Lesson 11: TS Class 10 Physical Science Lesson 11: Principles of Metallurgy - Important Q&A, and Objective Bits

⛏️ Telangana Class 10 Physical Science — Lesson 11

Principles of Metallurgy

Complete Chapter Guide: Ores & Minerals, Ore Concentration Methods, Calcination vs. Roasting, Thermite Welding, Electrolytic Refining of Copper & Part-B MCQs

📌 Essential Metallurgical Definitions & Ore Formulas

1. Mineral vs. Ore Distinction

A Mineral is a naturally occurring metallic compound. An Ore is a mineral from which metal is extracted conveniently & profitably:

All Ores are Minerals, but all Minerals are NOT Ores

2. Important Ores & Formulas

Key board exam ores and chemical compositions:

Bauxite: Al₂O₃ · 2H₂O  |  Hematite: Fe₂O₃  |  Galena: PbS

3. Thermite Reduction Equation

Highly exothermic reduction of Iron Oxide using Aluminium powder:

Fe₂O₃ + 2Al → 2Fe(l) + Al₂O₃ + Heat

🏭 Metallurgy Extraction Flowchart & Activity Series

Extraction methods depend directly on the reactivity level of the metal in the electrochemical activity series:

Extraction Strategy Based on Metal Reactivity

1. High Reactivity Metals

Metals: K, Na, Ca, Mg, Al
Method: Electrolysis of molten chloride/oxide salts.
Reason: Very strong affinity for oxygen.

2. Medium Reactivity Metals

Metals: Zn, Fe, Pb, Cu
Method: Reduction with Carbon (C/CO) or Thermite reaction after Calcination/Roasting.

3. Low Reactivity Metals

Metals: Hg, Ag, Au, Pt
Method: Thermal reduction / Heating alone or found in native free state.

4. Ore Dressing Techniques

• Froth Floatation: Sulphide ores.
• Magnetic Separation: Magnetic ores.
• Levigation / Washing: Oxide ores.

Key Metallurgical Terms: Gangue / Matrix: Earthy impurities (sand, clay) present in ore. | Flux: Substance added to convert gangue into fusible Slag (Gangue + Flux = Slag).

Comparison: Calcination vs. Roasting

Feature	Calcination	Roasting
Air Supply	Heating ore strongly in the absence or limited supply of air.	Heating ore strongly in the presence of excess air.
Ore Type Used	Used mainly for Carbonate and Hydrated ores.	Used specifically for Sulphide ores.
Gas Evolved	Carbon Dioxide (CO2) gas and moisture are driven off.	Sulfur Dioxide (SO2) gas is evolved.
Chemical Reaction Example	ZnCO3(s) →Δ→ ZnO(s) + CO2(g)↑ CaCO3(s) →Δ→ CaO(s) + CO2(g)↑	2ZnS(s) + 3O2(g) →Δ→ 2ZnO(s) + 2SO2(g)↑ 2PbS(s) + 3O2(g) →Δ→ 2PbO(s) + 2SO2(g)↑

📝 Short Answer Questions (2 Marks & 4 Marks)

QUESTION 1 - 2 MARKS

Q1. Differentiate between Minerals and Ores with suitable examples.

Answer:

• Mineral: A naturally occurring inorganic element or compound found in the Earth's crust. Example: Clay [Al₂O₃ · 2SiO₂ · 2H₂O] and Bauxite are both minerals of Aluminium.
• Ore: A mineral from which a metal can be extracted easily, conveniently, and economically. Example: Bauxite [Al₂O₃ · 2H₂O] is the ore of Aluminium (Clay is not an ore because extraction is expensive).
• Conclusion: All ores are minerals, but all minerals are not ores.

QUESTION 2 - 2 MARKS

Q2. Describe the Froth Floatation process for concentrating sulphide ores.

Answer:

• Principle: Based on the difference in wetting properties of ore particles and gangue impurities. Ore particles are preferentially wetted by oil, while gangue particles are wetted by water.
• Procedure: Crushed sulphide ore (e.g., Galena PbS or Zinc Blende ZnS) is mixed with water and pine oil in a large tank. Compressed air is blown to produce froth.
• The light sulphide ore particles stick to pine oil bubbles and float to the top as froth, which is skimmed off and dried. Gangue settles at the bottom.

QUESTION 3 - 4 MARKS

Q3. Explain the Thermite Reduction Process with a balanced chemical equation and write its industrial application.

