ICSE Class 10 Chemistry: Metallurgy — Extraction of Metals Notes 2026

Occurrence of Metals

• Native metals (Au, Pt) found free; reactive metals occur as ores (compounds)
• Common ores: haematite (Fe₂O₃), bauxite (Al₂O₃·2H₂O), galena (PbS), copper pyrite (CuFeS₂)
• Gangue (earthy impurities) must be removed before extraction

Steps in Metal Extraction

• 1. Mining and concentration of ore (froth flotation, gravity separation, magnetic separation)
• 2. Reduction of ore to metal oxide, then to metal
• 3. Refining of crude metal to high purity

Reduction Methods

• Carbon reduction: Fe₂O₃ + 3CO → 2Fe + 3CO₂ (blast furnace)
• Electrolytic reduction for very reactive metals: Al from Al₂O₃ (Hall-Héroult process)
• Thermite reduction (aluminothermy): Fe₂O₃ + 2Al → Al₂O₃ + 2Fe (used in welding)

Extraction of Iron — Blast Furnace

• Raw materials: haematite, coke (reducing agent), limestone (flux)
• Zones: combustion zone (2000°C), reduction zone (1500°C), slag-forming zone
• Pig iron (cast iron) contains ~4% C; converted to steel by reducing C content

Extraction of Aluminium

• Bauxite purified to alumina (Al₂O₃) by Bayer's process
• Hall-Héroult electrolysis: molten cryolite (solvent) + Al₂O₃; cathode = Al
• Energy-intensive; aluminium recycling saves 95% energy vs. primary extraction

Corrosion and Its Prevention

• Rusting: Fe + O₂ + H₂O → Fe₂O₃·xH₂O; electrochemical process
• Prevention: painting, galvanisation (zinc coating), cathodic protection, alloying
• Aluminium is self-protecting: thin layer of Al₂O₃ prevents further oxidation

ICSE Exam — Metallurgy

• Write reactions at cathode and anode in extraction of aluminium
• Explain why cryolite is added in Hall-Héroult process
• State one advantage of recycling metals over primary extraction