Pencils Through a Water Bag
Very little water leaks out.
Teaching & key ideas
What you do: Push pencils straight through both sides of the filled bag.
What students see: Very little water leaks out.
Why it works: Flexible plastic polymer chains stretch and seal around the pencil.
Question to ask: Why doesn't the hole stay open?
Lesson flow
Predict → demonstrate → observe → briefly explain → ask: Why doesn't the hole stay open?