| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Biology |
| Lesson Topic: explain how hydrogen bonding of water molecules is involved with movement of water in the xylem by cohesion-tension in transpiration pull and by adhesion to cellulose in cell walls |
Learning Objective/s:
- Describe the polar nature of water and its capacity for hydrogen bonding.
- Explain how cohesion creates a continuous water column in xylem.
- Explain how transpiration generates tension that pulls water upward.
- Describe how adhesion to cellulose walls prevents the water column from breaking.
- Compare the roles of cohesion and adhesion in the cohesion‑tension mechanism.
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Materials Needed:
- Projector and screen
- PowerPoint/Google Slides presentation
- Clear capillary tubes or a simple xylem model
- Water with food colouring
- Handout diagram of water movement in a leaf
- Worksheet with application questions
- Markers and whiteboard
- Online simulation link (e.g., PhET “Water Cycle”)
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Introduction:
Begin with the question “How do plants ‘drink’ water from the soil and move it to the top of a tall tree?” Students recall that water is polar and can form hydrogen bonds. Explain that today they will discover how these bonds enable both cohesion and adhesion, which together drive water ascent. Success will be measured by their ability to describe each process and compare their functions.
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Lesson Structure:
- Do‑now (5'): Students write a quick explanation of why water rises in a straw; teacher collects common misconceptions.
- Mini‑lecture with slides (10'): Present water polarity, hydrogen bonding, cohesion, tension, adhesion; show diagram of xylem cross‑section.
- Guided inquiry (15'): In pairs, students use capillary tubes filled with coloured water to observe rise and record observations.
- Whole‑class discussion (10'): Link observations to cohesion‑tension theory; fill a comparison table on the board.
- Worksheet activity (10'): Apply the capillary rise equation and answer questions on the step‑by‑step flow of water.
- Check for understanding (5'): Exit ticket – one sentence describing the role of adhesion in transpiration pull.
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Conclusion:
Recap that hydrogen bonding gives water its cohesive and adhesive properties, enabling a continuous column that can transmit tension while staying anchored to vessel walls. Collect exit tickets and remind students to complete the textbook reading (Chapter 12, section on water transport) and the online quiz for homework.
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