Question

What enables ice to float?

Answer 1

Because, unusually, the density of the solid phase is LESS than the density of the liquid phase.

Explanation:

An ice cube in a glass of water floats. An iceberg when it forms (when it `"calves"` from a glacier), floats in the ocean and becomes a hazard to shipping. That the solid phase is LESS dense than the liquid phase is a highly unusual phenomenon.

The structure of solid ice is ordered by hydrogen bonding between molecules; it happens that the arrangement of solid water molecules occupy 10% more volume than the liquid volume. Hence ice floats. Given that sea water contains a lot of salts, the buoyancy of a fresh water berg should also be greater.