Final answer:
Hydrogen bonding causes water to be less dense in the solid state than in the liquid state.
Step-by-step explanation:
Hydrogen bonding causes water to be less dense in the solid state than in the liquid state. When water solidifies into ice, the hydrogen bonding between water molecules forces them to line up in a way that creates empty space between the molecules, increasing the overall volume of the solid. This arrangement makes ice less dense than liquid water, allowing it to float.