Chemistry · Grade 12

Active learning ideas

Nernst Equation & Non-Standard Conditions

Students often struggle to visualize how concentration changes affect voltage because the Nernst equation’s logarithmic relationship isn’t intuitive. Active learning with hands-on labs and simulations lets them manipulate real or virtual systems, observe voltage shifts directly, and connect the formula’s abstract terms to measurable outcomes. This approach builds confidence by grounding theory in observable phenomena before moving to calculations.

• Ontario Curriculum Expectations
• HS-PS1-7

• 20–45 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Problem-Based Learning
• 45 min · Small Groups

Lab Build: Copper Concentration Cell

Students prepare two beakers with 0.1 M and 0.01 M CuSO4 solutions, insert copper electrodes, and connect with a salt bridge. Measure initial voltage, then dilute the concentrated side and remeasure. Calculate E using the Nernst equation before and after, discussing matches.

Calculate cell potentials under non-standard conditions using the Nernst equation.

Facilitation Tip

During the Copper Concentration Cell lab, remind students to rinse electrodes thoroughly between setups to avoid cross-contamination that skews voltage readings.

What to look for

Provide students with a scenario involving a specific electrochemical cell (e.g., a Daniell cell) where the concentration of one ion has changed. Ask them to: 1. Write the expression for Q. 2. Use the Nernst equation to calculate the new cell potential. 3. State whether the cell potential increased or decreased and why.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Activity 02

• Problem-Based Learning
• 30 min · Pairs

PhET Simulation: Vary Non-Standard Conditions

Pairs access the PhET electrochemistry simulation to adjust concentrations, temperature, and pressure for given cells. Predict E values with Nernst, run the sim to verify, and graph voltage versus log Q. Share findings in a class debrief.

Explain how changes in concentration affect cell potential.

Facilitation Tip

In the PhET Simulation, pause students after the first trial to discuss how changing one concentration affects Q and voltage before they proceed to more complex variations.

What to look for

On an index card, students should define 'concentration cell' in their own words and describe one factor that influences its voltage. They should also write one specific application where understanding non-standard cell potentials is important.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Activity 03

• Problem-Based Learning
• 25 min · Small Groups

Prediction Relay: Nernst Scenarios

In small groups, teams receive cards with cell diagrams and non-standard concentrations. One member calculates E, passes to next for explanation, then group builds a simple model cell or sketches voltage change. Compete for accuracy.

Design a concentration cell and predict its voltage.

Facilitation Tip

For the Prediction Relay, provide a quick reference chart of common log values (e.g., log 0.1 = -1) to speed calculations and reduce frustration with arithmetic.

What to look for

Pose the question: 'How does the Nernst equation help us understand why batteries lose their charge over time?' Facilitate a discussion where students connect the decrease in reactant concentration and increase in product concentration to a lowering of cell potential.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Activity 04

• Problem-Based Learning
• 20 min · Whole Class

Whole Class Demo: Zn-Cu Cell Dilution

Teacher demonstrates a Zn-Cu cell, measures E° first. Class predicts effect of diluting Cu²⁺ 10-fold using Nernst, then observes live measurement. Students record data and vote on predictions beforehand.

Calculate cell potentials under non-standard conditions using the Nernst equation.

Facilitation Tip

In the Whole Class Demo, have students predict the voltage change before dilution, then measure it to highlight the immediate impact of concentration shifts.

What to look for

Provide students with a scenario involving a specific electrochemical cell (e.g., a Daniell cell) where the concentration of one ion has changed. Ask them to: 1. Write the expression for Q. 2. Use the Nernst equation to calculate the new cell potential. 3. State whether the cell potential increased or decreased and why.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

A few notes on teaching this unit

Start with the Whole Class Demo to create a shared anchor for the topic, then use the lab to let students explore concentration cells firsthand. Follow with simulations to isolate variables like temperature or pressure, helping students see the equation’s parts in action. Avoid front-loading the algebra; instead, let students derive the logarithmic relationship from their own data patterns. Research shows that students grasp non-linear relationships better when they generate their own data before formalizing it with equations.

Students will confidently apply the Nernst equation to predict how voltage changes under non-standard conditions, using both concentration cells and redox cells as examples. They will justify their predictions with Q values, E° data, and the equation’s logarithmic term. Success looks like students explaining why a cell’s voltage drops as concentrations approach equilibrium, using both data and the formula.

---

Watch Out for These Misconceptions

• During the Copper Concentration Cell lab, watch for students assuming a direct proportional relationship between concentration and voltage.

  Have students plot their measured voltages against log Q and observe the curve, then revisit the Nernst equation to identify the logarithmic term. Point to the data points where concentration halves but voltage changes by a consistent logarithmic step, not a fixed amount.

• During the PhET Simulation, watch for students limiting the Nernst equation to concentration cells only.

  Ask students to input data for a standard redox cell (e.g., Zn-Cu) and vary concentrations, then observe how Q and voltage change. Facilitate a quick discussion where they compare their results to concentration cell data to see the equation’s universal application.

• During the Whole Class Demo, watch for students incorrectly stating that Q equals zero under standard conditions.

  After measuring the standard cell’s voltage, have students calculate Q using the given concentrations (1 M) to confirm it equals 1. Ask them to predict what happens if one concentration drops to 0.1 M, then measure to show the immediate effect of deviating from standard conditions.

---

Methods used in this brief

• Problem-Based Learning