A few months ago I was searching the internet, looking for a better way to teach stoichiometry to my pre-AP chemistry students. While my methods of dimensional analysis “got the job done” for most students, I would still always lose students and many lacked true understanding of what was happening in the reaction. I wanted to try something new that would promote a better chemical understanding. In my search for this elusive stoichiometry method, I came across Dena Leggett’s ChemEd X blog post entitled “Doc Save Everyone”, as well as other posts about BCA tables from Lauren Stewart, Lowell Thomson, and Larry Dukerich.
ChemEd X recently made a Call for Contributions soliciting input regarding the big ideas being put forth by organizations like AP. The first thing that came to mind was a lab I modified that is centered around making connections between topics. Admittedly, this lab is not a "big idea" per se. Rather, it's the big idea that students should be able to make connections between topics we study to solve problems. So in this blog post, I would like to share a lab activity that relies on these connections - between stoichiometry, esterification, equilibrium, kinetics, titrations and uncertainty of calculations. I will also share the resources I have created to support my students through the process of working through these calculations.
Three class periods
Day 1: setup of equilibrium mixture; roughly 30 minutes
Day 2: titration of equilibrium mixture (approximately 1 week after Day 1); roughly 60 minutes
Day 3: calculations; variable time required - typically 30-90 minutes depending on the student group
I recently stumbled across a blog about the use of BCA (Before Change After) tables for stoichiometry written by Lowell Thomson. I was thrilled to discover ChemEd Xchange! I wanted to share my journey, spurred on by my students, into the extensive use of the BCA approach in AP and