Lesson Plan

• Describe the role of cryolite in lowering the melting point and providing conductivity in the Hall–Héroult cell.
• Explain why carbon anodes are sacrificial and must be replaced regularly.
• Write and balance the ionic half‑equations for the cathode and anode reactions.
• Outline the overall steps of aluminium extraction from alumina.

• Projector and screen
• Slide deck with Hall–Héroult cell schematic
• Worksheet for half‑equation practice
• Physical model or diagram of a cryolite‑alumina bath (optional)
• Whiteboard and markers
• Exit‑ticket slips

Aluminium makes up over 8% of the Earth’s crust, yet pure metal is obtained only through a high‑temperature electrolytic process. Review the basic concepts of electrolysis and molten salts, then state that today students will see how cryolite enables the process and why the carbon anodes are consumable. Success will be measured by accurate half‑equations and clear explanations of each component.

1. Do‑now (5'): Quick quiz on electrolysis terminology and electrode reactions.
2. Mini‑lecture (10'): Overview of the Hall–Héroult method and the three functions of cryolite.
3. Diagram activity (8'): Students label a schematic of the electrolytic cell, identifying cathode, anode, and molten bath.
4. Guided practice (12'): Write the ionic half‑equations for Al³⁺ reduction and O²⁻ oxidation, then combine to the overall reaction.
5. Group discussion (10'): Explain why carbon anodes are consumed, list the products (CO/CO₂) and the impact on cell efficiency.
6. Check for understanding (5'): Exit‑ticket – one sentence describing the role of cryolite and one sentence explaining anode replacement.

We revisited how cryolite creates a workable molten environment and how the Hall–Héroult cell reduces aluminium ions while carbon anodes are gradually oxidised. Students hand in their exit tickets, and for homework they will complete a worksheet converting the overall reaction into mass‑balance calculations for a small‑scale cell.