🔩The World of Metals and Non-Metals – Class 7 Science Chapter Summary & NCERT Solution

Chapter 4 – The World of Metals and Non-Metals | Class 7 Science Chapter Summary, Notes, Explanation & NCERT Solution

Chapter Name: The World of Metals and Non-Metals
Subject: Science – Grade 7


🌟 Introduction – Chapter Summary of Chapter 4

We use metals and non-metals every day — from iron tools to oxygen for breathing. This chapter helps students understand the basic properties, uses, and differences between metals and non-metals, and how they behave in the presence of air, water, and heat. It also explains the importance of both in our daily lives, including their chemical and physical properties.


🧲 What Are Metals?

Metals are elements that are usually hard, shiny, malleable, ductile, and good conductors of heat and electricity. They are used in making utensils, wires, machines, and tools.

✅ Common Properties of Metals:

  • Lustrous (shiny) – Example: Copper, Aluminium
  • Malleable – Can be beaten into thin sheets (like silver foil)
  • Ductile – Can be drawn into wires (like copper wires)
  • Sonorous – Produce ringing sound when struck
  • Good conductors – Carry heat and electricity (used in cookware and wires)
  • Generally solid and hard – Except mercury (which is a liquid at room temperature)

🧪 What Are Non-Metals?

Non-metals are elements that are usually soft, dull, brittle, and poor conductors of heat and electricity. They are very important for life processes and the environment.

✅ Common Properties of Non-Metals:

  • Non-lustrous – Dull in appearance (like coal or sulfur)
  • Not malleable or ductile – They break when hammered
  • Poor conductors – Except graphite
  • Can be gases, liquids, or solids – Example: Oxygen (gas), Bromine (liquid)
  • Essential to life – Like oxygen for breathing, nitrogen for plant growth

🛠️ Activities that Show Metal Properties

🔨 Malleability:

When you beat copper, aluminium, or iron with a hammer, they flatten. This is malleability – a key property of metals.

🔌 Ductility:

Copper and aluminium can be made into thin wires used in electric cables. That’s called ductility.

🔔 Sonority:

Metals make a ringing sound when dropped. Try it with a metal spoon versus a wooden one – only the metal will sound clear and loud.

🔥 Conductivity:

When you place metal and wooden spoons in hot water, the metal heats up faster. Why? Because it conducts heat better.

⚡ Electrical Conductivity:

In a simple circuit, only metal objects make the bulb glow, showing they conduct electricity.


🧪 Reaction of Metals with Air and Water

🌬️ Rusting:

Iron reacts with air and moisture to form rust – a brown flaky substance. This is a chemical change and damages iron objects.

Rusting = Iron + Water + Oxygen → Iron Oxide (Rust)

Prevention:

  • Painting
  • Oiling
  • Galvanisation (coating with zinc)

🔥 Magnesium Reaction:

Magnesium ribbon burns with a bright white flame, forming magnesium oxide, which turns red litmus blue — showing it’s basic in nature.

💧 Sodium Reaction:

Sodium is a very reactive metal. It catches fire when it touches water or air, so it’s stored in kerosene.


🔬 Non-Metal Reactions

🌫️ Sulfur Burning:

Burning sulfur produces sulfur dioxide gas. When it dissolves in water, it forms an acidic solution that turns blue litmus red. Non-metal oxides are usually acidic.

❌ Water Reaction:

Most non-metals like sulfur and phosphorus do not react with water the way metals do. Phosphorus is stored in water to stop it from catching fire in air.


♻️ Are Non-Metals Important?

Absolutely! Non-metals are essential for life.

✅ Everyday Uses:

  • Oxygen – Vital for respiration
  • Carbon – Main element in all living things
  • Nitrogen – Used in fertilizers to help plants grow
  • Chlorine – Used to purify water
  • Iodine – Used as antiseptic on wounds

Non-metals may not be shiny or hard, but they are just as important as metals!


🧠 Metal vs Non-Metal – At a Glance

PropertyMetalsNon-Metals
AppearanceLustrous (shiny)Non-lustrous (dull)
MalleabilityMalleableNot malleable
DuctilityDuctileNot ductile
SonoritySonorous (ringing sound)Not sonorous
Heat ConductivityGood conductorPoor conductor
Electrical ConductivityGood conductorPoor conductor
Oxide NatureBasicAcidic
Reaction with WaterSome react (e.g., Sodium)Usually no reaction

🏛️ Ancient India and Iron

India’s skill in metallurgy was world-class even thousands of years ago. The Iron Pillar of Delhi, built during Chandragupta II’s time, hasn’t rusted in over 1600 years, showing the advanced metal knowledge of ancient India.


🧠 In a Nutshell – Chapter Recap

  • Metals are hard, shiny, malleable, ductile, and conduct heat and electricity.
  • Non-metals are dull, brittle, and are poor conductors.
  • Metals form basic oxides; non-metals form acidic oxides.
  • Rusting is a chemical change caused by moisture and air.
  • Combustion, burning, and corrosion are examples of metal reactions.
  • Non-metals are essential for life, health, agriculture, and environment.

*~*Summary Ends here*~*

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