Brown-coloured iron oxide formed when iron is exposed to moist air

A type of paint applied on iron

Why is sodium metal stored in kerosene?

Because sodium reacts vigorously with oxygen and water in air

Because sodium dissolves in water

What does 'metallic lustre' mean?

The shiny appearance characteristic of metals

A substance that cannot be broken down into simpler substances

Why is copper most commonly used for electrical wires despite silver being a better conductor?

Copper has lower cost and abundant supply compared to silver

Copper has higher melting point

Copper conducts electricity better at high temperatures

What experiment proves that BOTH air and water are needed for rusting?

Placing iron in dry air and water

Iron in bottle A (dry air) shows no rust — iron in bottle B (water without air) shows no rust — iron in bottle C (water and air) shows rust — confirming both are needed

One gram of gold can be drawn into a 2 kilometre long wire. What does this illustrate?

Gold's extreme ductility — the ability to be pulled into extremely thin wires without breaking

Why does the Iron Pillar of Delhi resist rusting despite being exposed to weather for over 1600 years?

Ancient Indian metallurgy created a phosphorus-rich protective layer on the iron through skilled craftsmanship that prevents corrosion

Modern maintenance prevents rusting

What is the difference between rusting (iron specifically) and corrosion (general)?

Rusting is the specific formation of iron oxide on iron when exposed to moist air — corrosion is the broader term for the gradual deterioration of ANY metal surface when exposed to air water or other substances

Corrosion is faster than rusting

Why are handles of metal cooking vessels made of wood or plastic — not metal?

Wood is a poor conductor of heat — making handles safer to touch while the metal body conducts heat efficiently to cook food

Sulfur forms an acidic oxide while magnesium forms a basic oxide. How does this difference connect to the broader metal vs non-metal classification?

Metal oxides are basic because metals tend to donate electrons during reactions while non-metals tend to accept electrons — this fundamental difference in electron behaviour explains their opposite oxide natures

This is an exception not a rule

Acid-base nature has nothing to do with metals

Why is phosphorus stored in water while sodium is stored in kerosene? What does this reveal about their different reactivities?

Phosphorus spontaneously ignites in air so water shields it from oxygen — sodium reacts violently with water so kerosene (which doesn't react with sodium) isolates it from both air and water — storage method reflects the specific reactivity of each substance

Both substances react with water

They are stored differently for transportation reasons

Why are non-metals such as oxygen nitrogen and carbon essential to life even though metals often appear more prominent in daily use?

Oxygen enables respiration — carbon forms the structural backbone of all organic molecules including DNA proteins and carbohydrates — nitrogen is essential for plant growth — non-metals operate invisibly as the chemistry of life itself

Metals are more important than non-metals

Non-metals are only used in industry

What does the metallic lustre of metals indicate at a structural level?

Metals have free electrons that interact with light waves causing reflection — the same free electrons that cause lustre also account for electrical conductivity — demonstrating that a single property (free electrons) explains multiple metal characteristics

Metals are polished artificially

Only some metals have free electrons

Why is recycling of metals like iron and aluminium in India considered important for sustainability?

Recycling conserves finite metal ore resources reduces energy consumption in metal extraction reduces mining damage to the environment and minimises waste — demonstrating that materials science connects directly to environmental sustainability

How does the transition from copper tools to iron tools represent a major advance in human civilisation?

Iron is harder and more abundant than copper — iron tools (ploughs axes weapons) enabled more efficient agriculture construction and warfare — the availability of a stronger more practical metal transformed the scale of human activity — demonstrating that materials science drives civilisational progress

How does the concept of ductility explain why metal wires (not non-metal strings) are used in musical instruments like sitar and veena?

Ductile metals can be drawn into precise gauges of thin wire that produce specific musical frequencies when vibrated — maintaining tension elasticity and consistent vibration — non-metals lack the structural properties to form stable strings at musical frequencies

Non-metals cannot be shaped into wires

Why does coal (a non-metal) break into pieces when hammered while metals flatten? What does this reveal about their internal structure?

