what happens if gold and cooled? explain both.
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Answer:
Gold occurs in association with ores of copper and lead, in quartz veins, ... After this solid solution cooled, its gold content was spread through such a ...
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Explanation:
The chemical element gold, atomic number 79, symbol Au (from the Latin aurum), is a soft, lustrous yellow, malleable metal. It is one of the transition metals and its atomic weight is 196.967; it belongs to group 1B in the periodic table along with copper and silver.
Although the Earth's crust averages a mere 0.004 grams of gold per ton, commercial concentrations of gold are found in areas distributed widely over the globe. Gold occurs in association with ores of copper and lead, in quartz veins, in the gravel of stream beds, and with pyrites (iron sulfide). Seawater contains astonishing quantities of gold, but the process of recovery is not economical. The ancients found quantities of gold in Ophir, Sheba, Uphaz, Parvaim, Arabia, India, and Spain. By the time of Christ, written reports were made of deposits in Thrace, Italy, and Anatolia. Gold is also found in Wales, in Hungary, in the Ural Mountains of Russia, and, in large quantities, in Australia. The greatest early surge in gold recovery followed the first voyage of Columbus. From 1492 to 1600, Central and South America, Mexico, and the islands of the Caribbean Sea contributed significant quantities of gold to world commerce. Colombia, Peru, Ecuador, Panama, and Hispaniola contributed 61% of the world's newfound gold during the 17th century. In the 18th century they supplied 80%. Following the discovery (1848) of gold in California, North America became the world's major supplier of the metal. From 1850 to 1875 more gold was discovered than in the previous 350 years. By 1890 the gold fields of Alaska and the Yukon edged out those in the western United States, and soon the African Transvaal exceeded even these. Today the world's unmined reserves are estimated at 1 billion troy oz (31 billion grams), about half in the Witwatersrand area of the Republic of South Africa.
The distribution of gold seems to validate the theory that gold was carried toward the Earth's surface from great depths by geologic activity, perhaps with other metals as a solid solution within molten rock. After this solid solution cooled, its gold content was spread through such a great volume of rock that large fragments were unusual; this theory explains why much of the world's gold is in small, often microscopic particles. The theory also explains why small amounts of gold are widespread in all igneous rocks; they are rarely chemically combined and seldom in quantities rich enough to be called an ore. Because of its poor chemical reactivity, gold was one of the first two or three metals (along with copper and silver) used by humans in these metals' elemental states. Because it is relatively unreactive, it was found uncombined and required no previously developed knowledge of refining. Gold was probably used in decorative arts before 9000 BC. Even civilizations that developed little or no use of other metals prized gold for its beauty.Elemental gold has a melting point of 1,063 deg C and a boiling point of 2,966 deg C.
In addition to its softness, it is both the most malleable and most ductile of all elements. This means that it can be hammered into extremely thin sheets (approaching a small number of atoms) and can be drawn into extremely fine wire. Gold in the form of very thin sheets, called gold leaf, has many decorative uses. Elemental gold is an excellent conductor of electricity and heat, surpassed only by the other members of group 1B, copper and silver. Gold usually forms compounds (and complexes) by giving up either one of three of its valence electrons. It is commonly alloyed with other metals, as in jewelry, in proportions that yield desired hardiness and colors, (see metal section). An alloy of gold, silver, and copper, in which the amounts of silver predominates, is called "green gold." An alloy of the same three elements in which copper predominates is called "red gold." An alloy of gold and nickel is called "white gold." The purity of alloyed gold is expressed by the karat system, where the percent of gold by weight is given as a fraction of 24. Therefore, pure gold is 24 karat, whereas 18 karat gold is 18/24, or 75%, gold by weight. Gold dissolves in very few solvents, among them aqua regia and the various solutions of cyanide that are used in ore extraction. When gold does dissolve, it is generally by forming complexes. Gold also forms amalgams with mercury and as such is used in dentistry.