Thermodynamics and Equilibrium

Active learning helps Year 12 students grasp thermodynamics by making abstract concepts concrete through calculations and simulations. Working with ΔG, ΔH, and ΔS in pairs or groups lets students test predictions and see how temperature shifts affect equilibrium in real time.

• Year 12
• Chemistry
• 4 activities
• 20 min–45 min

Learning Objectives

1. Calculate the change in Gibbs Free Energy (ΔG) using enthalpy (ΔH), entropy (ΔS), and temperature (T) to predict reaction spontaneity.
2. Explain the mathematical relationship between the standard Gibbs Free Energy change (ΔG°) and the equilibrium constant (K).
3. Analyze how changes in temperature affect the spontaneity and equilibrium position of endothermic and exothermic reactions.
4. Evaluate the feasibility of a chemical reaction occurring under varying temperature conditions based on thermodynamic data.

Concept Mapping

⏱ 30 min·Pairs

Pairs Calculation: ΔG at Varying Temperatures

Provide data tables with ΔH and ΔS values for five reactions. Pairs calculate ΔG at 298K, 373K, and 473K, then plot graphs to predict spontaneity changes. Discuss which reactions favor products at high T.

Prepare & details

Explain the relationship between Gibbs Free Energy and the equilibrium constant.

Facilitation Tip: During the Pairs Calculation activity, circulate and ask pairs to explain their sign choices for ΔH, ΔS, and T in their ΔG calculations before they compute the final value.

Setup: Tables with large paper, or wall space

Materials: Concept cards or sticky notes, Large paper, Markers, Example concept map

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Concept Mapping

⏱ 45 min·Small Groups

Small Groups: Equilibrium Shift Simulation

Use cobalt chloride solutions in test tubes; heat and cool to show color changes representing equilibrium shifts. Groups measure absorbance with colorimeters at different temperatures, calculate approximate K, and link to ΔG trends.

Prepare & details

Predict the spontaneity of a reaction based on changes in enthalpy and entropy.

Facilitation Tip: In the Small Groups Simulation, assign each group a different reaction so their observations can be compared during the whole-class discussion afterward.

Setup: Tables with large paper, or wall space

Materials: Concept cards or sticky notes, Large paper, Markers, Example concept map

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Concept Mapping

⏱ 40 min·Whole Class

Whole Class: Jigsaw on Spontaneity Factors

Assign expert groups to enthalpy-dominant, entropy-dominant, or temperature effects. Experts teach home groups using reaction examples, then home groups solve mixed problems collaboratively.

Prepare & details

Analyze how temperature influences the spontaneity and equilibrium position of a reaction.

Facilitation Tip: For the Jigsaw on Spontaneity Factors, provide a template with clear questions to guide group discussions so all students contribute and stay on task.

Setup: Tables with large paper, or wall space

Materials: Concept cards or sticky notes, Large paper, Markers, Example concept map

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Concept Mapping

⏱ 20 min·Individual

Individual: Reaction Feasibility Cards

Distribute cards with ΔH, ΔS, T values. Students sort into spontaneous/non-spontaneous categories, justify with ΔG calculations, then pair-share to verify.

Prepare & details

Explain the relationship between Gibbs Free Energy and the equilibrium constant.

Setup: Tables with large paper, or wall space

Materials: Concept cards or sticky notes, Large paper, Markers, Example concept map

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Teaching This Topic

Teach thermodynamics by focusing on the Gibbs Free Energy equation as a decision-making tool rather than just a formula. Use temperature as a variable to help students see patterns in spontaneity, not as a standalone factor. Avoid overemphasizing memorization of reaction types; instead, build intuition through repeated calculation and scenario testing.

What to Expect

Students will confidently calculate ΔG and explain how it relates to spontaneity and equilibrium position. They will also articulate why temperature changes shift equilibrium differently for endothermic versus exothermic reactions, using Gibbs Free Energy as a predictive tool.

Watch Out for These Misconceptions

Common Misconception

During the Pairs Calculation activity, watch for students who equate spontaneity with reaction speed. Redirect them by asking, 'If diamond slowly turns into graphite at room temperature, is this reaction spontaneous? What does that tell you about speed versus thermodynamic favorability?'

What to Teach Instead

During the Equilibrium Shift Simulation, students may think ΔG is always zero at equilibrium. Have them adjust concentrations to see ΔG values change while equilibrium is maintained, then ask, 'What stays constant at equilibrium, and what changes?'

Common Misconception

During the Small Groups Simulation, students might assume temperature always increases spontaneity. Provide a reaction with negative ΔH and negative ΔS, and ask groups to calculate ΔG at 298 K and 500 K to observe the effect.

What to Teach Instead

During the Jigsaw on Spontaneity Factors, address the idea that temperature always promotes spontaneity by having groups compare their cases and present the conditions under which high temperature reduces spontaneity.

Assessment Ideas

Quick Check

After the Pairs Calculation activity, provide a set of reactions with ΔH, ΔS, and T values. Ask students to calculate ΔG for each and classify spontaneity, then collect a sample of calculations to check accuracy.

Discussion Prompt

After the Jigsaw on Spontaneity Factors, pose the question: 'How can an endothermic reaction become spontaneous at high temperatures?' Have students discuss in groups, then select a few to share their reasoning based on the TΔS term.

Exit Ticket

During the Reaction Feasibility Cards activity, ask students to write the equation linking ΔG° and K, then predict whether a reaction with a large positive K has a positive or negative ΔG°. Collect responses to assess understanding of the relationship.

Extensions & Scaffolding

• For early finishers in the Pairs Calculation activity, challenge them to calculate the temperature at which a reaction becomes spontaneous or non-spontaneous for a given ΔH and ΔS.
• For students struggling in the Equilibrium Shift Simulation, provide a partially completed data table with missing ΔG values to guide their predictions.
• For extra time, have students research and present real-world applications where controlling temperature shifts equilibrium, such as in industrial ammonia synthesis.

Key Vocabulary

Gibbs Free Energy (ΔG)	A thermodynamic potential that measures the maximum reversible work that may be performed by a thermodynamic system at a constant temperature and pressure. It determines the spontaneity of a process.
Enthalpy (ΔH)	The total heat content of a system. A negative ΔH indicates an exothermic reaction (heat is released), while a positive ΔH indicates an endothermic reaction (heat is absorbed).
Entropy (ΔS)	A measure of the disorder or randomness in a system. A positive ΔS indicates an increase in disorder, while a negative ΔS indicates a decrease in disorder.
Equilibrium Constant (K)	A ratio of product concentrations to reactant concentrations at equilibrium, indicating the extent to which a reaction proceeds to completion.
Spontaneity	The tendency of a process to occur without the need for external intervention. Thermodynamically, a spontaneous process has a negative ΔG.