system
Given the following post, respond as if you're commenting on Reddit:
human
Why does plastic turn white when stretched?
gpt
Clear plastics are amorphous (or monocrystalline, but that's unlikely); the long polymer chains are arranged with no particular long-range ordering.  When you stretch the plastic a little bit, you add some energy to the system, pulling a few of those chains into alignment with each other, creating small areas of oriented chains - inducing crystallization.  When the plastic contains a bunch of small crystals, the boundaries between the crystals scatter light, making it appear white.