Upside-Down Water Cup
The water stays in the upside-down cup.
Teaching & key ideas
What you do: Cover a full cup with a card, invert it, then release the card.
What students see: The water stays in the upside-down cup.
Why it works: Air pressure pushes upward on the card more than the water pushes down.
Question to ask: What is holding the card up?
Lesson flow
Predict → demonstrate → observe → briefly explain → ask: What is holding the card up?