Sample Notes: Properties of Metals

O Level and IGCSE Chemistry – Detailed Notes

9.1 Properties of Metals

General Physical Properties of Metals vs Non-Metals

1. Thermal Conductivity

• Metals:
  • Excellent conductors of heat.
  • Delocalised electrons in metals transfer kinetic energy rapidly.
  • Examples: Copper, aluminium used in cookware and radiators.
• Non-metals:
  • Poor conductors of heat (except graphite).
  • No free-moving electrons to conduct thermal energy.

2. Electrical Conductivity

• Metals:
  • Good electrical conductors due to sea of delocalised electrons.
  • Electrical current flows easily through metallic bonds.
  • Applications: Electrical wiring (copper), electronics (silver).
• Non-metals:
  • Poor conductors (insulators), except graphite (a form of carbon).
  • Lack free-moving charged particles in solid state.

3. Malleability and Ductility

• Metals:
  • Malleable: Can be hammered or rolled into sheets.
  • Ductile: Can be drawn into wires.
  • Reason: Layers of atoms in metallic structure can slide over each other without breaking bonds.
• Non-metals:
  • Usually brittle when solid.
  • Tend to shatter or crumble under stress.
  • Do not possess layer structure that allows for movement.

4. Melting and Boiling Points

• Metals:
  • Generally high melting and boiling points.
  • Strong metallic bonds require large amounts of energy to break.
  • Exception: Mercury (liquid at room temperature).
• Non-metals:
  • Generally low melting and boiling points.
  • Many exist as gases or volatile solids.
  • Weak intermolecular forces (e.g., Van der Waals forces) in molecular non-metals.

General Chemical Properties of Metals

1. Reaction with Dilute Acids

• Typical reaction:
  Metal + Dilute acid → Salt + Hydrogen gas
  e.g.,
  Mg + 2HCl → MgCl₂ + H₂↑
• Observations: Effervescence (bubbling), temperature increase, metal dissolves.
• More reactive metals like magnesium, zinc, and iron react readily.
• Less reactive metals like copper and silver do not react.

2. Reaction with Cold Water and Steam

• Cold water:
  Only very reactive metals (e.g., potassium, sodium, calcium) react.
  e.g.,
  2Na + 2H₂O → 2NaOH + H₂↑
  • Observations: fizzing, floating, moving, possible flame with potassium.
• Steam:
  Less reactive metals like magnesium react with steam (not cold water).
  e.g.,
  Mg + H₂O (steam) → MgO + H₂↑
  • Metal oxide is formed instead of hydroxide.

3. Reaction with Oxygen

• General reaction:
  Metal + Oxygen → Metal oxide
  e.g.,
  2Mg + O₂ → 2MgO
• Metals form basic oxides (alkaline in nature when dissolved in water).
• More reactive metals like potassium and sodium oxidise very rapidly (even spontaneously in air).
• Less reactive metals like iron require heating.

Summary Table: Comparison of Metals and Non-Metals