Developing a\nThreshold Concept Assessment Rubric:\nUsing the Johnstone’s Triangle Framework for Understanding\nIntermolecular Forces

In undergraduate science education,\nlaboratory courses\nstand as\nessential cornerstones of experiential learning. Chemistry laboratory\ncourses offer students unique hands-on experiences that bridge the\ngap between theoretical knowledge and practical application. The journey\nthrough the undergraduate chemistry curriculum is paved with a series\nof conceptual gateways known as threshold concepts that can dramatically\nshape a student’s understanding and success. We identified\nthe idea of intermolecular forces (IMFs) as a threshold concept to\nstudents’ ability to link molecular structures, properties,\nand applications to real-world problems such as extraction and separation\nof compounds. The development of course-specific pedagogical tools\ncan provide students with the scaffolding necessary for the transition\nfrom novice to expert-level disciplinary comprehension. This work\npresents the development process of a Threshold Concept Assessment\nRubric (TCAR) based on Johnstone’s triangle framework and discusses\nits application for evaluating students’ progress in overcoming\na threshold concept. The rubric is used in a 200-level multilayer\nlaboratory course that is intentionally designed with intermolecular\nforces as the central theme. We analyze the role and structure of\ndifferent questions to provide a holistic assessment of students’\nlearning processes using sample assignments. Furthermore, we demonstrate\nhow insights from statistical analyses can highlight areas in which\nstudents struggle to gain expert or exemplary-level understanding\nof IMFs. This rubric development approach can be applied to other\nthreshold concepts.