| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Chemistry |
| Lesson Topic: State that an exothermic reaction transfers thermal energy to the surroundings leading to an increase in the temperature of the surroundings |
Learning Objective/s:
- Describe how thermal energy is transferred from an exothermic reaction to its surroundings.
- Explain why the temperature of the surroundings rises during an exothermic process (negative ΔH).
- Compare exothermic and endothermic reactions using energy‑flow diagrams and sign of ΔH.
- Interpret experimental data (temperature change) to identify an exothermic reaction.
- Apply the concept to real‑world examples such as combustion and neutralisation.
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Materials Needed:
- Projector or interactive whiteboard
- PowerPoint/slide deck
- Thermometer (calibrated)
- Beakers (100 mL)
- Solid sodium hydroxide (NaOH)
- Distilled water (≈50 mL per group)
- Stirring rods
- Safety goggles and gloves
- Worksheet with comparison table and exit‑ticket questions
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Introduction:
Begin with the question “Why does a hand‑warmer get hot when you shake it?” to spark curiosity about heat release. Review students’ prior knowledge of heat, temperature, and the sign of ΔH from previous lessons. State that by the end of the lesson they will be able to correctly describe the energy flow in an exothermic reaction and predict the temperature change in the surroundings.
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Lesson Structure:
- Do‑now (5') – Quick quiz on heat vs. temperature and sign of ΔH.
- Mini‑lecture (10') – Define exothermic & endothermic reactions, introduce ΔH < 0, and show energy‑profile diagram.
- Demonstration (15') – Students perform the NaOH + water experiment, record initial and final temperatures.
- Guided analysis (10') – Discuss observations, link temperature rise to energy transferred to surroundings.
- Comparison activity (10') – In pairs fill a table contrasting exothermic and endothermic reactions (energy flow, ΔH sign, temperature effect).
- Check for understanding (5') – Exit‑ticket: “State what happens to the surroundings in an exothermic reaction and why.”
- Homework assignment (2') – Worksheet with additional reaction examples to classify as exothermic or endothermic.
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Conclusion:
Summarise that exothermic reactions release thermal energy to the surroundings, causing a measurable temperature increase, and contrast this with endothermic processes. Collect the exit‑ticket responses to gauge understanding and assign the worksheet for reinforcement. Remind students to bring their notes for the next lesson on enthalpy calculations.
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