Chapter 9: Metals — Part 1

01 Physical Properties of Metals and Non-metals

Metals are giant structures held together by strong metallic bonding, which determines their physical characteristics.

• Thermal and Electrical Conductivity: Metals are excellent conductors because they contain delocalised electrons that are free to move throughout the structure to carry thermal energy or electrical charge. Non-metals are generally poor conductors.
• Malleability and Ductility: Metals can be bent, shaped (malleable), or drawn into wires (ductile) because their positive metal ions are arranged in uniform rows that are able to slide over one another.
• Melting and Boiling Points: Metals generally have high melting and boiling points due to the strong electrostatic attraction between positive metal ions and delocalised electrons, requiring large amounts of energy to overcome.

02 Chemical Properties of Metals

• Reaction with Dilute Acids: Metals above hydrogen in the reactivity series react with dilute acids to form a salt and hydrogen gas. This is a displacement reaction where the metal atoms lose electrons to form positive ions.
• Reaction with Water or Steam: Very reactive metals react with cold water to form metal hydroxides and hydrogen. Less reactive metals, like magnesium, react more vigorously with steam to produce a metal oxide and hydrogen.
• Reaction with Oxygen: Metals react with oxygen to form metal oxides; the speed of this reaction depends on the metal's reactivity.

03 Uses of Metals

Metals are chosen for specific tasks based on their physical properties:

• Aluminium: Used in aircraft manufacture due to its low density and in overhead electrical cables because it is both lightweight and a good conductor. Its resistance to corrosion (due to a protective oxide layer) makes it ideal for food containers.
• Copper: Used in electrical wiring because of its high electrical conductivity and ductility.

04 Alloys and Their Properties

An alloy is a mixture of a metal with other elements, such as brass (copper and zinc) or stainless steel (iron, chromium, nickel, and carbon).

• Hardness and Strength: Alloys are harder and stronger than pure metals.
• Structural Explanation: In pure metals, identically sized atoms are in neat layers that slide easily. In alloys, different sized atoms distort the regular lattice, preventing the layers from sliding over each other.