Balloon Won't Inflate in Sealed Bottle
Balloon is hard to inflate until air can escape.
Teaching & key ideas
What you do: Try inflating a balloon inside a sealed bottle, then open a small vent hole.
What students see: Balloon is hard to inflate until air can escape.
Why it works: Air already in the bottle takes space and pushes back.
Question to ask: What is stopping the balloon?
Lesson flow
Predict → demonstrate → observe → briefly explain → ask: What is stopping the balloon?