Exploring the Progression in Preservice ChemistryTeachers’ Pedagogical Content KnowledgeRepresentations: The Case of “Behavior of Gases”

Emine Adadan & Diler Oner

# Springer Science+Business Media Dordrecht 2014

Abstract This multiple case study investigated how two preservice chemistry teachers’pedagogical content knowledge (PCK) representations of behavior of gases progressed inthe context of a semester-long chemistry teaching methods course. The change in the partic-ipants’ PCK components was interpreted with respect to the theoretical PCK learning pro-gression trajectory criteria established in the literature. The data were collected using the PCKcapturing approach, called Content Representations, or “CoRes” (twice), and two interviewswith each preservice teacher during the semester. The results indicated that neither preserviceteacher initially held an extensive repertoire of representations for all components of PCK intheir knowledge base. However, these preservice teachers noticeably increased their number ofrepresentations over the course of the semester. The components of PCK did not progress tothe same extent for each participant. Likewise, the constituent elements of each PCK compo-nent indicated relatively dissimilar features across the participants. Implications for scienceteacher education and the methodological contributions of the study to educational research arediscussed.

Keywords Content representations (CoRes) . Pedagogical content knowledge . Preserviceteachers . Gases . Chemistry education

Introduction

The current vision of science education in different countries around the world emphasizesexcellence in science learning with a special focus on scientific literacy; however, students canrarely develop advanced levels of scientific understanding without access to professional

Res Sci EducDOI 10.1007/s11165-014-9401-6

E. Adadan (*)Department of Secondary School Science and Mathematics Education, Faculty of Education,Bogazici University, 34342, Bebek, Istanbul, Turkeye-mail: emine.adadan@boun.edu.tr

D. OnerDepartment of Computer Education and Educational Technology, Faculty of Education,Bogazici University, 34342, Bebek, Istanbul, Turkeye-mail: diler.oner@boun.edu.tr

science teachers (e.g., Millar and Osborne 1998; NRC 1996). In order to meet the expectationsfor student science learning, teachers need to possess a unique knowledge base that goesbeyond content knowledge. This knowledge base is called pedagogical content knowledge(PCK). Such a knowledge base requires that science teachers have “special understandings…that integrate their knowledge of science content, curriculum, learning, teaching, and stu-dents,” enabling them “to tailor learning situations to the needs of individuals and groups”(NRC 1996, p.62). In fact, developing a well-established PCK repertoire is an ongoing processthat starts in teacher preparation programs and continues with teaching practice and profes-sional development experiences. Along these lines, teacher educators have to offer powerfuland coherent learning opportunities to teacher candidates to assist their teaching knowledgeprogression (Magnusson et al. 1999). Therefore, an understanding of how teachers’ PCKprogresses from preparation through practice appears to be essential for creating effectivelearning instances.

Many researchers have examined science teachers’ PCK progression, mainly using induc-tive approaches. In other words, they looked for evidence regarding the existence of all (orsome) PCK components and described how each one developed among a targeted group ofteachers in a particular context over time (e.g., Brown et al. 2013; Davis 2004; De Jong et al.2005; Hashweh 2005; Nilsson and Loughran 2012; Rozenszajn and Yarden 2014; Van Driel etal. 2002). This line of inquiry provided an invaluable knowledge base, grounded in empiricalevidence, for our understanding of PCK development. However, until recently, no study hasproposed a hypothetical framework that describes the PCK learning progression routes alongwhich (science) teachers pass in developing their understanding of teaching. The work ofSchneider and Plasman (2011) recently addressed this need, suggesting a PCK progressiontrajectory based on the available research findings. In fact, this theoretical framework, whichportrays the progression of science teachers’ PCK at different stages of expertise, has not yetbeen empirically validated. Thus, there is a need to provide evidence for the recent PCKprogression framework and its usefulness in terms of examining PCK development.

The findings of some studies have led researchers to the view that preservice scienceteachers hold limited PCK in their knowledge repertoire due to their lack of classroomexperience (e.g., Hashweh 2005; Lederman et al. 1994). However, teaching experience doesnot necessarily ensure having strong knowledge of how to develop conceptually effectiveinstruction (Halim and Meerah 2002; Schneider and Plasman 2011). Other studies found thatpreservice science teachers are able to construct the foundational components of PCK whentheir teacher education courses offer useful tools, along with timely scaffolding (e.g., Humeand Berry 2011, 2013; Nilsson and Loughran 2012). Therefore, when preservice scienceteachers begin to practice teaching, their available PCK quite possibly comes into play asthey interact with students (Davis 2004). In this respect, exploring how preservice scienceteachers’ PCK repertoire progresses in response to the various opportunities provided for themto learn to teach science in their teacher education courses seems to be critical (Abell 2008;Davis 2004; De Jong et al. 2005).

A number of studies have explored the nature or development of preservice scienceteachers’ PCK in particular learning contexts (e.g., Brown et al. 2013; Davis 2004; De Jongand Van Driel 2004; De Jong et al. 2005; Halim and Meerah 2002; Kaya 2009; Nilsson 2008;Van Driel et al. 2002), but few of these studies involved preservice chemistry teachers asparticipants (e.g., De Jong and Van Driel 2004; De Jong et al. 2005; Hume and Berry 2011,2013; Van Driel et al. 2002). In addition, despite the centrality of subject matter knowledge toPCK (Abell 2008), few studies have portrayed the nature or development of teachers’ PCKconcerning a particular chemistry topic (e.g., De Jong et al. 2005; Padilla and Van Driel 2011;Van Driel et al. 1998). Because PCK is typically considered content specific, there is a need to

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investigate teachers’ PCK in relation to specific topics (Abell 2008). In this study, the behaviorof gases, which is included in secondary school science curricula worldwide, was randomlychosen to look into the progression in preservice chemistry teachers’ PCK.

Because PCK is multidimensional, and usually rooted in teachers’ practice, it largelyremains tacit as long as it is not thoroughly articulated. Loughran et al. (2004, 2008) developeda framework for capturing science teachers’ PCK in the form of a “Resource Folio,” com-prising both Content Representations (CoRes) and Pedagogical and Professional-experienceRepertoires (PaP-eRs). A CoRe specifies the aspects of the PCK that are associated with thefundamental concepts of a specific science topic (e.g., the key content ideas, students’alternative conceptions, ways of assessment for understanding, and ways of teaching tosupport student learning). A PaP-eR offers insights into teachers’ knowledge about teachingand learning of specific content in a particular context (e.g., grade level), making teachers’elusive knowledge about science teaching explicit. However, a PaP-eR alone does not fullydemonstrate the complexity of knowledge relevant to a specific content. Thus, a collection ofPaP-eRs associated with different aspects of the CoRe is critical in terms of identifying theparticular elements that jointly indicate PCK in that field (Loughran et al. 2004). In general,CoRes and PaP-eRs provide a means for articulating teachers’ reasoning involved in teaching.

Several researchers have used CoRes and PaP-eRs as PCK-capturing approaches withexperienced science teachers to uncover their implicit knowledge about teaching science(e.g., Loughran et al. 2004; Rollnick et al. 2008). A few studies have also utilized theseapproaches with preservice science teachers (Hume and Berry 2011, 2013; Loughran et al.2008; Nilsson and Loughran 2012), but they only examined the change in teachers’ percep-tions about teaching science. Only Hume and Berry (2011) attempted to document the natureof preservice chemistry teachers’ PCK using CoRes. Therefore, there is a need for carefullycapturing and examining the progression in preservice teachers’ PCK by involving them inconstructing their own CoRes.

Purpose of the Study

The purpose of the study was to examine whether Schneider and Plasmans’ (2011) frameworkwas useful in terms of explaining preservice chemistry teachers’ PCK development. Morespecifically, the current study focused on identifying and describing the progression in theextent and features of preservice chemistry teachers’ PCK representations on the topic of“behavior of gases” over a semester-long chemistry teaching methods course. Thus, thefollowing research question guided this study:

How do preservice chemistry teachers’ PCK representations on the topic of behavior ofgases progress over a semester-long chemistry teaching methods course?

Theoretical Framework

Shulman (1987) defined PCK as the ability of a teacher to transform the particular subjectmatter knowledge (e.g., science) into useful forms of instructional representations that can beadapted to a diverse group of students who vary in ability and background (e.g., havingalternative conceptions). This knowledge is unique to the work of teaching, and distinguishesthe expertise of science teachers from that of scientists (NRC 1996; Shulman 1987). SinceShulman’s initial introduction of the notion of PCK, other scholars have attempted to charac-terize it, and consequently multiple models of PCK have been proposed (e.g., Grossman 1990;

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Magnusson et al. 1999; Park and Oliver 2008). Each of these scholars identified the constituentcomponents of PCK with respect to their particular research agendas, beliefs, and empiricalfindings, so that they often differed in their labels and descriptions of PCK components.However, they all recognized Shulman’s two components as the key features of PCK,including (1) knowledge of instructional strategies and (2) knowledge of students’ learningdifficulties, both with regard to the particular content area. Teachers’ strong knowledge base inrelation to these components closely contributes to their effective structuring and utilization ofPCK (Park and Oliver 2008; Park and Chen 2012; Van Driel et al. 1998).

