Contact-Angle Race
Drops bead, spread, or soak differently.
Teaching & key ideas
What you do: Put equal drops on different surfaces.
What students see: Drops bead, spread, or soak differently.
Why it works: Balance between cohesion and adhesion depends on surface chemistry.
Question to ask: Why is the same water a different shape on each surface?
Lesson flow
Predict → demonstrate → observe → briefly explain → ask: Why is the same water a different shape on each surface?