CDS Chemistry · Metals and Non-Metals
Extraction of Metals and Alloys
Which ore gives which metal, roasting against calcination, why the most reactive metals need electrolysis, and what common alloys are made of.
Why this matters
Four CDS questions, all EASY or MODERATE: one ore, one process name, one extraction method and one alloy. Each is a single fact from the tables below.
Concept 1 of 2: Ores and how metals are extracted
Definition
The steps and the methods:
- Roasting: heating a sulphide ore strongly in excess air, giving the oxide (2ZnS + 3O₂ → 2ZnO + 2SO₂).
- Calcination: heating a carbonate ore in limited air, giving the oxide and CO₂.
- Smelting / reduction: the oxide is reduced to the metal, usually with carbon.
- Electrolysis of the molten compound for the most reactive metals (K, Na, Ca, Mg, Al): sodium from fused NaCl (Down's process), aluminium from alumina made from bauxite.
| Metal | Main ore | Extracted by |
|---|---|---|
| Aluminium | Bauxite (Al₂O₃·2H₂O) | Electrolysis of aluminaQ |
| Sodium | Rock salt (NaCl) | Electrolysis of fused NaClQ CDS 2025 (II): sodium is the metal won by electrolysis of its molten compound. |
| Iron | Haematite (Fe₂O₃) | Reduction with coke in a blast furnace |
| Zinc | Zinc blende (ZnS) | Roasting, then reduction with carbon |
| Mercury | Cinnabar (HgS) | Roasting |
| Copper | Copper pyrites (CuFeS₂) | Roasting and smelting |
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 1 · Metals and Non-Metals · Extraction of Metals and Alloys
Roasting is for sulphides, calcination for carbonates
Electrolysis is for the most reactive metals
Concept 2 of 2: Common alloys and what they are made of
Definition
The alloys to know:
- Solder: lead and tin; low melting point, used to join electrical wires.
- Brass: copper and zinc. Bronze: copper and tin.
- Steel: iron and a little carbon. Stainless steel: iron with chromium and nickel; it does not rust.
- Duralumin: aluminium with copper, magnesium and manganese; light and strong, for aircraft.
- An amalgam is any alloy of mercury.
| Alloy | Made of | Used for |
|---|---|---|
| Solder | Lead and tin | Joining wires (low melting point)Q |
| Brass | Copper and zinc | Fittings, instruments |
| Bronze | Copper and tin | Statues, medals |
| Stainless steel | Iron, chromium, nickel | Utensils; does not rust |
| Duralumin | Aluminium, copper, magnesium, manganese | Aircraft bodies |
| Amalgam | Mercury with another metal | Dental fillings |
Practice this concept4 quick reps
The same idea in a real exam question:
Example 2 · Metals and Non-Metals · Extraction of Metals and Alloys
Brass has zinc, bronze has tin
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
Ores and how metals are extracted6 rows
| Metal | Main ore | Extracted by |
|---|---|---|
| Aluminium | Bauxite (Al₂O₃·2H₂O) | Electrolysis of aluminaQ |
| Sodium | Rock salt (NaCl) | Electrolysis of fused NaClQ CDS 2025 (II): sodium is the metal won by electrolysis of its molten compound. |
| Iron | Haematite (Fe₂O₃) | Reduction with coke in a blast furnace |
| Zinc | Zinc blende (ZnS) | Roasting, then reduction with carbon |
| Mercury | Cinnabar (HgS) | Roasting |
| Copper | Copper pyrites (CuFeS₂) | Roasting and smelting |
Common alloys and what they are made of6 rows
| Alloy | Made of | Used for |
|---|---|---|
| Solder | Lead and tin | Joining wires (low melting point)Q |
| Brass | Copper and zinc | Fittings, instruments |
| Bronze | Copper and tin | Statues, medals |
| Stainless steel | Iron, chromium, nickel | Utensils; does not rust |
| Duralumin | Aluminium, copper, magnesium, manganese | Aircraft bodies |
| Amalgam | Mercury with another metal | Dental fillings |
Watch out for (3)
- Roasting is for sulphides, calcination for carbonates→ Ores and how metals are extracted
- Electrolysis is for the most reactive metals→ Ores and how metals are extracted
- Brass has zinc, bronze has tin→ Common alloys and what they are made of
Test yourself on Metals and Non-Metals
10 past CDS questions from this chapter, timed at 10 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.