Lesson Plan

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Lesson Plan
Grade: Date: 17/01/2026
Subject: Physics
Lesson Topic: define and use the terms mass defect and binding energy
Learning Objective/s:
  • Define mass defect and binding energy in nuclear physics.
  • Calculate the mass defect of a nucleus from given atomic masses.
  • Convert mass defect to binding energy using E = Δm c² (or 931.5 MeV / u).
  • Interpret binding energy per nucleon to assess nuclear stability.
  • Apply the concepts to solve short practice problems on fission and fusion.
Materials Needed:
  • Projector and screen for slides/diagrams.
  • Whiteboard and markers.
  • Handout with atomic‑mass tables and example calculations.
  • Scientific calculators (or calculator apps).
  • Periodic table of isotopes.
  • Worksheet with practice questions.
 Introduction:
Begin with a quick question: “If mass and energy are interchangeable, why does a nucleus weigh less than its parts?” Connect this to students’ prior knowledge of E = mc² and outline that today they will quantify that “missing mass.” Success will be measured by accurate calculations and clear explanations of stability trends.
Lesson Structure:
  1. Do‑now (5 min): Write the equation E = mc² and list two real‑world examples of mass‑energy conversion.
  2. Mini‑lecture (10 min): Introduce definitions of mass defect and binding energy; present the conversion factor 931.5 MeV / u.
  3. Guided example (15 min): Work through the ⁴He calculation step‑by‑step on the board, checking each arithmetic step.
  4. Paired activity (10 min): Students calculate mass defect and binding energy for ¹²C using the handout data; teacher circulates for support.
  5. Class discussion (5 min): Compare results, introduce binding‑energy‑per‑nucleon curve and why iron is most stable.
  6. Exit ticket (5 min): Write one sentence explaining why a higher E_b/A means a more stable nucleus.
Conclusion:
Recap the link between missing mass and the energy that holds a nucleus together, highlighting the calculation workflow. Collect exit tickets as a quick retrieval check, and assign a homework problem set that includes a fission and a fusion scenario for students to analyse using the concepts learned.