| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Biology |
| Lesson Topic: Investigate and describe the effects on plant tissues of immersing them in solutions of different concentrations. |
Learning Objective/s:
- Describe how water potential differences affect plant cell turgor in hypotonic, isotonic and hypertonic solutions.
- Explain the process of plasmolysis and its relationship to solute concentration.
- Analyse experimental data to determine the effect of solution concentration on cell length and tissue firmness.
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Materials Needed:
- Fresh onion or potato slices (≈5 mm thick)
- Distilled water and NaCl (or sucrose) solutions at 0.2 M, 0.5 M, 1.0 M
- Test tubes or small beakers (four)
- Timer or stopwatch
- Ruler or caliper for measuring cell length
- Microscope with slides (optional)
- Worksheet/data table for recording observations
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Introduction:
Begin with a quick demonstration of an onion slice placed in water, asking students what they expect to happen. Review prior knowledge of diffusion and water potential. Explain that by the end of the lesson they will be able to predict and describe tissue changes in solutions of varying concentration.
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Lesson Structure:
- Do‑now (5'): Students write the definition of water potential and list examples of hypotonic, isotonic, hypertonic solutions.
- Mini‑lecture (10'): Review osmosis, the water potential equation, and plasmolysis using the projector.
- Practical set‑up (10'): In groups, label containers, place tissue samples, add solutions, and start the timer.
- Observation period (30'): Students monitor tissues, record macroscopic changes on the worksheet.
- Microscope investigation (optional, 10'): Examine slides and note cell‑membrane position.
- Data analysis discussion (10'): Groups calculate cell‑length changes, compare results, and relate them to water potential.
- Formative check (5'): Quick quiz or exit ticket on key concepts.
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Conclusion:
Summarise how solution concentration determines water movement and tissue state, reinforcing the link between water potential and plasmolysis. Students complete an exit ticket describing the expected outcome for a new concentration. For homework, they sketch and label a turgid and a plasmolysed cell, citing the underlying osmotic principles.
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