What causes ice to float on water?

Ice floats on water because it is less dense than liquid water. This phenomenon is primarily due to the molecular structure of water. As water freezes, its molecules arrange themselves in a crystalline structure that is more spaced out compared to the arrangement of molecules in liquid water. This structure causes ice to occupy more volume with the same mass, resulting in lower density.

The unique properties of hydrogen bonding in water also contribute to this behavior, as they create an open and less compact structure in ice compared to the more densely packed molecules found in liquid water. This difference in density is crucial for many ecological systems, allowing ice to form an insulating layer on top of lakes and ponds while the water below remains liquid, providing a habitat for aquatic life even in cold environments.