01 — Explanation
Introduction: The Metallic Majority
The majority of the elements in the Periodic Table are metals. They are situated on the left and in the center of the table, separated from the non-metals by a zig-zag "staircase" of metalloids. Metals share a common set of physical and chemical traits that arise from their unique atomic structure—specifically, the presence of delocalised electrons. Understanding these properties is essential for materials science and for predicting the outcome of various chemical reactions. The IGCSE 0654 Core syllabus requires a comparison between metals and non-metals and a description of the general chemical reactivity of metals with air, water, and acids.
02 — Explanation
Physical Properties: Metals vs. Non-Metals
The physical properties of a substance are those that can be observed or measured without changing its chemical identity.
| Property | Metals | Non-Metals |
|---|---|---|
| Appearance | Shiny (lustrous) when freshly cut. | Dull (not shiny) as solids. |
| State at r.t.p. | Solids (except Mercury, which is liquid). | Gases, liquids, or solids. |
| Malleability | Can be hammered into shapes. | Brittle; shatters when hit. |
| Ductility | Can be drawn into thin wires. | Not ductile. |
| Conductivity | Excellent conductors of heat and electricity. | Generally insulators (except Graphite). |
| Density | Generally high (heavy for their size). | Generally low. |
| Melting Point | Generally high. | Generally low. |
| Sonority | Sonorous (make a ringing sound). | Not sonorous. |
03 — Explanation
Chemical Properties of Metals
The chemical behavior of metals is characterized by their tendency to lose electrons and form positive ions (cations).
(a) Reaction with Water and Steam
Metals react with water or steam to produce hydrogen gas, but the intensity of the reaction depends on the metal's reactivity.
- Reactive Metals (e.g., Sodium): React vigorously with cold water to form a metal hydroxide and hydrogen.
- Less Reactive Metals (e.g., Magnesium): React slowly with cold water but vigorously with steam to form a metal oxide and hydrogen.
(b) Reaction with Dilute Acids
Most metals react with dilute acids (like or ) to produce a salt and hydrogen gas. This is a type of single displacement reaction.
- General Equation: Metal + Acid Salt + Hydrogen
- Example:
- Note: Metals below hydrogen in the reactivity series (like copper, silver, and gold) do not react with dilute acids.
04 — Explanation
Conclusion
Metals are the primary structural and conductive materials of our world. Their high density and melting points, combined with their ability to be shaped and their predictable chemical reactivity with acids and water, make them indispensable for engineering and technology. By understanding the metallic character, we can select the appropriate material for any given chemical or physical challenge.