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The World of Metals and Non-Metals

NCERT Class 7 · Science Based on NCERT Class 7 Science textbook · Free CBSE study kit

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Chapter Notes

Overview
This chapter introduces students to the fundamental classification of materials into metals and non-metals based on their physical and chemical properties. It exists in the syllabus to build a foundational understanding of matter, which is essential for higher-grade chemistry and everyday scientific literacy. The one big idea a student must walk away with is that metals and non-metals have distinct, observable properties (like malleability, ductility, sonority, conductivity, and reaction with air and water) that determine their uses in daily life, and that these properties can be tested through simple experiments.
Key Concepts (13)
Malleability
The property by which materials can be beaten into thin sheets.
e.g. An ironsmith beats a red-hot iron block with a hammer to shape it into a flat axe; silver foil on sweets is made by beating silver into thin sheets.
Ductility
The property of materials by which they can be drawn into wires.
e.g. Copper and aluminium wires used in electrical fittings; gold can be drawn into a 2-kilometre-long wire from just one gram.
Sonority
The property of metals that enables them to produce a ringing sound when struck.
e.g. A metal spoon or coin dropped on the floor produces a ringing sound; the school bell and ghungroos produce sound due to sonority of metals.
Conduction of heat
The transfer of heat from one point to another of a material.
e.g. A metal spoon immersed in hot water becomes hot at the upper end, while a wooden spoon remains cool; cooking vessels are made of metals because they conduct heat well.
Conduction of electricity
The ability of a material to allow electric current to flow through it easily.
e.g. Aluminium foil, iron nail, and copper wire make a tester bulb glow; sulfur, coal, wood, rubber, and nylon do not.
Rusting
The process of formation of brown deposits (rust) on objects made of iron when exposed to moist air (both air and water).
e.g. Iron nails left in the open develop brown rust; the Iron Pillar of Delhi has barely any rust even after 1600 years.
Corrosion
The gradual deterioration of metal surfaces caused by air, water, or other substances.
e.g. Green coating on copper objects (like old copper vessels) and black coating on silver objects (like tarnished jewellery).
Metallic lustre
The shiny appearance shown by metals.
e.g. Copper, aluminium, and iron are lustrous; coal, sulfur, and wood are non-lustrous.
Brittle
A property of materials that break into pieces when beaten with a hammer.
e.g. A lump of sulfur or a piece of coal breaks into pieces when hammered.
Element
A substance that cannot be broken down into simpler substances.
e.g. Metals like iron, copper, gold and non-metals like oxygen, sulfur, carbon are elements; plastic, glass, wood, rubber, and paper are not elements.
Metal oxide
A compound formed when a metal reacts with oxygen; generally basic in nature.
e.g. Magnesium burns with a dazzling white flame to form magnesium oxide (white powder), which turns red litmus blue (basic).
Non-metal oxide
A compound formed when a non-metal reacts with oxygen; generally acidic in nature.
e.g. Sulfur burns to form sulfur dioxide gas, which dissolves in water to form sulfurous acid, turning blue litmus red (acidic).
Galvanisation
The method of protecting iron from rusting by applying a protective layer of zinc metal on it.
e.g. Iron sheets used for roofs are often galvanised to prevent rusting.
How It Works
Testing malleability of materials
  1. Collect waste pieces of copper, aluminium, an iron nail, a piece of coal, a pea-sized lump of sulfur, and a block of wood.
  2. Observe their appearance (lustrous/non-lustrous) and hardness (hard/soft).
  3. Place each item on a hard surface and beat it with a hammer.
  4. Observe whether the object becomes flattened into a thin sheet or breaks into pieces.
  5. Record observations in a table.
💡 Students often forget that wood neither flattens nor breaks — it is neither malleable nor brittle. Also, sodium and potassium are soft metals that can be cut with a knife, and mercury is a liquid metal at room temperature.
Testing conduction of heat (Activity 4.3)
  1. Place a glass tumbler on a table and fill it with hot water.
  2. Take a metal spoon and a wooden spoon of similar size and thickness.
  3. Immerse both spoons simultaneously into the hot water.
  4. Leave them undisturbed for a few minutes.
  5. Carefully touch the upper end of each spoon and note which feels hotter.
💡 The metal spoon becomes hotter because metals are good conductors of heat; the wooden spoon remains cooler because wood is a poor conductor. This is why cooking vessel handles are made of wood or plastic.
Testing conduction of electricity (Activity 4.4)
