Exploring Le Châtelier’s Principle: A Sample Lesson

Exploring Le Châtelier’s Principle: A Sample Lesson

Exploring Le Châtelier’s Principle: A Sample Lesson

One of my professional goals for the 2016-2017 school year was to incorporate more discovery-oriented labs into the curriculum for my 10th grade introductory chemistry course. While “cookie-cutter labs” may reinforce concepts that have already been taught, “discovery labs” allow students to practice scientific thinking by experimenting with topics they are still unfamiliar with. When students collect data, recognize patterns, and draw conclusions for themselves, the principles applied in the lab are more likely to stick with them in a meaningful way. My first attempt at designing such a lab was an exploration of Le Châtelier’s Principle.

Objective

The purpose of this activity was to investigate an equilibrium system and to gain a deeper understanding of equilibrium and Le Châtelier’s Principle. In this short experiment, deliberate stresses were added to the system to cause the equilibrium to shift and the color to change. The reaction, which produces cobalt chloride and water, is endothermic and reversible and can therefore be manipulated by changes in temperature and concentration.

Description

In the lab, students were given two test tubes with a few milliliters of 0.1 M CoCl2 solution. They began by making initial observations (color, temperature) and then placing the reaction tube in both a hot water bath and ice water bath for further observations. After that, water and HCl were separately added to the second reaction test tubes, and again, students observed and recorded any changes.

Once all students completed the experiment, we went over our results and explained them as a class through a lesson in the principle we’d just seen at work.

Instructional Artifacts

Click the link below to open and view the class notes.

Equilibrium Class Notes


The first few slides were presented before the lab to introduce the concept of equilibrium, and the rest were presented immediately after the lab in order to reiterate what we’d observed.

Click the link below to open and view the full assignment handout.

Le Chatelier Lab Handout

Student Work Artifacts

Click the link below to open and view a student’s completed worksheet.

Completed Student Handout

Students Nolan and Ryan pictured adding hydrochloric acid to their reaction in order to disturb its equilibrium.

 

Students Elliot and Anna pictured adding heat (via hot water bath) to their reaction in order to disturb its equilibrium.

Reflections

Overall, this lab successfully met the objectives of our lesson. Students were able to collect data, recognize patterns, and think scientifically in drawing conclusions for themselves. Because of that, I believe that the principles applied in the lab are more likely to stick with them in a meaningful way.

Photo Credit: Jay Jr. Flickr via Compfight cc

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