Although there is still no agreement in the literature concerning the nature of PCK and itscomponents, this study adopted the PCK model of Magnusson et al. (1999) for identifying thenature and extent of any PCK development in preservice teachers. Magnusson et al. describedPCK as “the transformation [emphasis in original] of several types of knowledge for teaching”(p.95), including subject matter knowledge, pedagogical knowledge, and knowledge about thecontext. However, Magnusson et al. included neither subject matter knowledge nor pedagog-ical knowledge in their PCK model. They considered these knowledge bases as the sources forthe development of PCK, but not the components of PCK. The model of Magnusson et al.consists of five interacting components of PCK: (1) orientations toward teaching science, (2)knowledge of science curriculum, (3) knowledge of students’ understanding of science, (4)knowledge of assessment, and (5) knowledge of instructional strategies. According toMagnussonet al., the last four components of PCK are all linked to the first, and teachers’ orientations towardteaching science strongly shape their instructional decisions about the design of activities, thecontent of students’ assignments, the evaluation of student learning, and the use of curriculummaterials. Other studies have further investigated the connection among these PCK componentsand found a strong relationship between orientations toward teaching science and knowledge ofstudents’ understanding of science and instructional strategies (Brown et al. 2013; Park and Chen2012). In addition, Park and Chen identified the most limited connection between knowledge ofscience curriculum and other components of PCK. The findings from the study of Brown et al.demonstrated thatmultiple components of PCK (knowledge of students’ understanding of scienceand instructional strategies) develop simultaneously. Moreover, Park and Chen claimed that thebuilding of PCK is largely affected by the interaction of different components, so that anexpansion in one component does not always simultaneously serve for the development of thewhole PCK if there is lack of coherence among the components.

Science Teachers’ PCK Progression

In reference to student science learning, learning progressions are described as empiricallygrounded, and testable hypotheses about how students’ understanding of, and ability to use,core scientific concepts grows and becomes more sophisticated over time, with appropriateinstruction (NRC 2007). Similarly, learning to teach science can be considered a long-termeffort in which teachers’ understanding of science teaching successively becomes moresophisticated as they spend more time in the classroom and are offered opportunities to learnto teach. In fact, individual teachers may follow different PCK progression routes due to theirinitial available knowledge and beliefs, as well as learning opportunities offered along the way(Rozenszajn and Yarden 2014; Schneider and Plasman 2011).

Drawing upon the PCK model of Magnusson et al. (1999), Schneider and Plasman (2011)proposed a set of learning progression trajectories for the five components of science teacherPCK by thoroughly reviewing the available research findings. These learning progressiontrajectories were not topic specific, but portrayed a possible learning progression path forscience teachers. Schneider and Plasman described such learning progression trajectories for

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subcategories of each PCK component (see p.538). Each trajectory reflected the professionalattributes that science teachers may demonstrate as they move from being novice to expert.Each progression path started with a low level of understanding and progressed toward a moresophisticated one. Progression trajectories included descriptive statements (criteria) and wereseparated with arrows in the original article. In this study, individual criteria statements in eachprogression trajectory were assigned a number starting from 1 (the lowest), with the value ofthat number indicating the level of progression in that particular trajectory. The levels ofprogression characterizations for subcategories of PCK components varied from 1 to 5. Table 1shows the progression criteria for each PCK component.

Research into science teachers’ PCK development usually adopts inductive (bottom-up)approaches when investigating the nature of their PCK progression. Schneider and Plasman(2011), on the other hand, proposed a deductive scheme aiming to describe science teachers’PCK development along their career path. Although Schneider and Plasman’s framework wasbuilt on previous research findings, their approach was top-down in the sense that theprogression criteria they proposed were not subject to empirical testing. In addition, thistheoretical framework failed to adequately describe the progression criteria for somecomponents of PCK, in particular knowledge of curriculum, due to lack of research inthis area. However, Schneider and Plasman’s framework is the only comprehensiveattempt to describe PCK progression trajectories for the components of PCK sug-gested by Magnusson et al. (1999). Therefore, the current study utilized Schneider andPlasman’s PCK progression criteria to interpret the level of progression in theparticipants’ PCK representations.

Sources for Science Teachers’ PCK Progression

Several research studies have shown that the quantity, quality, and organization of teachers’subject matter knowledge in science potentially affect the scope and depth of their PCKprogression (e.g., Kaya 2009; Lederman et al. 1994; Van Driel et al. 2002). For example,Cochran and Jones (1998) claimed that teachers who have low subject matter knowledge avoidwhole class discussions and instead rely on seatwork and lecturing. A study with preserviceteachers also provided evidence that teachers having good subject matter knowledge becameaware of students’ learning difficulties quite readily (Van Driel et al. 2002). In another study,Davis (2004) reported that good subject matter knowledge helped preservice teachers inselecting proper instructional strategies. Although the acquisition of strong subject matterknowledge is frequently associated with the number of college science courses taken, itactually has more to do with how those courses are taught (Lederman et al. 1994). In thisrespect, Van Driel et al. (2002) suggested explicitly addressing subject matter knowledge as abasis for the development of PCK by providing preservice science teachers with learninginstances that help them to be aware of their own conceptual issues.

Research has shown that reflection plays a key role in the progression of PCK in that itsupports the integration of PCK components, strengthening the coherence among them (DeJong et al. 2005; Magnusson et al. 1999; Nilsson 2008; Park and Oliver 2008; Shulman 1987).The National Science Education Standards also pointed to the need to provide science teachersopportunities to examine, elaborate upon, and integrate their subject matter knowledge andpedagogical knowledge to enable them to adapt particular learning situations to the needs ofstudents (NRC 1996, p. 62). Magnusson et al. argued that “this goal can be addressed throughactivities such as observing, analyzing, and reflecting upon one’s own or another’s teaching”(p.122). In the current study, the chemistry teaching methods course was designed accordingly—to help expand and elaborate upon the participants’ PCK.

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Table1

Summaryof

learning

progressioncriteriaforthecomponentsof

PCK

(adopted

from

SchneiderandPlasman

(2011))

Levelsof

Progression

12

34

Orientatio

nsto

Teaching

Science(O

TS)

Purposes

(4-Levela )

Topreparestudentsfor

thenext

levelof

schooling…

(p.541)

Topreparestudentsby

teaching

them

how

to…

develop

understanding…

bythem

selves

(p.541)

Topreparestudentsby

supportin

gconceptual

learning

toenablefurther

studyin

science(p.541)

Tohelp

studentsscientifically

understand

phenom

ena

ineveryday

life…

(p.541)

Goals(4-Levela )

Includeinform

ationand

concepts,are

identified

bythecurriculum

,and

should

bepresented

correctly

and

completely(p.542)

Includeinform

ationand

conceptsbutmay

includesomescience

processes,areidentified

bythecurriculum

,andstudentsshould

understand

concepts

(p.542)

Includeinform

ation,

concepts,p

rocesses,and

possibly

someaspectsof

thenature

ofscience;are

determ

ined

byscienceas

abody

ofknow

ledge;and

studentsshould

develop

thinking

skillsandlin

kideas(p.542)

Includeinform

ation,

concepts,

processes,andpossibly

someaspectsof

thenature

ofscience;aredeterm

ined

byscienceas

abody

ofknow

ledgeandphenom

ena

ineveryday

life;andstudents

should

benefitfrom

understandingtheideas

(p.542)

Knowledgeof

ScienceCurriculum

(KSC

)

Scope,sequence,and

resources(2-Levela )

Teachersareuncertain

aboutw

hattopicsare

appropriateandallow

thematerialstodefine

thescope,thinkabout

sequence

only

generally…,and

are

unfamiliarwith

available

resourcesandrely

heavily

oncurriculum

materials(p.553)

Teachersintegratescience

conceptsandother

subjects,are

flexible

intheirthinking

about

sequencing…,are

unfamiliar

with

available

resources,andrely

heavily

oncurriculum

materialforscopeand

sequence

(p.553)

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Table1

(contin

ued)

Levelsof

Progression

12

34

5

Knowledgeof

StudentUnderstanding

(KSU

)

Students’initialideas

(5-Levela )

Studentsdo

nothave

initialideasor

experiencesrelevant

toscienceexcept

for

ideasfrom

school

(p.546)

Studentsdo

have

initial

ideas…

relevant

toscience,buttheseare

misconceptio

ns…

orsimplyunknow

nto

theteacher(p.546)

Studentshave

initialideas…

relevant

toscienceand

itisim

portantforteachers

toknow

…or

uncover

theseideasas

aplace

tostartor

correct,…

(p.546)

Studentshave

initialideas

…relevant

toscienceand

itisim

portantforteachers

tolook

fortheseby

listening

tostudents,reading

students’

work,

orreadingtheliterature

onstudents’ideas…

(p.546)

Studentsthinkanddevelop

theirow

nideasfrom

multip

leexperiences

inandoutof

school

and

theseideasarethebasis

oflearning

(p.546)

Knowledgeof

Teaching

(KT)

InquiryStrategies

(4-Levela )

Activities

thatarehands

onor

thatlead

to“discovery”aredifficult

toenact,andmay

beinappropriatefor

students(p.550-551)

Are

prim

arily

opportunities

tocollectdatathrough

observations

orexperimentationand

canbe

teachercentered

(p.550-551)

Are

opportunities

forstudent

topose

questions

orcollect

andworkwith

theirow

ndata,and

traditionallessons

canbe

convertedto

inquiry

lessons(p.550-551)

Includestudentsposing

questio

ns,

designinginvestigations,

collectingevidence,and

makingclaims(p.550-551)

Knowledgeof

Assessm

ent(K

A)

Assessm

entStrategies

(4-Levela )

Traditionalform

ats

such

astestattheend

ofaunit…

(p.554)

Includeinform

alquestioning

toknow

whatstudents

arethinking

(p.554)

Includeavarietyof

strategies

such

asjournalentries,

portfolio

s,presentatio

ns…

(p.554)

Require

planning

such

asdeveloping

criteriaandshould

bematched

with

specific

scienceideas(p.554)

aThese

levelsindicatethetotalnumberof

hierarchically

definedcriteria

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Research has indicated that when teachers work collaboratively together to make sense ofchallenging science concepts and articulate their pedagogical reasoning concerning students’conceptual difficulties and instructional strategies in relation to particular content, not only arethey able to refine their subject matter knowledge but also develop a sophisticated level ofPCK (Daehler and Shinohara 2001). Moreover, Hume and Berry (2011) found that whenpreservice science teachers designed their CoRe document in collaboration with their peers,this contributed greatly to their preparation for teaching. Taking these findings into account,the participants of the current study also worked together with their peers outside of class,discussing their ideas about student learning, instructional strategies, assessment of studentlearning, and other teaching issues associated with the topic of behavior of gases.

