Lesson Plan

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Lesson Plan
Grade: Date: 25/02/2026
Subject: Physics
Lesson Topic: recall and use W = p∆V for the work done when the volume of a gas changes at constant pressure and understand the difference between the work done by the gas and the work done on the gas
Learning Objective/s:
  • Recall the formula W = pΔV for work at constant pressure.
  • Distinguish between work done by the gas and work done on the gas using sign conventions.
  • Apply the formula to calculate work in expansion and compression problems.
  • Explain how the work term fits into the first law of thermodynamics.
  • Identify common errors such as sign misuse and incorrect units.
Materials Needed:
  • Projector or interactive whiteboard
  • Slides with derivation and example
  • Worksheet with practice problems
  • Piston‑cylinder diagram handout
  • Calculator for each student
  • Whiteboard and markers
 Introduction:
Begin with a quick demonstration of a syringe expanding against a fixed weight to illustrate work. Ask students what they notice about the force and movement, linking to prior work on pressure–volume relationships. Explain that today they will formalise this observation using W = pΔV and clarify the sign convention for work by and on the gas. Success will be measured by correctly solving a worked example and explaining the sign choices.
Lesson Structure:
  1. Do‑now (5') – Short recall quiz on pressure, volume and sign conventions.
  2. Mini‑lecture (10') – Derive W = pΔV using the piston model; emphasise constant external pressure.
  3. Guided practice (12') – Work through the expansion example, highlighting unit conversion and sign.
  4. Interactive activity (10') – Pairs calculate work for both expansion and compression scenarios on the worksheet and share answers.
  5. Misconception check (8') – Present common errors; students correct sign or unit mistakes via clicker questions.
  6. Summary & exit ticket (5') – Students write one sentence describing the difference between work by and on the gas and submit a quick problem.
Conclusion:
Review the key points: W = pΔV, the sign convention, and its role in the first law. Students complete an exit ticket that asks for the work sign in a compression case. Assign homework to solve two additional problems, one with constant pressure and one requiring the integral form for varying pressure.