Using AACT Resources to Teach Equilibrium
By Kim Duncan on April 24, 2018
As chemistry teachers 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 focused on resources for teaching thermochemistry and thermodynamics. Now we are moving on to lessons and activities that can be used to support a unit plan for teaching equilibrium. This includes establishing equilibrium, equilibrium constants, the reaction quotient, and Le Châtelier’s Principle.
Start with an introduction by having your students collect data that models chemical equilibrium with the Equilibrium Introduction classroom resource. By the end of this activity, students should be able to recognize when equilibrium is reached and that at equilibrium the rate of the forward and reverse reactions are equal. They will also understand that equilibrium can be approached from many starting points and from both directions. Additionally, they will learn that the concentration of products and reactants remain constant at equilibrium. This lesson is based on the article Equilibrium: A Teaching/Learning Activity by Audrey H. Wilson from the Journal of Chemical Education, Vol. 75, No. 9, September 1998.
Then use the lesson plan, Discovering Equilibrium, to allow your students to manipulate sets of given conditions to discover what equilibrium is, and how equilibrium is established from different starting conditions. By the end of this lesson, students will be able to understand the concept of dynamic equilibrium, the meaning of K, compare K to Q in order to predict which direction a system must proceed to reach equilibrium, perform calculations involving K, and use a graph to recognize the establishment of chemical equilibrium. Your AP Chemistry students can refer back to this activity as the foundation framework for the rest of Essential Knowledge 6.A, 6.B.1 and 6.B.2.
Another hands-on activity to help students visualize equilibrium is the Dynamic Equilibrium Simulation. In this activity, students explore equilibrium using paper clips to mimic a chemical reaction. By the end of this activity, students will be able to better understand what it means for a system to reach equilibrium.
Help your students to further visualize equilibrium with our Equilibrium Animation which shows the dissociation of water and its interaction with a piece of chalk (calcium carbonate) at the particle level.
Use our Le Châtelier’s Principle demonstration to introduce this topic and allow your students to witness how different stresses cause the equilibrium of a system to shift. This will allow students to better understand how equilibrium shifts and to recognize that a change in concentration does not change K but a change in temperature does. It will also help them understand how to use Q to see if reaction conditions have reached equilibrium.
Follow up with the new simulation, Predicting Shifts in Equilibrium: Q vs K, which allows students to take a 15 question quiz to help them reinforce their understanding of shifts in equilibrium through the comparison of Q and K. Each quiz question has two parts. The first part requires the student to calculate the value of the reaction quotient, Q. The second portion of the question requires students to compare the value of Q to the equilibrium constant, K, and to predict which way the reaction will shift to reach equilibrium. The simulation includes five different reactions which each have three scenarios: Q > K, Q = K, and Q < K.
Then use the Le Châtelier’s Soda lab to allow your students to observe how the equilibrium of a chemical reaction is affected when a change in pressure, temperature, and concentration is applied to the system. By the end of this lab, students should be able to determine how changing pressure, temperature, or concentration can affect the equilibrium shift of a chemical reaction. This resource includes alignment with AP Chemistry Curriculum Framework and NGSS.Finally, use the demonstration, Milk of Magnesia Magic, to connect the concept of equilibrium to indicators, acid/base chemistry, limiting reactants, and reaction rates. In this demonstration, students observe a color change in a milk of magnesia solution as vinegar is added. By the end of this demonstration, students should be able to understand that a chemical change is taking place, recognize that an indicator causes a color change, realize that an acid base reaction occurs, identify the limiting and excess reactants during the reaction, and apply Le Châtelier’s principle to explain the color change. This demonstration also includes alignment with AP Chemistry Curriculum Framework.