sublimaatioon

Sublimation is the phase transition in which a solid changes directly into a gas, bypassing the liquid phase. This occurs when the solid’s vapor pressure exceeds the surrounding pressure, a condition common at low pressures or at sufficiently high temperatures relative to the substance’s melting point. The process is the reverse of deposition, where a gas becomes a solid.

Common examples include dry ice (solid carbon dioxide), which at room temperature steadily sublimes into carbon dioxide gas, and iodine, which readily forms a violet vapor. In nature, snow and frost can sublimate under dry, windy conditions, slowly turning into water vapor. Sublimation rates depend on temperature, pressure, surface area, and the presence of vacuum or cooling.

Applications and uses

Sublimation is exploited in purification and analytical techniques, where a volatile component is separated from non-volatile impurities. Freeze-drying (lyophilization) uses sublimation to remove water from preserved materials without passing through a liquid phase. Sublimation printing transfers dye from a solid to a substrate by converting the dye to gas and then depositing it onto textiles or other materials, producing durable, vibrant images.

Key thermodynamic properties include the enthalpy (latent heat) of sublimation and the conditions under which sublimation occurs for a given substance. Safety considerations include the potential hazards of sublimed vapors and the need for adequate ventilation, especially with toxic or suffocating gases.

In psychology, sublimation also refers to a defense mechanism in which unacceptable impulses are redirected into socially acceptable actions, a usage distinct from the physical process.