Safety boundary
Use equation cards, simulations, and supplied energy data only. No combustion or reactive demonstrations are required.
Explicit chemistry instruction
Breaking bonds requires energy input; forming bonds releases energy.
Average bond energies can estimate reaction enthalpy by ΣE_broken−ΣE_formed.
Because tabulated bond energies are averages, the estimate is approximate.
Vocabulary: bond energy; bond breaking; bond formation; estimate.
Worked example
Breaking 2 H–H bonds requires more energy than breaking one identical H–H bond; coefficients matter in the accounting.
Guided question
Why can a bond-energy estimate differ from measured ΔH?
Independent work
- Count broken/formed bonds for three reactions.
- Estimate one ΔH.
- State one approximation.
Misconception check
Bond breaking does not release energy; it requires input.
Formative check
What sign contribution does bond formation make in the bookkeeping?
Reveal response
Negative/releasing contribution in the chosen convention.
Mentor evidence conference
Ask Archaemenes to audit signs, pathway logic, units, and model limits.
Teacher guidance
Foundation: Use bond-count tables.
Core: Estimate reaction ΔH.
Extended: Compare estimates with measured values and discuss model error.