Lesson Plan

Resources → Subject Notes → Physics → Notes
Lesson Plan
Grade: Date: 25/02/2026
Subject: Physics
Lesson Topic: compare pV = 31Nm with pV = NkT to deduce that the average translational kinetic energy of a molecule is 23 kT, and recall and use this expression
Learning Objective/s:
  • Describe how the kinetic‑theory form of the ideal‑gas equation relates pressure to molecular motion.
  • Derive and state the result ⟨Eₜᵣₐₙₛ⟩ = 3⁄2 kT from the two forms of the ideal‑gas law.
  • Apply the expression ⟨Eₜᵣₐₙₛ⟩ = 3⁄2 kT to solve problems involving rms speed, internal energy and temperature changes.
Materials Needed:
  • Projector and screen
  • PowerPoint slides with derivation and diagrams
  • Worksheet containing guided derivation steps and a worked example
  • Scientific calculators (one per pair)
  • Whiteboard and markers
 Introduction:
Begin with a quick poll: “What do we already know about the ideal‑gas law?” Follow with a short recap of pV = NkT and explain that today we will connect this macroscopic law to molecular motion. State that by the end of the lesson students will be able to derive and use the kinetic‑theory expression for average translational kinetic energy.
Lesson Structure:
  1. Do‑now (5'): Students write the two forms of the ideal‑gas equation from memory on a sticky note.
  2. Mini‑lecture (10'): Present the kinetic‑theory derivation, highlighting each algebraic step.
  3. Guided activity (15'): In pairs, students complete a worksheet that walks them through equating the two expressions and isolating ⟨Eₜᵣₐₙₛ⟩.
  4. Worked example (10'): Teacher models the helium problem, students follow on calculators.
  5. Concept‑check (5'): Think‑pair‑share – “Why does each degree of freedom contribute ½kT?”
  6. Summary & exit ticket (5'): Students write one real‑world application of ⟨Eₜᵣₐₙₛ⟩ on a slip of paper.
Conclusion:
Recap the key steps that led to ⟨Eₜᵣₐₙₛ⟩ = 3⁄2 kT and emphasize its role in energy‑based gas problems. Collect the exit tickets to gauge understanding, and assign a short homework task: calculate the rms speed of oxygen molecules at 298 K using the derived expression.