Expanding Straw Wrapper
The paper 'worm' grows longer.
Teaching & key ideas
What you do: Scrunch wrapper tightly, then drip water onto it.
What students see: The paper 'worm' grows longer.
Why it works: Water enters the fibers and causes them to swell and straighten.
Question to ask: Why does the paper get longer?
Lesson flow
Predict → demonstrate → observe → briefly explain → ask: Why does the paper get longer?