The reason ice floats on water, unlike most solids that sink in liquids, is due to the unique property of water related to its density and molecular structure. When water freezes into ice, it forms a crystal lattice structure held together by hydrogen bonds. This lattice arrangement spaces the water molecules farther apart than in liquid water, making ice about 9% less dense than liquid water. Because ice is less dense, it displaces a weight of water equal to its own weight and therefore floats on the surface

. In more detail, water molecules are polar and form hydrogen bonds, which in liquid water are flexible and allow molecules to pack closely. As water cools and freezes, these hydrogen bonds create a rigid, hexagonal crystal lattice that holds molecules at a fixed distance, increasing the volume and decreasing the density of ice compared to liquid water. This is why ice expands when it freezes and why it floats rather than sinks

. This property is crucial for aquatic life and Earth's climate because it causes bodies of water to freeze from the top down, allowing life to survive beneath the ice layer

. Summary:

• Ice is less dense than liquid water due to its crystal lattice structure formed by hydrogen bonds.
• This structure causes ice to occupy more volume and have lower density.
• Lower density makes ice float on water, unlike most solids which sink.

This unique property of water explains why ice floats when placed in water.