Explain why energy input is necessary to extract a metal from its ore. In your response compare the energy requirements to extract inactive metals (such as copper) to those of more active metals (such as aluminium).
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Ores contain compounds of metals with non-metals, as oxides, sulphides, carbonates, chlorides etc. All these compounds exist as such in nature because they are more stable than the free metals themselves. For extraction of elemental metal, these metal-non metal bonds have to be broken first. This requires significant amount of energy. Depending upon the degree of oxidation of the metal in the chemical compound that is its ore, positive ions of the metals are its main component, which needs to be reduced to obtain the pure metal. This reduction step also requires energy.
Energy is not only involved in the extraction reaction. That is only one part of the total amount of energy used. Energy is also used to purify the ore, maintain the high temperatures that are necessary for the usually endothermic extraction reactions, to purify the raw metal and to arrange for proper storage of the more active metals.
So, extraction of metals from ores is a highly energy-intensive process. Only, the energy requirement varying with the electropositivity of the metal. More electropositive a metal is, higher is the energy required for its extraction.
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