Research has revealed that there is a synergistic relationship between beliefs about teachingand the progression of PCK (Veal 2004). Veal’s study showed that the main components ofpreservice science teachers’ PCK developed at different rates because of previous experiencesthat formed their beliefs about teaching. Moreover, Park and Oliver (2008) viewed teacherefficacy beliefs as one of the components of PCK, and emphasized the critical role these playsin the re/organization of PCK. They claimed that increased teacher efficacy supports teachers’learning relative to all components of PCK, leading to the growth of PCK.

Note that exploring the contributing sources for PCK progression was not the primary focusof this study, but each aspect discussed above informed the design of this research and theteaching methods course in which this study was conducted.

Methods

Case studies usually investigate “a particular situation, event, program, or phenomenon”(Merriam 1998, p.29). For the current study, a multiple case study approach grounded in aconstructivist framework was utilized, with the focus on the progression in preservice chem-istry teachers’ PCK representations (Charmaz 2000; Merriam 1998). The case study wasconducted with two preservice chemistry teachers. Although the purpose of this study wasto map out the two participants’ PCK progression with respect to Schneider and Plasman’s(2011) PCK progression framework, given the content specificity of PCK (Baxter andLederman 1999), the topic of behavior of gases was selected as a case. Data from multiplesources were analyzed, employing both qualitative and quantitative methods.

Participants

Two females, Ada and Ela (pseudonyms), who were in their early twenties, took part in thisstudy. Ada and Ela were enrolled in their final year of a 5-year chemistry teacher educationprogram. Both had completed all their subject matter courses and general pedagogy courses atthe time of the study. In addition, Ada and Ela held grade point averages (GPAs) of 2.72 and3.10 out of 4.00, respectively. Compared to the GPAs of the other students in the teachingmethods course in which this study took place, the two participants’ GPA scores were quiteabove the average, which to some extent reflected the participants’ subject matter knowledge. Atthe time of this study, the participants were starting field-based experiences, spending 4 h/weekin assigned high schools to observe classes, but they did not teach classes during this period.

The participants of the study were identified through a process of purposeful sampling tostudy distinct (deviant) cases (Patton 2002). Park and Oliver (2008) recognized teachingefficacy beliefs as a component of PCK, and other scholars (e.g., Kind 2009; Shulman1987) emphasized the teacher’s self-efficacy as an essential contributor to PCK development.

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Therefore, the participants’ science teaching efficacy scores were used as a criterion forselecting the cases. The selection process was as follows: A total of 13 preservice teacherswere enrolled in the chemistry teaching methods course. At the first class meeting, all studentsattending this course chose a specific topic for their CoRes design project, as well as filling outThe Science Teaching Efficacy Belief Instrument - Preservice Science Teachers (STEBI-B),which was revised by Bleicher (2004). This instrument includes 23 items with a five-pointLikert-type response scale. Among 13 students, seven picked the topic “behavior of gases” fortheir CoRes design project. The two participants were selected from among these seven basedon their scores on the science teaching efficacy beliefs scale. The maximum possible totalscore was 115, and Ada and Ela scored 93 and 78, respectively, on the STEBI-B scale. Thesewere the highest and the lowest scores among the seven cases.

Context of the Study

The secondary science teacher education program that the participants attended was structuredsuch that students took a total of 22 subject matter courses—mostly chemistry, but also physicsand mathematics—and five general pedagogy courses (e.g., Learning and Development,Classroom Management) in the first 3 years of the program. In the remaining 2 years, studentsstudied nine different subject-specific pedagogy courses (e.g., Science Teaching Methods,Teaching Practicum, and so on). The participants took subject matter courses from the Schoolof Arts and Sciences, and general and subject-specific pedagogy courses were offered in theSchool of Education.

The present study was situated in the “Teaching Methods in Chemistry” course offered inthe first semester for final-year students in the science teacher education program. Theparticular course was the third one involving science teaching methods that the preservicechemistry teachers took in sequence. The first course was “Secondary School ChemistryLaboratory Applications.” This course addressed preservice chemistry teachers’ conceptualdifficulties with different chemistry topics (e.g., the particle theory of matter, bonding,chemical reactions, solutions, etc.) as they actually engaged in inquiry-based laboratoryactivities so that they gained firsthand experience of what inquiry classroom environmentslook like. The second course is called “Science Teaching Methods,” and it was offered to bothpreservice chemistry and physics teachers. In this course, preservice teachers learned about theparticular learning theories relevant to how students learn science, as well as discussing andexperiencing examples of discipline-specific teaching methods such as the types of inquiryinstruction (e.g., open-ended, guided, the learning cycle, etc.).

The “Teaching Methods in Chemistry” course in which this study took place wasoffered by the first author, and was specifically designed for preservice chemistryteachers. Magnusson et al. (1999) claimed that if preservice science teachers are to besuccessful in creating classroom environments in which subject matter knowledge andpedagogical knowledge are synthesized into a type of knowledge that promotes studentlearning, they must experience such learning environments themselves. In light of thissuggestion, this course intended to help the participants develop their PCK by providingthem with diverse in-class opportunities during which they could integrate subject matterknowledge and pedagogical knowledge into a form that would enable them to properlyaddress students’ learning difficulties. In addition, Kind (2009) suggested that engagingteachers in the creation of CoRes promotes the development of reflective practice skills,offering a means of acknowledging changes in their PCK. Thus, outside of class, theparticipants developed their own CoRe documents as a semester-long task in collaborationwith their peers (see the following section for details).

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The course meetings were held twice per week throughout a 14-week-long semester. Inthis course, the instructor modeled several teaching methods within the context of a specificchemistry topic (e.g., chemical reactions) by actually engaging the preservice teachers in theactivity as students. The preservice teachers were also provided with an opportunity to viewthe best practices of chemistry teaching methods through video-recorded lessons availableonline. Following these experiences, class discussions were held, and the preservice teachersreflected on their direct experiences with various teaching methods or on the video-recordedonline lessons that they viewed. They expressed their understandings of these experiences, aswell as discussing the possible benefits of, and their concerns about, practicing such methodswith different groups of students. Moreover, the preservice teachers in the class discussedweekly assigned readings on different teaching approaches, ways of assessment, and studentlearning, focusing particularly on students’ conceptions of various chemistry topics, includ-ing the behavior of gases. The course also addressed science teaching goals and alternativemethods of classroom assessment. It is important to note that the participants did not take anyother courses that focused specifically on the assessment of student learning.

Data Collection

Using multiple data sources of evidence is strongly recommended when conducting casestudies (Yin 2003). In addition, because PCK is a tacit and a highly complex construct, theassessment of PCK requires a blend of multiple sources of data (Baxter and Lederman 1999).Thus, the two participants’ PCK representations were captured using a CoRes approach(Hume and Berry 2011; Loughran et al. 2004) and interviews. In the current study, in orderto establish a common ground across the participants, the key content ideas, including a total ofeight “key concepts” about the behavior of gases, were provided to them (see Table 2). Foreach key concept, the participants offered responses to the following prompts in the tabulatedform: (1) Why is it important for students to know this concept? (2) What is your knowledgeabout students’ thinking that influences your teaching of this concept? (3) What else do youknow about this concept that you do not intend students to know yet? (4) What are some otherdifficulties (except student thinking) or limitations associated with teaching this concept? (5)What kind of instructional methods or strategies would you use to teach this concept? (6) Howwould you assess students’ understanding of this concept?

In the first week of the semester, CoRes were introduced to the class, along with anexplanation of the construct of PCK and its role in teaching practice. First, each studentattending the class individually created a CoRes document in out-of-class time about the

Table 2 Key concepts provided for the PCK representations

Number Key concepts

1 Gases have mass and volume

2 Particles of gases move in all directions and spread out to fill the container that they are in

3 Gases homogeneously mix in any proportion

4 Gases are compressible

5 At constant temperature (T) and n (the number of moles of a gas), the pressure of a gas is inverselyproportional to its volume

6 At constant pressure (P) and n, the volume of a gas is directly proportional to its T

7 At constant volume (V) and n, the pressure of a gas is directly proportional to its T

8 At constant P and T, the volume of a gas is directly proportional to its n

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topic they had chosen at the beginning of the semester. This was the document collected asthe evidence of the preservice teachers’ initial PCK representation. Then, students worked inpairs with their classmates to discuss their ideas about the different aspects of the CoRedocuments. Each student was paired twice with different students who worked on the PCKrepresentation of the same topic. That is, each student collaborated with two differentpartners, and each pair worked together for a further 4 weeks. (Note that two participantsin the study never became a pair.) Pairs had to meet outside of class for at least an hour eachweek. Although the students interacted with their peers to discuss various aspects of theCoRes task, all students, including the participants, individually created and modified theirsecond CoRe documents. These documents were collected as a record of students’ PCKrepresentations at the end of the semester.

After the first PCK representation, the course instructor provided individual feedback to allstudents, addressing the strong and weak areas of their CoRe documents. While the preserviceteachers were working in pairs, the course instructor did not directly respond to their questionsabout the content of their documents, but suggested resources or challenged their ideas withfurther questions.

Interviews The two study participants were individually interviewed twice, immediately afterthe completion of each CoRe document. Their documents provided a context for the inter-views, and in the interviews the participants were asked for further explanation or clarificationfor their PCK representations in their CoRe document. Following the participants’ initialexplanations during the interviews, they were asked additional questions to elicit furtherdetails about their PCK representations. Thus, interviews provided the participants withopportunities for elaborating, modifying or expanding their PCK representations. Each inter-view took 50 to 90 min.

