What happens to ice in comparison to liquid water in terms of density?

Ice is less dense than liquid water due to the unique molecular structure of water and how it behaves as it freezes. Water molecules are composed of two hydrogen atoms and one oxygen atom (H₂O) and, when in liquid form, they are more closely packed together. As water cools and begins to freeze, the molecules form a crystalline structure that causes the molecules to be spaced further apart than they are in the liquid state. This increased distance between the water molecules in ice results in a lower density compared to liquid water.

This phenomenon is critical to understanding why ice floats on water, as substances with lower density will always float when placed in a fluid of higher density. The fact that ice is less dense than liquid water also has implications for aquatic life, as it insulates the water below and allows living organisms to survive even in freezing conditions.