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

beyond the phase shift from fluid (water) to solid (ice) water is just all around one of the weirder elements due to how its molecules can be grouped together.

in my eyes the most curious part is that at 4°C, so slightly above freezing, water has the highest density meaning “has contracted the most” compared to both 0°C and 10°C water.

if you heat it up close to the boiling point it will expand (very slightly), so the general trend/rule still applies.