Professional knowledge is an important source of science teachers' actions in the classroom (e.g., personal professional content knowledge [pedagogical content knowledge, PCK] is the source of enacted PCK in the refined consensus model [RCM] for PCK). However, the evidence for this claim is ambiguous at best. This study applied a cross‐lagged panel design to examine the relationship between professional knowledge and actions in one particular instructional situation: explaining physics. Pre‐ and post a field experience (one semester), 47 preservice physics teachers from four different universities were tested for their content knowledge (CK), PCK, pedagogical knowledge (PK), and action‐related skills in explaining physics. The study showed that joint professional knowledge (the weighted sum of CK, PCK, and PK scores) at the beginning of the field experience impacted the development of explaining skills during the field experience (β= .38**). We interpret this as a particular relationship between professional knowledge and science teachers' action‐related skills (enacted PCK): professional knowledge is necessary for the development of explaining skills. That is evidence that personal PCK affects enacted PCK. In addition, field experiences are often supposed to bridge the theory‐practice gap by transforming professional knowledge into instructional practice. Our results suggest that for field experiences to be effective, preservice teachers should start with profound professional knowledge.

Instructional explanations have sometimes been described as an ineffective way to teach science, representing a transmissive view of learning. However, science teachers frequently provide instructional explanations, and students also offer them in cooperative learning. Contrary to the transmissive view regarding explanation, studies suggest that instructional explanations might be successful if they are based on an interaction between explainers and explainees, including the diagnosis of understanding and adaptation to the explainee’s needs. The present article has three goals: (1) It will propose a framework for potentially effective instructional explanations, presenting five core ideas of what constitutes effective instructional explanations and two concerning how they should be implemented into science teaching. (2) To justify the framework, the article will review studies on the effectiveness of instructional explanations. It will identify factors that have been researched for their impact on the effectiveness of instructional explanations and discuss them for their applicability to science teaching. (3) This article will connect the research on instructional explanations with the idea of basic dimensions of instructional quality in science. It will discuss the core ideas as particular expressions of the basic dimensions of instructional quality, specifically ‘cognitive activation’ and ‘constructive support’.

Some of the online explainer videos for physics present misconceptions as scientifically correct explanations. Even so, some of these videos achieve good ratings on online platforms. A possible reason is that explainer videos with misconceptions foster an “illusion of understanding”—the mistaken belief that a topic has been understood. Misconceptions close to everyday experiences might appear more attractive than scientifically correct explanations. This experimental study (N = 149 physics learners with a low prior knowledge on average, sample of convenience) was conducted to explore this effect. Two explainer videos were developed to be comparable in terms of comprehensibility and duration. The explanatory approach was the only difference between the two videos. While the experimental group watched a video introducing the concept of force using misconceptions, the control group watched a scientifically correct video. Learners from the experimental group developed an equal belief of understanding, but more misconceptions and fewer scientifically correct conceptions than those from the control group. We argue that this illusion of understanding might become problematic (a) in physics instruction because students who have watched a misleading video might regard further teaching in school as irrelevant, and (b) learners might tend to rate videos including misconceptions better on an online platform like YouTube. Future studies should examine these two possible consequences.