Eli5: How does water expand in a closed container? Shouldn’t it shrink and be compact as it forms into a solid which has tighter molecules?

Question

Context: I was trying to figure out why my coke glass bottle exploded in my freezer.

Update: As it turns out, water is a weird one amongst other liquids.

In: 3

Answer 1

Plutonium is of the few other substances that behaves in the same way.
When plutonium melts it forms a denser liquid than the solid metal – and plutonium being plutonium this means things could get very exciting indeed as a subcritical block of plutonium metal could become critical simply by melting – shortly after which everything else begins melting.
In fact plutonium is just plain weird – it has six different crystal forms with wildly different densities. Heating and cooling the metal makes it change crystal form – and once again it can go from reasonably safe sub criticality to ruin-your-day criticality just by a temperature change. Nuclear weapons avoid this problem by alloying plutonium with a small amount of gallium, aluminium or indium which prevent it from changing crystal forms.