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Research in Organic Chemistry education has revealed students' challenges in mechanistic reasoning. When solving mechanistic tasks, students tend to focus on explicit surface features, apply fragmented conceptual knowledge, rely on rote-memorization and, hence, often struggle to build well-grounded causal explanations. When taking a resource perspective as a lens, students' difficulties may arise from either an unproductive or a missing activation of cognitive resources. Instructors' explanations and their guidance in teaching situations could serve as a lynchpin to activate these resources. Compared to students' challenges in building mechanistic explanations in Organic Chemistry, little is known about instructors' explanations when solving mechanistic tasks and how they shape their targeted explanations for students in terms of the construction and embedding of cause-effect rationales. This qualitative study aims to contribute to the growing research on mechanistic reasoning by exploring instructors' explanatory approaches. Therefore, we made use of the framing construct, intended to trigger certain frames with explicit instruction. Ten Organic Chemistry instructors (university professors and lecturers) were asked to solve case comparison tasks while being prompted in two scenarios: an expert frame and a teaching frame. Our analysis shows that there is a shift from instructors' mechanistic explanations in the expert frame towards more elaborated explanations in the teaching frame. In the teaching frame, contrary to what might be expected, complete cause-effect relationships were not always established and instructors differed in how they shaped their explanations. Additional explanatory elements were identified in both frames and their shift in use is discussed. Comparing approaches between frames sheds light on how instructors communicate mechanistic explanations and allows us to derive implications for teaching Organic Chemistry.

In this eye-tracking experiment, we compared instructional videos with static signals, dynamic signals and no signaling in a within-subject design. We tracked eye movements from 28 undergraduate chemistry students while they were watching instructional videos about reaction mechanisms in the different signaling conditions. Further, we assessed students' cognitive load, as well as retention performance. We employed a Latin square design to control for sequencing and content effects of the instructional videos. Our data showed that dynamic signals helped students to better focus their attention to the relevant features of the representations virtually across the entire time of the video presentation. Furthermore, dynamic signals increased retention performance while they decreased extraneous cognitive load. Overall, our findings show the crucial role of pairing the signaling principle with the temporal contiguity principle in instructional videos to help students navigate through complex symbolic representations and improve their learning success.

Research in science education agrees that one of the key challenges of learners in the discipline is certainly connecting domain-specific representations to the underlying concepts. One way of supporting students to make applicable connections is using purposefully designed highlighting techniques in multimedia instructions. In order to examine the influence of different highlighting techniques on learning, 171 chemistry undergraduate students were provided with tutorial videos either with static, dynamic or without highlighting. The results show that students viewing tutorial videos with dynamic highlighting gave more sophisticated answers in direct retention tasks. Furthermore, results indicate that low prior knowledge is compensated by both static and dynamic highlighting techniques. This finding is supported by causal mediation analysis, which indicates that the effect of prior knowledge is moderated by the different highlighting techniques. Besides student learning outcomes, students' evaluation of the different tutorial videos shows significant benefits of the highlighted instructions in terms of perceiving higher comprehensibility. The results support the use of appropriate highlighting techniques in instructional formats to foster a stronger link between conceptual knowledge and representations.

Reaction mechanisms commonly used in organic chemistry are a great challenge for students in terms of understanding the representation and inferring the appropriate chemical concepts. In order to support the process of identifying and selecting chemical concepts, purposefully designed case comparisons are widely used. While these tasks place great demands on students' problem-solving capabilities, it is unknown how learners distribute their attention on the complex and information-rich representations. Understanding students' visual decoding behavior when dealing with case comparisons could provide valuable insights into supporting students' problem-solving process. In this exploratory study, we employed eye-tracking methodology to observe beginner and advanced undergraduate chemistry students when working through case-comparison tasks. By establishing a novel eye-tracking measure, the fixation/transition ratio, distinct viewing behaviors could be observed. Results indicate significant differences between both status groups. Advanced students are overall faster in their decision-making and transition more frequently between the representations, indicating a higher selectivity for chemically relevant entities. Further, the results show a significant impact of the visual complexity of a representation on students' visual behavior. Implications for designing case comparisons and supporting students' decoding process are discussed.