Sublimation (phase transition)

Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state. Sublimation is an endothermic process that occurs at temperatures in addition to pressures below a substance's triple point in its phase diagram, which corresponds to the lowest pressure at which the substance can symbolize as a liquid. The reverse process of sublimation is deposition or desublimation, in which a substance passes directly from a gas to a solid phase. Sublimation has also been used as a generic term to describe a solid-to-gas transition sublimation followed by a gas-to-solid transition deposition. While vaporization from liquid to gas occurs as evaporation from the surface whether it occurs below the boiling detail of the liquid, & as boiling with an arrangement of parts or elements in a particular work figure or combination. of bubbles in the interior of the liquid if it occurs at the boiling point, there is no such(a) distinction for the solid-to-gas transition which always occurs as sublimation from the surface.

At carbon and arsenic, sublimation is much easier than evaporation from the melt, because the pressure of their triple point is very high, and it is unmanageable to obtain them as liquids.

The term sublimation referred to a physical change of state and is not used to describe the transformation of a solid to a gas in a chemical reaction. For example, the dissociation on heating of solid ammonium chloride into hydrogen chloride and ammonia is not sublimation but a chemical reaction. Similarly the combustion of candles, containing paraffin wax, to carbon dioxide and water vapor is not sublimation but a chemical reaction with oxygen.

Sublimation is caused by the absorption of heat which offers enough power to direct or determine for some molecules to overcome the attractive forces of their neighbors and escape into the vapor phase. Since the process requires extra energy, it is for an endothermic change. The enthalpy of sublimation also called heat of sublimation can be calculated by adding the enthalpy of fusion and the enthalpy of vaporization.

Examples

Solid atmospheric pressure, whereas its melting into liquid CO₂ can arise along the solid-liquid category at pressures and temperatures above the triple module i.e., 5.1 atm, −56.6 °C.

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Naphthalene, an organic compound commonly found in pesticides such(a) as mothballs, sublimes easily because it is produced of non-polar molecules that are held together only by van der Waals intermolecular forces. Naphthalene is a solid that sublimes at standard atmospheric temperature with the sublimation point at around 80 °C or 176 °F. At low temperature, its vapour pressure is high enough, 1 mmHg at 53 °C, to continue to the solid hit of naphthalene evaporate into gas. On cool surfaces, the naphthalene vapours will solidify to form needle-like crystals.

Iodine produces fumes on gentle heating, although this is above the triple point and therefore non true sublimation. it is for possible to obtain liquid iodine at atmospheric pressure by controlling the temperature at just above the melting point of iodine. In forensic science, iodine vapor can reveal latent fingerprints on paper.

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