How Hot Water Becomes Steam: Vaporization & Condensation

Molecular Process

1. Heating: Kinetic energy of H₂O molecules increases.
2. Hydrogen bond breaking: Intermolecular forces weaken; molecules escape liquid phase.
3. Vaporization: At boiling point (100°C at 1 atm), vapor pressure = atmospheric pressure. Bubbles form throughout liquid—boiling.
4. Steam formation: Invisible water vapor rises.
5. Condensation: Vapor cools in air → tiny liquid droplets (aerosol)—visible as "steam" (technically wet steam/condensate cloud).

Key Points

• Steam ≠ vapor: True steam is invisible gas; visible "steam" is condensed droplets.
• Pressure dependence: Boiling point drops with altitude (lower pressure).
• Latent heat: 2,260 kJ/kg absorbed at phase change—massive energy storage.

This physics powers steam engines, turbines, cooking, heating—and the water cycle itself.