Metals and Non-Metals

1. Introduction

Matter: Anything that has mass and occupies space.

Classification of Matter:

Pure substances: Elements and compounds.

Impure substances: Mixtures.

Elements: Substances that cannot be broken down into simpler substances by chemical methods.

Total known elements: 118.

Elements are classified as:

Metals: Usually shiny, malleable, ductile, good conductors of heat and electricity.

Non-Metals: Dull, brittle, poor conductors of heat and electricity.

Metalloids: Have properties of both metals and non-metals.

2. Minerals

Definition: Naturally occurring inorganic, solid, crystalline substances with a definite chemical composition.

Source of metals: Most metals are obtained from minerals.

Examples: Hematite (Fe₂O₃), Malachite [Cu₂(OH)₂CO₃], Bauxite (Al₂O₃·2H₂O), Talc, Limestone, Granite, Coal.

Properties of minerals:

• Inorganic
• Solid
• Crystalline
• Fixed chemical formula

Note: Non-reactive metals like gold and silver can be found in pure state, whereas reactive metals like sodium, potassium, calcium, and iron are found in compound form.

3. Ores

Definition: A mineral from which a metal can be extracted economically and easily.

Difference between mineral and ore:

All ores are minerals, but not all minerals are ores.

Examples of Ores

Iron ores: Hematite (Fe₂O₃ – chief ore), Magnetite (Fe₃O₄), Limonite (2Fe₂O₃·3H₂O), Siderite (FeCO₃), Pyrite (FeS)

Aluminium ores: Bauxite (2Al₂O₃·2H₂O – chief ore), Cryolite (Na₃AlF₆), Corundum (Al₂O₃)

Copper ores: Chalcocite (Cu₂S), Chalcopyrite (CuFeS₂ – chief ore), Cuprite (Cu₂O), Malachite [Cu₂(OH)₂CO₃]

Silver ores: Argentite (Ag₂S – chief ore), Horn silver (AgCl), Ruby silver (Ag₃SbS₃), Silver copper glance (Ag(Cu)₂S)

Gold: Found in pure state or in alluvial soil.

4. Metallurgy

Definition: The branch of science that deals with extraction, properties, purification, and production of metals.

Steps in Metallurgy:

Step 1: Mining

Definition: Process of extracting ores and minerals from the earth's crust.

Metals like coal, petroleum, gold, and metallic ores are obtained through mining.

Step 2: Grinding

Definition: Crushing ores into small particles to facilitate separation of impurities.

Step 3: Concentration (Purification of Ore)

Definition: Removal of impurities (gangue) to increase the metal content.

Methods:

Gravity or Hydraulic separation – based on density differences.

Magnetic separation – magnetic vs. non-magnetic substances.

Froth flotation – hydrophilic vs. hydrophobic differences.

Activity example: Separating iron dust from sand and aluminum using a magnet.

Step 4: Oxidation

Definition: Conversion of ores into metal oxides for easier extraction.

Types:

Roasting: Heating sulfide ores in presence of oxygen.

Example: ZnS → ZnO + SO₂

Calcination: Heating carbonate ores in absence of oxygen.

Example: CaCO₃ → CaO + CO₂

Step 5: Reduction

Definition: Removing oxygen from metal oxides to obtain metals.

Methods:

Using carbon, CO, or hydrogen.

Reactive metals (Na, K, Ca, Al) need electrolysis.

Example reactions:

CuO + C → Cu + CO

ZnO + C → Zn + CO

Step 6: Smelting

Definition: Heating metal oxides with reducing agents above melting point to obtain molten metal and remove impurities as slag.

Step 7: Refining

Definition: Purifying metals obtained from reduction.

Methods:

Distillation – for metals with low boiling points (e.g., Mercury).

Electro-refining – uses electrolysis:

Impure metal → anode

Pure metal → cathode

Electrolyte → metal salt solution (e.g., CuSO₄ for copper)

Example: Electro-refining of copper deposits pure copper on cathode.

5. Key Terms

Gangue: Impurities present in ores.

Ore: Mineral from which metal can be extracted economically.

Mineral: Naturally occurring solid substance with fixed composition.

Roasting: Heating sulfide ores in presence of oxygen.

Calcination: Heating carbonate ores in absence of oxygen.

Smelting: Extraction of metal from oxide ore above melting point.

Refining: Purification of metals.

6. Examples of Common Metals and Their Ores

7. Summary

Metals are mostly reactive and found in ores; non-metals may be found pure.

Metallurgy involves: Mining → Grinding → Concentration → Oxidation → Reduction → Smelting → Refining.

Metals like Fe, Cu, Al, Ag, Au are obtained through specific ores and processes.

Key Points: Minerals, ores, gangue, roasting, calcination, smelting, refining.