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

Probably worth noting here. We are very lucky this is the case. If a lake froze and ice was denser than water, it would sink down until the lake was frozen solid and all marine life was dead.

Also, water has 19 known solid states! Some of them are actually denser than liquid water. They depend on pressure and temperature conditions for the most part.