Warm-Bottle Balloon Inflation
Balloon inflates/deflates without blowing.
Teaching & key ideas
What you do: Put balloon over bottle; move bottle between warm and cold water.
What students see: Balloon inflates/deflates without blowing.
Why it works: Warm air expands; cooler air contracts.
Question to ask: What changed inside the bottle?
Lesson flow
Predict → demonstrate → observe → briefly explain → ask: What changed inside the bottle?