Data Analysis

The data from the first and second PCK representation of each participant in the form of CoResand corresponding interviews were jointly coded by utilizing the constant comparative meth-od, which allowed for “joint coding and analysis” of the data (Glaser, 1965, p.437). Datacoding started with dividing each participant’s PCK representations in the CoRe documents andinterview transcriptions into meaningful units (Merriam 1998). The length of a meaningful unitranged from one sentence to a large paragraph. Each unit of data was related to one particularissue, and conveyed information relevant to the study. Each unit in the CoRe documents wascompared to the relevant unit in the interview transcription, and a joint code wasassigned. The interview data either confirmed the data from the CoRe documents (jointcode) or provided further information about the participants’ PCK representation (addi-tional code from a single source). NVivo8® qualitative data analysis software (QSR 2008)was used in data coding.

The emerging categories were named and defined, and as the coding proceeded, somecategories were modified to reflect the participants’ PCK more precisely. The categories thatemerged were first tentatively classified into overarching themes. It was noted that suchoverarching themes reflected the PCK components described by Magnusson et al. (1999).Thus, their labels for PCK components were borrowed, with minor modifications, to namethese overarching themes. Table 3 summarizes the descriptions of the categories (theelements of PCK components) accumulated under the particular overarching theme (PCKcomponent).

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Descriptions of each category, related to the PCK components (in italics) of Magnusson etal. (1999) are presented below.

Orientations to teaching science Orientations to teaching science (OTS) is exhibited in thepreservice teachers’ motivation for why they intended to teach the behavior of gases(purposes) and what they believe is important to teach about this particular topic (goals—concepts, science process skills) to the students (see Table 1). In the data, the preservice

Table 3 Coding key

The components of PCK Categories Definition

Orientations to TeachingScience (OTS)

DSPS Developing science process skills

FRC Understanding further or related scientific concepts

SUDP Developing a scientific understanding of daily phenomena

Knowledge of ScienceCurriculum (KSC)

ARK Awareness of advanced or related knowledge

Knowledge of StudentUnderstanding (KSU)

AC Describing a form of possible alternative conception abouta certain concept

PPS Possible presuppositions (e.g., without external factors [wind,stirring] gases do not mix.)

PPM Physical properties of matter (e.g., colorless, invisible)

DMR Difficulty with moving between macroscopic, submicroscopic,and symbolic levels of representation

MOS Mismatch between daily life observations and scientificexplanations for phenomena

ITP Improper transfer of preknowledge (e.g., when we increasethe volume, the pressure of a gas increases, thinking likeif we study hard we achieve more)

LPK Stating the possible difficulties that students may have due to alack of prior knowledge

Knowledge of Teaching (KT)

Difficulties associatedwith teaching

DCR Difficulty with providing concrete representations

DTM Difficulties with instructional materials or methods (e.g., usingstatic representations, using lab instruments, physicalproperties of substances)

ITI Improper textbook images

IN Not paying attention to certain issues (e.g., temperature unitsKelvin vs. Celsius)

Teaching methods DEMO Demonstration

POE Predict-Observe-Explain

POE-M POE with missing elements

GINQ Guided inquiry

Knowledge of Assessment (KA) SQ Specific question

WE Written explanation

JE Journal entry

DRW Drawing

MP Modeling a principle

CSPS Checklist for observing science process skills

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teachers’ purposes and goals for teaching science were expressed in their responses to theCoRe prompt: “Why is it important for students to know each key concept?” The participantsusually aimed at developing understandings of key concepts of behavior of gases to supportstudents’ learning about further or related concepts of science (FRC, see Table 3). Theparticipants also intended to provide students with opportunities to develop scientific under-standings of daily phenomena (SUDP). Moreover, the participants planned to promote thedevelopment of science process skills (DSPS) as students learned about the behavior of gases.

Knowledge of science curriculum Knowledge of science curriculum (KSC) referred to thepreservice teachers’ knowledge about the extent and depth to which the behavior of gasesneeds to be taught at the high school level (see Table 1). The preservice teachers’ responses tothe CoRe prompt, “What else do you know about this concept that you do not intend studentsto know yet?” provided information about how well they knew the content itself and thecurriculum coverage of such content at the secondary level. The participants particularlyidentified advanced or related knowledge (ARK) about topics that high school students didnot need to know (see Table 3).

Knowledge of student understanding Knowledge of student understanding (KSU) referred tothe preservice teachers’ knowledge about the nature and sources of students’ commonalternative conceptions (see Table 1). The data were drawn from preservice teachers’ responsesto the prompt: “What do you know about students’ thinking that might influence your teachingof this concept?” The participants’ representations not only indicated students’ specificalternative conceptions (AC) but also referred to the sources of these conceptions that play arole in the generation of such ideas. Thus, the categories described the sources of alternativeconceptions and included (see Table 3): possible presuppositions (PPS), physical properties ofmatter (PPM), difficulty with moving between multiple levels of representation (DMR),mismatch between observations and scientific explanation of phenomena (MOS), and improp-er transfer of preknowledge (ITP). The participants also pointed out a lack of prior knowledge(LPK) as a barrier to further science learning.

Knowledge of teaching Knowledge of teaching (KT) consisted of two components. Oneinvolved the preservice teachers’ knowledge of difficulties associated with teaching (seeTable 3 for categories), and the other was about their knowledge of specific instructionalmethods that they planned to use in teaching the behavior of gases (see Table 1). Thisinformation came from their responses to the CoRe prompts concerning the difficulties andlimitations associated with teaching the particular concept and the methods they could use toteach the key concepts of the behavior of gases.

Four main teaching methods emerged from the data, namely demonstrations (DEMO),predict-observe-explain with some missing elements (POE-M), predict-observe-explain(POE), and guided inquiry (GINQ). If the participants just intended to demonstrate particularscientific ideas to students by using specific equipment, such instruction was coded as being aDEMO. In the present case, the POE referred to the method in which teacher-selecteddemonstrations started with a focusing question (prediction) and continued with observationand explanation (Bell et al. 2005). GINQ indicated a method in which the teacher providedmaterials or tools (concrete or virtual) along with a question to be investigated, and studentsdesigned experiments, collected evidence, generated possible explanations with respect to dataat hand, and came up with principles or identified the relations between variables (Bell et al.2005).

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Knowledge of assessment Knowledge of assessment (KA) indicated the assessment strategiesthat the participants planned to employ to ascertain student understanding of each key conceptinvolving the behavior of gases (see Table 1). This was reflected in their responses to the CoReprompt: “How would you assess students’ understanding of this concept?” The participantspreferred to assess students’ understanding with various tasks: (1) specific questions (SQ)involving everyday phenomena in which students used what they learned for this given case,(2) written explanation (WE) in which students explain their understanding of the key conceptin written form, (3) journal entries (JE) including responses to prompts asking students tocompare and contrast their previous and current knowledge concerning the particular keyconcept, (4) drawing (DRW) tasks in which students represented the particular phenomenonat the submicroscopic level, (5) modeling a principle (MP) involving tasks in whichstudents generated a symbolic and visual model of a principle based on available data,and (6) checklist for observing students’ science process skills (CSPS) while performing anexperiment.

To address the research question, the frequency of each category was calculated for thefirst and second PCK representation of each participant. Then, the total frequencies of eachPCK component were identified by adding up the frequencies of categories accumulatedunder the relevant PCK component. In the “Findings” section, the progression in theparticipants’ PCK components is represented both numerically, by providing frequencies ofrelevant categories (the elements of PCK components), and descriptively, by providingrepresentative excerpts of those categories. Based on the feature of categories at each instanceof PCK representation, each participant’s level of progression for each PCK component isidentified by comparing it against the criteria provided by Schneider and Plasman (2011) (seeTable 1).

The reliability of the data coding was established in two different ways. Seventy-twopercent of the categories (18 of 25) defined here were created a year prior to the study bycoding the same type of data collected from a different group of preservice science teachers.When the current data were coded, these categories fit into the data with minor modifications.The remaining categories (e.g., PPS, ITP, improper textbook images (ITI), POE-M, GINQ,JE, and MP) emerged from the present data and were defined accordingly. In addition, thefirst author coded the entire set of data and developed coding decision rules in relation to thedata. Next, both authors recoded the entire set of data. While recoding the data, codingdecision rules were slightly modified. Then, after six months time to reduce the impact offamiliarity with the coded data, the first author recoded 25 % of the data to check for internalrater reliability. The percentage of agreement between the final two coding instances wascalculated by dividing the number of agreements in coding by the number of agreements anddisagreements (Miles and Huberman 1994). Agreement was found to be 94 %. Other studieshave used similar reliability procedures (e.g., Falk 2012).

Findings

Figure 1 shows the frequency of Ada and Ela’s representations of five PCK components basedon their two PCK representations (indicated in Tables and Figures as PCK1, PCK2). Inaddition, Table 4 summarizes the progression in the nature of participants’ representations ofthe five PCK components, which was identified considering the PCK learning progressioncriteria developed by Schneider and Plasman (2011). The following sections describe howeach participant’s PCK representation features progressed over the semester.

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The Case of Ada

Orientations to teaching science In her first PCK representation, Ada did not provide anyevidence about her purposes or goals for teaching the behavior of gases, but in the second one,her priority in teaching this particular topic seemed to be almost equally distributed among thethree categories (see Fig. 2). Her purposes were to develop students’ scientific understandingof behavior of gases for further science learning (FRC, 6; PCK2, see Fig. 2) as well as todevelop students’ understandings of daily phenomena (SUDP, 8; PCK2). In addition, whileteaching the key concepts of the behavior of gases, Ada suggested developing students’science process skills (DSPS, 8; PCK2). Representative excerpts for each specific purposeor goal for the teaching of the behavior of gases follow:

Hmm, the topic of behavior of gases… is included in the Grade 10 curriculum, whereasthe topic of entropy is expected to be learned in the beginning of Grade 11. Studentsusually link the concept of entropy with disorder in their mind so that if they know thatparticles of gases move in every direction, and they fill up the container they are in,students can associate the movement of gases with entropy (coded as FRC, data source:Interview 2).If students know the idea that gases have mass, they may relate it with daily life such aswhen we open a soda can, its weight decreases because of gas bubbles (coded as SUDP,data source: CoRe2).…for the last three key concepts … I expect students to collect data, and draw andinterpret a graph… hmm, in fact in my instructional plan, particularly for the first fivekey concepts… students first make a prediction, and then they observe and generate anexplanation. Then, they are shown animations so they compare their explanation withthe animation, and if needed, they modify their explanations… (DSPS, Interview 2).

