Determining the formula of hydrated salts is ubiquitous to introductory chemistry curricula as an extension of the mass-to-mole concept and formula determination from mole ratios.  In our introductory lab, we utilize the heating to constant mass method to determine waters of hydrate described by Klingshirn <i>et al.</i> 2008 and spectrophotometric determination described by Barlag and Nyasulu 2011 in consecutive weeks. We then asked students to compare the two methods in their lab reports. We anticipated that mass analysis in the first week would prepare students for using spectrophotometry to determine formulae in the second week. This presentation explores students’ learning in the laboratory and their perceptions of formula determination, gravimetric analysis, spectrophotometry, and the intersection of these concepts.<br/>We analyzed students’ written reports through the lens of meaningful learning, coding for psychomotor, cognitive, and affective categories. Most students expressed confidence in their ability to carry out gravimetric analysis and in their understanding of it. Students consistently reported greater inaccuracy with spectrophotometry and more difficulty conceptualizing the process. Most perceived spectrophotometry as a series of disjointed steps and attributed the inaccuracy of their formulae to the greater number of steps in the experiment. Additionally, some students thought spectrophotometry is an expensive technology and not a useful tool.  These negative attitudes towards spectrophotometry were an unexpected consequence of our scaffolding spectrophotometric determination with gravimetric determination of hydrates. We discuss the implications of these results on curriculum design and student learning in the chemistry laboratory.

Mass is better than light: Analyzing meaningful learning from the perceptions of students in hydrate determination using gravimetric analysis and spectrophotometry in the introductory chemistry laboratory

Where thousands of chemistry professionals meet to share ideas and advance scientific and technical knowledge. Spring 2023 abstracts, posters, and presentations will launch at the end of March.

ACS Spring 2023

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.