| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Chemistry |
| Lesson Topic: State that bond breaking is an endothermic process and bond making is an exothermic process and explain the enthalpy change of a reaction in terms of bond breaking and bond making |
Learning Objective/s:
- Describe why bond breaking absorbs energy (endothermic) and bond making releases energy (exothermic).
- Explain how the overall enthalpy change (ΔH) is calculated using the sum of bond‑breaking and bond‑forming energies.
- Apply bond‑energy data to predict whether a given reaction is exothermic or endothermic.
- Interpret an energy‑profile diagram to relate ΔH to heat flow.
|
Materials Needed:
- Projector and screen
- PowerPoint slides with diagrams
- Printed bond‑energy tables (exam style)
- Worksheet with example and practice reactions
- Scientific calculators
- Whiteboard and markers
- Molecular model kit (optional)
|
Introduction:
Begin with a short video clip of fireworks to illustrate the dramatic release of energy in a chemical reaction. Ask students to recall the difference between exothermic and endothermic processes they have studied. Explain that today they will link these ideas to bond breaking and making, and they will be able to predict the heat flow of any reaction using bond‑energy data.
|
Lesson Structure:
- Do‑now (5'): Quick quiz on definitions of exothermic and endothermic reactions.
- Mini‑lecture (10'): Introduce bond breaking (endothermic) and bond making (exothermic); present the ΔH equation = Σ(bonds broken) – Σ(bonds formed) with an energy‑profile diagram.
- Guided example (15'): Work through the combustion of methane using the provided bond‑energy table; calculate E_break, E_form, and ΔH.
- Paired activity (10'): Students receive a new reaction (e.g., formation of water) and, using the tables, determine whether it is exothermic or endothermic; teacher circulates to check reasoning.
- Concept check (5'): Think‑pair‑share: “If ΔH is negative, what does that tell us about the relative energies of bonds broken vs. formed?”
- Summary & exit ticket (5'): Each student writes one concise sentence summarising the bond‑energy concept and answers a short question on ΔH sign; collect for assessment.
|
Conclusion:
Recap that bond breaking requires energy input, bond making releases energy, and the net ΔH tells us whether a reaction is overall exothermic or endothermic. Collect the exit tickets as a formative check. For homework, students complete a worksheet with two additional reactions, using the bond‑energy tables to calculate ΔH and state the heat flow.
|