Class 7 Science — Chapter 4: The World of Metals and Non-Metals

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Class 7 Science – Chapter 4: The World of Metals and Non-Metals | Basic Concepts

🧪 Class 7 Science — Chapter 4: The World of Metals and Non-Metals

Part-1: Basic Concepts — simple, student-friendly explanations with emojis, blocks, and pointers.

Syllabus: NCERT • Grade 7 Topic: Properties • Uses • Reactions Designed for Phone + Laptop
Chapter at a Glance 👀
This chapter helps you clearly understand what metals and non-metals are, how they look and behave, why they are useful in daily life, and how they react with air and water. You’ll also see why iron rusts, how to prevent it, and why some substances (like sulfur) behave very differently from metals.
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Story Start: Yashwant and Anandi visit a village ironsmith (Sudarshan) who makes tawas, buckets, tongs and farming tools from iron. By heating iron till it is red hot and hammering it, he changes its shape — this introduces you to the idea that metals can be shaped and worked upon.

1) What are Metals and Non-Metals? 🧲🌿

Metals (धातु)

Shiny (Metallic Lustre) Usually Hard Malleable Ductile Sonorous Good Conductors
  • Look shiny (e.g., copper, aluminium, iron).
  • Often hard and strong (but exceptions exist).
  • Can be beaten into sheets (malleable).
  • Can be drawn into wires (ductile).
  • Produce a ringing sound when struck (sonorous).
  • Conduct heat and electricity well (used in utensils & wiring).
Exceptions: Sodium and potassium are very soft (cut with a knife). Mercury is liquid at room temperature.

Non-Metals (अधातु)

Usually Dull Brittle Not Malleable Not Ductile Poor Conductors
  • Usually dull (e.g., sulfur, coal, phosphorus).
  • Break easily if hit (often brittle).
  • Cannot be made into sheets or wires easily.
  • Do not produce ringing sound.
  • Generally poor conductors of heat and electricity.
Remember: Materials like plastic, glass, wood or rubber are not elements; they are not classified as metals or non-metals.

2) Key Properties Explained with Daily-Life Clues ✨🔔⚡

Metallic Lustre ✨

Metals shine because of their surface property called metallic lustre. That’s why utensils and statues made of copper or brass look shiny.

Clue: Foils (silver, aluminium) also look lustrous.

Malleability 🔨

Metals can be beaten into thin sheets. The ironsmith hammers hot iron to change its shape (like an axe head).

Examples: Silver foil on sweets, aluminium foil for wrapping.

Ductility 🧵

Metals can be drawn into wires. Copper/aluminium wires are used in electrical fittings. Steel wire ropes lift heavy loads.

Gold is so ductile that 1 g can be drawn into ~2 km wire!

Sonority 🔔

When struck, metals make a clear ringing sound. Think of a metal bell or a coin vs. a piece of coal/wood (dull sound).

Reason: Metals vibrate uniformly and carry sound well.

Conduction of Heat 🍲

Heat travels quickly through metals. Cooking vessels are metal; their handles are often wood/plastic (poor conductors).

Wood is a poor conductor → safer for handles.

Conduction of Electricity ⚡

Metals like copper, aluminium, iron allow current to pass. Non-metals like sulfur, coal, wood, rubber do not.

Electricians use screwdrivers with plastic handles + rubber gloves for safety.

Hands-on Thinking: If a bulb in a simple circuit glows when you insert a material, the material is a good conductor; if it doesn’t, it’s a poor conductor.

3) What Happens with Air and Water? 🌬️💧🔥

1

Rusting of Iron (Corrosion) 🧱→🟤

Iron develops a brown flaky deposit (rust) when exposed to moist air (both air + water needed). In dry air alone or in only water (without air), rust doesn’t form.

Prevention: Painting, oiling/greasing, or galvanisation (coating iron with zinc).

Why we care: Rusting damages bridges, gates, tools; prevention saves money and resources.

2

Other Metals with Oxygen 🔥

Magnesium burns with a dazzling white flame forming a white powder magnesium oxide (MgO). This makes a basic solution in water (turns red litmus blue).

Sodium is highly reactive with air/water and is stored in kerosene.

3

Non-Metals with Oxygen 🌫️

Sulfur burns to form sulfur dioxide (SO₂); dissolved in water, it forms sulfurous acid → turns blue litmus red (i.e., acidic).