Fig. 1 Frequency of the participants’ overall representations for each component of PCK in the first and secondPCK representation

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According to Schneider and Plasman’s (2011) four-level progression trajectory for the purposeof teaching science, expert teachers help students understand everyday phenomena andconceptually prepare them to further study science (see Table 1). In planning her teaching,Ada also intended to focus on achieving such purposes (see the excerpts above [SUDP and

Fig. 2 The nature and frequency of the participants’ orientations to teaching science (OTS) representations in thefirst and second PCK representation

Table 4 Summary of the partici-pants’ PCK representation progres-sion identified with respect toSchneider and Plasman’s (2011)PCK learning progression trajectorycriteria

aThese levels indicate the totalnumber of hierarchically definedcriteria for each progressiontrajectory

PCK components Ada Ela

Orientations to Teaching Science (OTS)

Purposes (4-Levela)

PCK1 NA 3

PCK2 4 4

Goals (4-Levela)

PCK1 1 1

PCK2 2 1

Knowledge of Science Curriculum (KSC)

Scope, sequence, and resources (2-Levela)

PCK1 NA NA

PCK2 NA NA

Knowledge of Student Understanding (KSU)

Students’ initial ideas (5-Levela)

PCK1 5 5

PCK2 5 5

Knowledge of Teaching (KT)

Inquiry Strategies (4-Levela)

PCK1 2 2

PCK2 3 2

Knowledge of Assessment (KA)

Assessment Strategies (4-Levela)

PCK1 NA NA

PCK2 3&4 3&4

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FRC], and Fig. 2). The evidence from Ada’s second PCK representation concerning the PCKcomponent of OTS, in the subcategory of purposes, included elements of the highest progres-sion criteria (Level 4, see Table 1). In addition to teaching concepts, in her second PCKrepresentation, Ada set the development of science process skills as a goal for teaching (DSPS)and planned her instruction accordingly (see the excerpt above [DSPS] and Fig. 2). Thisevidence indicated the features of second-level criterion in Schneider and Plasman’s progres-sion trajectory for the PCK component of OTS, in the subcategory of goals (Level 2, seeTables 1 and 4).

Knowledge of science curriculum In her first PCK representation, Ada pointed out only twoideas that counted towards her KSC (see Fig. 1, e.g., “gas particles …move with differentvelocities, but we should only talk about an average velocity, not the velocity of one particle”[ARK, CoRe1]). In the second PCK representation, Ada’s representation about this particularcomponent of PCK not only changed in quantity (ARK, 9; PCK2, see Fig. 1) but also showedher awareness about the discrepancy between her subject matter knowledge and what wasincluded in the curriculum. For example, to indicate what should be excludedwhile teaching therelationship between volume and temperature at constant pressure and the number of moles,Ada stated that “the Boltzman constant should not be mentioned, and the calculations ofentropy by multiplying the Boltzman constant and the number of microstates (Ω) do not needto be shown either” (ARK, CoRe2). Moreover, in the context of gas laws, she stated that “theteacher mentions elastic collisions between gas particles. Actually, they are not elastic; particleslose energy with collisions, but this information needs to be ignored” (ARK, CoRe2).

Because the participants were not practicing teachers, it seemed inappropriate to comparetheir KSC representations with Schneider and Plasman’s (2011) two-level progression trajectoryfor KSC (see Tables 1 and 4). This is because such a trajectory has been defined with respect toteaching practice actions. However, based on the available evidence (see the excerpts above), asAda worked on the CoRe documents, she became familiar with the scope of the particular topicincluded in the chemistry curriculum, in that she was able to make certain decisions about whatto exclude while teaching the behavior of gases to high school students.

Knowledge of student understanding In her first PCK representation, Ada provided severalideas about students’ alternative conceptions about the behavior of gases (AC) as well assuggesting a few sources of such conceptions (DMR, MOS). She also paid attention to theissue of students’ LPK, which could possibly impede students’ further learning. Table 5 showsthe frequency of each element of KSU and provides exemplifying excerpts from Ada’s firstand second PCK representations.

In her second PCK representation (see Table 5), Ada’s representations about KSU expand-ed considerably, and the features of the issues she offered about student thinking varied. Adadescribed numerous AC involving the behavior of gases, and she referred to a number ofpossible sources of such conceptions (PPS, PPM, DMR, MOS, ITP, and LPK, see Table 5 forexcerpts). For example, Ada suggested that what students actually observe sometimes misleadsthem in learning scientific concepts, because what is observed at the macroscopic levelsometimes provides little information about what is happening at the molecular level(MOS); likewise, the physical properties of gases (e.g., being colorless, odorless etc.) can bean obstacle to understanding the gaseous phenomenon (PPM). Ada also recognized the issuewith students’ intuitive presuppositions in the generation of alternative conceptions (PPS). Inaddition, Ada stated that students sometimes intuitively develop general rules between partic-ular variables and apply the same relationship to every instance without actually consideringthe phenomenon (ITP).

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In both her PCK representations, Ada demonstrated knowledge about the existence ofalternative conceptions among students (AC, see Table 5). However, over the course of thesemester, not only did Ada extend her KSU representations in number, but she was also able toidentify several possible sources of such alternative conceptions that students might have aboutthe behavior of gases (e.g., PPS, PPM, DMR, MOS, see Table 5). These features in Ada’sknowledge repertoire reflected the highest level criterion in Schneider and Plasman’s (2011)progression trajectory for students’ initial science ideas (Level 5, see Tables 1 and 4).

Knowledge of teaching In her first PCK representation, Ada offered four different difficultiesassociated with teaching the behavior of gases (DCR, difficulties with instructional materialsor methods (DTM), ITI, and IN). From the first to the second PCK representation, the natureand frequency of such representations did not change. Table 6 shows the nature and frequencyof such teaching difficulties with exemplifying excerpts from her first and second PCKrepresentation instances.

In her first PCK representation, Ada did not provide any ideas about how she would teachfour key concepts (1, 6, 7, and 8, see Table 2). Ada’s representations about ways of instructionfor key concepts 2 and 3 fit into the POE approach, but her planning of instruction for keyconcepts 4 and 5 did not, as it was missing some elements. For example, she stated: “I provideeach group three syringes that contain a solid, a liquid, and air, and I want students to predictwhether they are compressible or not [prediction]. They try to compress them and observe thatgases are compressible [observation] (POE-M, CoRe1).” In this statement, the explanation

Table 5 The nature and frequency of Ada’s knowledge of student understanding (KSU) representations in thefirst and second PCK representation

Categories # Exemplifying excerpts

AC 6 “Students may think that when gases are compressed, particles become smaller or their shapeschange so that they [gases] occupy less volume” (CoRe1)

DMR 1 “Students may have difficulties with thinking in molecular level and making connections withmacroscopic level or vice versa” (CoRe1)

MOS 1 “Students may have problems with homogeneous mixing of gases, because they cannot observethis phenomenon for many gases at the macroscopic level” (CoRe1)

LPK 2 “If students have a lack of knowledge about the fact that gases have mass, they may notunderstand the concept of gas pressure” (CoRe1)

AC 16 “…changing temperature changes the size of gas particles, so the volume of a gas eitherincreases or decreases depending on the change in temperature” (CoRe2)

PPS 2 “Students think that pressure resulted from compression; gases have no pressure when they arenot compressed” (CoRe2)

PPM 2 “Because most gases are invisible at the macroscopic level, and they are colorless, so studentsmay think that gases do not have mass” (CoRe2)

DMR 1 “Students may have difficulties with thinking in molecular level and making connections withmacroscopic level or vice versa” (CoRe2)

MOS 3 “Students think that gases have no pressure because they do not feel the pressure of air on them”(CoRe2)

ITP 1 “Students sometimes consider P and T proportional, so they may think…there is no change in Pwhen volume is changed, because there is no change in energy of particles due to constant T”(CoRe2)

LPK 4 In relation to key concept 6 where pressure is constant: “if students do not know the atmosphericpressure is 1 atm at standard conditions, students may have difficulty understanding themechanism of gas container with a free moving piston” (CoRe2)

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element is missing. Figure 3 shows the type and frequency of instructional methods that Adaplanned to use in her first and second PCK representations.

