Water is the only known non-metallic substance that expands when it freezes; its density decreases and it expands approximately 9% by volume.Doesn't liquid expand when it freezes? Always gotta short fill the ice cube tray or it overflows when ya freeze it. Pipes split when the liquid in the freezes. Don't get me started on the mess ya have to clean up when ya accidentally freeze a stubby or tinny of the good stuff. Returning frozen liquid to it's natural fluid state should slightly shrink the volume. Heating it towards boiling temp might expand it, but we're not getting that warm just yet.
4 degrees C turns out to be the temperature at which liquid water has the highest density. If you heat it or cool it, it will expand. The expansion of water when you cool it to lower temperatures is unusual, since most liquids contract when they're cooled.