UBSE • Class X • Science • Ch 3

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Metals and Non-Metals

In Class 7 Science, Chapter 4 "The World of Metals and Non-metals" investigates the elemental materials shaping civilization. Grounded in the 2026–27 NCERT Curiosity curriculum, this master material explores physical traits (malleability, ductility, sonority, conductivity), chemical reactions with oxygen, water, and acids, displacement reactions in aqueous solutions, and industrial applications.

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🪙 Have You Ever Wondered?

Why can you beat silver into tissue-thin foil, but a lump of coal shatters into dust?

The shiny silver foil (vark) decorating festive Indian sweets is beaten until it is only $0.0002\text{ mm}$ thick! Yet, if you hit a piece of charcoal or sulfur with the exact same hammer, it crumbles into useless black powder.

Why do church and school bells ring with a deep, echoing musical tone, while striking a wooden block produces only a dull "thud"? Why are electrical transmission lines made of copper rather than plastic?

All solid materials in our universe divide into two great kingdoms: Metals and Non-metals. From the iron hemoglobin carrying oxygen in your blood to the silicon chips powering your smartphone, their physical and chemical behaviors govern the modern world.

Why This Chapter Matters

Before You Begin (Prerequisites)

Classification of matter: elements, compounds, and mixtures.
Litmus test from Chapter 2: acidic oxides turn blue litmus red; basic oxides turn red litmus blue.
Basic states of matter: solids, liquids, and gases.

What You Will Learn (Core Objectives)

Differentiate between metals and non-metals based on physical properties (malleability, ductility, lustre, sonority, conductivity).
Identify key exceptions to physical rules (mercury is liquid, sodium is soft, graphite conducts electricity).
Explain how metals form basic oxides while non-metals form acidic oxides.
Predict the outcomes of metal displacement reactions using the reactivity principle.
Match metals and non-metals to their vital applications in engineering, medicine, and agriculture.

Chapter Roadmap & Progression

1 1. Physical Properties: The Structu...

2 2. Chemical Properties: Reactions w...

3 3. Displacement Reactions & The Rea...

Complete Concept Guide (100% Curriculum Coverage)

1. Physical Properties: The Structural Fingerprint

1. Five Defining Physical Traits

Property	Metals	Non-metals
Malleability	Can be hammered into thin sheets without breaking (e.g. Aluminum foil, gold foil).	Brittle: shatter into powder when hammered (e.g. Coal, sulfur).
Ductility	Can be drawn into thin wires (e.g. Copper, platinum).	Non-ductile: cannot be drawn into wires.
Sonority	Produce a resonant, musical ringing sound when struck (e.g. School bells, guitar strings).	Non-sonorous: produce a dull thud.
Electrical & Thermal Conductivity	Good conductors of heat and electricity (e.g. Copper, silver, aluminum).	Poor conductors / insulators (e.g. Wood, plastic, sulfur).
Lustre	Metallic shine on freshly cut surfaces.	Dull surface appearance.

2. The Famous Exceptions (High-Yield Exam Traps)

⚠️ Must-Memorize Exceptions:
• Mercury ($\text{Hg}$): The ONLY metal that is liquid at room temperature.
• Sodium ($\text{Na}$) and Potassium ($\text{K}$): Metals so soft they can be sliced with a butter knife!
• Graphite (Carbon): A non-metal that is an excellent conductor of electricity (used in pencil leads and battery electrodes).
• Iodine: A non-metal that possesses a bright, shining metallic lustre.
• Diamond: A non-metal (carbon allotrope) that is the hardest naturally occurring substance known and an exceptional heat conductor.

2. Chemical Properties: Reactions with Oxygen, Water & Acids

1. Reaction with Oxygen (Oxide Acidity)

Metals form BASIC Oxides: When magnesium burns with a dazzling white flame: $$2\text{Mg} + \text{O}_2 \longrightarrow 2\text{MgO}$$ Dissolving $\text{MgO}$ in water produces magnesium hydroxide [$\text{Mg(OH)}_2$], which turns red litmus paper blue!
Non-metals form ACIDIC Oxides: When sulfur burns in air, it produces sulfur dioxide: $$\text{S} + \text{O}_2 \longrightarrow \text{SO}_2$$ Dissolved in water, it forms sulfurous acid [$\text{H}_2\text{SO}_3$], which turns blue litmus paper red!

