# Is solid water more or less dense than liquid water? Why?

The density of ice is $0.9168 \cdot g \cdot c {m}^{-} 3$ at $0$ ""^@C, The density of liquid water is $0.9999 \cdot g \cdot c {m}^{-} 3$ at $0$ ""^@C. That the solid phase is less dense than the liquid phase is an highly unusual phenomenon. If it were the other way round, as is usually observed for phase transitions, ice-bergs would sink rather than float, and this planet's oceans would probably be ice-bound.