Melting
From Wikipedia, the free encyclopedia
Categories: Articles lacking sources from July 2007 | All articles lacking sources | Mechanical failure modes | Metallurgy | Phase changes | Amorphous liquids
"Molten" redirects here. For the Japanese company, see Molten Corporation.
Melting is a process that results in the phase change of a substance from a solid to a liquid. The internal energy of a solid substance is increased (typically by the application of heat) to a specific temperature (called the melting point) at which it changes to the liquid phase. An object that has melted completely is molten. The melting point of a substance is a characteristic property. The melting point may not be equal to the freezing point. This is evident in the phenomenon known as supercooling. This occurs when a liquid is cooled below the melting point without the nucleation of crystals. In the case of water, ice crystals typically require a seed on which to begin formation. Water on a very clean glass surface will often supercool several degrees below the melting point without freezing. This is why, on a cold morning, windshield wipers will swipe condensation from a windshield only to have any remaining moisture rapidly freeze due to the disturbance. Fine emulsions of pure water have been cooled to -38 degrees celsius without the nucleation of ice taking place. For this reason, melting point is a characteristic property of a substance while freezing point is not.
Molecular vibrationsWhen the internal energy of a gas is increased by the application of an external energy source, the molecular vibrations of the substance increases. As these vibrations increase, the substance becomes more and more ordered. Constant temperatureSubstances melt at a constant temperature, the melting point. Further increases in temperature (even with continued application of energy) do not occur until the substance is molten. The thermodynamics of meltingFrom a thermodynamics point of view, at the melting point the change in Gibbs free energy (Failed to parse (Missing texvc executable; please see math/README to configure.): \Delta G ) of the Material is zero, because the enthalpy (Failed to parse (Missing texvc executable; please see math/README to configure.): H ) and the entropy (Failed to parse (Missing texvc executable; please see math/README to configure.): S ) of the material are increasing (Failed to parse (Missing texvc executable; please see math/README to configure.): \Delta H, \Delta S > 0 ). Melting phenomenon happens when the Gibbs free energy of the liquid becomes lower than the solid for that material. At various pressures this happens at a specific temperature. It can also be shown that: Failed to parse (Missing texvc executable; please see math/README to configure.): \Delta S = \frac {\Delta H} {T}
Books
Other meanings Look up melting in Wiktionary, the free dictionary.
In genetics, melting DNA means to separate the double-stranded DNA into two single strands by heating or the use of chemicals.which means that your dna is made of two different parts
See also
ca:Fusió (canvi d'estat) cs:Tání da:Smeltning de:Schmelzen et:Sulamine el:Τήξη es:Fusión (cambio de estado) eu:Urtze fa:ذوب fr:Fusion (physique) it:Fusione (fisica) he:התכה lv:Kušana lt:Lydymasis nl:Smelten (faseovergang) ja:融解 nds:Smölten pl:Topnienie pt:Fusão ru:Плавление simple:Melting sk:Topenie sl:Taljenje fi:Sulaminen sv:Smältning tr:Erime uk:Плавлення | |||||||||||||||||||||||||||||||||||||||||||||||
