Summary

The AACT high school classroom resource library and multimedia collection has everything you need to put together a unit plan for your classroom: lessons, activities, labs, projects, videos, simulations, and animations. We constructed a unit plan using AACT resources that is designed to teach equilibrium to your students.

Grade Level

High School

Objectives

By the end of this unit, students should be able to

• Recognize when equilibrium is reached.
• Recognize that at equilibrium the rate of the forward and reverse reactions are equal.
• Recognize that the concentration of products and reactants remain constant at equilibrium.
• Understand that equilibrium can be approached from many starting points and both directions.
• Understand the concept of dynamic equilibrium.
• Understand the meaning of K, and what its value signifies.
• Know how to use Q to see if reaction conditions have reached equilibrium.
• Compare K to Q in order to predict which direction a system must proceed to reach equilibrium.
• Perform calculations involving K and manipulations of K.
• Use a graph to recognize the establishment of chemical equilibrium.
• Understand how equilibrium shifts.
• Predict what will happen if a system at equilibrium is disturbed.
• Recognize that a change in concentration does not change K but a change in temperature does.
• Qualitatively assess how a stress on a system changes Q.
• Qualitatively compare Q vs K to determine how a system will respond to a stress.
• When appropriate, use Le Chatelier’s principle to explain how a system will respond to a stress.
• Understand that a chemical change is taking place.
• Recognize that an indicator causes the color change.
• Realize that an acid base reaction is taking place.
• Recognize the limiting and excess reactants during the reaction.
• Determine how changing pressure can affect the equilibrium shift of a chemical reaction.
• Analyze how changing temperature can affect the equilibrium shift of a chemical reaction.
• Interpret how changing concentration can affect the equilibrium shift of a chemical reaction.
• Explain the molecular changes that occur when an equilibrium system is disturbed
• Relate the symbolic representation to the particle representation for changes in an equilibrium system.

Chemistry Topics

This unit supports students’ understanding of

• Chemical Equilibrium
• Establishing Equilibrium
• Reversible Reactions
• Equilibrium Constant (K)
• Reaction Quotient (Q)
• ICE tables
• Le Chatelier’s Principle
• Indicators
• Acid/base neutralization reaction
• Limiting Reactant
• Reaction Rates
• Pressure
• Temperature
• Concentration

Time

Teacher Preparation: See individual resources.

Lesson: 8-12 class periods, depending on class level.

Materials

• Refer to the materials list given with each individual activity.

Safety

• Refer to the safety instructions given with each individual activity.

Teacher Notes

• Some of the resources in this unit plan were written for AP Chemistry. However, most can easily be adapted for an on-level or honors class.
• The activities shown below are listed in the order that they should be completed.
• The teacher notes, student handouts, and additional materials can be accessed on the page for each individual activity.
• Please note that most of these resources are AACT member benefits.

Classroom Resources

• Start the unit 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. This lesson includes alignment with the AP Chemistry Big Ideas.
• 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. This lesson includes alignment with the AP Chemistry Big Ideas.
• Next, follow-up with the lesson plan,Q, K, and Le Châtelier to provide students with practice applying Q vs K as an explanatory tool in a simulation and demonstration. In both activities, students will consider how a change in concentration of one species subsequently effects all the species as equilibrium is reestablished. This lesson plan includes alignment with the AP Chemistry Big Ideas and uses two other AACT classroom resources:
  • The AACT simulation, Predicting Shifts in Equilibrium: Q vs K 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.
  • Part two of the lesson plan uses 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 lesson includes alignment with the AP Chemistry Big Ideas.
• Use the Le Châtelier’s Soda lab next 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 lesson includes alignment with the AP Chemistry Big Ideas and NGSS performance expectations.
• Students often form misconceptions about equilibrium and what happens at the particle level during the process. Use the activity, Equilibriumin a Beaker to help them model equilibrium reactions using plastic chips to represent atoms. The goal of the lesson is to connect the symbolic model of an equilibrium reaction to its particle model. Read more about this activity in an article from the November 2018 issue of Chemistry Solutions. This lesson includes alignment with the AP Chemistry Big Ideas and NGSS performance expectations.
• If you teach equilibrium after teaching kinetics and thermochemistry, the following resources can be used to help students make important connections between the topics.
  • Students understand the connections between the equilibrium constant (K) and the reaction quotient (Q) as well as how they determine the favorability of a reaction with the lesson plan, Making Connections in Kinetics, Equilibrium, and Thermochemistry. Additionally students will be able to determine if a reaction is kinetically favored or thermodynamically favored. This lesson includes alignment with the AP Chemistry Big Ideas.
  • In the Kinetics and Equilibrium lab, students investigate the reaction of the hydrogen sulfite ion (HSO₃^-) and the iodate ion (IO₃^-) to determine the effect that changing concentration and temperature has on the reaction rate. This lesson includes alignment with the AP Chemistry Big Ideas and NGSS performance expectations.