1What they're made of, way up close
Two ways to build a stretchy thing
If we shrink down small enough to see the tiny pieces, rubber and clay look completely different. Watch each one wiggle:
Rubber: long coiled chains
Rubber is made of super-long molecule chains, all tangled and coiled like springs. Links between chains keep the network connected while the chains change shape.
Clay: loose sliding grains
Clay is made of tiny grains packed loosely together. Wet clay contains tiny platelets that can slide and rearrange when the force is large enough.
2Two kinds of "stretchy"
The springy stuff vs the slidey stuff
Both samples below are held at the same extension. Look at their different internal arrangements.
The springy-chain stuff
Pulling straightens some connected, coiled chains. The grips still hold both ends here.
The sliding-grain stuff
A strong pull rearranges the platelets. The grips still hold both ends here.
3Your turn — pull on the tiny pieces
Pick one and stretch it yourself
Choose a material, then drag the slider to pull it. You're zoomed way in, so you can watch what its tiny pieces actually do while you stretch — keep your eye on them.
zoomed in on a rubber band
4Now stretch both — and let go
Same pull, then release. Which one comes home? 🪃
Here's the real test. Both pieces are stretched the exact same amount. The only question is what happens the moment you let go. Guess first — then release them together and watch.
Guess before you let go
A rubber band and a clay snake are stretched the same amount. You let go of both at once. Which one springs back to its old shape?