a) Roasting:
Roasting is a process where a sulfide ore is heated in the presence of oxygen to convert it into an oxide. This process is typically used for ores of metals such as zinc, copper, and lead.
Example: Roasting of lead sulfide (PbS):
In this case, lead (II) sulfide is heated with oxygen to form lead (II) oxide and sulfur dioxide gas. The lead oxide can later be reduced to extract pure lead metal.
b) Smelting:
Smelting is the process of extracting metal from its ore by heating the ore with a reducing agent (often carbon) in the presence of heat.
Example: Smelting of iron ore (Fe₂O₃):
Here, iron oxide reacts with carbon (in the form of coke) to produce iron metal and carbon monoxide.
c) Flotation:
Flotation is a method used to separate hydrophobic materials (like metals) from hydrophilic materials (like gangue) by using air bubbles to attach to the materials and float them to the surface.
Example: In the flotation of copper ore, copper sulfide minerals are made hydrophobic by adding collectors (such as pine oil), and they float on the surface, allowing the gangue (unwanted materials) to sink.