Properties and uses of copper

Copper is a chemical element with the symbol Cu (Latin: cuprum) and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is rather soft and malleable, and a freshly-exposed surface has a pinkish or peachy color. It is used as a thermal conductor, anelectrical conductor, a building material, and a constituent of various metal alloys.

A copper disc made bycontinuous casting andetching.

Copper metal and alloyshave been used for thousands of years. In the Roman era, copper was principally mined onCyprus, hence the origin of the name of the metal as Cyprium, "metal of Cyprus", later shortened to Cuprum. There may be insufficient reserves to sustain current high rates of copper consumption. Some countries, such as Chileand the United States, still have sizable reserves of the metal which are extracted through large open pit mines.

Copper compounds are known in several oxidation states, usually +2, where they often impart blue or green colors to natural minerals such as turquoise and have been used historically widely as pigments. Copper metal architectural structures and statuary eventually corrode to acquire a characteristic green patina. Copper as both metal and pigmented salt, has a significant presence in decorative art.

Copper(II) ions (Cu2+) are soluble in water, where they function at low concentration as bacteriostatic substances, fungicides, and wood preservatives. For this reason, copper metal can be used as an anti-germ surface that can add to the anti-bacterial and antimicrobial features of buildings such as hospitals. In sufficient amounts, copper salts can be poisonous to higher organisms as well. However, despite universal toxicity at high concentrations, the Cu2+ ion at lower concentrations is an essential trace nutrient to all higher plant and animal life. In animals, including humans, it is found widely in tissues, with concentration in liver, muscle, and bone. It functions as a co-factor in various enzymes and in copper-based pigments.

Applications

Copper is malleable and ductile and is a good conductor of both heat and electricity.

The purity of copper is expressed as 4N for 99.99% pure or 7N for 99.99999% pure. The numeral gives the number of nines after the decimal point when expressed as a decimal (e.g. 4N means 0.9999, or 99.99%). Copper is often too soft for its applications, so it is incorporated in numerous alloys. For example, brass is a copper-zinc alloy, and bronze is a copper-tin alloy.

It is used extensively, in products such as:

Piping

Assorted copper fittings
  • including water supply.
  • used extensively in refrigeration and air conditioningequipment because of its ease of fabrication and soldering, as well as high conductivity to heat.

Electrical applications

Copper roof on the Minneapolis City Hall, coated with patina

Architecture and industry

Old copper utensils in a Jerusalem restaurant
  • Copper is used to prevent a building being directly struck by lightning. High above the roof, copper spikes (lightning rods) are connected to a very thick copper cable which leads to a large metal plate underneath the ground. Thevoltage is dispersed throughout the ground harmlessly, instead of destroying the main structure.[43]

Household products

Coinage

Biomedical applications

Chemical applications

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