Chemistry · 10th Grade

Active learning ideas

Chemical Equilibrium and Equilibrium Constant (Keq)

Active learning works for chemical equilibrium because students must confront their misconceptions directly. Writing Keq expressions and comparing systems with different Keq values helps them move beyond the idea that equilibrium means equal concentrations. Engaging with particle-level diagrams and calculations makes the abstract concept of dynamic equilibrium concrete and measurable.

• Common Core State Standards
• STD.HS-PS1-6
• STD.CCSS.ELA-LITERACY.RST.9-10.9

• 20–40 min
• Pairs → Whole Class
• 3 activities

Activity 01

• Think-Pair-Share
• 20 min · Pairs

Think-Pair-Share: Writing Keq Expressions

Give pairs three different balanced reversible reactions. Each student writes the Keq expression independently, then compares with their partner. Pairs must resolve any differences by working through the rules together before the class debrief identifies the most common errors.

Explain what the equilibrium constant (Keq) represents.

Facilitation Tip

During the Think-Pair-Share on writing Keq expressions, circulate and listen for students who mistakenly include pure solids or liquids, then ask them to revisit the rule with a peer.

What to look for

Present students with 3-4 different reversible reactions. Ask them to write the equilibrium expression for each. Then, provide Keq values for two reactions and ask students to predict which reaction favors products more strongly.

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

Activity 02

• Gallery Walk
• 25 min · Small Groups

Gallery Walk: Large vs. Small Keq

Post six reaction scenarios around the room with a Keq value given. Students rotate and write whether products or reactants are favored and what the reaction mixture would predominantly contain at equilibrium. A class discussion connects these predictions to real-world examples like the Haber process.

Construct an equilibrium expression for a given reversible reaction.

Facilitation Tip

For the Gallery Walk, place one diagram with a large Keq and one with a small Keq side by side, so students immediately see the difference in particle distributions.

What to look for

Provide students with a balanced chemical equation. Ask them to write the equilibrium expression. On the back, have them explain in one sentence what a Keq value of 1.5 x 10^-5 means for this reaction.

• Understand
• Apply
• Analyze
• Create
• Relationship Skills
• Social Awareness

Activity 03

• Jigsaw
• 40 min · Small Groups

Jigsaw: Keq Calculation

Groups each receive a different set of equilibrium concentration data. Each group calculates Keq and then prepares a two-minute explanation of their process. Groups then mix so each new group contains at least one expert from each original group, and they compare their Keq values and reasoning.

Analyze the significance of Keq values (large vs. small) for reaction extent.

Facilitation Tip

In the Jigsaw Keq calculation, assign each group a different reaction type, so they teach each other how to handle coefficients and excluded phases.

What to look for

Pose the question: 'If a reaction has a very large Keq, does it mean the reaction has gone to completion and no reactants are left?' Guide students to discuss the dynamic nature of equilibrium and the meaning of a large Keq value.

• Understand
• Analyze
• Evaluate
• Relationship Skills
• Self-Management

A few notes on teaching this unit

Teach Keq by starting with the particle-level model of equilibrium. Have students draw diagrams of systems at equilibrium with varying Keq values to see that concentrations aren’t equal but rates are. Avoid rushing to the formula; let students derive the expression from their diagrams first. Research shows that students who visualize the dynamic nature of equilibrium grasp Keq more deeply and retain it longer.

Students will confidently write correct Keq expressions for any reaction, explain why pure solids and liquids are excluded, and interpret Keq values to predict reaction favorability. They should articulate that equilibrium is a state of equal forward and reverse rates, not equal concentrations, and use Keq to compare reactions.

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Watch Out for These Misconceptions

• During Think-Pair-Share: Writing Keq Expressions, watch for students who assume equilibrium means equal concentrations of reactants and products.

  Ask these students to revisit their particle diagrams from the Gallery Walk or create new ones for the reactions they’re writing expressions for. Have them compare two systems with very different Keq values to see that concentrations aren’t equal, even though the system is at equilibrium.

• During Jigsaw: Keq Calculation, watch for students who include pure solids or liquids in the Keq expression.

  Provide a set of equilibrium expressions with and without solids or liquids included. Have students compare the two versions and explain to their group why one is correct and the other isn’t, using the particle diagrams or phase labels as evidence.

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Methods used in this brief

• Think-Pair-Share
• Gallery Walk
• Jigsaw