My 7yo snapped the clip off of a transparent pink plastic pen. He noticed that at the place where it broke, the transparent pink plastic became opaque white. Why does that happen (instead of it remaining transparent throughout)?
This is best illustrated by the pic I took of the [broken pen](https://imgur.com/S8rasqb).
In: Physics
[This has popped up on reddit before](https://www.reddit.com/r/askscience/comments/1fyf6y/why_does_plastic_turn_white_when_you_bend_it/)
[And elsewhere](https://chemistry.stackexchange.com/questions/15084/why-do-many-transparent-plastics-turn-opaque-when-deformed)
ELI5 explanation:
Plastics are like glass, they are a jumble of molecules fused into a lump. When you bend plastic you can cause tiny internal surfaces to form, like smashing a piece of glass into powder will now be white looking. You are also causing changes in density of those molecules in the plastic. You can undo it by melting the plastic like melting that powdered glass back into a single lump.
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