waterdamp

Waterdamp, or water vapor, is the gaseous state of water. It forms when liquid water evaporates or boils and disperses within air or other gases. In Earth’s atmosphere, waterdamp is usually invisible in small amounts, though visible plumes can appear when large amounts condense into droplets, such as steam or fog.

Properties: Waterdamp participates in gas mixtures and has a partial pressure that depends on temperature. The maximum quantity the air can hold at a given temperature is its saturation vapor pressure; warmer air can contain more waterdamp. Relative humidity expresses how close the air is to saturation, as the ratio of actual vapor pressure to saturation vapor pressure, usually shown as a percentage. Specific humidity and mixing ratio measure the amount of waterdamp per unit mass of air or per kilogram of dry air. The dew point is the temperature at which air becomes saturated and condensation begins.

Formation and phase changes: Evaporation transfers water from liquid to gas, while condensation reverses the process, releasing latent heat. When moist air cools to its dew point, droplets form, producing fog, dew, or clouds.

Role in environment and climate: Waterdamp is a major greenhouse gas and a key driver of Earth’s energy balance. Its concentration increases with temperature, creating feedback that can amplify warming. Waterdamp also influences weather through cloud formation, precipitation, and the distribution of heat.

Measurement and applications: Humidity is measured with hygrometers or psychrometers and monitored via remote sensing. Practical uses include steam generation, sterilization, humidity control in buildings and manufacturing, and various food-processing applications.

Safety and health: High humidity can affect comfort and health; exposure to high-temperature steam can cause severe burns.