Why are hydrogen bonds important to the properties of water and ice?

Hydrogen bonds are essential to the unique physical and chemical properties of water and ice because they dictate how water molecules interact and organize themselves.12

The Role of Hydrogen Bonds

Water molecules contain oxygen atoms with lone-pair electrons that attract the hydrogen nuclei of adjacent molecules, forming hydrogen bonds. While these bonds are relatively weak, they significantly influence water's behavior:12

• Density and Floating: In liquid water, hydrogen bonds allow molecules to form shifting, polymeric structures. As water freezes, these bonds force molecules into a rigid, open hexagonal lattice. This structure increases the space between molecules, making ice less dense than liquid water—a rare property that allows ice to float and insulate aquatic environments.13
• Boiling and Melting Points: Hydrogen bonding explains why water has unusually high boiling and melting points compared to similar compounds like hydrogen sulfide. Significant thermal energy is required to break these bonds to transition water from a solid to a liquid or from a liquid to a gas.42
• Structural Integrity: These bonds also influence properties like viscosity and surface tension by maintaining short-range order among molecules in the liquid state.2