Non-metal oxides are generally acidic; metal oxides are generally basic.

4

Non-Metals & Water 💧

Substances like sulfur show no reaction with water in simple conditions. Phosphorus is stored under water because it catches fire in air.

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Safety First: Many reactions involve heat/fire or gases. Always perform under adult/teacher supervision, wear safety gear, and work in ventilated spaces.

4) Why Are Metals and Non-Metals Important in Daily Life? 🏠📱🌿

Metals: Everyday Heroes 🛠️

  • Utensils & cookware (good heat conduction).
  • Wires & circuits (good electrical conduction).
  • Tools, machines, bridges (strength & durability).
  • Alloys like steel improve properties (stronger, more useful).
  • Recycling (iron, aluminium) helps sustainability.
History Link: Iron technology boosted agriculture and tools in India — stronger ploughs and better implements.

Non-Metals: Silent Essentials 🌬️

  • Oxygen (O₂) — essential for breathing.
  • Carbon (C) — backbone of life (proteins, fats, carbohydrates).
  • Nitrogen (N₂) — used in fertilizers; vital for plant growth.
  • Chlorine (Cl₂) — water purification.
  • Iodine — antiseptic on wounds.
Metals → Shiny • Strong • Conductors Non-Metals → Often Dull • Poor Conductors Metal Oxides → Basic Non-Metal Oxides → Acidic Rusting → Moist Air Needed Prevention → Paint • Oil • Galvanise

5) Quick Concept Checks 🧠✅

Spot the Metal vs Non-Metal 🔍

  • Shiny spoon that rings when dropped → Metal
  • Dull, brittle lump that breaks when hit → Non-Metal
  • Wire used in electric cable → Metal
  • Rubber gloves/shoe soles for electricians → Non-Metal (insulator)

Air + Water + Iron = ? 🧪

Both air and water together cause rusting of iron. Remove either one, and rusting stops.

Protect iron by painting, oiling, or zinc-coating (galvanisation).

6) From Activities to Understanding 🧪➡️🧠

Beating Test (Malleability) 🔨

When you beat copper, aluminium, iron on a hard surface, they flatten (malleable). But coal or sulfur break (brittle). Wood is neither malleable nor brittle — it doesn’t flatten or shatter easily.

Heat Transfer Test 🍵

A metal spoon in hot water quickly becomes hot at the handle — proof of heat conduction in metals, unlike wood.

Electric Tester 💡

Make a simple bulb circuit. Metals (aluminium foil, copper wire, iron nail) make the bulb glow (good conductors); coal, wood, rubber, nylon rope do not (poor conductors).

Burning & Oxides 🔥

  • Magnesium → burns with white flame → MgO (basic in water).
  • Sulfur → burns to SO₂ → in water makes sulfurous acid (acidic).
  • Takeaway: Metal oxides are generally basic; Non-metal oxides generally acidic.
Measurement vs. Reasoning: In geometry-like thinking, we use reasoning to know relationships (e.g., linear pairs add to 180°). In science here, we use observations (tests/activities) + reasoning to conclude properties reliably.

7) Big-Picture Recap 🧭

  • Metals are usually shiny, hard, malleable, ductile, sonorous, and good conductors of heat/electricity.
  • Non-metals are generally dull, brittle, not malleable/ductile, poor conductors, and not sonorous.
  • Metal oxides → mostly basic; Non-metal oxides → mostly acidic.
  • Rusting of iron needs both air + water (moist air). Prevent by paint, oil/grease, or galvanisation.
  • Metals and non-metals are elements — basic building blocks of matter. (118 known; some natural, some man-made.)
  • Both groups are essential in daily life: from utensils and machines to oxygen for breathing and fertilizers for plants.
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Exam Hint: Be ready to give examples for each property, and to state whether a given oxide is basic or acidic based on whether it comes from a metal or a non-metal.
What’s Next? 📚
This was Part-1: Basic Concepts. In the next parts, we’ll add: Key Terms (Eng+Hindi), Facts, Concept Map, Diagrams (explained), and full Practice Sections (MCQs, Objective, Fill-ups, T/F, Match, HOTS, Textbook Q&A, Summary).
🧠Understand ✍️Practice 🏆Revise