Metals have a crystalline structure with layers that can slide past each other — this is malleability — coal and non-metals like sulfur have rigid brittle crystalline or molecular structures where atomic layers cannot slide and thus break under stress

NCERT Solutions Class 7 Science Chapter 4 – The World of Metals and Non-metals

Name: The World of Metals and Non-metals – Class 7 Science
Uploaded: 2026-07-24T05:14:33+00:00
Description: Metals and non-metals differ in their properties. Metals are generally shiny, malleable, ductile, and good conductors of heat and electricity, while non-metals are dull, brittle, and poor conductors. Both have essential uses in daily life and technology.

Class 7 Science

Last Updated: 24 July 2026

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Chapter Introduction

Metals and non-metals differ in their properties. Metals are generally shiny, malleable, ductile, and good conductors of heat and electricity, while non-metals are dull, brittle, and poor conductors. Both have essential uses in daily life and technology.

हिंदी में (Hindi)

धातु और अधातु अपनी विशेषताओं में भिन्न होते हैं। धातुएँ सामान्यतः चमकीली, लचीली, तंतुकारक और गर्मी व विद्युत की अच्छी चालक होती हैं, जबकि अधातु मंद, भंगुर और कमजोर चालक होते हैं। दोनों का दैनिक जीवन और तकनीक में महत्वपूर्ण उपयोग है।

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Important Points

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Practice MCQ Questions (28 questions)

Q1. What is the property of metals that allows them to be beaten into thin sheets called?

Q2. What is the property of metals that allows them to be drawn into wires called?

Q3. Which two metals are the most malleable?

Q4. What is sonority in metals?

Q5. What is rust?

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Frequently Asked Questions (FAQ)

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Tough Words (Glossary)

ironsmith

Meaning: a person who makes or repairs iron objects

अर्थ: लोहे का काम करने वाला कारीगर

"We interviewed the village ironsmith about his tools."

craftsperson

Meaning: a skilled worker who makes things by hand

अर्थ: हस्तकला में निपुण कारीगर

"The craftsperson shaped the metal carefully."

tongs

Meaning: a tool used to hold or pick up something hot

अर्थ: चिमटा / चिमटे

"Sudarshan used tongs to hold the red‑hot iron."

spade

Meaning: a tool with a flat blade used for digging

अर्थ: फावड़ा

"The farmer lifted soil with a spade."

axe

Meaning: a tool with a heavy blade used for cutting

अर्थ: कुल्हाड़ी

"He forged an axe from the iron block."

trowel

Meaning: a small hand tool used for digging or smoothing

अर्थ: खुरपी

"Gardeners use a trowel to plant saplings."

rake

Meaning: a tool with teeth for collecting leaves or leveling soil

अर्थ: जेली / कुदाल-जैसा रेक

"They used a rake to level the field."

furnace

Meaning: an enclosed structure for heating materials to high temperatures

अर्थ: भट्ठी

"The iron block was heated in the furnace."

malleability

Meaning: the ability of a material to be beaten into thin sheets

अर्थ: आसंयोज्यता/पीटकर चादर बनाने की क्षमता (मृदुता)

"Gold has very high malleability."

lustrous

Meaning: shiny; reflecting light well

अर्थ: चमकीला / दीप्तिमान

"Copper looks lustrous when freshly polished."

brittle

Meaning: easily broken or cracked; not flexible

अर्थ: भंगुर

"Sulfur is brittle and breaks into pieces."

ductility

Meaning: the ability to be drawn out into a wire

अर्थ: तन्यता / तार में खिंचने की क्षमता

"Aluminium shows good ductility."

sonority

Meaning: the property of producing a ringing sound

अर्थ: घनत्व/घनघनाहट (ध्वनि-गुण)

"Metals are identified by their sonority."

conductor (electricity)

Meaning: a material that allows electric current to pass through

अर्थ: चालक (विद्युत)

"Copper is a good conductor of electricity."

insulator

Meaning: a material that does not allow electric current to pass through easily

अर्थ: रोधक

"Rubber is used as an insulator on wires."

conduction (heat)

Meaning: transfer of heat through a material

अर्थ: चालन (ऊष्मा)

"The metal spoon became hot due to conduction."

corrosion

Meaning: gradual damage of a metal by reaction with air, water, etc.

