Metals Ores, Alloys, Corrosion and Smelting

ORES An ore is a rock or mineral that a useful metal can be removed from.   Some metals are found free in nature. These include iron, copper, lead, and aluminum. Native Copper Native Iron

ORES Most metals are combined with other elements in nature. Some ores and their metals include: Iron can be removed from iron disulfide, or pyrite (FeS2) Aluminum can be removed from bauxite (Al2O3) Litharge (PbO) gives up the mineral lead. ZnS, or sphalerite, is zinc combined with sulfur. Magnesium can be removed from magnesite (MgCO3)

Metal + _____ If the metal combines with oxygen, it is called a oxide. If the metal combines with sulfur, it is called a sulfide. If the metal combines with carbon and oxygen, it is called a carbonate.

SMELTING An ore must be found and mined. The ore is broken into small pieces, which are trucked/delivered to a smelting facility. Removing a metal from its ore is called smelting. Each type of ore requires a different chemical reaction to remove its metal.

Smelting involves more than just "melting the metal out of its ore" Smelting involves more than just "melting the metal out of its ore". Most ores are a chemical compound of the metal with other elements, such as oxygen, sulfur or carbon and oxygen. To produce the metal, these compounds have to undergo a chemical reaction. Smelting therefore consists of using suitable reducing substances that will combine with those elements to free the metal.

Smelting uses heat and a chemical reducing agent to change the oxidation state of the metal ore; the reducing agent is commonly a source of carbon such as coke, or in earlier times charcoal. As most ores are impure, it is often necessary to use flux, such as limestone, to remove the accompanying rock (slag).

ALLOYS Mixtures of two or more metals are called alloys. Alloys are made because the combination of metals give different properties to the alloy. Remember a mixture is not chemically combined. An amalgam is an alloy of mercury.

ALLOYS Brass = copper and zinc. Brass is harder and lasts longer without corroding than either copper or zinc by itself.  Steel = iron, chromium and carbon and is used in buildings, cars, and knives. Bronze = iron and tin. Pewter = tin, copper and antimony. Cups and dishes can be made from it. Sterling silver = silver & copper. Jewelry and silverware are made from sterling silver. Nichrome = nickel, iron, chromium and manganese, and is used in electrical wire. Alnico = iron, aluminum, nickel and cobalt , and is used to make electromagnets.

CORROSION Corrosion is the wearing away of metal. It is a chemical change. When a metal corrodes, it changes its color and loses its shine. It also weakens the metal. The most common example of corrosion is rust (Fe2O3), when oxygen chemically combines with the metal iron. Rust is reddish-brown.

Tarnish is another example of corrosion Tarnish is another example of corrosion. Tarnished silver is dark and dull, while untarnished silver is shiny. Corrosion happens to the top layers of a metal, so at times it can be removed. Corrosion happens because of oxidation, or loss of the metal’s electrons to oxygen.

Three ways to stop corrosion: 1. Paint protects the metal from air and moisture. 2. Coating the surface with oil also protects from air and moisture. 3. Using an alloy, as alloys can be made that do not corrode.

Corrosion can be expensive. Cars rust, and lose value and just look bad. Rust can weaken metal, and make iron things break. Corrosion can be harmful to people. If your skin is broken by a piece of rusty metal, you can get an infection called tetanus, which can be life-threatening.

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