In her second PCK representation, Ada’s instructional methods followed either the POE orguided inquiry approach (see Fig. 3). Her instructional planning for all the key concepts,except key concept 7, exhibited the features of the POE approach, and the instructionalplanning she described for the key concepts 5, 6, 7, and 8 was in line with GINQ. Ada’srepresentative descriptions for each type of instructional method follow:

…If I turn the small beaker upside down into the water, what do you think happens?… Iask students ‘what did you observe?’ and ‘what is there in the part that is not filled withwater?’… ask them ‘why the beaker did not fully fill with water?’… I let some bubblesto go out from the beaker… they observe… Students explain what the reason is for theirobservation… I expect students to explain that the pressure on the surface of the bubblesdecreases while they are going up in water, so they are getting bigger… (POE, CoRe2)

Table 6 The nature and frequency of Ada’s knowledge of teaching (KT) representations about the difficultiesassociated with teaching the behavior of gases in the first and second PCK representation

Categories # Exemplifying excerpts

DCR 1 “Most gases are invisible at macroscopic level, so students cannot directly observe gases, and it isdifficult to help students develop the understanding that gases have mass and volume”(CoRes1, CoRes2)

DTM 1 “If students do not know about constant atmospheric pressure acting on the container with apiston and the mechanism of such a container, they may have difficulty understanding thevolume and temperature relation at constant P and n” (CoRes1, CoRes2)

ITI 1 “Even if students think about the movement of gas particles, they may not believe that suchmovement occurs in all directions; I guess the static and two-dimensional textbook images ofgases affect this idea” (CoRes1, CoRes2)

IN 1 “The Kelvin scale should be used if Celsius is given in the questions, so students should convertdegrees Celsius to degrees Kelvin before plugging numbers into the formula…but studentsusually do not pay attention” (CoRes1, CoRes2)

Fig. 3 The nature and frequency of the participants’ knowledge of teaching (KT) representations about teachingmethods in the first and second PCK representation

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I show the simulation from the following website (http://phet.colorado.edu/sims/ideal-gas/gas-properties_en.jnlp) and… then I tell students that you will explore therelationship between T and P at constant V and n. How would you manipulate thissimulation tool for this purpose? …what happens to the box [container], as soon as weselect constant V? Students identify the dependent and independent variables… I putsome amount of gas particles into box, and ask them to read and record the pressurevalues as I change T by using the simulation tool… I ask them to notice the number ofcollisions between the molecules and the container wall as I change T… They generate agraph using the data they recorded, and… explain the relationship between P and Twithrespect to their graph… and what it means at the molecular level… (GINQ, CoRe2)

In her first PCK representation, Ada planned to offer students firsthand experiences withmaterials (POE), but such experiences were limited to observations at the macroscopic level(e.g., testing the compression of a gas with air-filled syringes). In her second PCK repre-sentation, however, not only did Ada intend to allow students to observe the phenomenon,but she also asked them to collect data in different forms, through observation (descriptive)or manipulation of online tools/concrete materials (numeric). Based on her planning, studentswould work with their own data and represent these in a meaningful manner (graphicalrepresentation) as well as offer explanations of such illustrations at the different representa-tional levels (see above for instructional planning excerpts). From the first to the second PCKrepresentation, Ada demonstrated a notable expansion and elaboration in her KT, particularlyin terms of adapting an inquiry learning method to her PCK repertoire (see Fig. 3). Such achange in the features of Ada’s KT representations satisfied the third-level criterion inSchneider and Plasman’s (2011) four-level progression trajectory for teachers’ inquirystrategies (Level 3, see Tables 1 and 4). That is, over the semester-long course, Ada movedtoward an exploratory inquiry strategy that involved multiple forms of data collection andrepresentation.

Knowledge of assessment In her first PCK representation, Ada only offered three differentways of assessment for different key concepts. In her second PCK representation, Ada offeredat least one way to assess students’ understanding of each key concept. Table 7 represents thefrequency and features of the assessment tasks that Ada utilized in her first and second PCKrepresentations for assessing student understanding of the behavior of gases. It is important tonotice that the nature of Ada’s assessment tasks was in line with her teaching purposes. Forexample, one of her teaching purposes was to develop students’ scientific understanding ofdaily phenomena. Accordingly, she planned to ask students to come up with applications of agas law to daily life (WE, see Table 7). In addition, she integrated her assessment tasks into herinstruction, such that she considered collecting students’ written products for assessmentpurposes (MP, see Table 7).

In her first PCK representation, the available representations offered by Ada were notsufficient for comparison with the criteria provided by Schneider and Plasman (2011) for KA.In the second one, however, Ada intended to employ multiple assessment strategies, and eachof Ada’s assessment tasks targeted students’ understandings of a specific concept (see Table 7).For almost all key concepts, Ada planned to integrate assessment of student learning intoinstruction, in the sense that the products students generated during the instruction wereintended to be used for assessment purposes (SQ, DRW, MP, see Table 7). Thus, from thefirst to the second PCK representation, the nature of Ada’s representations about KA indicatedthe features of the third and fourth-level criteria in Schneider and Plasman’s progressiontrajectory for assessment strategies (Level 3 and Level 4, see Tables 1 and 4)

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The Case of Ela

Orientations to teaching science In her first and second PCK representations, the nature ofEla’s representations about the purposes of science teaching was the same, but their frequencyincreased from the first to the second (see Fig. 2 above). In the first PCK representation, Ela’smajor concern was to develop her students’ scientific understanding of the behavior of gases toestablish a basis for FRC. However, in the second PCK representation, Ela placed moreemphasis on the purpose of developing an understanding of daily phenomena associated withthe behavior of gases (SUDP). Table 8 shows the evidence from her PCK representations,along with the number of her representations.

In her first PCK representation, concerning science teaching purposes, Ela primarily con-sidered conceptual learning critical for further study of science (FRC), which indicated align-ment with the third-level progression criterion in Schneider and Plasman’s progression trajec-tory. However, in the second PCK representation, her purpose of teaching science shifted

Table 7 The nature and frequency of Ada’s knowledge of assessment (KA) representations in the first andsecond PCK representation

Categories # Exemplifying excerpts

SQ 1 “…what happens when someone pours cologne on his/her hands, and how does its smell dispersearound the room?” (CoRes1)

DRW 1 “Draw what happens to the gas particles before and after compressing the gas in the syringe”(CoRes1)

SQ 1 “If I open the door of the class, do students smell the fragrance of the perfume? Please provideevidence for you answer” (CoRes2)

WE 4 “Find a daily life example related to Gay-Lussac’s Law…and write a paragraph about theexample by explaining how that example represents the law” (CoRes2)

DRW 2 “Students…to observe how the perfume spray particles disperse into the air, then…they draw thedispersion of perfume particles in air at the microscopic level just after spraying perfume andsome time later” (CoRes2)

MPa 4 Integrating into Boyle’s Law (key concept 5) instruction: “Students draw a P-V graph by usingthe data they collected from the simulation during the class and infer the relationship between Pand V from the graph, explaining the behavior of particles as the volume changes” (CoRes1,CoRes2)

a This code and the excerpt presented here was the same for both PCK representations

Table 8 The nature and frequency of Ela’s orientations to teaching science (OTS) representations in the first andsecond PCK representations

Categories # Exemplifying excerpts

FRC 3 “Learning of key concept 1 is important for understanding the gas pressure, phase changes, andgas laws” (CoRe1)

SUDP 1 “If students know about the relationship between V and n at constant pressure, they can realizethe science behind why a balloon blows out when they try to make it bigger” (CoRe1)

FRC 5 “Gas pressure is a result of the collision of the gas particles with the walls of the container. Ifstudents know that gas particles can move in all directions independently, they may easilyunderstand the concept of gas pressure” (CoRe2)

SUDP 9 “When students learn about the behavior of gases, they should be able to explain the followingphenomena such as ‘the existence of a liquid gas in deodorant bottles’ or ‘the change inpressure of automobile tires in summer and winter” (CoRe2)

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toward the development of scientific understanding of everyday phenomena among students(SUDP, see Table 8), reflecting the highest level criterion in Schneider and Plasman’s (2011)progression trajectory for the purpose of science teaching (Level 4, see Table 1). In addition, Eladid not include the DSPS as part of her teaching goals (see Table 8). Based on this evidence,Ela’s representations regarding science teaching goals exhibited the features of the lowest endof the progression trajectory (see Tables 1 and 4), implying that she intended to just teach relatedconcepts without considering the development of science process skills.

Knowledge of science curriculum From the first to the second PCK representation, the natureand frequency of Ela’s representations about KSC did not noticeably change (see Fig. 1, ARK;PCK1, 7; PCK2, 9). For example, in relation to the key concept 5 that involves Boyle’s Law, Elastated that “students do not need to learn the behavior of real gases at the high school level. Infact, if a gas exists in an insulated container, when compressed, there can be an increase intemperature (adiabatic process)” (ARK, CoRe1, CoRe2). Moreover, regarding the key concept3, the mixing of gases, she mentioned that “the factors that affect the occurrence of diffusion arenot necessarily known yet, such as the size of gas particles and temperature” (ARK, CoRe2).

In her first PCK representation, Ela identified particular ideas concerning the extent towhich she planned to teach the behavior of gases in high school classrooms, but she onlyadded a few ideas in the second PCK representation (see Fig. 1). Based on the availableevidence (see excerpts above), she was aware of the scope of the curriculum involving theparticular topic; however, because Schneider and Plasman’s (2011) progression criteria forKSC involved teaching practice actions, her progression of KSC was not interpreted in light ofsuch criteria (see Tables 1 and 4).

Knowledge of student understanding In her first PCK representation, Ela’s representationsincluded a few AC, along with the possible sources of such alternative conceptions (PPS,MOS); she also referred to the possibility of conceptual problems due to a LPK. Table 9 showsthe extent and features of her KSU representations in the two PCK representations.

Table 9 The nature and frequency of Ela’s knowledge of student understanding (KSU) representations in thefirst and second PCK representations

Categories # Exemplifying excerpts

AC 3 “Big or heavy particles have big size, so gas molecules cannot mix in any proportion” (CoRe1)

PPS 3 In relation to Boyle’s Law, students may think that “volume is only related to the mass and thenumber of particles. If no gas enters or leaves the container, volume remains constant under anycondition” (CoRe1)

MOS 1 “Because students cannot see the gases, they may think that gases have no mass or volume”(CoRe1)

AC 12 “When students think that there is air between gas particles…students may also think that if thecontainer is full of gas, we cannot add more gas to it” (CoRe2)

PPS 1 “External factors such as circulation or wind are important for movement of gases” (CoRe2)

DMR 1 Ela was able to identify the sources of alternative conceptions, such as the difficulty withmoving between the macroscopic and submicroscopic levels (CoRe2)

MOS 2 “If gases have mass why do we not feel any mass on us?” (CoRe2)

LPKa 2 “The gas laws require mathematical calculations; if students do not understand what inverse ordirect proportion are and do not know how to manipulate variables, this can be a limitation,and they may not make sense of the relations between variables” (CoRe1, CoRe2)

a The frequency of this code was the same for both PCK representations

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In her second PCK representation, Ela offered at least one commonly observed AC for eachkey concept. In addition, she expanded the extent and features of her representationsconcerning the possible sources of students’ alternative conceptions (PPS, DMR, MOS, andLPK, see Table 9).