Answer:

• Process: The reduction of metal oxides (like Iron Oxide Fe₂O₃) using Aluminium powder as a reducing agent.
• Exothermic Nature: The reaction releases an immense amount of heat, causing the produced Iron metal to form in a molten liquid state.
• Balanced Chemical Equation:
  Fe₂O₃(s) + 2Al(s) →Δ→ 2Fe(l) + Al₂O₃(s) + Heat
• Industrial Application: Used in Thermite Welding to join cracked railway tracks and heavy iron machinery parts on-site.

🧮 Solved Process Guides & Essay Questions

4 MARKS - IMPORTANT ORES TABLE

Q4. Complete the table of important metals, their common ores, and chemical formulas.

Metal	Name of the Ore	Chemical Formula	Type of Ore
Aluminium (Al)	Bauxite	Al2O3 · 2H2O	Oxide / Hydrated
Iron (Fe)	Hematite / Magnetite	Fe2O3 / Fe3O4	Oxide Ore
Lead (Pb)	Galena	PbS	Sulphide Ore
Zinc (Zn)	Zinc Blende / Calamine	ZnS / ZnCO3	Sulphide / Carbonate
Mercury (Hg)	Cinnabar	HgS	Sulphide Ore

6 MARKS - ESSAY ON ELECTROLYTIC REFINING

Q5. Describe the Electrolytic Refining of impure Copper with a neat explanation of Anode, Cathode, Electrolyte, and Anode Mud.

Answer:

• Aim: To obtain 99.99% pure Copper from crude impure copper blocks.
• Cell Setup:
  • Anode (+): Thick block of Impure Copper.
  • Cathode (-): Thin sheet of Pure Copper.
  • Electrolyte: Acidified solution of Copper Sulfate (CuSO₄ + dil. H₂SO₄).
• Working Mechanism on Passing Electric Current:
  1. At Anode (+): Impure copper dissolves into electrolyte as Cu²⁺ ions:
     Cu (impure) → Cu²⁺(aq) + 2e^-
  2. At Cathode (-): Pure Cu²⁺ ions from electrolyte deposit onto the thin copper sheet:
     Cu²⁺(aq) + 2e^- → Cu (pure deposited)
• Anode Mud: Insoluble impurities like Gold (Au), Silver (Ag), and Platinum (Pt) settle down at the bottom below the anode as Anode Mud, which is recovered as valuable by-products.

🎯 PART-B Objective Bits Bank (10 MCQs)

BIT 1

1. Bauxite is an important ore of which metal?

• Iron
• Copper
• Aluminium
• Zinc

✓ Correct Option: C (Aluminium - Al₂O₃·2H₂O)

BIT 2

2. Which concentration method is used specifically for Sulphide ores like Galena (PbS)?

• Magnetic Separation
• Froth Floatation
• Hydraulic Washing
• Calcination

✓ Correct Option: B (Froth Floatation)

BIT 3

3. The process of heating a carbonate ore strongly in the absence of air is called:

• Roasting
• Calcination
• Smelting
• Refining

✓ Correct Option: B (Calcination)

BIT 4

4. In the Thermite Reaction used for joining railway tracks, the reducing agent used is:

• Carbon (C)
• Carbon Monoxide (CO)
• Aluminium powder (Al)
• Hydrogen gas (H₂)

✓ Correct Option: C (Aluminium powder)

BIT 5

5. What is the chemical formula of Cinnabar (ore of Mercury)?

• HgO
• HgS
• PbS
• ZnS

✓ Correct Option: B (HgS)

BIT 6

6. The earthy impurities like sand and clay associated with ores are collectively called:

• Slag
• Flux
• Gangue / Matrix
• Anode Mud

✓ Correct Option: C (Gangue / Matrix)

BIT 7

7. Highly reactive metals like Sodium, Calcium, and Aluminium are extracted by:

• Reduction with Carbon
• Electrolysis of their molten salts
• Roasting in air
• Reduction with CO

✓ Correct Option: B (Electrolysis of molten salts)

BIT 8

8. In the electrolytic refining of copper, the pure metal is deposited at the:

• Anode (+)
• Cathode (-)
• Bottom of the tank
• Electrolyte solution

✓ Correct Option: B (Cathode - negative electrode)

BIT 9

9. Which oil is added in the Froth Floatation process to form froth?

• Kerosene oil
• Pine oil
• Mustard oil
• Coconut oil

✓ Correct Option: B (Pine oil)

BIT 10

10. Magnetite (ore of Iron) is chemically represented as:

• Fe₂O₃
• Fe₃O₄
• FeS₂
• FeCO₃

✓ Correct Option: B (Fe₃O₄)