अर्थ: क्षरण / जंग लगना

"Corrosion weakens iron bridges."

rusting

Meaning: formation of reddish‑brown rust on iron in moist air

अर्थ: जंग लगना (लोहे पर)

"The gate showed rusting after the rains."

galvanisation

Meaning: coating iron with zinc to prevent rusting

अर्थ: गैल्वनाइजेशन (लोहे पर जस्ता चढ़ाना)

"Pipes are protected by galvanisation."

silica gel

Meaning: a drying agent used to absorb moisture

अर्थ: सिलिका जेल (नमी सोखने वाला पदार्थ)

"Silica gel kept the bottle dry."

kerosene

Meaning: a type of fuel oil

अर्थ: मिट्टी का तेल

"Sodium is stored in kerosene."

magnesium ribbon

Meaning: a thin strip of magnesium metal used in experiments

अर्थ: मैग्नीशियम रिबन

"The magnesium ribbon burned with a bright flame."

oxide

Meaning: a compound of oxygen with another element

अर्थ: आक्साइड / ऑक्साइड

"Magnesium oxide forms after burning magnesium."

sulfurous acid

Meaning: an acid formed when sulfur dioxide dissolves in water

अर्थ: सल्फ्यूरस अम्ल

"Sulfurous acid turns blue litmus red."

deflagrating spoon

Meaning: a long‑handled metal spoon for safely burning substances

अर्थ: डिफ्लैग्रेटिंग स्पून (दूरदंड़ी धातु चम्मच)

"The teacher used a deflagrating spoon to burn sulfur."

ignite

Meaning: to set on fire

अर्थ: प्रज्वलित करना

"We used a spirit lamp to ignite the ribbon."

dazzling

Meaning: extremely bright; blinding

अर्थ: चमचमाता / चकाचौंध वाला

"Magnesium burns with a dazzling white flame."

vigorous

Meaning: strong, forceful, or energetic

अर्थ: प्रबल / तीव्र

"Sodium shows a vigorous reaction with water."

moisture

Meaning: tiny amount of water present in the air or a material

अर्थ: नमी

"Moisture in air causes iron to rust."

deterioration

Meaning: the process of becoming worse or damaged

अर्थ: क्षय / बिगड़ावट

"Paint prevents deterioration of metal surfaces."

discolouration

Meaning: a change in colour, often due to a reaction

अर्थ: वर्ण-परिवर्तन / रंग फीका पड़ना

"Copper shows green discolouration over time."

alloy

Meaning: a mixture of two or more metals or a metal and a non‑metal

अर्थ: मिश्रधातु

"Brass is an alloy of copper and zinc."

utensils

Meaning: tools or containers used for cooking or serving

अर्थ: बर्तन

"Steel utensils are used in most kitchens."

purification

Meaning: the process of making something clean and safe

अर्थ: शुद्धिकरण

"Chlorine is used in water purification."

antiseptic

Meaning: a substance that prevents infection by killing germs

अर्थ: प्रतिजैविक / एंटीसेप्टिक

"Iodine solution works as an antiseptic."

fertilisers

Meaning: substances added to soil to help plants grow

अर्थ: उर्वरक

"Nitrogen is important in making fertilisers."

sustainability

Meaning: using resources in a way that does not harm the future

अर्थ: स्थिरता / टिकाऊपन

"Recycling metals supports sustainability."

aerospace

Meaning: industry related to aircraft and spacecraft

अर्थ: वैमानिकी व अंतरिक्ष क्षेत्र

"Titanium is used in aerospace parts."

recycled

Meaning: processed to be used again

अर्थ: पुनर्चक्रित

"Aluminium cans are easily recycled."

suspension bridge

Meaning: a bridge hung from cables supported by towers

अर्थ: झूला पुल / लटकता पुल

"Steel ropes hold a suspension bridge."

mercury

Meaning: a silvery liquid metal at room temperature

अर्थ: पारा (धातु)

