vapors

Vapors are gaseous substances that originate from liquids or solids through processes such as evaporation, boiling, sublimation, or chemical reactions. In everyday language the term often refers to the visible mist produced when a liquid rapidly changes to gas, as seen with steam from hot water or the aerosols generated by inhalers and humidifiers. Scientifically, vapors are distinguished from gases by their source material and their tendency to condense back to a liquid or solid when temperature or pressure conditions change.

The formation of a vapor involves the overcoming of intermolecular forces that hold particles together in the condensed phase. When sufficient kinetic energy is supplied—by heating, a reduction in pressure, or the addition of a volatile solvent—molecules escape into the surrounding atmosphere as vapor. The equilibrium between a liquid and its vapor is described by vapor pressure, a measure of the tendency of a substance to evaporate at a given temperature.

Vapors play important roles in natural and technological contexts. In the water cycle, atmospheric water vapor condenses to form clouds, enabling precipitation. In industrial settings, vapor‑phase processes such as chemical vapor deposition are used to create thin films and coatings. Occupational exposure to certain vapors, especially those containing hazardous chemicals like solvents or anesthetic agents, is regulated to protect health, as inhalation can lead to acute or chronic effects.

In scientific literature the term “vapor” is often replaced by more specific descriptors—e.g., “steam” for water vapor, “volatile organic compound vapor” for organic solvents—to convey precise composition and properties. Understanding vapor behavior is essential for fields ranging from meteorology and environmental science to engineering and medicine.