Subject: Stoichiometry Skel1etons

In teaching stoichiometry, I have noticed that about a third of my students have considerable difficulty understanding the thought processes required to successfully perform the necessary calculations. Some of these students just don't have a strong math background. But with further observation I noticed that the remainder of this group of students appeared to be visual learners. In an effort to help them fully grasp the concepts involved in performing stoichiometry calculations, I developed a tool for my visual learners to use. I have called them "skeletons" because they provide a framework for the student to build on.

I began designing the skeletons while I was student teaching. They have remained in this form for a while now (I think the revisions are complete). I only use them with those students who seem to have trouble performing stoichiometry calculations the 'normal' way. While using the skeletons, each portion of a stoichiometry calculation is performed separately, with that answer being used in the next calculation until a final answer is reached.

The skeleton pictured below (the mass skeleton) would be used for mole-mass, mass-mole, or mass-mass calculations. In this specific case I have set it up for a mass-mole problem. The red arrow indicates the path taken to perform this calculation, which is actually a process involving two calculations - mass of Mg to moles of Mg, then moles Mg to moles MgO. These separate calculations are, at this point, easy for the students to perform. I inform them that they are only allowed to travel vertically within a column, and they can only go horizontally to another column along the "mole" row.

I always teach stoichiometry the 'normal' way to begin. The next day, I show all of my students how to perform several of our homework problems with this new tool and tell them that they have the option to use the method of their choice. Most students don't like the skeletons, but a few know immediately that they need it to succeed.

The students are given the blank worksheets. They must read a problem and decide what is being asked of them. They learn to fill in the proper blanks and work a series of calculations that takes them from their starting box to the ending box (which is their final answer). Many of the students that end up using the skeletons say they are able to really understand what is going on with stoichiometry. A few of them are very bright students who just need to have a picture of the process they are working, and this meets that need.

I hope these skeletons prove useful in helping you reach a few more students, and that you enjoy using them as much as I do. Describing the use of this tool is sometimes difficult without being able to demonstrate. If you have any questions, comments or suggestions about them please feel free to contact me.

Michael Geyer (m_geyer@thecatalyst.org)
Deer Park High School, Cincinnati, OH