Research into students' conceptions of the nature of chemical equilibrium has been underway since the 1960s. A number of studies have identified common alternative conceptions held by students at the secondary and tertiary level (1-5). These studies have made a number of recommendations for those engaged in teaching this difficult topic. Hackling and Garnett (6 ) suggest that greater emphasis on the quantitative aspects of equilibrium may help students gain a clearer picture of the relationship between the concentrations of reactants and products in equilibrium systems. Wheeler and Kass (1) recommend greater differentiation in the range of examples presented to students when discussing Le Châtelier's principle. They also suggest that concentrationversus-time graphs may help students to visualize what is happening when a change is made to a system at equilibrium and that a greater emphasis on a laboratory approach may benefit students by providing concrete situations. Jordaan (7) suggested that when using Le Châtelier's principle to predict the effect of changes to equilibrium mixtures, these disturbances can be viewed as being due to one of only two factors: a change in temperature or a change in concentration of one of the species in the mixture relative to the others.Despite this large body of research and numerous recommendations, the same alternative conceptions are found consistently in our classrooms today (8). It is not enough to simply alert students to the common errors made in examinations and tests because research has shown that their ideas are extremely resistant to change (9). Teachers need to be able to monitor students' understanding of scientific principles so that they may develop their teaching strategies to accommodate their students' current ideas.

The COVID-19 pandemic has fundamentally changed many aspects of our world including the way we teach chemistry. Our emergence from the pandemic provides an opportunity for deep reflection and intentional action about what we teach, and why, as well as how we facilitate student learning. Focusing on foundational postsecondary chemistry courses, we suggest that we cannot simply return to "normal" practice but need to design and implement new ways of teaching and learning based on fundamentally reimagined learning outcomes for our courses that equip students for life after the rupture they have experienced. We recommend that new learning objectives should be guided both by an analysis of existing global challenges and the types of understandings and practices needed to confront them, and by research-based frameworks that provide insights into important areas of knowledge, skill, and attitude development. We identify a core set of competencies along three major dimensions (crosscutting reasoning, core understandings, and fundamental practices) that we believe should guide the design, implementation, and evaluation of chemistry curricula, teaching practices, and assessments in foundational courses for science and engineering majors. The proposed framework adopts systems thinking as the underpinning form of reasoning that students should develop to analyze and comprehend complex global systems and phenomena.

As a result of research into students' understandings, we have lists of student misconceptions, often accompanied by bland statements about preventative or curative actions. We have an enhanced knowledge of the conditions for effective learning, but little guidance as to how this knowledge might be applied to the teaching of particular topics. Research has not had the impact on science teaching that we might have hoped. Furthermore, science education research seems to be looking for direction. Much of chemical education research has used subject matter simply as a vehicle to develop domain-independent pedagogical theory. Commenting on the criteria used for evaluation of teaching, Shulman (1986) asked "Where did the subject matter go?" Perhaps a productive path for us to travel is what Shulman has labelled pedagogical content knowledge (PCK): knowledge about teaching and learning that takes into account the particular learning demands of the subject matter. Science teaching is afflicted with 'professional amnesia' in the sense that the understandings that drive the strategies of competent teachers are seldom recorded, so new teachers grow largely through experience. The chemical education enterprise is crying out for 'applied research' that probes and documents the topic-specific PCK of respected teachers. Some examples of research findings that support the claims are presented. [Chem. Educ. Res.

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