| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Chemistry |
| Lesson Topic: Draw and label reaction pathway diagrams for exothermic and endothermic reactions using information provided, to include: (a) reactants (b) products (c) enthalpy change of the reaction, $Delta H$ (d) activation energy, $E_{mathrm{a}}$ |
Learning Objective/s:
- Describe the concepts of enthalpy change (ΔH) and activation energy (Eₐ) for exothermic and endothermic reactions.
- Explain how ΔH determines whether a reaction releases or absorbs energy.
- Construct and label accurate energy‑profile diagrams showing reactants, products, ΔH and Eₐ for both reaction types.
- Compare the effect of catalysts on activation energy using diagram modifications.
- Interpret given ΔH and Eₐ values to predict reaction temperature dependence.
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Materials Needed:
- Projector or interactive whiteboard
- Teacher‑prepared handouts with reaction data
- Worksheet with practice reactions and space for diagrams
- Colored markers or pens for drawing diagrams
- Calculator (optional) for energy calculations
- Sample reaction cards (e.g., methane combustion, CaCO₃ decomposition)
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Introduction:
Begin with a quick demonstration: ignite a small piece of methane‑air mixture to illustrate an exothermic reaction. Review prior knowledge of energy, bonds, and the definitions of ΔH and Eₐ. State that today’s success criteria are to correctly draw and label energy‑profile diagrams for both exothermic and endothermic reactions.
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Lesson Structure:
- Do‑now (5’) – Students answer a short question on ΔH sign and identify reaction type from a given equation.
- Mini‑lecture (10’) – Review key concepts (ΔH, Eₐ, energy profile) using projector slides and the two example reactions.
- Guided practice (12’) – Teacher models drawing an exothermic diagram step‑by‑step; students follow on their worksheets.
- Collaborative activity (15’) – In pairs, students choose an endothermic reaction, construct and label its diagram, then swap for peer feedback.
- Concept check (8’) – Whole‑class quiz using clickers or show‑of‑hands to address common misconceptions (e.g., ΔH vs. reaction speed).
- Extension / Catalyst discussion (5’) – Brief explanation of how a catalyst lowers Eₐ and how this appears on the diagram.
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Conclusion:
Summarise that ΔH indicates energy released or absorbed while Eₐ controls the reaction rate, and both are clearly shown on the energy‑profile diagram. Students complete an exit ticket by sketching a diagram for a new reaction and noting its ΔH sign. Assign homework: finish the worksheet with two additional reactions and write a short explanation of how temperature would affect each rate.
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