Why water defies the rules of physics by floating as ice
In short: Most substances shrink and sink when they freeze, but water behaves differently. This video explores the unique molecular architecture that allows ice to remain buoyant, a phenomenon essential for life on Earth.
Unlike most solids, ice is less dense than liquid water because of how its molecules organize as they cool. In a liquid state, water molecules form loose chains connected by weak hydrogen bonds. However, as water freezes, these molecules lock into a rigid, open hexagonal lattice where each oxygen atom coordinates with four neighbors.
This geometric arrangement creates more space between molecules than in the liquid phase. Specifically, ice has a density of approximately 917 kilograms per cubic meter, compared to about 1,000 kilograms per cubic meter for liquid water. This lower density allows icebergs to displace enough weight to stay afloat, creating an insulating layer that protects aquatic life from extreme cold.
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Sources
- Summary by Intellect · source: Why Does Ice Float? Unlocking Water's Mysteries | BBC Earth Science
- Also: Why Does Ice Float on Water? | Structure, Density, & Buoyancy | Britannica
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