Bouncing Water Drop on Hydrophobic Surface

1. Bouncing Water Drop on Hydrophobic Surface Materials: Hydrophobic-coated surface or waxed sheet; dropper What you do: Drop water from low height onto surface. What students see: Drops bead and may bounce/roll. Question: Why doesn't the water spread out? 2. Diaper Polymer Drinks Water Materials: Clean disposable diaper; extracted sodium polyacrylate; water; cup What you do: Add water to small polymer sample. What students see: Tiny powder traps a large volume of water into gel. Question: How can a little powder hold so much water? 3. Soap Film Minimal Surfaces Materials: Wire frames of different shapes; bubble solution What you do: Dip frames and compare film geometry. What students see: Unexpected interior surfaces form. Question: Why does soap film solve a geometry problem by itself?

Predict → observe three demonstrations → compare what changed → choose independent activity station → cleanup/share. Guiding questions: Question: Why doesn't the water spread out? Question: How can a little powder hold so much water? Question: Why does soap film solve a geometry problem by itself?