In its most common usage, the term phase change indicates that a substance has changed among the three classical phases of matter: solid, liquid and gas. A change from solid to liquid is called melting, while the reverse is called freezing. A change from liquid to gas is called boiling, while the reverse is called condensation. And a change from solid to gas is called sublimation, while the reverse is called deposition. For pure compounds, phase changes occur at well defined temperature and pressure conditions, as shown in a phase diagram. For mixtures of materials, a phase change may occur over a range of conditions. As studied in the field of thermodynamics, melting, boiling and sublimation absorb heat, while freezing, condensation and deposition give off heat. In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... A solid is a phase of matter, characterized by resistance to deformation and changes of volume. ... A liquid will assume the shape of its container. ... A gas is one of the phases of matter. ... Physics In physics, melting is the process of heating a solid substance to a point (called melting point) where it turns liquid. ... In physics and chemistry, freezing is the process of cooling a liquid to the temperature (called freezing point) where it turns solid. ... Boiling is the rapid vaporization of a liquid, which typically occurs when a liquid is heated to a temperature such that its vapor pressure is above that of the surroundings. ... Condensation can refer to: The change in phase of a substance to a denser phase, such as gas to a liquid. ... Sublimation of an element or substance is a conversion between the solid and the gaseous phases of matter, with no intermediate liquid stage. ... Deposition is the process by which, in sub-freezing air, water vapor changes directly to ice without first becoming a liquid. ... Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ... Pressure is the application of force to a surface, and the concentration of that force in a given area. ... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... This article needs to be cleaned up to conform to a higher standard of quality. ... A red-hot iron rod cooling after being worked by a blacksmith. ...

A phase changing material (from liquid to gas for example) is used in thermal energy (heat) transfer. This technology is used in refrigeration and air conditioning equipment. A heat pump uses an expansion valve and a gas compressor to change the refrigerant repeatidly from a liquid to a gas (absorbs the latent heat) and from a gas to a liquid (releases latent heat). The process is also used as a form of computer cooling where a freon compressor based cooler is used. A Phase Change Material is matter which undergos a phase change at a specific temperature and gives off or takes in large amounts of energy in the process. ... Refrigeration (from the Latin frigus, frost) is generally the cooling of a body by the transfer of a portion of its heat away from it. ... Note: in the broadest sense, air conditioning can refer to any form of heating, ventilation, and air-conditioning. ... A heat pump is a machine which moves heat from a low temperature reservoir to a higher temperature reservoir under supply of work. ... A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. ... Latent heat describes the amount of energy in the form of heat that is required for a material to undergo a change of phase. ... A computer is a device or machine for processing information according to a program — a compiled list of instructions. ... Freon is a trade name for a group of chlorofluorocarbons used primarily as a refrigerant. ...

Phase change and optical disc technology

Phase change technology is also used to write to optical discs, such as CD-RW or DVD-RW discs. This is accomplished by including both a read laser and a more powerful write laser inside the drive. The discs are made of a crystalline material that, when hit by a pulse of laser light from the write laser, changes to an amorphous state, thus changing its reflectivity. The read laser is not powerful enough to induce a phase change, but can be used by the drive to tell whether a bit is "on" or "off" based on an area of the disc's reflectivity. In computing, sound reproduction, and video, an optical disc is flat, circular, usually polycarbonate disc whereon data is stored. ... In computing and data storage, Compact Disc Rewritable, or CD-RW, is a rewritable version of CD-ROM. Whereas standard prerecorded compact discs have their information permanently stamped into an aluminium reflecting layer, CD-RW discs have a phase-change recording layer made of silver, indium, antimony and tellurium, and... The title given to this article is incorrect due to technical limitations. ... Crystal (disambiguation) Insulin crystals A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... Laser (US Air Force) A LASER (Light Amplification by Stimulated Emission of Radiation) is an optical device which uses a quantum mechanical effect called stimulated emission (discovered by Einstein while researching the photoelectric effect) in order to generate a coherent beam of light from a lasing medium of controlled purity... An amorphous solid is a solid in which there is no long-range order of the positions of the atoms. ... In optics, reflectivity is the reflectance (the ratio of reflected power to incident power, generally expressed in decibels or percentage) at the surface of a material so thick that the reflectance does not change with increasing thickness; , the intrinsic reflectance of the surface, irrespective of other parameters such as the... This article is about the unit of information. ...

History of phase change optical disc technology

• 1995: PD (Phasewriter Dual) by Panasonic, store 650 MB.
• 1996: CD-RW (Compact Disc ReWritable) by Philips, Sony, Hewlett-Packard, Mitsubishi Chemical Corp. and Ricoh, store initially 650 MB and later 700 MB.
• 1998: DVD-RAM (DVD-Random Access Memory) by Panasonic, store initially 2.6 GB and later 4.7 GB.
• 199x: DVD±RW (DVD-ReWritable) by supplier consortium, store 4.7 GB.
• 2004: PDD (Professional Disc for Data) by Sony, store 20.5 GB.
• 2004: UDO (Ultra Density Optical) by Plasmon, store 28 GB.

Phase-Change Dual (PD) is a rewritable optical disc format introduced by Panasonic in 1995. ... Panasonic is principal sponsor of the Toyota F1 team Panasonic was also the name of a road bicycle racing team and a Finnish electronic music duo. ... This article is about a unit of data measurement. ... In computing and data storage, Compact Disc Rewritable, or CD-RW, is a rewritable version of CD-ROM. Whereas standard prerecorded compact discs have their information permanently stamped into an aluminium reflecting layer, CD-RW discs have a phase-change recording layer made of silver, indium, antimony and tellurium, and... Philips logo Koninklijke Philips Electronics N.V. (Royal Dutch Philips Electronics Ltd. ... Sony Corporation (Japanese katakana: ソニー) (TYO: 6758), NYSE: SNE is a global consumer electronics corporation based in Tokyo, Japan. ... The Hewlett-Packard Company (NYSE: HPQ), commonly known as HP, is a very large, global company headquartered in Palo Alto, California, United States. ... Categories: Stub | Companies traded on the Tokyo Stock Exchange ... You can recognize a DVD-RAM immediately because visually there are lots of little rectangles distributed on the surface of the data carrier. ... Panasonic is principal sponsor of the Toyota F1 team Panasonic was also the name of a road bicycle racing team and a Finnish electronic music duo. ... This article is about the unit of measurement, for the computer hardware manufacturer see Gigabyte Technology. ... The title given to this article is incorrect due to technical limitations. ... Sony Corporation (Japanese katakana: ソニー) (TYO: 6758), NYSE: SNE is a global consumer electronics corporation based in Tokyo, Japan. ... In physics, the plasmon is the quasiparticle resulting from the quantization of plasma oscillations, which are density waves of the charge carriers in a conducting medium such as a metal, semiconductor, or plasma. ...

See also

• CD-RW
• DVD-RW
• DVD+RW
• DVD-RAM
• MultiLevel Recording
• Phase-change Dual