Stoichiometry is arguably one of the most difficult concepts for students to grasp in a general chemistry class. Stoichiometry requires students to synthesize their knowledge of moles, balanced equations and proportional reasoning to describe a process that is too small to see. Many times teachers default to an algorithmic approach to solving stoichiometry problems, which may prevent students from gaining a full conceptual understanding of the reaction they are describing.
A description of a quick and easy lesson that is sure to add some spark into your next lesson on stoichiometry.
There is a traditional stoichiometry lab I have done before. It involves adding dilute hydrochloric acid to sodium bicarbonate, boiling off the fluid and then getting the mass of the sodium chloride. Students then can solve the percent yield for the sodium chloride based on the amount of sodium bicarbonate they use. It is not a bad lab. Something about having hot ceramic watch glasses with acid just makes me a bit nervous. I am not sure where I got this new lab, but it has been one that has evolved over the years It is quick, dirty, relatively simple and uses over the counter (mostly) materials.
Are students reflecting on what their calculated values indicate? This question constantly runs through the minds of chemistry teachers across the country. Recently educators have seen shifts in instruction that promote connections to real-world phenomena using conceptual depth in understanding.
We, as teachers, can see that life is sometimes like this and we care enough about our students that we want to try to prepare them for careers and problems that we can’t even imagine….because we believe that good education can empower people to go further and reach higher than they could ever dream….and maybe the journey we will start together begins with a simple question in which the answer may not seem immediately obvious...and that is O.K….
Check out this overview of what a PBL unit has looked like in my classroom. I provide concrete examples and an outline of how I plan a project.
These tenets set PBL (the big once-per-semester projects) apart from day to day activities and inquiry:
PBL poses an authentic problem with multiple solutions.
PBL requires core subject knowledge to propose solutions to a problem to an authentic audience.
Have you read “Making Thinking Visible”? You should. It focuses on making student thinking visible to the teacher. While still learning to use the visible thinking routines, I really feel more conscious of students’ understandings than ever.
Here is a sample activity that I adapted to fit my honor chemistry students’ needs:
In a recent contribution to ChemEd X "Stoichiometry is Easy", the author states that he has "vacillated over the years between using an algorithmic method, and an inquiry-based approach to teaching stoichiometry. " I would like to suggest that there is another approach to mastering stoichiometry and that it should precede the algorithmic one: it is the conceptual approach based on a particle model to represent the species involved in chemical reactions.
This article describes a three week lesson plan for teaching stoichiometry using an algorithmic method. Two labs (one designed as a laboratory quiz) several cooperative learning exercises, student worksheets and guided instructional frameworks (forcing students to develop good habits in writing measures and doing problem solving) are included. The highlight of the lessons is the "chemistry carol" (based on Felix Mendelssohn's music for "Hark! The Herald Angels Sing") in which students recite a five-step algorithm for completing stoichiometry problems.