Eli5: Materials expand when heated and contracts when cooled. So why does water expand when it freezes instead of contracting?

Question

Eli5: Materials expand when heated and contracts when cooled. So why does water expand when it freezes instead of contracting?

In: 24

Answer 1

Water molecules are polarized, you can think of them like little magnets in some ways.

Say you put a bunch of rocks in a bag and shook it then let it settle. The rocks are gonna settle in next to each other and fill in a lot of space, it’ll be more compact than before.

Then put a bunch of magnets into a bag and shake it, the magnets aren’t gonna want to bunch in next to each other the wrong way once it settles. They’ll form structures that make the magnets happy. These structures don’t use all of the space efficiently and they’ll be more spread out which increases volume

Not a perfect metaphor but I hope it gets the point across