Marshmallow in a Vacuum Jar
Marshmallow expands then shrinks.
Teaching & key ideas
What you do: Pump air out, then let air back in.
What students see: Marshmallow expands then shrinks.
Why it works: Lower outside pressure lets trapped gas pockets expand.
Question to ask: What is pushing on the marshmallow normally?
Lesson flow
Predict → demonstrate → observe → briefly explain → ask: What is pushing on the marshmallow normally?