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Copper

Copper

Gist

Copper is a reddish-brown metallic chemical element, known for its excellent conductivity of heat and electricity. It has the symbol Cu and atomic number 29. Copper is a soft, malleable, and ductile metal used in various applications, including electrical wiring, plumbing, and as a component in many alloys.

Copper is a reddish-brown metal known for its excellent electrical and thermal conductivity, malleability, and ductility. It's also highly corrosion-resistant, especially when it develops a protective patina. These characteristics make it a versatile material used in various applications, including electrical wiring, plumbing, and heat exchangers.

Summary

Copper is a chemical element; it has symbol Cu (from Latin cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orange color. Copper is used as a conductor of heat and electricity, as a building material, and as a constituent of various metal alloys, such as sterling silver used in jewelry, cupronickel used to make marine hardware and coins, and constantan used in strain gauges and thermocouples for temperature measurement.

Copper is one of the few metals that can occur in nature in a directly usable, unalloyed metallic form. This means that copper is a native metal. This led to very early human use in several regions, from c. 8000 BC. Thousands of years later, it was the first metal to be smelted from sulfide ores, c. 5000 BC; the first metal to be cast into a shape in a mold, c. 4000 BC; and the first metal to be purposely alloyed with another metal, tin, to create bronze, c. 3500 BC.

Commonly encountered compounds are copper(II) salts, which often impart blue or green colors to such minerals as azurite, malachite, and turquoise, and have been used widely and historically as pigments.

Copper used in buildings, usually for roofing, oxidizes to form a green patina of compounds called verdigris. Copper is sometimes used in decorative art, both in its elemental metal form and in compounds as pigments. Copper compounds are used as bacteriostatic agents, fungicides, and wood preservatives.

Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the respiratory enzyme complex cytochrome c oxidase. In molluscs and crustaceans, copper is a constituent of the blood pigment hemocyanin, replaced by the iron-complexed hemoglobin in fish and other vertebrates. In humans, copper is found mainly in the liver, muscle, and bone. The adult body contains between 1.4 and 2.1 mg of copper per kilogram of body weight.

Details

Copper (Cu), chemical element, a reddish, extremely ductile metal of Group 11 (Ib) of the periodic table that is an unusually good conductor of electricity and heat. Copper is found in the free metallic state in nature. This native copper was first used (c. 8000 bce) as a substitute for stone by Neolithic (New Stone Age) humans. Metallurgy dawned in Mesopotamia as copper was cast to shape in molds (c. 4000 bce), was reduced to metal from ores with fire and charcoal, and was intentionally alloyed with tin as bronze (c. 3500 bce). The Roman supply of copper came almost entirely from Cyprus. It was known as aes Cyprium, “metal of Cyprus,” shortened to cyprium and later corrupted to cuprum.

Element Properties

atomic number  :  29
atomic weight  :  63.546
melting point  :  1,083 °C (1,981 °F)
boiling point  :  2,567 °C (4,653 °F)
density  :  8.96 at 20 °C (68 °F)
valence  :  1, 2

Occurrence, uses, and properties

Native copper is found at many locations as a primary mineral in basaltic lavas and also as reduced from copper compounds, such as sulfides, math, chlorides, and carbonates. (For mineralogical properties of copper, see the table of native elements.) Copper occurs combined in many minerals, such as chalcocite, chalcopyrite, bornite, cuprite, malachite, and azurite. It is present in the ashes of seaweeds, in many sea corals, in the human liver, and in many mollusks and arthropods. Copper plays the same role of oxygen transport in the hemocyanin of blue-blooded mollusks and crustaceans as iron does in the hemoglobin of red-blooded animals. The copper present in humans as a trace element helps catalyze hemoglobin formation. A porphyry copper deposit in the Andes Mountains of Chile is the greatest known deposit of the mineral. By the early 21st century Chile had become the world’s leading producer of copper. Other major producers include Peru, China, and the United States.

