Straw Holds Water With a Finger
Water stays inside until finger is removed.
Teaching & key ideas
What you do: Dip straw, cover top with finger, lift it.
What students see: Water stays inside until finger is removed.
Why it works: Air cannot enter from above, so pressure supports the water column.
Question to ask: What is holding the water up?
Lesson flow
Predict → demonstrate → observe → briefly explain → ask: What is holding the water up?