Sublimation

sublimation, in chemistry

sublimation (sŭblĭmā`shən), change of a solid substance directly to a vapor without first passing through the liquid state. The term is also used to describe the reverse process of the gas changing directly to the solid again upon cooling. An example of sublimation is seen when iodine, on being heated, changes from a dark solid to a purplish vapor that condenses directly to a crystalline solid upon striking a cool surface. In this way pure crystals of iodine are prepared. Some other substances, e.g., mercuric chloride, can be prepared by sublimation. Solid carbon dioxide, commonly known as dry ice, sublimes at −78.5°C; (−109.3°F;). Sublimation also occurs when air saturated with water vapor is suddenly cooled below the freezing point of water. Frost and snowflakes are thus formed by water changing directly from the gaseous to the solid state.

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sublimation, in psychology

sublimation, in psychology: see defense mechanism; psychoanalysis.

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sublimation

In physics, the change of state of a substance from a solid to a gas without first becoming liquid. One example is the vaporization of frozen carbon dioxide, or dry ice, at ordinary atmospheric pressure and temperature. The phenomenon occurs at pressures and temperatures (both relatively low) where solid and vapour phases coexist in equilibrium. Preservation of food by freeze-drying involves sublimation of water from the food in a frozen state under vacuum.

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sublimation [‚səb·lə′mā·shən]

(psychology)

A defense mechanism whereby the energies of undesirable instinctual cravings and impulses are converted into socially acceptable activities.

(thermodynamics)

The process by which solids are transformed directly to the vapor state or vice versa without passing through the liquid phase.

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Sublimation 

the transition of a substance from the crystalline state directly into the gaseous state without melting; it occurs with the absorption of heat (first-order phase transition).

Sublimation is a type of vaporization and is possible over the entire range of temperatures and pressures at which the solid and gaseous phases coexist. The energy required for sublimation is called the heat of sublimation, or latent heat of sublimation. The relationship between the heat of sublimation, the saturation vapor pressure above the solid, and the temperature under equilibrium conditions is given by the Clausius-Clapeyron equation. Sublimation of metal crystals leads to the formation of mon-atomic vapors. Ionic crystals, upon evaporation, often form polar molecules in the gaseous phase. Molecular crystals form vapors consisting of molecules.

The main kinetic characteristic of sublimation is the rate of sublimation, which is the mass of a substance that sublimes per unit time. The dependence of the limiting rate of sublimation of substances on the temperature and the properties of the gaseous phase is the basis for selection of materials for heat-shielding of spacecraft. Sublimation with the subsequent growth of pure crystals in a gaseous medium is widely used for the purification of solids.

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Sublimation 

in psychology, the psychological process by which the energy of affective drives is transformed and transferred to goals of social action and cultural creativity. The concept of sublimation was introduced by S. Freud in 1900. In Freudian psychoanalysis, sublimation is viewed as one form of transformation of a drive—such as the libido—and as the opposite of repression. In social psychology, sublimation is associated with the processes of socialization. The problems of sublimation are a subject of special study in such areas as child psychology, sports psychology, and the psychology of creativity.