"Old thermometers contain mercury."

sodium

Meaning: a soft, reactive metal stored in kerosene

अर्थ: सोडियम (धातु)

"Sodium reacts violently with water."

potassium

Meaning: a soft, very reactive metal

अर्थ: पोटैशियम (धातु)

"Potassium must be handled carefully."

element

Meaning: a pure substance made of only one kind of atom

अर्थ: तत्व

"Oxygen is an element essential for life."

non‑metal

Meaning: an element that is usually dull and a poor conductor

अर्थ: अधातु

"Sulfur is a common non‑metal."

properties

Meaning: features or qualities of a material

अर्थ: गुण / विशेषताएँ

"We compared the properties of metals and non‑metals."

metallic lustre

Meaning: the shiny appearance typical of metals

अर्थ: धात्विक चमक

"Fresh aluminium shows metallic lustre."

brittleness

Meaning: the quality of being easily broken

अर्थ: भंगुरता

"Coal shows brittleness under hammering."

ductile

Meaning: able to be drawn into a wire

अर्थ: तन्य

"Gold is ductile and can form very thin wires."

sonorous

Meaning: producing a deep or ringing sound

अर्थ: घनघनाहट वाला / निनादित

"A bell is sonorous due to the metal."

conductor (heat)

Meaning: a material that easily lets heat pass through

अर्थ: ऊष्मा-चालक

"Metal pans are good conductors of heat."

poor conductor

Meaning: a material that does not allow heat/electricity easily

अर्थ: कमज़ोर चालक / रोधी

"Wood is a poor conductor of heat."

greasing

Meaning: applying grease to protect or make smooth

अर्थ: चिकनाई लगाना

"Greasing can protect iron from rust."

oiling

Meaning: applying oil as a protective layer

अर्थ: तेल लगाना

"Oiling the tools prevents corrosion."

protective layer

Meaning: a coating that guards the surface from damage

अर्थ: सुरक्षात्मक परत

"Zinc forms a protective layer on iron."

prominence

Meaning: the state of being important or well‑known

अर्थ: प्रमुखता

"Iron gained prominence in later times."

civilisation

Meaning: a developed human society with culture and technology

अर्थ: सभ्यता

"Iron tools helped the civilisation progress."

plough

Meaning: a farming tool used to turn over soil

अर्थ: हल

"An iron plough makes farming easier."

metallurgy

Meaning: the science and technology of metals

अर्थ: धातु विज्ञान

"The Iron Pillar shows ancient metallurgy."

exposure

Meaning: the state of being in contact with something

अर्थ: संपर्क / खुला पड़ना

"Exposure to moist air leads to rusting."

atmospheric

Meaning: related to the air around us

अर्थ: वायुमंडलीय

"Atmospheric oxygen reacts with metals."

vessel

Meaning: a container used for cooking or holding liquids

अर्थ: बरतन / पात्र

"Use metal vessels for quick heating."

coating

Meaning: a thin layer covering a surface

अर्थ: लेप / परत

"A paint coating prevents corrosion."

moist air

Meaning: air containing water vapour

अर्थ: आर्द्र वायु / नम हवा

"Moist air speeds up rusting."

react

Meaning: to undergo a chemical change with another substance

अर्थ: अभिक्रिया करना

"Metals react with oxygen to form oxides."

basic (nature)

Meaning: having the properties of a base; opposite of acidic

अर्थ: क्षारीय (स्वभाव)

"Metal oxides are generally basic in nature."

acidic (nature)

Meaning: having the properties of an acid

अर्थ: अम्लीय (स्वभाव)

"Non‑metal oxides are often acidic."

neutral (nature)

Meaning: neither acidic nor basic

अर्थ: तटस्थ (स्वभाव)

"Pure water is neutral in nature."

oxygen

Meaning: a gas essential for breathing and burning

अर्थ: ऑक्सीजन

"Oxygen helps things burn and living beings breathe."

chlorine

Meaning: a greenish gas used to purify water

अर्थ: क्लोरीन

"Chlorine kills germs in drinking water."