Why Copper(Cu) has higher melting point than Ag and Au?
This metal is softer than iron but harder than zinc. It can be polished to impart a brighter finish. It is placed in group 11 of the periodic table with silver and gold. It has a very low chemical reactivity, and dissolves in hot concentrated hydrochloric or sulfuric acid. It gets corroded by salt water and forms a chloride.
An ancient metal like copper was used to make ornaments, coins, utensils, statues, etc. It is ductile, and has a high thermal and electrical conductivity. It is denoted with the symbol ‘Cu’. It has been used for over a thousand years, and was first mined in Cyrus during the Roman era. This gave rise to its name ‘Cyprium’, and is also called ‘metal of Cyprus’. It was discovered in ancient times in a native form, thus giving rise to the ‘Copper Age’ after the ‘Stone Age’.
The melting point of this element is 1357.77° K, 1084.62° C, or 1984.32° F. Pure copper and high copper content alloys are very difficult to melt. It is also susceptible of gassing. When copper chromium is melted, it leads to a loss of ‘Cr’. This problem is solved by melting this compound under a floating flux that prevents oxidation, and it also picks up hydrogen from the atmosphere. When the molten metal reaches 1260° C, calcium boride or lithium is plunged into the molten bath that helps in deoxidizing it.
This compound is found in weathered brass, copper, and bronze. You can easily identify it with its bright blue to green color. Copper in moist air oxidizes to a dull green color, and therefore is used by architects to create some interesting features on buildings. The melting point of copper carbonate is 200° C. At a high temperature, copper carbonate decomposes to carbon dioxide and copper (II) oxide.
CuCO3 (solid) → CuO (solid) + CO2 (gas)
These are divided into three groups according to their freezing range. The solidification of these alloys occur when the temperatures drops below liquidus (temperature at which metals begin to freeze), and is completed before the temperature reaches solidus (temperature at which metal is completely frozen). Speculum metal and bronze are some alloys of copper and tin, which have a melting point of 1900° – 1950° F. Brass is an alloy of copper and zinc, and has a melting point of 900° – 940° C.
Thus, all the properties of copper that are described above, especially in relation to its melting point, are very important in different fields of chemistry and metallurgy.