Lesson Plan

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Lesson Plan
Grade: Date: 17/01/2026
Subject: Biology
Lesson Topic: State that some substances move into and out of cells by diffusion through the cell membrane.
Learning Objective/s:
  • Describe diffusion as passive movement of particles down a concentration gradient.
  • Identify the factors that affect the rate of diffusion across a cell membrane.
  • Explain why gases and water diffuse through the plasma membrane without using cellular energy.
  • Compare the diffusion directions of O₂, CO₂, and water in cells.
  • Predict how changes in temperature or membrane thickness alter diffusion rate.
Materials Needed:
  • Projector or interactive whiteboard
  • Slides/PowerPoint on diffusion concepts
  • Handout with cell‑membrane diagram and diffusion examples
  • Food‑color diffusion demonstration (beaker, water, food coloring)
  • Worksheet with scenario questions
  • Exit‑ticket cards
 Introduction:
Begin with a quick demonstration: drop a few drops of food coloring into a beaker of water and ask students what they observe. Connect this to prior learning about concentration gradients and the cell membrane’s semi‑permeable nature. State that by the end of the lesson they will be able to describe diffusion, list the factors influencing its rate, and explain its importance for cellular function.
Lesson Structure:
  1. Do‑Now (5') – Students answer a short prompt on their worksheet about what happens when a scent spreads in a room.
  2. Mini‑lecture (10') – Explain diffusion definition, key features, and show a diagram of the cell membrane.
  3. Interactive discussion (8') – Explore factors affecting diffusion rate; students predict outcomes of changing each factor.
  4. Demonstration (7') – Food‑color diffusion experiment; students record observations and relate them to the factors.
  5. Guided practice (10') – Small groups complete a worksheet matching substances (O₂, CO₂, water) to direction and reason for diffusion.
  6. Check for understanding (5') – Quick quiz via Kahoot or show‑of‑hands questions.
  7. Summary & exit ticket (5') – Students write one key point and one question on an exit‑ticket card.
Conclusion:
Recap the main ideas: diffusion moves substances down concentration gradients without energy, and its rate depends on gradient, temperature, membrane area, thickness, and particle properties. Ask students to write an exit ticket describing one factor that would speed up diffusion in a cell. Assign a short homework: find a real‑world example of diffusion and explain the influencing factors.