Copper is commercially produced mainly by smelting or leaching, usually followed by electrodeposition from sulfate solutions. The major portion of copper produced in the world is used by the electrical industries; most of the remainder is combined with other metals to form alloys. (It is also technologically important as an electroplated coating.) Important series of alloys in which copper is the chief constituent are brasses (copper and zinc), bronzes (copper and tin), and nickel silvers (copper, zinc, and nickel, no silver). There are many useful alloys of copper and nickel, including Monel; the two metals are completely miscible. Copper also forms an important series of alloys with aluminum, called aluminum bronzes. Beryllium copper (2 percent Be) is an unusual copper alloy in that it can be hardened by heat treatment. Copper is a part of many coinage metals. Long after the Bronze Age passed into the Iron Age, copper remained the metal second in use and importance to iron. By the 1960s, however, cheaper and much more plentiful aluminum had moved into second place in world production.

Copper is one of the most ductile metals, not especially strong or hard. Strength and hardness are appreciably increased by cold-working because of the formation of elongated crystals of the same face-centred cubic structure that is present in the softer annealed copper. Common gases, such as oxygen, nitrogen, carbon dioxide, and sulfur dioxide are soluble in molten copper and greatly affect the mechanical and electrical properties of the solidified metal. The pure metal is second only to silver in thermal and electrical conductivity. Natural copper is a mixture of two stable isotopes: copper-63 (69.15 percent) and copper-65 (30.85 percent).

Because copper lies below hydrogen in the electromotive series, it is not soluble in acids with the evolution of hydrogen, though it will react with oxidizing acids, such as nitric and hot, concentrated sulfuric acid. Copper resists the action of the atmosphere and seawater. Exposure for long periods to air, however, results in the formation of a thin green protective coating (patina) that is a mixture of hydroxocarbonate, hydroxosulfate, and small amounts of other compounds. Copper is a moderately noble metal, being unaffected by nonoxidizing or noncomplexing dilute acids in the absence of air. It will, however, dissolve readily in nitric acid and in sulfuric acid in the presence of oxygen. It is also soluble in aqueous ammonia or potassium cyanide in the presence of oxygen because of the formation of very stable cyano complexes upon dissolution. The metal will react at red heat with oxygen to give cupric oxide, CuO, and, at higher temperatures, cuprous oxide, Cu2O. It reacts on heating with sulfur to give cuprous sulfide, Cu2S.

Principal compounds
Copper forms compounds in the oxidation states +1 and +2 in its normal chemistry, although under special circumstances some compounds of trivalent copper can be prepared. It has been shown that trivalent copper survives no more than a few seconds in an aqueous solution.

cuprite
cupriteCuprite from Namibia.
Copper(I) (cuprous) compounds are all diamagnetic and, with few exceptions, colourless. Among the important industrial compounds of copper(I) are cuprous oxide (Cu2O), cuprous chloride (Cu2Cl2), and cuprous sulfide (Cu2S). Cuprous oxide is a red or reddish brown crystal or powder that occurs in nature as the mineral cuprite. It is produced on a large scale by reduction of mixed copper oxide ores with copper metal or by electrolysis of an aqueous solution of sodium chloride using copper electrodes. The pure compound is insoluble in water but soluble in hydrochloric acid or ammonia. Cuprous oxide is used principally as a red pigment for antifouling paints, glasses, porcelain glazes, and ceramics and as a seed or crop fungicide.

Cuprous chloride is a whitish to grayish solid that occurs as the mineral nantokite. It is usually prepared by reduction of copper(II) chloride with metallic copper. The pure compound is stable in dry air. Moist air converts it to a greenish oxygenated compound, and upon exposure to light it is transformed into copper(II) chloride. It is insoluble in water but dissolves in concentrated hydrochloric acid or in ammonia because of the formation of complex ions. Cuprous chloride is used as a catalyst in a number of organic reactions, notably the synthesis of acrylonitrile from acetylene and hydrogen cyanide; as a decolourizing and desulfurizing agent for petroleum products; as a denitrating agent for cellulose; and as a condensing agent for soaps, fats, and oils.

