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Subject: Physics
Semester: 2
Period: 6
Week: 33
School Name:
Teacher’s Name:
Subject: Physics
Grade Level: Grade 10
Week & Period: Week 33, Period VI
Date:
Sub-topic: Forces Between Molecules: Cohesion and Adhesion
Learning Objectives: By the end of the lesson, learners should be able to:
- Define and differentiate between cohesion and adhesion.
- Explain molecular interactions and bonding forces.
- Describe examples of cohesive and adhesive forces in everyday life.
- Demonstrate how cohesion and adhesion affect liquids.
Instructional Materials:
- Clean glass slides
- Water and mercury droppers
- Wax paper
- Capillary tubes
- Beakers
- Colored dyes
- Chart paper for group work
Anticipation (Warm-Up): Ask learners: “Why do water droplets form beads on a leaf but spread on glass?” Use student responses to introduce cohesion and adhesion.
Building Knowledge (Main Lesson):
- Cohesion: The attractive force between like molecules (e.g., water–water)
- Adhesion: The attractive force between unlike molecules (e.g., water–glass)
- Surface tension: A result of cohesive forces; forms a ‘skin’ on liquid surfaces
- Capillary action: Movement of liquid through small spaces due to cohesion and adhesion
- Examples: Meniscus in measuring cylinders, water climbing tissue paper
Activities:
- Compare water and mercury drops on wax paper and glass
- Use capillary tubes to demonstrate capillary rise
- Group sketching of molecular diagrams showing cohesive and adhesive forces
Experiment: Investigating Capillary Action
- Materials: Capillary tubes, colored water, beakers, measuring scale
- Procedure: Place tubes in water. Observe the height of liquid rise.
- Observation: Water rises higher in narrow tubes. Mercury shows depression.
- Conclusion: Capillary rise is due to adhesive and cohesive forces working together.
Assessment:
- Define cohesion and adhesion with examples.
- What causes capillary action in plants?
- Explain why mercury forms convex meniscus and water forms concave meniscus.
Homework:
- Observe and record five examples of adhesion or cohesion at home.
- Draw the molecular arrangement during cohesion and adhesion.
Expanded Notes:
- Cohesive and adhesive forces are both molecular attractions, but their direction and interactions differ.
- Adhesion helps liquids stick to surfaces while cohesion keeps them together.
Differentiation:
- Visual demos for spatial learners
- Practical lab work for hands-on learners
- Collaborative sketches for social learners
Teacher’s Reflection:
- Did students grasp the distinction clearly?
- Were they able to apply real-world observations to theory?
- Did capillary experiments enhance understanding?