Chapter-Chapter 4. The World of Metals and Non-Metals Science Curiosity class 7 in english Medium CBSE Notes

Chapter 4: The World of Metals and Non-Metals

Definitions:

Metal: Metals are substances that are generally hard, shiny, and good conductors of heat and electricity.

Non-metal: Non-metals are substances that are generally dull, soft, and poor conductors of heat and electricity.

Lustre: Lustre is the property of a material to shine.

Hardness: Hardness is the property of a material to resist scratching or cutting.

Malleability: Malleability is the property of metals by which they can be beaten into thin sheets.

Ductility: Ductility is the property of metals by which they can be drawn into thin wires.

Conductor: A conductor is a material that allows heat and electricity to pass through it.

Insulator: An insulator is a material that does not allow heat and electricity to pass through it.

Corrosion: Corrosion is the process of slow damage of metals due to reaction with air, water, or chemicals.

Rusting: Rusting is a type of corrosion in which iron reacts with oxygen and moisture to form rust.

Alloy: An alloy is a mixture of two or more metals or a metal and a non-metal.

Quick Revision Points:

• Metals are shiny, hard, and good conductors.
• Non-metals are dull, soft, and poor conductors.
• Metals are malleable and ductile.
• Non-metals are generally brittle.
• Copper and aluminium are good conductors.
• Plastic and rubber are insulators.
• Mercury is a liquid metal (exception).
• Graphite is a non-metal that conducts electricity.
• Corrosion damages metals over time.
• Rusting occurs in presence of air and moisture.
• Painting and galvanization prevent rusting.
• Alloys improve properties of metals.

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