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Answer: Condensation is the process by which water vapor in the air is changed into liquid water; it's the opposite of evaporation. Condensation is crucial to the water cycle because it is responsible for the formation of clouds.

An everyday example

Water on the outside of a cold glass on a humid day is condensation. If you wear glasses and go from a cold, air-conditioned room to outside on a humid day, the lenses fog up as small water droplets coat the surface via condensation.

What happens to the molecules

The arrangement of water molecules changes as water changes between its gaseous (vapor), liquid, and solid forms. Water molecules in the vapor form are arranged more randomly than in liquid water. As condensation occurs and liquid water forms from the vapor, the water molecules become more organized, and heat is released into the atmosphere as a result.

Its place in the water cycle

• The air is full of water vapor, although most of the time we can't see it.
• Clouds are formed by water condensing in the atmosphere.
• These clouds may produce precipitation, which is the primary route for water to return to the Earth's surface.
• Both condensation and precipitation are important fluxes in our water cycle.

Claims

• id: C1 claim: Condensation turns water vapor into liquid water. source: S1 evidence: "Condensation is the process of gaseous water (water vapor) turning into liquid water."
• id: C2 claim: Condensation is the opposite of evaporation. source: S1 evidence: "it’s the opposite of evaporation."
• id: C3 claim: Clouds are formed by water condensing in the atmosphere. source: S2 evidence: "Clouds are formed by water condensing in the atmosphere."

Sources

• [S1] Condensation and the Water Cycle. USGS. https://www.usgs.gov/special-topics/water-science-school/science/condensation-and-water-cycle . License: US government work, public domain. Accessed 2026-11-04.
• [S2] Water cycle. USGS. https://www.usgs.gov/special-topics/water-science-school/science/water-cycle . License: US government work, public domain. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_qt8wwenf,
  author = {{iinventedlight}},
  title = {{Condensation: how water vapor becomes clouds}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/condensation/},
  note = {Permanent ID iil:note:qt8wwenf. License: CC-BY-4.0.},
}

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