2) Know the Terms — English + Hindi 📚

Simple, student-friendly meanings in plain English and common Hindi. Read once, revise twice!
# Keyword Meaning (Simple English) हिंदी अर्थ (साधी भाषा)
1 Metal A shiny, usually hard substance that lets heat and electricity pass easily. धातु — आम तौर पर चमकीला और कड़ा पदार्थ, जिसमें से ऊष्मा व बिजली आसानी से गुजरती है।
2 Non-metal Usually dull, not easily shaped into sheets or wires, and a poor conductor. अधातु — ज़्यादातर बिना चमक का, चादर/तार बनाना मुश्किल, और बिजली-ऊष्मा का खराब चालक।
3 Metallic Lustre The shiny look seen on metals. धात्विक चमक — धातुओं की खास चमक।
4 Malleability Can be beaten into thin sheets with a hammer. मैलियबिलिटी — हथौड़े से पीटकर पतली चादर बन सके।
5 Ductility Can be stretched into thin wires. डक्टिलिटी — खींचकर पतला तार बनाया जा सके।
6 Sonority Makes a ringing sound when struck. नादिता — चोट करने पर घंटी जैसी आवाज़ आना।
7 Conduction (Heat) Passing of heat through a material. ऊष्मा चालन — किसी पदार्थ के अंदर गर्मी का फैलना/गुज़रना।
8 Conduction (Electricity) Passing of electric current through a material. विद्युत चालन — किसी पदार्थ में से धारा का गुजरना।
9 Conductor Material that allows heat/electricity to pass easily (e.g., copper). चालक — जिसमें से ऊष्मा/बिजली आसानी से निकलती है (जैसे तांबा)।
10 Insulator Material that does not allow heat/electricity to pass easily (e.g., rubber). रोधक — जो ऊष्मा/बिजली को रोकता है (जैसे रबर, प्लास्टिक)।
11 Brittleness Breaks into pieces when hit or hammered. भंगुरता — चोट लगने पर टुकड़े-टुकड़े हो जाना।
12 Corrosion Slow damage of metals by air, water or chemicals. क्षरण — वायु/जल/रसायनों से धातु का धीरे-धीरे खराब होना।
13 Rusting Brown flaky layer on iron formed in moist air. जंग लगना — नम हवा में लोहे पर भूरी परत बनना।
14 Metal Oxide Compound made when a metal reacts with oxygen; usually basic. धातु ऑक्साइड — धातु + ऑक्सीजन से बना यौगिक; आमतौर पर क्षारीय।
15 Non-metal Oxide Compound made when a non-metal reacts with oxygen; usually acidic. अधातु ऑक्साइड — अधातु + ऑक्सीजन से बना; आमतौर पर अम्लीय।
16 Magnesium Oxide (MgO) White powder from burning magnesium; forms a basic solution. मैग्नीशियम ऑक्साइड — मैग्नीशियम जलाने पर बना सफ़ेद पाउडर; क्षारीय घोल बनाता है।
17 Sulfur Dioxide (SO₂) Gas from burning sulfur; in water makes an acidic solution. सल्फर डाइऑक्साइड — गंधक जलाने पर बनने वाली गैस; पानी में घुलकर अम्ल बनाती है।
18 Galvanisation Coating iron with zinc to stop rusting. जस्तीकरण — लोहे पर जिंक की परत चढ़ाकर जंग से बचाना।
19 Alloy Mixture of metals (or metal + non-metal) with better properties (e.g., steel). मिश्रधातु — धातुओं/धातु-अधातु का मिश्रण, जिनके गुण बेहतर होते हैं (जैसे स्टील)।
20 Element Pure substance made of one kind of atom; cannot be broken into simpler substances. तत्त्व — एक ही प्रकार के परमाणुओं से बना शुद्ध पदार्थ; साधारण तरीकों से और सरल भागों में नहीं टूटता।
💡 Tip: Revise 5–5 terms daily. Speak aloud the English meaning, then the Hindi meaning to build strong memory connections.

3) Know the Facts — Quick, Exam-Friendly Points 📌

Handy list of the most useful facts from this topic — perfect for last-minute revision and one-markers. Use the chips and cards below to remember what matters most.