  1. Design a simple tester circuit (like in the chapter 'Electricity: Circuits and their Components').
  2. Collect objects: aluminium foil, iron nail, lump of sulfur, copper wire, piece of coal, dry wood, stone, rubber eraser, nylon rope.
  3. Predict which objects will make the bulb glow.
  4. Test each object by placing it in the circuit and observing whether the bulb glows.
  5. Record observations in a table and classify as good or poor conductors.
💡 Only metals (aluminium, iron, copper) make the bulb glow. Non-metals like sulfur, coal, wood, stone, rubber, and nylon do not conduct electricity. Plastic covering on screwdrivers and rubber gloves protect electricians because they are poor conductors.
Rusting of iron (Activity 4.5)
  1. Take three shining iron nails (clean with sandpaper if old).
  2. Take three clean, dry glass bottles with tight-fitting caps. Label A, B, C.
  3. Bottle A: Place one iron nail and some silica gel (to keep air dry). Tighten cap.
  4. Bottle B: Place one iron nail, pour freshly boiled and cooled water to fully dip the nail, then pour a layer of oil on top to prevent air from dissolving. Cap tightly.
  5. Bottle C: Place one iron nail, pour some water so the nail is partially dipped. Keep bottle unstoppered (exposed to air).
  6. Leave all bottles undisturbed at room temperature for 8–10 days.
  7. Observe and record the formation of brown deposits on the nails.
💡 Rusting requires both air (oxygen) and water. Nail in dry air (A) or in boiled water with oil layer (B) does not rust. Only the nail exposed to both air and water (C) rusts. Students often wrongly think water alone or air alone causes rust.
Burning of magnesium ribbon (Activity 4.6)
  1. Take a magnesium ribbon 3–4 cm long and clean it with sandpaper.
  2. Hold it with a pair of tongs and ignite one end using a spirit lamp or candle.
  3. Observe: magnesium burns with a dazzling white flame and changes into a white powder (magnesium oxide).
  4. Collect the white powder on a watch glass.
  5. Add a few drops of warm water to the powder, stir well.
  6. Test the solution with red and blue litmus paper: red litmus turns blue, indicating the solution is basic.
💡 Metal oxides are generally basic in nature. Magnesium oxide turns red litmus blue. Students must not confuse this with non-metal oxides, which are acidic.
Burning of sulfur (Activity 4.7)
  1. Take a small amount of powdered sulfur in a deflagrating spoon (or improvised metal cap with wire).
  2. Heat it on a flame until sulfur starts burning.
  3. Introduce the spoon into a gas jar or glass tumbler and cover with a lid.
  4. After 3–4 minutes, remove the lid and spoon, add a small quantity of water, replace lid, and shake to dissolve the gas.
  5. Test the solution with red and blue litmus paper: blue litmus turns red, indicating the solution is acidic.
💡 Non-metal oxides are generally acidic in nature. Sulfur burns to form sulfur dioxide, which dissolves in water to form sulfurous acid (acidic). Students often forget that sulfur does not react with water directly — it reacts with oxygen first, then the oxide dissolves in water.
Exam Traps — Don't Make These Mistakes
⚠ Confusing 'malleable' with 'ductile'
✗ Gold is malleable because it can be drawn into wires.
→ Malleability is the ability to be beaten into sheets, not drawn into wires. Drawing into wires is ductility.
✓ Gold is the most malleable metal because it can be beaten into very thin sheets (foils). It is also highly ductile because one gram can be drawn into a 2-kilometre-long wire.
⚠ Thinking all metals are hard and solid
✗ All metals are hard and solid at room temperature.
→ Some metals like sodium and potassium are so soft they can be cut with a knife. Mercury is a liquid metal at room temperature.
✓ Most metals are hard and solid, but exceptions exist: sodium and potassium are soft metals, and mercury is a liquid metal at room temperature.
⚠ Confusing rusting conditions
✗ Iron rusts when it comes in contact with water.
→ The experiment shows that iron does not rust in water alone (bottle B with oil layer). Both air (oxygen) and water are required for rusting.
✓ Iron rusts only when it comes into contact with both air (oxygen) and water (moist air). Dry air alone or water alone does not cause rusting.
⚠ Thinking non-metals react with water like metals
✗ Sulfur reacts with water to form an acid.
→ Sulfur does not react directly with water. First, sulfur burns in oxygen to form sulfur dioxide, which then dissolves in water to form sulfurous acid.
✓ Sulfur does not react with water directly. When sulfur burns in air, it forms sulfur dioxide gas, which dissolves in water to produce sulfurous acid (acidic).
⚠ Calling plastic, glass, or wood 'non-metals'
✗ Plastic and wood are non-metals.
→ Non-metals are elements (like oxygen, sulfur, carbon). Plastic, glass, wood, rubber, and paper are not elements — they are materials made from various substances and are not classified as metals or non-metals.