Based on her representations regardingKSU at two PCK representation instances, Ela believedin the existence of alternative conceptions among students (see Table 9), and she recognized theprobable origins of such alternative conceptions (PPS, DMR, MOS). These features in her PCKrepresentations met the highest level criterion in Schneider and Plasman’s (2011) progressiontrajectory for students’ initial science ideas (Level 5, see Tables 1 and 4).

Knowledge of teaching From the first to the second PCK representation, Ela’s representationsconcerning the difficulties associated with teaching the behavior of gases changed minimallyin terms of their frequencies and features (see Table 10). However, unlike the first one, in hersecond PCK representation she noted the difficulty of finding animations or simulations thataccurately showed the concepts associated with the behavior of gases at the submicroscopiclevel (DTM, see Table 10 for an excerpt).

In her first PCK representation, Ela described her instructional method for teaching all thekey concepts except 3 and 4. All of her instructional descriptions exhibited the features ofDEMO (see Fig. 3). For example,

… I will use a bath scale, one 60 mL syringe, and a wooden block. Students will recordthe numeric values on the scale while I press the syringe where its tip hits the woodenblock placed on the scale. Then, the students will draw a graph. This graph is aboutForce (F) vs. Volume, and students will find out the relation between Pressure andForce… (DEMO, CoRe1).

In her second PCK representation, Ela provided one possible instructional plan for each keyconcept. Five of her instructional methods were in the form of a DEMO, two of herinstructional methods were in line with POE, and one of her instructional methods lookedlike POE but lacked some of its elements (POE-M) (see Fig. 3 above). A representativeexample for each one follows:

…I will push on the open button on it [spray perfume] from the one corner of the class.…when they smell the odor, they raise their hands. After 5-10 min all the students willsmell the odor. I want them to answer the question: “Which property of gases causesthis?” They will discuss in the class. Then I will show the simulation from an onlinesource… (DEMO, CoRe2)…They will predict what will happen when they add vinegar into the flask that includessome baking soda. …They will cover the mouth of flask with a balloon as soon as theyput some vinegar into the flask. They will observe the balloon … it will blow up.Students will measure the circle of the balloon after it is filled with gas. This will beevidence for the volume of gases. Students will weigh the balloon before the experi-ment… After the experiment…students will weigh it again. There will be a massdifference between them. This is an evidence for mass of gases (POE, CoRe2).

Based on Ela’s representations of KT in the two PCK representations, although Elaintended to provide students with opportunities to collect data while teaching the behaviorof gases, the data were mostly obtained through observation or with limited measurements.That is, she did not plan to provide students with extensive opportunities for doing science.With respect to her instructional descriptions, for almost all the key concepts it seemed that herinstructional methods, to a large extent, were teacher directed (see instructional method

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excerpts above). In both PCK representations, instructional features evidenced in Ela’s instruc-tional planning were consistent with the second-level criterion in Schneider and Plasman’s (2011)four-level progression trajectory for teachers’ inquiry strategies (Level 2, see Tables 1 and 4).

Knowledge of assessment In her first PCK representation, Ela did not suggest any ideas forassessing students’ understanding of any key concept (see Fig. 1 and Table 11). In the secondone, she offered one possible way of assessing almost all key concepts, except key concept 8,and she utilized a range of strategies to assess students’ understanding of the behavior of gases(see Table 11). Although Ela did not identify the development of science process skills as oneof her goals for teaching, she suggested using the CSPS during the instruction of key concept1—the concept that gases have mass and volume (see POE excerpt above).

As evidenced in her second PCK representation (see Table 11), Ela’s KA representationsprogressed in terms of adopting a variety of strategies to assess students’ science learning,matching assessment tasks with specific science concepts, and employing assessment in

Table 11 The nature and frequency of Ela’s knowledge of assessment (KA) representations in the second PCKrepresentation

Categories # Exemplifying excerpts

SQ 2 “Explain why a can of soda explodes if it is left in the hot sun” (CoRe2)

WE 1 Integrating into key concept 4: “Why do you think gases are compressible? What two propertiesof gases may account for the compression of air?” (CoRe2)

JE 1 “Students will write a journal responding to the following prompts: What was the activity about?What do you know about it right now? Were there things that confused you? Were there thingsthat you did not understand?…” (CoRe2)

DRW 2 “Consider that you are blowing a balloon. You blew up a little bit, and then blew up more. Drawyour observations at the molecular level with your explanations in terms of pressure,temperature, volume, and the number of moles” (CoRe2)

MP 1 Integrating into key concept 5: “Draw a graph by using numerical data about the relationshipbetween the P and V…explain what the graph means” (CoRe2)

CSPS 1 “I will prepare a science process skills Table… I will assess the basic science process skills ofstudents which are inferring, observing, measuring, predicting, and communicating” (CoRe2)

Note: There was no evidence of KA in the first PCK representation

Table 10 The nature and frequency of Ela’s knowledge of teaching (KT) representations about the difficultiesassociated with teaching the behavior of gases in the first and second PCK representation

Categories # Exemplifying excerpts

DTM 2 Her representations involved difficulties with teaching materials: “If students do not know how acontainer with a piston works under constant atmospheric pressure, they may not be able torecognize that different positions of the piston correspond to the same pressure” (CoRe1)

DTM 3 “There are a lot of animations or simulations available online, but they are not all good in terms ofrepresenting specific concepts…they may create misconceptions, if teachers are not aware ofthe limitations of animations or simulations” (Interview 2)

INa 2 “Students usually do not pay attention to unit conversions of temperature or pressure in numericalcalculations” (CoRe1, CoRe2)

a The frequency of this code was the same for both PCK representations

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conjunction with instruction. Such features in her representation reflected the “highest levels”criteria in Schneider and Plasman’s (2011) progression trajectory for assessment strategies(Level 3 and Level 4, see Tables 1 and 4).

Discussion

The purpose of this study was to identify and describe how the extent and nature of theparticipant teachers’ PCK representations about the behavior of gases progressed in the contextof a semester-long chemistry teaching methods course. Initially, neither of the participants helda broad repertoire of representations for all five components of PCK in their knowledge base,and the representations they offered were limited in number and diversity of ideas (see Fig. 1;Table 4). In the second PCK representation, however, both participants noticeably increasedtheir number of representations, but the extent of growth across the participants was ratherdifferent (see Fig. 1; Ada, PCK1 23, PCK2 86; Ela, PCK1 30, PCK2 62).

Similarly, the constituent elements of each PCK component indicated relatively dissimilarfeatures across the participants (see Tables 5, 6, 7, 8, 9, 10, and 11, Figs. 2 and 3). Thesefindings were consistent with the findings of previous studies (De Jong et al. 2005; Magnussonet al. 1999; Rozenszajn and Yarden 2014; Schneider and Plasman 2011; Veal 2004). Thesescholars associated such uneven development in the extent and features of PCK componentswith differences in the amount of knowledge held by the preservice science teachers in thedomains of subject matter knowledge and pedagogical knowledge (De Jong et al. 2005;Magnusson et al. 1999) or the participants’ unique prior experiences that shaped their (teachingefficacy) beliefs about teaching science (Park and Oliver 2008; Rozenszajn and Yarden 2014;Veal 2004). In the current case, both participants were identified as having strong subjectmatter knowledge about the behavior of gases, as reflected in their high GPAs. Although thisstudy did not intend to explore the association between teaching efficacy beliefs and theparticipants’ PCK progression, it might be cautiously argued that the discrepancy in theparticipants’ teaching efficacy beliefs may be related to the differences observed in theprogression of their PCK representations.

Concerning the component of OTS, in the subcategory of purposes for teaching science, inthe second PCK representation, both participants’ PCK representations exhibited the featuresof fourth-level (highest) progression criteria developed by Schneider and Plasman (2011) (seeTables 1 and 4). In the subcategory of goals for teaching science, Ada progressed from the firstto the second level of progression during the semester by including the development of scienceprocess skills as a goal in her representations, in addition to teaching science concepts, whereasEla did not demonstrate progress within this particular subcategory (see Tables 1 and 4).

At the beginning of the semester, a general whole-class discussion was held on whyteachers need to teach science (purposes) and what they need to teach in science classes(goals). In this discussion, without referring to particular topics, the preservice teachersspontaneously pointed out the same themes (e.g., SUDP and FRC) identified in the availabledata about the purposes of teaching chemistry; however, regarding the goals for teachingchemistry, the preservice teachers focused on teaching the concepts, likely because theyviewed the curriculum content coverage as a priority in teaching due to the comprehensiveexamination at the end of high school. While constructing the CoRes document, the partici-pants further considered their own chemistry teaching orientations regarding the behavior ofgases. Thus, they came up with content-specific reasons for teaching this topic. Given that theparticipants had no classroom teaching experience, Ada’s addition of the development ofscience process skills into her PCK repertoire as a teaching goal probably had to do with the

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emphasis on the inquiry approach during the chemistry teaching methods course. Teachersusually develop such ideas in their science teaching goals over time, as they continue to workwith students; however, if learning to teach the nature of science and inquiry skills is includedin the teacher education courses, they begin indicating such ideas as a possible goal forteaching (Schneider and Plasman 2011).