Metals: Must-Know Facts 🛠️

Shiny (metallic lustre) Malleable Ductile Sonorous Good conductors
  1. Most metals are lustrous, hard, and strong (e.g., iron, copper, aluminium).
  2. Malleability: Metals can be beaten into sheets (silver foil on sweets, aluminium foil for food).
  3. Ductility: Metals can be drawn into wires (copper/aluminium wiring; steel ropes for lifting).
  4. Sonority: Metals ring when struck (school bell, coin sound).
  5. Heat conduction: Metals heat up quickly — that’s why utensils are metal but handles are wooden/plastic.
  6. Electrical conduction: Metals allow current to pass; electricians use plastic/rubber for insulation.
  7. Exceptions: Sodium and potassium are very soft; mercury is liquid at room temperature.

Non-Metals: Must-Know Facts 🌿

Usually dull Brittle Poor conductors Acidic oxides
  1. Non-metals are usually dull and brittle (e.g., sulfur, coal), and not malleable or ductile.
  2. They do not produce a ringing sound when hit.
  3. Generally poor conductors of heat and electricity (rubber, wood, plastic are used as insulators).
  4. Non-metal oxides (like SO₂) are usually acidic (turn blue litmus red).
  5. Phosphorus is stored under water because it catches fire in air.
  6. Oxygen is essential for breathing; nitrogen for plants (fertilisers); chlorine for water purification; iodine as antiseptic.

Reactions & Oxides 🔥🌬️💧

  1. Magnesium burns with a bright white flame to form magnesium oxide (MgO) — its solution is basic (turns red litmus blue).
  2. Sulfur burns to form SO₂; dissolved in water it makes sulfurous acid — acidic (turns blue litmus red).
  3. Rule of thumb: Metal oxides → usually basic; Non-metal oxides → usually acidic.
  4. Sodium reacts vigorously with air/water → stored in kerosene.
  5. Non-metals like sulfur typically show no reaction with water in simple conditions.

Rusting & Corrosion 🧱➡️🟤

  1. Rusting is the brown flaky deposit that forms on iron.
  2. Rusting needs both air and water (moist air). In dry air only, or only water (without air), rusting does not happen.
  3. Corrosion is the gradual damage of metal surfaces by air/water/chemicals (green on copper, black on silver).
  4. Prevention: Painting, oiling/greasing, and galvanisation (zinc-coating iron).
  5. Why important? Corrosion causes huge losses by damaging structures, tools, and machines.

Elements, Alloys & Society 🌍

  1. Element: A pure substance made of one kind of atom; cannot be broken into simpler substances. About 118 elements are known (some natural, some man-made).
  2. Metals & non-metals are both types of elements.
  3. Alloy: Mixture of metals (or metal + non-metal) with improved properties (e.g., steel = iron + carbon).
  4. Everyday importance: Metals for utensils, wiring, machines; Non-metals like oxygen, nitrogen, chlorine, iodine are vital for life, agriculture, health, and sanitation.
  5. Recycling: Aluminium and iron are widely recycled to reduce waste and protect the environment.
  6. Indian heritage: The Iron Pillar of Delhi (about 1600+ years old) shows exceptional resistance to rust — a marvel of ancient metallurgy.
Exam Tip: If the oxide turns red litmus blue → Basic (usually metal oxide). If it turns blue litmus red → Acidic (usually non-metal oxide).
Quick Statement Category Why / Example
Metals are malleable and ductile. Property Sheets (foil), wires (copper wiring) can be made.
Non-metals are often brittle and dull. Property Sulfur and coal break on hammering; no shine.
Metal oxides are generally basic. Reaction MgO solution turns red litmus blue.
Non-metal oxides are generally acidic. Reaction SO₂ in water turns blue litmus red.
Rusting needs both air and water. Corrosion Moist air causes iron to rust; dry air or only water doesn’t.
Iron can be protected by galvanisation. Prevention Zinc coating prevents rust.
Sodium is stored in kerosene. Reactivity It reacts vigorously with air/water.
Mercury is a liquid metal at room temperature. Exception Used earlier in thermometers.
Oxygen, nitrogen, chlorine, iodine are useful non-metals. Applications Breathing, fertilisers, water purification, antiseptic.
Metals and non-metals are elements. Definition Pure substances; ~118 known elements.

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