🌟 Class
7 Science Curiosity – Chapter 4 Notes
🧲 The
World of Metals and Non-metals | Amresh Academy
📘
Introduction
Materials around us are broadly classified into:
👉 Metals and Non-metals
These have different physical and chemical properties
which decide their uses.
⚙️ 1.
Properties of Metals
🔨
Malleability
👉
Ability to be beaten into thin sheets
- 🪙
Metals → Malleable (copper, aluminium, iron)
- Examples:
Aluminium foil, silver foil
❌
Non-metals → Brittle (coal, sulfur)
⚠️
Exceptions:
- Sodium
& Potassium → Soft metals
- Mercury
→
Liquid metal
🔌
Ductility
👉
Ability to be drawn into wires
- Metals
→
Copper, aluminium, gold
- Used
in electrical wires
💡 Fact:
👉 1 gram of gold can make
a 2 km long wire
🔔
Sonority
👉
Ability to produce ringing sound
- Metals
→
Sonorous (bells, ghungroos) 🔔
- Non-metals
→
Dull sound
🔥
Conduction of Heat
- Metals
→
Good conductors (cooking utensils) 🍳
- Non-metals
→
Poor conductors (wooden handles)
⚡
Conduction of Electricity
- Metals
→
Good conductors (copper wires)
- Non-metals
→
Poor conductors (plastic, rubber)
🌧️ 2.
Effect of Air and Water on Metals (Iron)
🧱
Rusting
👉
Formation of brown layer (rust) on iron
Conditions:
- Air
+ Water
⚠️
Corrosion
👉 Slow
damage of metals
Examples:
- Copper
→
Green coating
- Silver
→
Black coating
🛡️
Prevention Methods:
- 🎨
Painting
- 🛢️
Oiling/Greasing
- 🧪
Galvanisation (zinc coating)
🏛️
Interesting Fact:
👉 Iron
Pillar of Delhi has not rusted for 1600+ years
🔥 3.
Effect on Other Metals
🔥
Magnesium
- Burns
with bright white flame
- Forms
magnesium oxide
⚡ Sodium
- Highly
reactive
- Stored
in kerosene
🌿 4.
Non-metals
📌
Properties:
- ❌ Non-lustrous
- ❌ Soft & brittle
- ❌ Non-ductile
- ❌ Non-sonorous
- ❌ Poor conductors
🧪
Examples:
- Sulfur
- Phosphorus
- Oxygen
- Carbon
- Nitrogen
🔥
Sulfur:
- Burns
→
forms sulfur dioxide (acidic)
💧
Phosphorus:
- Stored
in water
👉 Prevents reaction with air
🌍 5.
Importance of Non-metals
- 🌬️
Oxygen → Respiration
- 🧬
Carbon → Life molecules
- 🌱
Nitrogen → Fertilisers
- 💧
Chlorine → Water purification
- 🩹
Iodine → Antiseptic
📊 Key
Differences
|
Feature |
Metals 🪙 |
Non-metals 🌿 |
|
Appearance |
Lustrous ✨ |
Dull |
|
Nature |
Hard |
Soft/Brittle |
|
Malleability |
Yes |
No |
|
Ductility |
Yes |
No |
|
Sound |
Sonorous 🔔 |
Non-sonorous |
|
Conductivity |
Good ⚡ |
Poor |
|
Oxides |
Basic |
Acidic |
📌 Final
Summary
👉
Metals:
- Strong,
shiny, conductive ⚡
- Used
in tools, utensils, machines
👉
Non-metals:
- Essential
for life 🌱
- Used
in medicines, fertilisers
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