Ice floats on water because it is less dense than its liquid form. In the liquid state, most water molecules are associated in a polymeric structure—that is, chains of molecules linked by weak hydrogen bonds. As water freezes, these molecules become more rigidly organized, forming an open, hexagonal lattice in which each oxygen atom is tetrahedrally coordinated with four neighboring molecules. This structure increases the space between molecules, reducing the density of ice compared to water. The density of water in its solid form (ice) is approximately 917 kilograms per cubic meter, while in its liquid form, it is about 1,000 kilograms per cubic meter.

According to Archimedes’ principle, an object will float if the buoyant force, equal to the weight of the displaced fluid, exceeds the object’s weight. The lower density of ice ensures this condition is met, which is why icebergs remain afloat. Floating ice accumulates on the surface of lakes and oceans, creating an insulating cover that regulates the temperature below and protects aquatic life during cold periods.