Teaching requires more than transmitting disciplinary knowledge; it involves the integration of multiple forms of professional knowledge to support meaningful learning (Wilson, Shulman, & Richert, 1987). Shulman (1987) conceptualized this specialized knowledge as pedagogical content knowledge (PCK), defined as the blending of content and pedagogy that enables teachers to transform subject matter into forms understandable for students. PCK is widely recognized as a multidimensional and topic-specific construct, encompassing knowledge of student understanding, instructional strategies, curriculum, and assessment (Baumert & Kunter, 2013; Park & Chen, 2012). Among these dimensions, knowledge of student understanding is particularly central to coherent teaching practice.

Contemporary learning theories emphasize that students interpret new ideas through their existing conceptions (Duit & Treagust, 2012), highlighting the importance of teachers’ awareness of students’ alternative conceptions. Research indicates that teachers’ PCK strongly influences instructional quality and student outcomes (Coe et al., 2014). Despite growing interest in PCK, studies focusing on physics teachers remain limited (Chan et al., 2019). Heat and temperature represent a topic in which students frequently hold persistent alternative conceptions (Osborne & Cosgrove, 1983; Jasien & Oberem, 2002). However, little is known about how in-service physics teachers interpret these conceptions, underscoring the need for further research.

In this regard, this study explores in-service physics teachers’ understanding of pervasive student alternative conceptions about heat. In particular, the study focuses on two student alternative conceptions frequently stated in literature: (1) treating heat as a substance-like material which is possessed by objects, and (2) assuming that objects receiving the same amount of heat should have equal internal energy. The study employs a qualitative descriptive design and uses a vignette-based paper-and-pencil form for data collection. The study participants are 90 in-service physics teachers. Vignette-based items were used because they present teachers with authentic classroom situations. Specifically, the vignettes presented physics teachers with snapshots of classroom situations related to teaching heat and temperature, and asked them to identify underlying alternative conceptions or possible incorrect statements that students might produce. The results suggested that physics teachers had difficulty identifying students’ underlying conceptions about heat and internal energy presented in the vignettes. They frequently relied on overly broad generalizations, and in some cases, teachers’ responses suggested that they themselves held the alternative conception of heat as a substance-like entity possessed by objects. Specifically, most physics teachers tend to oversimplify the alternative conception of “substances possess heat” with a more broad student difficulty as “students confuse heat and temperature. Moreover, most of the physics teachers could not infer the alternative conception “objects receiving the same amount of heat should have equal internal energy” and made irrelevant interpretations regarding students’ understanding.

A qualitative descriptive design was used in this study. Ninety in-service physics teachers participated in the study. A vignette-based paper-and-pencil form was used as the main data collection tool. Descriptive statistics were employed to classify teachers’ responses as correct, partially correct, or false/irrelevant. In addition, expert opinions were obtained from two physics education professors regarding the content and clarity of the items. The items specifically targeted the following two alternative conceptions: (1) treating heat as a substance-like material that is possessed by objects, and (2) assuming that objects receiving the same amount of heat should have equal internal energy. Teachers’ responses to the written form were qualitatively analyzed and classified as correct, partially correct, or false/irrelevant using a classification scheme. The classification scheme consisted of exemplary teacher responses for each category and was developed based on analyses of the relevant literature. Interrater reliability was calculated to examine the consistency of the coding process.

Findings of the study indicated that all physics teachers were aware that students hold problematic ideas about heat and temperature and commonly cited examples such as “heat and temperature are the same.” However, most teachers were unable to accurately identify the alternative conception that substances possess heat. When asked to interpret a student statement reflecting this idea, very few teachers explicitly wrote that heat is an energy transferred between objects and cannot be possessed by matter. The remaining teachers tended to focus on secondary aspects of student thinking, such as neglecting mass or attending only to temperature, suggesting that they did not recognize the underlying source of the error. In addition, one physics teacher implicitly demonstrated this alternative conception by claiming that an ocean has more heat than a matchstick, indicating that the teacher himself viewed heat as a property of objects. Teachers’ understanding of alternative conceptions about internal energy also appeared fragile. In one item, teachers were asked to select possible incorrect student responses and explain the reasoning behind them. Although 69% of teachers correctly identified plausible incorrect answers, only 36% were able to articulate the underlying alternative conception. Several teachers merely repeated students’ incorrect statements or offered vague explanations, such as insufficient understanding of heat and temperature, rather than identifying specific misconceptions. In sum, results showed that most teachers recognized that students experience difficulties with heat and temperature, yet their interpretations of students’ alternative conceptions lacked depth. This pattern is consistent with previous studies indicating that teachers often describe student errors in broad terms and seldom explore their conceptual origins. Overall, these findings suggest important gaps in teachers’ ability to diagnose the conceptual roots of students’ thinking about heat and internal energy.

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