Hydrophobic Sand Stays Dry
Sand looks dry even after being underwater.
Teaching & key ideas
What you do: Pour sand into water, then remove a clump/spoonful.
What students see: Sand looks dry even after being underwater.
Why it works: A water-repellent coating prevents water from wetting the grains.
Question to ask: How can something be underwater but not wet?
Lesson flow
Predict → demonstrate → observe → briefly explain → ask: How can something be underwater but not wet?