Impurities are substances inside a confined amount of liquid, gas, or solid, which differ from the chemical composition of the material or compound. in philosophy, Substance is that element of an object without which it would not exist. ... A liquid will assume the shape of its container. ... A gas is one of the four main phases of matter (after solid and liquid, and followed by plasma), that subsequently appear as a solid material is subjected to increasingly higher temperatures. ... In jewelry, a solid gold piece is the alternative to gold-filled or gold-plated jewelry. ... The chemical composition of a substance refers to the elements of which the substance is composed. ...

Impurities are either naturally occurring or added during synthesis of a chemical or commercial product. During production, impurities may be purposely, accidentally, inevitably, or incidentally added into the substance. Synthesis (from the Greek words syn = plus and thesis = position) is commonly understood to be an integration of two or more pre-existing elements which results in a new creation. ...

The level of impurities in a material are generally defined in relative terms. Standards have been established by various organizations that attempt to define the permitted levels of various impurities in a manufactured product. Strictly speaking, then, a material's level of purity can only be stated as being more or less pure than some other material. Standardization, in the context related to technologies and industries, is the process of establishing a technical standard among competing entities in a market, where this will bring benefits without hurting competition. ...

Destructive impurities

Impurities can be destructive when they obstruct the working nature of the material. Examples include ash and debris in metals and leaf pieces in blank white papers. The removal of impurities is usually done chemically. For example, in the manufacturing of iron, calcium carbonate is added to the blast furnace to remove silicon dioxide from the iron ore. Zone refining is an economically important method for the purification of semiconductors. Debris (French, pronounced (IPA) dibri) is a word used to describe the remains of something that has been otherwise destroyed. ... For alternative meanings see metal (disambiguation). ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... Blast furnace diagram A blast furnace is a type of furnace for smelting metal ore. ... R-phrases R42 R43 R49 S-phrases S22 S36 S37 S45 S53 Flash point non-flammable Supplementary data page Structure and properties n, εr, etc. ... Iron ore (Banded iron formation) Manganese ore Lead ore Gold ore An ore is a volume of rock containing components or minerals in a mode of occurrence which renders it valuable for mining. ... Zone melting is a method of separation by melting in which a series of molten zones traverses a long ingot of impure metal or chemical. ...

However, some kinds of impurities can be removed by physical means. A mixture of water and salt can be separated by distillation, with water as the distillate and salt as the solid residue. Impurities are usually only physically removed from liquids and gases. Removal of sand particles from metal ore powders is one example with solids. A magnified crystal of a salt (halite/sodium chloride) In chemistry, a salt is any ionic compound composed of positively charged cations and negatively charged anions, so that the product is neutral and without a net charge. ... Strathisla whisky distillery in Keith, Scotland Distillation is a method of separation of substances based on differences in their vapor pressures. ... A residue, broadly, is anything left behind by a reaction or event. ...

No matter what method is used, it is usually impossible to separate an impurity completely from a material. What technicians can do is to increase the purity of a material to as near 100% as possible or economically feasible. ...

Constructive impurities

Impurities can, though, add constructive properties to a material. Alloys are metals with impurities. The resulting combination has desirable properties not found in the constituent materials. Steel, for example, is made by introducing a controlled amount (less than 2%) of carbon into pure iron. In the manufacturing of solar cells, pure silicon is mixed with a very small portion of impurities (0.001% to 0.01%) in the form of phosphorus and boron atoms in order to generate electricity. This is known as doping of silicon and is constructive, although the phosphorus and boron could be called impurities. A property is an intrinsic or extrinsic quality of an object—where an object may be of any differing nature, depending on the context and field — be it computing, philosophy, etc. ... Alloy is a combination, either in solution or compound, of two or more elements, which has a combination of at least one metal, and where the resultant material has metallic properties. ... The old steel cable of a colliery winding tower Steel is a metal alloy whose major component is iron, with carbon being the primary alloying material. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... A solar cell, a form of photovoltaic cell, is a device that uses the photoelectric effect to generate electricity from light, thus generating solar power (energy). ... General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance dark gray, bluish tinge Atomic mass 28. ... This article is about the chemical element. ... General Name, Symbol, Number boron, B, 5 Chemical series metalloids Group, Period, Block 13, 2, p Appearance black/brown Atomic mass 10. ... In semiconductor production, doping refers to the process of intentionally introducing impurities into an intrinsic semiconductor in order to change its electrical properties. ...

Impurities and nucleation

When an impure liquid is cooled to its melting point the liquid, undergoing a phase transition, crystallizes around the impurities and becomes a crystalline solid. If there are no impurities then the liquid is said to be pure and can be supercooled below its melting point without becoming a solid. This occurs because the liquid has nothing to condense around so the solid cannot form a natural crystalline solid. The solid is eventually formed when dynamic arrest or glass transition occurs, but it forms into an amorphous solid — a glass, instead, as there is no long-range order in the structure. The melting point of a solid is the temperature at which it changes state from solid to liquid. ... In physics, a phase transition, (or phase change) is the transformation of a thermodynamic system from one phase to another. ... Quartz crystal 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. ... Supercooling is the process of chilling a liquid below its freezing point, without its becoming solid. ... A simplistic view of a materials glass transition temperature (Tg) is the temperature below which molecules have very little mobility. ... A simplistic view of a materials glass transition temperature (Tg) is the temperature below which molecules have very little mobility. ... An amorphous solid is a solid in which there is no long-range order of the positions of the atoms. ... This article refers to the material. ... In physics, long-range order characterizes physical systems in which remote portions of the same sample exhibit correlated behavior. ...

Impurities play an important role in the nucleation of other phase transitions. For example, the presence of foreign elements may have important effects on the mechanical and magnetic properties of metal alloys. Iron atoms in copper cause the renowned Kondo effect where the conduction electron spins form a magnetic bound state with the impurity atom. Magnetic impurities in superconductors can serve as generation sites for vortex defects. Point defects can nucleate reversed domains in ferromagnets and dramatically affect their coercivity. In general impurities are able to serve as initiation points for phase transitions because the energetic cost of creating a finite-size domain of a new phase is lower at a point defect. In order for the nucleus of a new phase to be stable, it must reach a critical size. This threshold size is often lower at an impurity site. The Kondo effect refers to the non-trivial physics associated with the presence of a magnetic impurity in a solid (generally, a metal). ... Superconductivity is a phenomenon occurring in certain materials at low temperatures, characterised by the complete absence of electrical resistance and the damping of the interior magnetic field (the Meissner effect. ... Vortex created by the passage of an aircraft wing, revealed by coloured smoke A vortex is a spinning turbulent flow (or any spiral whirling motion) with closed streamlines. ... A ferromagnet is a piece of ferromagnetic material, in which the microscopic magnetized regions, called domains, have been aligned by an external magnetic field (e. ... In material science, the Coercivity of a ferromagnetic material is the intensity of the magnetic field required to reduce the magnetization of that material to zero after the magnetization of the sample has reached saturation. ... In physics, a phase transition, (or phase change) is the transformation of a thermodynamic system from one phase to another. ...

See also

• dross
• fineness
• semiconductor
• spin wave

Dross is a mass of solid impurities floating on a molten metal bath. ... The fineness of a precious metal refers to the ratio of the primary metal to any additives or impurities. ... A semiconductor is a material with an electrical conductivity that is intermediate between that of an insulator and a conductor. ... Spin waves are low-lying collective excitations that occur in magnetic lattices with continuous symmetry. ...

References

1. Longman's English-Chinese Dictionary of Chemistry, Hong Kong, 1997.