Cuprous sulfide occurs in the form of black powder or lumps and is found as the mineral chalcocite. Large quantities of the compound are obtained by heating cupric sulfide (CuS) in a stream of hydrogen. Cuprous sulfide is insoluble in water but soluble in ammonium hydroxide and nitric acid. Its applications include use in solar cells, luminous paints, electrodes, and certain varieties of solid lubricants.

Copper(II) compounds of commercial value include cupric oxide (CuO), cupric chloride (CuCl2), and cupric sulfate (CuSO4). Cupric oxide is a black powder that occurs as the minerals tenorite and paramelaconite. Large amounts are produced by roasting mixed copper oxide ores in a furnace at a temperature below 1,030 °C (1,900 °F). The pure compound can be dissolved in acids and alkali cyanides. Cupric oxide is employed as a pigment (blue to green) for glasses, porcelain glazes, and artificial gems. It is also used as a desulfurizing agent for petroleum gases and as an oxidation catalyst.

Cupric chloride is a yellowish to brown powder that readily absorbs moisture from the air and turns into the greenish blue hydrate, CuCl2∙2H2O. The hydrate is commonly prepared by passing chlorine and water in a contacting tower packed with metallic copper. The anhydrous salt is obtained by heating the hydrate to 100 °C (212 °F). Like cuprous chloride, cupric chloride is used as a catalyst in a number of organic reactions—e.g., in chlorination of hydrocarbons. In addition, it serves as a wood preservative, mordant (fixative) in the dyeing and printing of fabrics, disinfectant, feed additive, and pigment for glass and ceramics.

Cupric sulfate is a salt formed by treating cupric oxide with sulfuric acid. It forms as large, bright blue crystals containing five molecules of water (CuSO4∙5H2O) and is known in commerce as blue vitriol. The anhydrous salt is produced by heating the hydrate to 150 °C (300 °F). Cupric sulfate is utilized chiefly for agricultural purposes, as a pesticide, germicide, feed additive, and soil additive. Among its minor uses are as a raw material in the preparation of other copper compounds, as a reagent in analytic chemistry, as an electrolyte for batteries and electroplating baths, and in medicine as a locally applied fungicide, bactericide, and astringent.

Other important copper(II) compounds include cupric carbonate, Cu2(OH)2CO3, which is prepared by adding sodium carbonate to a solution of copper sulfate and then filtering and drying the product. It is used as a colouring agent.

Additional Information:

Appearance

A reddish-gold metal that is easily worked and drawn into wires.

Uses

Historically, copper was the first metal to be worked by people. The discovery that it could be hardened with a little tin to form the alloy bronze gave the name to the Bronze Age.

Traditionally it has been one of the metals used to make coins, along with silver and gold. However, it is the most common of the three and therefore the least valued. All US coins are now copper alloys, and gun metals also contain copper.

Most copper is used in electrical equipment such as wiring and motors. This is because it conducts both heat and electricity very well, and can be drawn into wires. It also has uses in construction (for example roofing and plumbing), and industrial machinery (such as heat exchangers).

Copper sulfate is used widely as an agricultural poison and as an algicide in water purification.

Copper compounds, such as Fehling’s solution, are used in chemical tests for sugar detection.
Biological role
Copper is an essential element. An adult human needs around 1.2 milligrams of copper a day, to help enzymes transfer energy in cells. Excess copper is toxic.

Genetic diseases, such as Wilson’s disease and Menkes’ disease, can affect the body’s ability to use copper properly.

Unlike mammals, which use iron (in haemoglobin) to transport oxygen around their bodies, some crustaceans use copper complexes.

Natural abundance

Copper metal does occur naturally, but by far the greatest source is in minerals such as chalcopyrite and bornite. Copper is obtained from these ores and minerals by smelting, leaching and electrolysis. The major copper-producing countries are Chile, Peru and China.

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