2. Reaction with Water and Acids

Reaction with Water: Sodium reacts violently with cold water, catching fire and releasing hydrogen gas. Hence, sodium is stored safely submerged under kerosene oil. Non-metals do not react with water (white phosphorus is stored in water to prevent it catching fire in air).
Reaction with Acids (The "POP" Sound Test): Active metals react with dilute hydrochloric acid to produce hydrogen gas: $$\text{Zn} + 2\text{HCl} \longrightarrow \text{ZnCl}_2 + \text{H}_2 \uparrow$$ Bringing a burning matchstick near the mouth of the test tube causes the hydrogen gas to burn with a distinctive "POP" sound! Non-metals generally do not react with dilute acids.

3. Displacement Reactions & The Reactivity Hierarchy

1. What is a Displacement Reaction?

A chemical reaction in which a more reactive metal displaces a less reactive metal from its aqueous salt solution is called a displacement reaction.

$$\mathbf{\text{Fe} + \text{CuSO}_4 \longrightarrow \text{FeSO}_4 + \text{Cu}}$$

The Classic Iron-Copper Experiment:

• Drop clean iron nails into a bright blue copper sulfate solution ($\text{CuSO}_4$).

• After 30 minutes, the blue color fades to light green due to the formation of iron sulfate ($\text{FeSO}_4$).

• A reddish-brown coating of displaced copper metal ($\text{Cu}$) settles onto the iron nails!

2. Pitfall & Examiner Trap

⚠️ Trap: Can a Less Reactive Metal Displace a More Reactive One?
If you drop a copper strip into green iron sulfate ($\text{FeSO}_4$), will iron be displaced?
Answer: NO REACTION! Copper is less reactive than iron, so it cannot displace iron. The reaction only goes downhill!

3. Why This Matters in Life

Industrial galvanization coats steel car bodies with a thin layer of zinc; zinc sacrifices itself to protect the underlying iron from rust through displacement chemistry.

Visual Learning & Conceptual Map

Oxide Litmus Test Comparison

Metallic oxides are basic; non-metallic oxides are acidic

METALLIC OXIDES (e.g. MgO)

BASIC

Turns Red Litmus → BLUE

NON-METALLIC OXIDES (e.g. SO₂)

ACIDIC

Turns Blue Litmus → RED

Chapter Summary & 10 Key Takeaways

Takeaway 1

Physical Properties: Metals are malleable, ductile, sonorous, lustrous, and good conductors of heat and electricity.

Takeaway 2

Key Exceptions: Mercury is liquid; sodium/potassium are soft enough to cut with a knife; graphite is a non-metal that conducts electricity.

Takeaway 3

Oxide Nature: Metals form basic oxides (turn red litmus blue); non-metals form acidic oxides (turn blue litmus red).

Takeaway 4

Hydrogen Pop Test: Active metals react with dilute acids to evolve hydrogen gas, which burns with a characteristic pop sound.

Takeaway 5

Displacement Reaction: A more reactive metal displaces a less reactive metal from its salt solution ($\text{Fe} + \text{CuSO}_4 \to \text{FeSO}_4 + \text{Cu}$).

Check Your Understanding (Diagnostic Practice Questions)

Diagnostic questions testing core conceptual clarity. Answers are hidden initially — solve each problem first, then click to reveal the step-by-step verified solution.

Why is sodium stored under kerosene oil while phosphorus is stored in water?

Reveal Answer & Explanation

Answer: Sodium is an extremely reactive metal that catches fire vigorously in contact with air or water, so it is kept under kerosene. Phosphorus is a non-metal that catches fire spontaneously in air, but does not react with water, so it is stored safely submerged in water.
Think about what each element reacts with.

What color change is observed when an iron nail is immersed in copper sulfate solution for 30 minutes? Explain the chemical reason.

Reveal Answer & Explanation

Answer: The blue copper sulfate solution turns light green due to the formation of iron sulfate ($\text{FeSO}_4$), and a reddish-brown layer of displaced copper settles on the nail, because iron is more reactive than copper.
Recall the displacement reaction formula.

Can lemon pickle be stored in an aluminum container? Explain why or why not.

Reveal Answer & Explanation

Answer: No, lemon pickle contains citric acid. Acids react with aluminum metal to produce toxic salts and hydrogen gas, spoiling the pickle and damaging the container.
Metals react with acids.

Name a non-metal that is: (a) essential for living beings during respiration (b) used in water purification (c) applied on wounds as a purple antiseptic.

Reveal Answer & Explanation

Answer: (a) Oxygen (b) Chlorine (c) Iodine (Tincture of iodine).
Three vital non-metallic elements.

Explain the meaning of malleability and ductility with one example of each.

Reveal Answer & Explanation

Answer: Malleability is the property of being hammered into thin sheets without breaking (e.g. aluminum foil). Ductility is the property of being drawn into thin wires (e.g. copper electrical wiring).
Sheets vs wires.

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