Metals

Question 1

Compare Metals & Non Metals in terms of electricity conductivity, malleability, ductility, melting and boiling points

Answer 1

Electrical Conductivity:

Metals: Excellent electrical conductivity due to delocalized electrons.
Non-metals: Poor electrical conductivity, except for graphite and select non-metallic elements under specific conditions.

Malleability and Ductility:

Metals: Malleable (can be hammered into thin sheets) and ductile (can be drawn into wires).
Non-metals: Typically brittle and lack malleability or ductility.

Melting Points and Boiling Points:

Metals: Generally high melting and boiling points.
Non-metals: Variable melting and boiling points, typically lower than metals.

Question 2

Reactions of Metals with
- Dilute Acids
- Water
- Steam
- Oxygen

Answer 2

Reactions with Dilute Acids:
Metal + Dilute Acid → Salt + Hydrogen Gas

Reactions with Cold Water:
Metal + Water → Metal Hydroxide + Hydrogen Gas

Reactions with Steam:
Metal + Steam → Metal Oxide + Hydrogen Gas

Reactions with Oxygen:
Metal + Oxygen → Metal Oxide

Question 3

Brass & Stainless Steel

Answer 3

Brass:
Composition: Copper and zinc.
Characteristics: Combines corrosion resistance, durability, and appealing appearance.

Stainless Steel:
Composition: Iron, chromium, nickel, and carbon.
Characteristics: Exceptional corrosion resistance, strength, and versatility.

Question 4

Strength of Alloys

Answer 4

Alloys can be harder and stronger than pure metals.

Presence of different sized atoms disrupts regular atomic arrangement.

Prevents easy sliding of layers, enhancing resistance to deformation and overall strength.

Question 5

Reactivity Series

Answer 5

Reactivity decreases down the list:

Potassium
Sodium
Calcium
Magnesium
Aluminum
Carbon
Zinc
Iodine
Tin
Lead
Hydrogen
Copper
Silver
Gold

Question 6

Rusting & Barrier Methods

Answer 6

Rusting of Iron and Steel:

Occurs in presence of oxygen and water, leading to formation of hydrated iron(III) oxide (rust).
Barrier Methods:

Common methods: Painting, greasing, plastic coating.
Provide protective layers to prevent direct contact with external elements.
Create physical barrier, excluding oxygen and water to inhibit rusting.

Question 7

Zinc in Galvanizing & Sacrificial Protection

Answer 7

Zinc in Galvanizing:

Acts as barrier method and sacrificial protection.

Zinc coating serves as physical shield, preventing direct contact between iron/steel and oxygen/water to hinder rust formation.

Sacrificial Protection:

Involves connecting more reactive metal to metal to be protected.

More reactive metal corrodes instead, serving as sacrificial anode.

Sacrificial metal loses electrons readily, corroding preferentially to protect the main metal.

Question 8

Extraction of iron from hematite (5 Steps)

Answer 8

(a) Burning of carbon (coke):
C + O₂ → CO₂

(b) Reduction of carbon dioxide: C + CO₂ → 2CO

(c) Reduction of iron(III) oxide by carbon monoxide:
Fe₂O₃ + 3CO → 2Fe + 3CO₂

(d) Thermal decomposition of calcium carbonate (limestone): CaCO₃ → CaO + CO₂

(e) Formation of slag:
CaO + SiO₂ → CaSiO₃

Question 9

Extraction of aluminium

Answer 9

(a) Cryolite is used as a flux to lower the melting point of aluminium oxide, facilitating its electrolysis at lower temperatures.

(b) Carbon anodes degrade during the electrolysis process due to oxidation, forming carbon dioxide gas. Hence, they need replacement to maintain the efficiency of the process.

(c) Half Ionic Equations

Anode (+):
2O²− → O₂ +4e−

Cathode (-):
Al³+ + 3e− → Al

Overall:
2Al₂O₃ → 4Al + 3O₂