Using AACT Resources to Teach Stoichiometry
By Kim Duncan on January 16, 2018
As chemistry teachers continue to plan activities for their students, AACT will highlight resources from our high school library that help to reinforce topics in different units throughout the school year.
In our last news post we looked at resources that focused on teaching chemical equations. Now we are moving on to lessons and activities that can be used to support a unit plan for teaching stoichiometry. This includes the following topics: setting up stoichiometry calculations, determining limiting and excess reactants, and calculating percent yield.
Start off the unit with a quick review of the mole concept with the lab, It’s Mole Time. Your students will collect lab measurements to help them determine the number of moles of chalk used to write their name, the moles of sucrose ingested while chewing gum, and the moles of alcohol evaporated when using hand sanitizer. This lab will help your students remember how to calculate molar mass, calculate the number of moles of a compound when given a mass, and calculate the number of molecules of a compound when given a mass.
The lesson plan, How to do Stoichiometry Problems, provides your students with a template for performing stoichiometry problems and offers instructions for performing mole-to-mole, mole-to-mass, and mass-to-mass stoichiometry problems. They can then practice the method with the worksheet that is included with this resource. An answer key is also available for download.
If your students are struggling with the concept of stoichiometry you might try the BCA (Before, Change, After) Table set up described in a recent webinar, A Visual and Intuitive Approach to Stoichiometry. The process outlined in this presentation emphasizes proportional reasoning and explicitly connects the calculations to the particulate nature of matter. You might also consider reading the article Stoichiometry Set-up Method or A Map to Solving Limiting Reactant Problems from our online periodical, Chemistry Solutions.
Introduce the topic of limiting and excess reactants using our Limiting reactant Animation, which allows students to visualize what happens in a limiting reactant problem on the particulate level. A number of limiting reactant scenarios are animated, including a simple example of how to build a bike to introduce the concept of a limiting reactant. Conservation of mass is also demonstrated by calculating masses from given mole quantities of the reactants and products.
Next, use our demonstration, Understanding Limiting Reactants, to engage your students. They will observe a series of reactions between acetic acid and varying amounts of baking soda used to inflate several balloons. They then analyze the quantities of reactants used as well as the amount of gas produced in order to understand the concept of limiting reactants. A video of the demonstration is included with the resource.
Use the lesson plan, Map to Solving Limiting Reactant Problems, to introduce the calculations needed for problem solving. The Limiting Reactant Map is very valuable for students who struggle to complete multi-step calculations and dimensional analysis. The student handouts can be used as guides when introducing limiting and excess reactant stoichiometry problems. For more information about the map, read an article about it in the November 2016 issue of Chemistry Solutions.
Follow up with the hands on Limiting Reactant lab. In this lab activity, students react varying amounts copper (II) chloride with aluminum foil to determine the limiting and excess reactants. They then use the mass of one of the products to calculate the percent yield of the reaction. Additionally, you can use the Baking Soda Stoichiometry lab to assess student understanding of the concepts of stoichiometry. In this lab, students decompose baking soda by heating it in a crucible and then use stoichiometry to determine the proper decomposition chemical equation.
We hope that these activities can help you to reinforce several of the topics covered in a stoichiometry unit. Most of these lessons were made possible by great teachers who shared their own resources. We need your help to keep the collection growing. Do you have a great demonstration, activity, or lesson related to this topic that you would like to share with the community? Please send it along for consideration.