Lesson Plan

• Describe the concept of enthalpy change (ΔH) and distinguish exothermic from endothermic processes.
• Calculate reaction enthalpies using bond‑energy tables and standard enthalpies of formation.
• Apply Hess’s law to combine known ΔH values and determine the enthalpy of a target reaction.
• Perform basic calorimetry calculations to find heat transferred and ΔH per mole of reactant.
• Interpret tabulated data to predict whether a reaction will release or absorb heat.

• Projector and screen
• Whiteboard and markers
• Printed handout with bond‑energy and ΔH°_f tables
• Scientific calculators
• Coffee‑cup calorimeter set (beakers, thermometer, stirrer)
• Worksheet with practice problems

Begin with a quick demonstration of a fizzing reaction in a coffee‑cup calorimeter to spark curiosity about heat flow. Ask students what they already know about heat changes at constant pressure and how they might measure them. Explain that by the end of the lesson they will be able to predict and calculate these energy changes using data tables and Hess’s law.

1. Do‑Now (5′): Students answer a short quiz on exothermic vs. endothermic reactions.
2. Mini‑lecture (10′): Introduce ΔH, standard conditions, and bond‑energy concept with examples.
3. Guided practice (12′): Work through a bond‑energy calculation on the board; students complete a similar problem in pairs.
4. Hess’s Law activity (10′): Small groups manipulate given equations to derive a target reaction’s ΔH; share results.
5. Calorimetry demonstration (8′): Perform the fizzing reaction, record temperature change, and calculate q_rxn.
6. Independent worksheet (10′): Mixed problems covering ΔH_f calculations, Hess’s law, and calorimetry.
7. Check for understanding (5′): Quick exit ticket – one sentence summarising how to choose the appropriate method for ΔH calculation.

Recap the key strategies: using bond energies for estimates, Hess’s law for indirect measurements, and calorimetry for experimental data. Students complete an exit ticket describing which method they would use for a given reaction and why. For homework, assign a set of enthalpy calculations requiring the use of both ΔH_f tables and Hess’s law.