How do densities of ice, liquid water, and vapor compare?

Water’s density changes depending on whether it’s liquid, solid (ice), or gas (vapor). The order goes like this: liquid water (highest density), ice (lower), and vapor (lowest).

Liquid water is denser than ice because its molecules are packed closely together. Ice, on the other hand, has a more open, cage-like structure. Vapor is the least dense since its molecules are spread far apart.

Density Comparison

• Liquid Water: The densest form, about 1000 kg/m³ or 1 g/cm³.
• Ice (Solid Water): Less dense than liquid water at about 917 kg/m³ or 0.917 g/cm³. This is why ice floats on water.
• Water Vapor (Steam): The least dense, only about 0.001 kg/m³ (around 0.02 g/ml under normal conditions).

Why the Difference?

• Molecular Arrangement: The way water molecules are organized in each state changes the density.
• Ice’s Crystalline Structure: Molecules form a hexagonal lattice with lots of empty space, reducing density.
• Liquid Water’s Compactness: Molecules are bonded but shift around, allowing them to pack closer together, making liquid water denser.
• Water Vapor’s Gaseous State: Molecules are far apart and move freely, giving vapor the lowest density.