. As evidenced in this study, observations in teaching practicum courses may contribute to STO development. Another reason for this contradiction may be related to the longitudinal nature of this research. Though it may not be possible within the limited period, pre-service teachers may have dynamic STOs as a result of long exposition to pedagogical content knowledge courses. This explanation is coherent with how Park (2019) viewed PCK development.

The results showed notable development for participants’ knowledge of objectives and knowledge of links of the effect of temperature on reaction rate topic to prior topics (e.g. collision theory, effective collisions, activation energy, threshold energy, potential, and kinetic energy) and aspects of KC (Aydin et al., 2013; Ekiz-Kiran et al., 2021). On the contrary to Subramaniam (2021), who found lesson planning as a facilitator in pre-service science teachers’ PCK development for all components of PCK except knowledge of curriculum, it is found in this context as a valuable mediator for participants’ development in terms of knowledge of objectives. Although preservice teachers were not aware of the curriculum before taking any pedagogical content knowledge courses, they commenced to write objectives directly from it, consult it, criticize it generally, and criticize it topic-specifically after taking all pedagogical content knowledge courses. As evidenced in this research, the curriculum development course (i.e. time 2) is the hallmark for the realization of the curriculum. At the end of that course, participants begin to gain a skeptical point of view about cognitive levels of objectives and instances of whether objectives are useful. In these ways, pre-service teachers learn to recommend essential objectives for a specific topic or a specific lesson. Correspondingly, it can be said that pre-service teachers need to spend time within educational courses (e.g. curriculum development course, laboratory experiments course, methods course, school experience course) to be able to internalize curricular saliency and the microscopic language of chemistry.

Regarding other aspects of KC, that is links of the effect of temperature on reaction rate topic to subsequent topics and links of this topic to other disciplines, the results showed slight development. Participants stated chemical equilibrium as the subsequent topic from the beginning to the end of all pedagogical content knowledge courses. In that sense, longitudinal attendance to courses solely was not a sufficient way. Though both participants indicated subtle development, the results revealed a difference in the levels of Barbara and Deborah concerning their knowledge of links to other disciplines. This conclusion may imply the idiosyncratic nature of PCK; that is, certain aspects of KC can be viewed as personalized knowledge. Specificity of KC was found by other researchers as well (Aydin et al., 2015; Ekiz-Kiran et al., 2021).

For the knowledge of learner, both participants’ knowledge of pre-requisite knowledge showed development. However, this development did not show the same pattern for Deborah and Barbara. Time 4 was the milestone for Barbara's development whereas Deborah's development was not sharp rather a gradual one. Her explanations for the pre-requisite knowledge required for the effect of temperature on reaction rate topic became more scientific as she took pedagogical content knowledge courses. Deborah elaborated on her view of the particulate nature of matter and expressed conditions of collision theory as the pre-requisite to the effect of temperature on reaction rate topic. This can also be explained by the tacit and idiosyncratic nature of PCK (Loughran et al., 2008; Nilsson and Loughran, 2012; Aydin et al., 2013; Aydin et al., 2015; Ekiz-Kiran et al., 2021).

In terms of students’ difficulties, both participants’ knowledge enhanced and the pattern for this development was nearly the same for these participants. For both Barbara and Deborah, time 3 was a crucial point for this development. At time 3, they completed most of the pedagogical content knowledge courses (e.g. methods courses, school experience courses, etc.). Both of them were successful in terms of providing detailed explanations for areas of student difficulties. This may be a result of the transformation of the tacit nature of KSU to a more explicit one (Loughran et al., 2008; Nilsson and Loughran, 2012; Aydin et al., 2013) as participants observe peers' microteaching, which was found in this research as a significant factor for PCK development. Moreover, preparation of CoRes and discussions of students' difficulties and misconceptions in theoretical courses, especially methods and laboratory experiments in science education courses, may also have helped pre-service teachers' development of students' difficulties.

Regarding students’ misconceptions, both participants’ knowledge developed. However, the development of Deborah's knowledge of students’ misconceptions was more than that of Barbara. Deborah not only stated misconceptions but also gave detailed explanations for the reasons for them and she also suggested a way of eliminating them. Findings regarding the knowledge of students’ understanding are in line with other studies’ results of KSU, which was reported as being the most easily developed component of PCK (Henze et al., 2008; Park and Oliver, 2008). The reason for this development may be related to the development of participants’ content knowledge (CK) as previous researchers have placed CK as the basis for PCK development (Johnston and Ahtee, 2006; Kind, 2017). Kaya (2009) concluded that pre-service teachers with higher CK better define students’ misconceptions. Pre-service teachers’ CK may have developed as they are planning lessons, discussing misconceptions on educational courses, and observing peer's instruction. Correspondingly, they possess fewer misconceptions and are better at diagnosing their students’ misconceptions.

The idiosyncrasy of PCK was also observed regarding the knowledge of assessment. Though both participants' knowledge of assessment was enhanced, Deborah's development was more. Both the knowledge of subject-specific and topic-specific strategies aspects of the KIS component of PCK developed as participants took pedagogical content knowledge courses, which corresponds with other research findings that KIS is one of the most easily developed components (Henze et al., 2008; Park and Oliver, 2008; Aydin et al., 2015; Ekiz-Kiran et al., 2021). The methods course helped participants develop mainly KIS. Specifically, both participants preferred to use the 5E learning cycle model (Bybee et al., 2006) to teach the effect of temperature on reaction rate topic after completing methods courses. Brown et al. (2013) also stated that pre-service teachers began to use the 5E instructional model widely after attending a teacher education program. In addition to methods courses, preparation of lesson plans, teaching experience, observation of peers' instruction, and feedback given on their instruction by tutors, mentors, and students were reported to affect their knowledge of instructional strategy, which was compatible with the previous research (Abell, 2007; Aydin et al., 2013; Ekiz-Kiran et al., 2021).

The present study has several implications for teacher educators and teacher education programs. Discussions about students’ possible difficulties and misconceptions regarding chemistry concepts, critical evaluation of chemistry curriculum, learning about different teaching strategies in the theoretical courses in the university, preparation of lesson plans, CoRes, observations of both students in high school and microteaching sessions made by their peers, teaching experience in the university and schools and feedback given by mentors, tutors and students were found to influence pre-service chemistry teachers’ development of PCK with respect to the temperature effect on reaction rate topic. Therefore, in chemistry teacher education programs, we suggest that pre-service teachers should be given enough experience to practice chemistry teaching both in the university and schools. Afterward, constructive and useful feedback given by mentors, tutors, and their peers based on different aspects of their chemistry instruction, e.g. assessment, instructional strategies, etc. would help pre-service teachers enhance their PCK. Moreover, pre-service teachers should be allowed to prepare lesson plans and CoRes for different chemistry concepts. In the present study, teaching practicum courses were also found to influence pre-service teachers' PCK development. To illustrate, Deborah mentioned that observing assessment strategies that assess students' higher-order thinking skills and well-prepared questions in the classrooms helped her enhance her knowledge of assessment. Therefore, we could suggest placing pre-service teachers in schools where they can observe chemistry instruction that can serve as a model for them.

The present study was limited to two pre-service chemistry teachers in the context of the temperature effect on reaction rate topic. For further studies, pre-service teachers’ development of PCK can be investigated with respect to other topics.

Conflicts of interest

There are no conflicts to declare.

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