Safety boundary
Use virtual equilibrium perturbations and supplied datasets only; no unsupervised color-change chemistry.
Explicit chemistry instruction
Le Châtelier's principle is most reliable when grounded in equilibrium expressions and thermodynamics.
Concentration and pressure stresses primarily change Q; temperature can change K.
Catalysts alter the approach rate but not equilibrium composition.
Vocabulary: Le Châtelier; Q; K; catalyst; perturbation.
Worked example
A catalyst helps a system reach equilibrium faster from either direction but leaves K and the equilibrium composition unchanged.
Guided question
Explain why catalyst addition is not an equilibrium shift.
Independent work
- Predict one concentration case.
- Predict one pressure case.
- Predict one temperature case.
- Classify whether Q, K, or both change.
Spiral retrieval bridge
- From Week 26: explain Q versus K.
- From Week 23: distinguish heat flow from temperature.
- From Week 21: distinguish catalyst effects on rate from thermodynamics.
Misconception check
Not every change to a system changes equilibrium position.
Formative check
What does a catalyst change?
Reveal response
Rates/pathway, not K or equilibrium position.
Mentor evidence conference
Ask Archaemenes to audit whether Q, K, and rate effects are being kept distinct.
Teacher guidance
Foundation: Use a perturbation matrix.
Core: Integrate Q/K and temperature.
Extended: Analyze coupled disturbances.