Adapting Meaningful Learning Strategies to Teach Liquid–Liquid Extractions

Abstract

Although teaching laboratories offer students the opportunity to act and think like chemists, in many cases students simply follow written procedures to generate predetermined outcomes. In recent years, there has been a movement toward inquiry-, problem-, and discovery-based learning. In a similar vein, the first-semester introductory organic chemistry laboratory curriculum at the University of Michigan was recently overhauled, informed by the strategies of meaningful learning. The new course consists of three interconnected modules, and we present herein the second module, which focuses on liquid−liquid extraction (LLE). In the first week, students learn how to perform LLE by designing their own separation of a dye mixture, gaining an understanding of how the solution pH impacts molecular structure and solubility. In the second week, they practice using LLE by designing a separation method to remove a pollutant from water, and then, in the third week, they apply LLE to isolate a reaction product. We assessed student learning through a writing assignment at the end of the three-week module. We also assessed how the overall course affects student understanding of LLE concepts and their confidence in the lab. Our findings suggest that this learn, practice, apply approach for teaching LLE leads to modest learning gains and increased confidence.

Visually Tracking Acid–Base Extractions Using Colorful Compounds

“…This enables students to visually follow the solubility change and partition between the two immiscible layers after shaking the separatory funnel. Dyes have been widely used to illustrate a variety of chemical properties and concepts such as solubility, acid–base chemistry, chromatographic separation, distillation, and LLE. ,,,− ,− In previous work describing laboratory experiments on LLE, authors employed these colored compounds as a visual aid to help students determine the partitioning of molecules into different layers as a function of pH. Sudan Blue and Congo Red, or Nile Blue and 2,6-dichloroindophenol, are among the most common dyes utilized for this purpose.…”

“…Depending on the pH of the aqueous solution and the p K a of different functional groups, molecules will exist in their ionic or nonionic states and dissolve better in either the aqueous or organic layer (Figure ). Although there have been several laboratory experiments designed to teach students this technique, − beginning students of organic chemistry continue to struggle to connect the concepts involved in acid–base extraction . Therefore, additional methods such as demonstrations should be implemented to increase and support students’ learning.…”

“…Although there have been several laboratory experiments designed to teach students this technique, 1−7 beginning students of organic chemistry continue to struggle to connect the concepts involved in acid−base extraction. 8 Therefore, additional methods such as demonstrations should be implemented to increase and support students' learning. Classroom demonstrations are a valuable tool that instructors can take advantage of in order to help students be more involved with chemical concepts and develop a connection between them.…”

Separation of Food Colorings via Liquid–Liquid Extraction: An At-Home Organic Chemistry Lab

“…While the procedure itself is of moderate complexity for the novice organic chemistry student, the underlying concepts and their interconnectedness provide a more nuanced opportunity to probe student understanding of solubility/miscibility, density, and acid–base chemistry. In the classic liquid–liquid extraction separation procedure, two components (or more) are separated by using base to selectively deprotonate one component rendering it soluble in water while the other component remains soluble in the organic phase. − After separation of the phases, the aqueous phase is then acidified, reprotonating the water-soluble conjugate base to yield an insoluble material that can be removed by filtration or by extraction with an organic phase. Alternately, a component that readily protonates may be extracted into an aqueous phase using acid, and then base to return the component to the organic phase.…”

Uso combinado de software libre y de técnicas analíticas para facilitar la comprensión de los diagramas de equilibrio químico

“…No obstante, Selmer et al también concluyó que la utilización de herramientas informáticas no puede sustituir el trabajo práctico y activo por parte de los estudiantes en el laboratorio de química(Selmer et al, 2007). En el caso de las prácticas de laboratorio químico, el uso de técnicas colorimétricas en las cuales se percibe un cambio en la materia de forma visual constituye un recurso valioso para aumentar el aprendizaje cognitivo de los alumnos y su motivación(Ibanez et al, 2011;Wu et al, 2019). Existen múltiples ejemplos de dichas prácticas.…”