Water is unique because it is less dense as a solid than as a liquid. How can you account for this unusual attribute?
A. The liquid phase of water is unusually dense in comparison to other liquids because of its ability to hydrogen bond; the solid phase is not unusual.
B. Solids are, as a rule, less dense than liquids for most substances.
C. The solid phase of water has molecules tightly packed together in low parallel rows. This tight packing allows ice to float evenly on the surface of liquid water.
D. Ice exists in an open crystalline lattice that has large "gaps" that lower its density compared to liquid water where the molecules are close together.