Metals and Non-metals

3.1 PHYSICAL PROPERTIES

This section introduces the physical properties that help distinguish metals from non-metals. Metals generally exhibit metallic lustre, meaning they have a shiny surface when polished. They are mostly solids at room temperature, except mercury which is a liquid. Metals are generally hard, but hardness varies among different metals. They are malleable, meaning they can be beaten into thin sheets, and ductile, meaning they can be drawn into thin wires. Metals are good conductors of heat and electricity, which is why they are widely used in electrical wiring and cooking utensils. They are also sonorous, producing sound when struck, which is why metals are used in bells and musical instruments. Non-metals, on the other hand, are mostly dull, brittle, and poor conductors of heat and electricity (except graphite). They exist in various physical states: solids, liquids (bromine), or gases. The section includes several activities to observe these properties practically, such as cutting metals with a knife, hammering metals, testing conductivity, and observing lustre. It also highlights exceptions like iodine (a lustrous non-metal) and carbon allotropes (diamond and graphite) which have unique properties. These observations show that physical properties alone cannot always classify elements definitively as metals or non-metals, leading to the need for chemical property analysis.

• Metals have metallic lustre and are mostly solids at room temperature except mercury.
• Metals are malleable and ductile, allowing shaping into sheets and wires.
• Metals conduct heat and electricity well; non-metals generally do not.
• Metals are sonorous; non-metals are not.
• Non-metals can be solids, liquids, or gases and usually have dull surfaces.
• Physical properties have exceptions; chemical properties provide clearer classification.
• 📌 Metallic lustre: The shiny appearance of metals when polished.
• 📌 Malleability: Ability of metals to be beaten into thin sheets.
• 📌 Ductility: Ability of metals to be drawn into thin wires.

3.1.2 Non-metals

Non-metals are elements that generally lack the physical properties of metals. They are usually dull in appearance, brittle, and poor conductors of heat and electricity, with the notable exception of graphite, an allotrope of carbon that conducts electricity. Non-metals exist in all three physical states: solids (carbon, sulphur, iodine), liquids (bromine), and gases (oxygen, hydrogen). The section includes activities where students observe the physical properties of non-metals and compare them with metals. For example, non-metals cannot be beaten into sheets or drawn into wires, and they do not produce sound when struck. Some exceptions to general trends are noted, such as iodine which is lustrous, and carbon which exists in allotropes with very different properties: diamond is the hardest natural substance and an electrical insulator, while graphite is a good conductor. Alkali metals like sodium and potassium are soft enough to be cut with a knife, showing that physical properties alone are insufficient for classification. The section concludes that chemical properties are more reliable for distinguishing metals and non-metals. **Table on page 3 (2×8)** | Element | Symbol | Type of surface | Hardness | Malleability | Ductility | Conducts Electricity | Sonority | | --- | --- | --- | --- | --- | --- | --- | --- | | | | | | | | | | **Table on page 10 (5×5)** | Metal | Iron(II) sulphate | Copper(II) sulphate | Zinc sulphate | Silver nitrate | | --- | --- | --- | --- | --- | | A | No reaction | Displacement | No reaction | Displacement | | B | Displacement | No reaction | No reaction | Displacement | | C | No reaction | No reaction | No reaction | No reaction | | D | No reaction | No reaction | No reaction | No reaction | **Table on page 13 (2×1)** | QUESTIONS | | --- | | 1. (i) Write the electron-dot structures for sodium, oxygen and magnesium. **Table on page 19 (4×4)** | Metal | Zinc | Magnesium | Copper | | --- | --- | --- | --- | | Zinc oxide | | | | | Magnesium oxide | | | | | Copper oxide | | | |

• Non-metals are usually dull, brittle, and poor conductors of heat and electricity.
• Non-metals exist as solids, liquids (bromine), or gases.
• Graphite is a non-metal that conducts electricity.
• Iodine is a lustrous non-metal, an exception to the dullness rule.
• Carbon exists in allotropes with very different properties (diamond and graphite).
• Physical properties alone cannot classify elements definitively.
• 📌 Allotrope: Different forms of the same element with different physical properties.
• 📌 Brittle: Breaking easily without bending.