Yes, water does expand when it freezes. This is why ice is less dense than liquid water and floats on top.

Quick Scoop

What actually happens

  • As water cools down, it contracts until about 4 °C, getting slightly denser.
  • Below 4 °C and especially at 0 °C, the molecules lock into a crystal structure (a hexagonal lattice) that forces them farther apart.
  • Because the molecules are held in this open structure, the same amount of water now takes up more volume as ice.

How much does it expand?

  • When water turns to ice, its volume increases by roughly 9–10%.
  • That is enough to burst rigid containers like glass bottles or cans if they are completely filled with water and frozen.

Why this is unusual

  • Most liquids get denser when they freeze and therefore contract, but water is one of the exceptions.
  • Other substances that also expand on freezing include bismuth, gallium, and a few others, but water is the most familiar everyday example.

Real‑world effects

  • Ice floats because it is less dense than liquid water; if it sank, lakes and oceans could freeze solid from the bottom up, which would be devastating for aquatic life.
  • The expansion of freezing water contributes to weathering of rocks (freeze–thaw cycles) and to things like cracked pavement and damaged pipes in winter.

Information gathered from public forums or data available on the internet and portrayed here.