Metals and Their Uses


Extracting Metals

Rock that contains enough of a metal or a metal compound to make it worth extracting is called an ore.

Mining for ores often involves digging up large amounts of rock. The ore may need to be concentrated before the metal is extracted. These processes can produce large amounts of waste and could have major impacts on the surrounding environment.

A few metals low in the reactivity series, such as gold are found in the earth as the metal. Gold can be seperated from these rocks by physical methods . However most metals are found as compounds, in this case the metals are extracted by chemical reactions. 

Metals can be extracted from compounds by displacemet using a more reactive element:

Metals which are less reactive than carbon can be extracted from oxides by heating with carbon. A reduction reaction then takes place as carbon removes the oxygen from the oxide to produce the metal. 

An example of a reduction reaction is :  copper oxide + hydrogen → copper + water

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Aluminium and Titanium

Aluminimum has a low density and, although it is quite high in the reactivity series, it is resistant to corrosion. It is more reactive than carbon so it can not be reduced using carbon. It has be extracted by electrolysis of molten aluminimum oxide. 

Electrolysis requires high tempertures and alot of electricity. This makes aluminimum expensive to extract.

Pure aluminimum is not very strong, but aluminimum alloys are much stonger and harder. They have many uses.

Titanium is resistant to corrosion and is very strong. It also has a low density compared with other strong metals.

Titanium oxide can be reduced by carbon, but the metal reacts with carbon making it brittle.

Titanium is extracted from its ore by a proscess that involves several stages and large amounts of energy. The high costs of this process make titanium expensive.

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Metal Alloys

An alloy is a mixture of a metal with at least one other element.

Many of the ores used to produce iron, contain iron oxide. Iron oxide is reduced at high temperatures in a blast furnace using carbon. The iron produced contains 96% iron. Removing all the impurities makes pure iron, however this is too soft for many uses.

Most iron is used to make steels. Steels are alloys of iron because they are mixtures of iron with carbon and other elements. Alloys can be made so that they ahve properties for specific uses.

The amounts of carbon and other elements are carefully adjusted when amking steels. Low carbon steels are easily shaped and high-carbon steels are hard.

Some steels, such as stainless steels, contain larger quantities of other metals. They resist corrosion. 

Steels have many uses in modern buildings. Steels are more useful than pure iron because they are harder, can be made with specific properties and can be made to resist corrosion. 

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Transition Metals

Transition metals are found in the central block on the periodic table. They have many useful properties: they conduct heat and electricity, they are ductile and malleable.

Ductile - The ability to be stretched into wire withouth breaking.

Malleable - The ability to be hammered into shape without breaking or cracking.

Smelting - It main use is to produce metaal from its ore.

Electrolysis - The process in which ionic substances are decomposed into similar substances.

Displacement - If a reactive element comes into contact with the compound of a less reactive element a chemical reaction may take place.

Phytoming - The planting of a vegatetion that selectivley concentrate specific metals from the environment in their tissues, for the primary or subsidiary purpose of commercial exploitation of the extracted metal.

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