✓ Non-metals are elements such as oxygen, hydrogen, nitrogen, carbon, sulfur, and chlorine. Materials like plastic, glass, wood, rubber, and paper are not classified as metals or non-metals because they are not elements.
Compare & Contrast
Nature of oxide (acidic/basic)
Metal oxide
Non-metal oxide
Metal oxides (e.g., magnesium oxide) are generally basic in nature — they turn red litmus blue. Non-metal oxides (e.g., sulfur dioxide) are generally acidic in nature — they turn blue litmus red.
Property of metals
Malleability
Ductility
Malleability is the ability to be beaten into thin sheets (e.g., silver foil on sweets). Ductility is the ability to be drawn into wires (e.g., copper wires). Both are properties of metals, but they describe different forms of shaping.
Scope of the term
Rusting
Corrosion
Rusting is the specific process of brown deposit formation on iron objects due to moist air. Corrosion is a broader term for the gradual deterioration of any metal surface caused by air, water, or other substances (e.g., green coating on copper, black coating on silver).
Exam Focus
Marks pattern: 2 MCQs (1 mark each), 1 Very Short Answer (1 mark), 1 Short Answer (3 marks) on properties or rusting, 1 Long Answer (5 marks) comparing metals and non-metals or explaining rusting experiment
Most asked: Properties of metals (malleability, ductility, sonority, conductivity of heat and electricity) · Rusting of iron — conditions required and prevention methods · Difference between metals and non-metals (tabular form) · Nature of metal oxides vs non-metal oxides (basic vs acidic) · Examples of metals and non-metals in everyday life
Don't skip: Explain with an activity the conditions required for rusting of iron (5 marks); Tabulate the differences between metals and non-metals based on at least five properties (5 marks); What is malleability and ductility? Give examples (3 marks)
One-Line Revision (read aloud before the exam)
  1. Metals are generally lustrous, hard, malleable, ductile, sonorous, and good conductors of heat and electricity.
  2. Non-metals are generally non-lustrous, brittle (if solid), not malleable, not ductile, not sonorous, and poor conductors of heat and electricity.
  3. Malleability is the property of being beaten into thin sheets; ductility is the property of being drawn into wires.
  4. Sonority is the property of metals to produce a ringing sound when struck.
  5. Metals are good conductors of heat — that is why cooking vessels are made of metals and their handles are made of wood or plastic.
  6. Metals are good conductors of electricity — that is why electric wires are made of copper or aluminium.
  7. Rusting of iron requires both air (oxygen) and water; dry air alone or water alone does not cause rust.
  8. Rust is the brown deposit formed on iron; the process is called rusting.
  9. Corrosion is the gradual deterioration of any metal surface due to air, water, or chemicals — e.g., green coating on copper, black coating on silver.
  10. Metal oxides are generally basic in nature — they turn red litmus blue.
  11. Non-metal oxides are generally acidic in nature — they turn blue litmus red.
  12. Sodium and potassium are soft metals that can be cut with a knife; mercury is a liquid metal at room temperature.
  13. Gold is the most malleable and ductile metal; one gram of gold can be drawn into a 2-kilometre-long wire.
  14. Non-metals like oxygen, carbon, nitrogen, chlorine, and iodine are essential for life and daily use — oxygen for breathing, carbon in food, nitrogen in fertilisers, chlorine in water purification, iodine as antiseptic.
  15. Plastic, glass, wood, rubber, and paper are not classified as metals or non-metals because they are not elements.
  16. Sulfur does not react with water directly; it burns in oxygen to form sulfur dioxide, which dissolves in water to form an acid.
  17. Magnesium burns with a dazzling white flame to form magnesium oxide, which is basic in nature.
  18. Phosphorus catches fire when exposed to air and is stored in water.
  19. Sodium is stored in kerosene because it reacts vigorously with oxygen and water.
  20. Galvanisation is coating iron with zinc to prevent rusting.

MCQs — 10 Questions with Answers

Q1. Which of the following is a property of metals?

  • A. They are lustrous and conduct heat ✓
  • B. They are dull and brittle
  • C. They break into pieces when hammered
  • D. They do not conduct electricity

Answer: A — Metals are shiny (lustrous) and are good conductors of both heat and electricity, while non-metals are dull and brittle.

Q2. What happens when a piece of copper is beaten with a hammer?

  • A. It breaks into pieces
  • B. It becomes flattened into a thin sheet ✓
  • C. It produces a loud sound
  • D. It melts immediately

Answer: B — Copper is malleable, so it can be beaten into thin sheets without breaking, which is why thin copper foils can be made.

Q3. Which material would be best for making the handle of a cooking pot?

  • A. Copper metal
  • B. Aluminium metal
  • C. Wood or plastic ✓
  • D. