Which fundamental principle explains why ice floats on water?

The principle that explains why ice floats on water is density. Density is defined as the mass of a substance per unit volume. In the case of water, it reaches its maximum density at approximately 4 degrees Celsius. As water cools further and freezes into ice, its structure becomes more open due to the hydrogen bonding between water molecules, leading to a crystalline arrangement. This structure causes ice to occupy more volume compared to the same mass of liquid water, resulting in a lower density for ice—a property that is quite unique for water.

Since ice has a lower density than liquid water, it is buoyant and can float. In contrast, more dense substances will sink in water. This phenomenon of ice floating is crucial in nature, as it creates an insulating layer on bodies of water, allowing aquatic life to survive underneath during cold weather. The other principles listed, such as buoyancy, viscosity, and surface tension, do not directly explain this specific behavior related to density differences between ice and water.