Final answer:
In its liquid state, water forms and breaks hydrogen bonds as molecules move, which allows liquid water to have a fluid nature. Upon freezing, the hydrogen bonds in water form a crystalline structure that is less dense than liquid water.
Step-by-step explanation:
In the liquid state, the hydrogen bonds of water are dynamic. They can break and reform as the molecules move around, enabling the water to flow. As water is cooled, the molecular movement slows down, and upon freezing, these hydrogen bonds form a crystalline structure that makes ice less dense than liquid water, allowing ice to float. Water's ability to form and break hydrogen bonds gives it many of its unique properties, crucial for life and the environment. This dynamic bonding is contrasted with the more permanent hydrogen bonding seen in ice, which results in a molecular structure that maximizes gaps due to the angular shape of water molecules, leading to its unusual lower density in the solid state compared to the liquid state.