Occurrence of Metals-concentration of ore

Question 1 Why most of the metals do not occur as free elements?

Question 2 What are minerals?

Question 3 Define the term ore?

Question 4 Define the term metallurgy?

Question 5 Define the term extraction?

Question 6 Name the three steps of metallurgy?

Question 7 What is gangue?

Question 8 What do you mean by concentration of ore?

Occurrence of Metals
Most of the metals are quite reactive and hence they do not occur as free elements in nature but in the form of their compounds.
The compounds of metals are present in the form of oxides,sulphides,carbonates,chlorides.
The natural material in which the metals or their compounds are found in earth are called minerals.
Some of the minerals may contain a large percentage of metal whereas others may contain only a small percentage .
Those minerals from which metals can be extracted conveniently and profitably are called ores.
All ores are minerals but all minerals are not ores.

       Metals       Ore
SodiumRock Salt
AluminiumBauxite
ManganesePyrolusite
ZincCalamine

Zinc blende

IronHematite
CopperCuprite

Copper glance

MercuryCinnabar

 

The metals at the bottom of activity series are least reactive and are often found in free state.

Metals at the top of activity series are reactive and never found in free state.

To obtain a metal from its ore is called extraction of metal.

The processes involved in the extraction of metal from their ores and refining is called metallurgy.

The three steps of metallurgy are:

1)Concentration of ore

2)Conversion of ore into metal

3)Refining of impure metal.

Concentration of ore
The unwanted impurities such as sand,rocky material,earthy particles etc present in an ore are called gangue.
The method for removing gangue from ore depend on some differences in physical or chemical properties of ore and gangue.

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