Ada and Ela demonstrated the least development in the PCK component of KSC (seeFig. 1). Even though the findings of previous research revealed that experienced teachers heldadequate KSC in their PCK repertoire (e.g., Park and Oliver 2008), preservice teachers havebeen found to have weak curricular knowledge (e.g., Kaya 2009). Davis (2004) pointed outthat the development of KSC requires extensive experience in teaching. Thus, the limiteddevelopment in the participants’ KSC might be explained by their lack of experience inteaching. In addition, during the course, the instructor did not allot time to discuss or criticallyexplore the enacted curriculum. However, it is important to acknowledge the role played by theCoRe task, which provided an opportunity for the preservice chemistry teachers to examine thenational curriculum and some available materials (e.g., textbooks).

It was evident in their first PCK representations that both participants were aware of theexistence of students’ alternative conceptions and how students might generate such naiveideas. The nature of both participants’ representations of KSU fit into the fifth-level (highest)PCK progression criterion in two PCK representation instances (see Tables 1 and 4). More-over, over the course of the study, both participants made extensive progress by adding anumber of different students’ nonscientific conceptions and their sources into their PCKrepertoires (see Tables 5 and 9).

As evidenced in other studies, teachers with a lot of classroom experience alone did notshow the same progress, but preservice teachers indicated great progress in their thinking aboutstudents’ science ideas due to their formal instruction on student thinking (Schneider andPlasman 2011). In the current case, the different activities in three different courses may havesupported such progress. First, the participants’ initial awareness about students’ preconcep-tions may have derived from their own experience in the first course taken in a sequence,namely “Secondary School Chemistry Laboratory Applications.” In this course, the partici-pants’ ideas about diverse topics of chemistry were challenged by engaging them in variousconflicting situations so that they were faced with their own nonscientific conceptual issues.Second, in the “Science Teaching Methods” course, the participants learned about construc-tivist views of learning and the value of students’ initial conceptions in science teaching. Third,in the current course, the preservice teachers benefitted from studying students’ conceptions inrelation to a specific chemistry topic (e.g., the behavior of gases, chemical bonding, and so on).Every week, one class meeting was allotted for this activity. However, students in the class,including the participants, individually read several papers about students’ conceptions of thebehavior of gases, and they discussed them with their peers while they were creating the CoRedocuments. During this course, the preservice teachers frequently mentioned that this activitygreatly contributed to their understanding of students’ possible nonscientific conceptions andlearning difficulties. The participants also faced their own conceptual issues as they read aboutthose papers, which might have positively affected their subject matter knowledge.

Although Halim and Meerah (2002) mentioned their concern about preservice scienceteachers’ lack of awareness of students’ nonscientific conceptions, the findings of this studyshowed that carefully designed teacher education courses have the potential to improvepreservice teachers’ knowledge about students’ science ideas. Consistent with the findingsof this study, other studies (e.g., Van Driel et al. 1998, 2002) also found that reading aboutresearch into students’ conceptions about various science topics helped preservice scienceteachers develop understandings of the existence of particular nonscientific conceptions among

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students. De Jong and Van Driel (2004) stated that before teaching in actual settings, preservicescience teachers rarely report the possible difficulties associated with teaching a topic. Thus,the finding about difficulties associated with teaching the behavior of gases (see Tables 6 and10) showed that the participants could generate initial ideas about some likely difficulties withteaching the behavior of gases.

Regarding the PCK component of KT, in the subcategory of inquiry strategies, Ada progressedfrom second to third level over a semester by incorporating amore authentic inquiry approach intoher instructional planning (see Fig. 3; Tables 1 and 4). However, the nature of the change in Ela’steaching strategies did not move her to a more proficient level(s), demonstrating no progression inthis particular component from the first to the second PCK representation (see Fig. 3; Tables 1 and4). Even if she adapted the POE approach in her second PCK representation, other thandemonstrations, her instructional planning still appeared to be teacher centered, providingstudents with limited opportunities for doing science (e.g., making observations). The progressiondifference between the two participants’ representations about the PCK component of KT mightbe associated with a variety of issues or teachers’ knowledge bases, one of which would be thestrength of their teaching efficacy beliefs. Previous research has indicated that high teachingefficacy could facilitate teachers’ ability to develop and implement new teaching strategies (Parkand Oliver 2008). In the current case, Ada reported strong teaching efficacy, and she was able tosuccessfully incorporate her learning about inquiry teaching in the class into her representations ofKT. However, Ela, who reported low teaching efficacy, merely started to indicate some changes inher representations of KT over the course of the semester (see Fig. 3).

The changes in profiles such profiles in the participants’ teaching strategies over the courseof the semester possibly resulted from the features of the particular course (see Fig. 3) in whichthe instructor provided the preservice teachers with firsthand experiences of different methodsof instruction, the types of inquiry (POE, guided inquiry, and open-ended inquiry), argumen-tation, and the use of multiple representations. The instructor modeled such approaches byinvolving the preservice teachers in content-specific activities (none were about the behaviorof gases). Past research (e.g., Windschitl 2004) also recommended involving preserviceteachers in inquiry experiences to develop their conceptions of inquiry and to transform theirdispositions to use it in their own teaching. In addition to the firsthand experiences withinquiry, following each activity, the preservice teachers critically reflected on those experiencesand shared their ideas with the class. Thus, the role of reflection also needs to be acknowledgedin possibly changing the nature of participants’ teaching methods representations. Consistentwith previous research (e.g., De Jong et al. 2005; Nilsson 2008; Park and Oliver 2008), theparticipants’ critical reflection on their experiences with diverse methods of science teachingprobably assisted the process of transformation, particularly in Ada’s views about scienceteaching as reflected in her representations of KT.

Compared to their first PCK representations, in the second ones, both participants improvedtheir KA representations in terms of quantity and diversity of assessment strategies (see Fig. 1;Tables 7 and 11). Due to the incorporation of a variety of assessment strategies into the secondPCK representation, the nature of the participants’ KA representations reflected the features ofboth third- and fourth-level progression criteria for the PCK component of KA (see Tables 1and 4). The participants’ low initial KA may be associated with not having taken courses onclassroom assessment before the course in which this study took place. However, the partic-ipants possibly developed their KA repertoire in the course, in which the preservice teachersdiscussed the purposes and uses of classroom assessment extensively. In addition, the instruc-tor provided the preservice teachers with specific assessment examples and talked about theaim and usefulness of each one. Then, the preservice teachers generated their own sample ofassessments in relation to specific content (not involving the topic of the behavior of gases),

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exemplifying each type of assessment (e.g., specific questions coming from daily life, conceptmaps, etc.). Although the findings of earlier studies showed frequent use of traditional ways ofassessment by teachers (paper-and-pencil tests) (Kaya 2009; Padilla and Van Driel 2011;Rollnick et al. 2008), this study revealed that pertinent instruction on current ways ofassessment in teacher education courses could help to change and expand the preservicescience teachers’ KA.

Implications

Although this study was conducted with a limited number of participants, the study docu-mented the progression in the extent and features of two preservice chemistry teachers’ PCKcomponents. Thus, science teacher educators might wish to consider adapting the instructionalfeatures of the chemistry teaching methods course (e.g., providing firsthand experiences aboutinquiry strategies, reflecting on those experiences, reading and discussing research articles onstudents’ conceptions, and creating samples of assessment products) to promote the develop-ment of preservice science teachers’ PCK.

Second, the instructional value of constructing CoRes needs to be recognized. As anintentionally planned task, creating CoRe documents offers preservice teachers an excellentopportunity for explicitly building their understandings of the nature of PCK components andlearning to consider all possible aspects of PCK in their instructional planning of a given topic.Given the limitation of their inexperience in teaching, as evidenced in the findings of the study,with carefully designed CoRe tasks (e.g., peer collaboration), preservice science teachers couldbegin constructing their initial knowledge base for the components of PCK.

Third, this study also contributes to the methodology for examining PCK by clearlyidentifying, naming, and counting the frequency of possible elements of the PCK componentssuggested by Magnusson et al. (1999) (see Table 3 and Fig. 1). Other researchers mightconsider using the coding scheme of the study in their own research. Moreover, the PCKmodel of Magnusson et al. is a conceptual tool that is not based entirely on empirical data, andLoughran et al. (2004) did not design CoRes with a specific PCK model in mind. In thisrespect, findings from this study indicate the connection between the PCK capturing means(CoRes) and the conceptual model of PCK, as well as identifying what would be the particularelements of each PCK component.

More importantly, Schneider and Plasman (2011) theoretically developed a learning pro-gression trajectory for the components of PCK based on the available research, and thefindings from this study provide empirical evidence for validating their PCK learning pro-gression trajectory routes. Overall, this theoretical framework was useful for evaluating theparticipants’ PCK progression. However, the existing progression criteria for all componentsof PCK, in particular for the KSC component of PCK, can be further portrayed by extendingthe levels of PCK progression criteria, or adding more details to the available progressioncriteria. Such modification would help distinguish between the PCK progression levels, as wellas across the cases, but would require accumulation of extensive data involving all professionalstages of teaching.

This study also had some limitations. First, the data collection relied on CoRe documentsand interviews, but additional data might have been collected by asking participants to keepreflective diaries. Second, the participants were two preservice chemistry teachers who had noclassroom teaching experience, so the extent and the nature of progression observed in thecollected data reflected the participants’ representations of their available PCK repertoire. Thismay not represent the PCK enacted in and shaped by classroom teaching practice, but the

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strong PCK repertoire could facilitate handling of issues they could experience duringinstruction (student learning difficulties) and managing the multiple teaching tasks (lessonplanning, assessing learning etc).

Suggestions for Further Research

Researchers might consider the following issues when designing studies about teachers’ PCKdevelopment. In the current study, the progression in the participants’ PCK repertoire did notderive from classroom experience. Thus, researchers may consider designing longitudinalstudies and seek evidence for long-term maintenance of newly built PCK repertoire. Re-searchers might also explore to what extent the PCK repertoire developed in the particularteaching methods course would help participants to actually teach the topic in the classroom.

Acknowledgments The authors would like to acknowledge the financial support provided by the BogaziciUniversity Scientific Research Projects Fund with the project number 09HD201P.

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