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In chemistry, it is the change of a substance from the solid state to steam without going through the liquid state.
Some of the molecules in a solid can vibrate very quickly, overcome cohesion forces and escape as gaseous molecules into free space: the solid sublimates. Conversely, when these gaseous molecules collide with the surface of the solid, they can be retained, condensing the vapor. The equilibrium that occurs when the sublimation and condensation rates are the same is characterized by a vapor pressure that depends on the nature of the solid and the temperature.
The characteristic odors of many solid substances, such as iodine, naphthalene, iodoform and solid perfumes, are due to the fact that these substances have an appreciable vapor pressure at room temperature.
The sublimation process is necessarily accompanied by an absorption of thermal energy. The amount of thermal energy that is needed to sublimate a kilogram of solid-state substance at constant temperature is known as latent heat or sublimation heat. The latent heat of sublimation of a substance is equal to the sum of the latent heat of fusion plus the latent heat of vaporization.
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