Class 8 Science – Materials: Metals and Non-metals

1. Introduction

• Metals and non-metals are two main categories of elements found in nature.

• They differ in physical and chemical properties.

• Understanding their properties helps in choosing materials for different purposes.

Key Concept:

• Metals are generally strong, shiny, and good conductors, while non-metals are brittle, dull, and poor conductors.

2. Properties of Metals

Physical Properties

• Shiny appearance (lustrous)

• Good conductors of heat and electricity

• Malleable (can be hammered into sheets)

• Ductile (can be drawn into wires)

• Strong and hard (except some like sodium and potassium)

• High melting and boiling points (except mercury)

• Usually solid at room temperature

Chemical Properties

• React with oxygen to form oxides (some are basic in nature)

• React with water or acids to produce hydrogen gas (most metals)

• Can displace less reactive metals from their compounds

• Some metals corrode over time (like iron rusting)

Common Examples: Iron, Copper, Aluminum, Sodium, Zinc

3. Properties of Non-metals

Physical Properties

• Dull appearance, not shiny

• Poor conductors of heat and electricity (insulators)

• Brittle and break easily when force is applied

• Low melting and boiling points

• Usually gases or solids at room temperature (except bromine – liquid)

Chemical Properties

• React with oxygen to form oxides (usually acidic in nature)

• Can react with metals to form salts

• Do not react with acids to produce hydrogen

• Some are highly reactive (like chlorine, fluorine), others are inert (like helium)

Common Examples: Sulfur, Oxygen, Carbon, Chlorine, Phosphorus

4. Uses of Metals and Non-metals

Metals

• Construction: Steel, iron

• Electrical wiring: Copper, aluminum

• Cooking utensils: Aluminum, stainless steel

• Coins and machinery: Nickel, zinc

Non-metals

• Making fertilizers: Nitrogen, phosphorus

• Medicines and disinfectants: Iodine, chlorine

• Fuel and energy: Carbon (coal)

• Insulators in electrical circuits: Sulfur, rubber

5. Key Differences

6. Key Points to Remember

• Metals: Lustrous, malleable, ductile, conductors, often solid.

• Non-metals: Dull, brittle, poor conductors, can be solid, liquid, or gas.

• Metals react with oxygen, water, and acids; non-metals react mainly with metals and oxygen.

• Choosing materials depends on their physical and chemical properties.

• Everyday applications depend on strength, conductivity, and reactivity.