Buffers in Context: Baby Wipes As a Buffer System

Abstract

An understanding of buffers is important in a variety of chemistry subdisciplines, with relevant applications to the life sciences and health profession-related fields. Here, we describe the development and implementation of a lab that involves creating a buffer solution using baby wipes and deionized water. The goal of this lab was to emphasize a conceptual understanding of buffers within a context that would be interesting and relevant for students in a nonmajors general chemistry course, a population composed primarily of health/human science and agricultural science majors. The prelaboratory assignment and postlaboratory discussion focus on modeling by making connections between laboratory observations and the particulate-level view of a buffer. Overall, the experiment seeks to prompt students to think beyond the macroscopic view that buffers resist changes in pH and guide students toward thinking mechanistically about how a buffer resists changes in pH, a process that depends largely on the buffer components and their respective amounts.

Student Conceptions of pH Buffers Using a Resource Framework: Layered Resource Graphs and Levels of Resource Activation

“…2−7 A few of these studies included assessments of student learning. 4−7 For example, effective student understanding was reported by Barreto et al 4 after intervention with "Khan style" videos in a biochemistry course and by Rodriguez et al 5 after an experiment using baby wipes to prepare a buffer. Another study showed an increase in correct buffer answers after a guided inquiry laboratory involving discussion of pooled class data.…”

“…Most published reports concerning learning of buffer concepts are laboratory experiment or classroom innovations. − A few of these studies included assessments of student learning. − For example, effective student understanding was reported by Barreto et al after intervention with “Khan style” videos in a biochemistry course and by Rodriguez et al . after an experiment using baby wipes to prepare a buffer.…”

Measurement of the Speciation Diagram of Thymol Blue Using Spectrophotometry

“…17 preparation of solutions with fixed pH values, students also prepared several buffer solutions, which gave them an opportunity to master this important skill. 18,19 This laboratory experiment helps students integrate concepts from acid/base equilibria, acid/base buffers, and spectrophotometry to experimentally visualize the regions where different forms of a diprotic acid are predominant.…”

“…Specifically, students used the absorbance spectra of 15 solutions, each at integer pH values in the pH range 0–14 to determine the relative abundance of different protonation forms of thymol blue. Because this experiment requires the preparation of solutions with fixed pH values, students also prepared several buffer solutions, which gave them an opportunity to master this important skill. , This laboratory experiment helps students integrate concepts from acid/base equilibria, acid/base buffers, and spectrophotometry to experimentally visualize the regions where different forms of a diprotic acid are predominant.…”

Making Acids and Bases MORE Basic: Supporting Students’ Conceptualization of Acid–Base Chemistry through a Laboratory Exercise That Connects Molecular-Level Representations to Symbolic Representations and Experimentally Derived Evidence

“…Several recent works have addressed more advanced topics. ,− Laboratories have been developed that describe phenomena, calculations, or familiar products . Our work is unique in its focus on p K a conceptualization and use of experimental evidence to support molecular-level representations.…”