Lesson Plan

• Describe the concept of reversible reactions and dynamic equilibrium.
• Explain why the forward and reverse reaction rates are equal at equilibrium.
• Identify laboratory observations that indicate a system has reached equilibrium.
• Apply Le Chatelier’s principle to predict how changes in conditions shift the equilibrium position.

• Projector and screen
• Whiteboard and markers
• Printed worksheet with equilibrium diagrams and tables
• Demonstration kit (coloured reaction that produces gas)
• Lab safety goggles and gloves
• Calculators for concentration calculations

Begin with a quick question: “Have you ever seen a reaction stop changing in colour even though it’s still happening?” Students recall prior learning about reaction rates and concentration changes. Explain that today they will be able to state the precise definition of chemical equilibrium and recognise it in experimental data.

1. Do‑now (5’) – short quiz on forward vs. reverse reactions.
2. Mini‑lecture (10’) – define reversible reactions, dynamic equilibrium, and present the equilibrium expression.
3. Demonstration (10’) – colour‑change reaction; students note when the colour stops changing and discuss observations.
4. Guided analysis (10’) – students complete a table linking observations (colour, gas evolution, temperature) to equilibrium criteria.
5. Le Chatelier activity (10’) – small groups predict shifts when concentration, pressure, or temperature are altered.
6. Check for understanding (5’) – exit‑ticket question: “State the two conditions that define equilibrium in a closed system.”

Recap that equilibrium is characterised by equal forward and reverse rates and constant concentrations. Collect exit tickets to gauge understanding and assign homework: complete the worksheet on equilibrium observations and Le Chatelier’s principle.