Lesson Plan

• Describe the definition of an endothermic reaction and identify its positive enthalpy change (ΔH > 0).
• Explain how thermal energy is transferred from the surroundings to the reaction system, causing a temperature drop.
• Interpret energy‑profile diagrams for endothermic processes.
• Predict the temperature change in a demonstration involving ammonium nitrate and water.
• Compare endothermic and exothermic reactions in terms of heat flow and ΔH.

• Projector and screen
• Whiteboard and markers
• Thermometer (digital or liquid)
• Beaker of water
• Solid ammonium nitrate (instant‑cold‑pack material)
• Safety goggles and gloves
• Worksheet with energy‑profile diagram
• Exit‑ticket slips

Begin with the question, “Why does an instant cold pack become cold when you squeeze it?” to spark curiosity. Review students’ prior knowledge of exothermic reactions and heat flow. State that by the end of the lesson they will be able to articulate how an endothermic reaction draws heat from its surroundings, causing a temperature decrease.

1. Do‑now (5’) – Quick quiz on heat flow terms (heat released vs. absorbed).
2. Mini‑lecture (10’) – Define endothermic reactions, ΔH > 0, and show an energy‑profile diagram.
3. Guided comparison (8’) – Use the provided table to contrast exothermic and endothermic features; discuss temperature changes.
4. Practical demonstration (12’) – Add solid ammonium nitrate to water, students record temperature before and after.
5. Data interpretation (8’) – Students write a brief explanation linking the observed temperature drop to energy absorption.
6. Check for understanding (7’) – Exit ticket: “State in one sentence how an endothermic reaction affects its surroundings.”

Summarise that endothermic reactions have a positive ΔH and cause the surrounding temperature to fall by drawing in heat. Collect exit tickets to gauge understanding, and remind students to complete the worksheet on energy‑profile diagrams for homework.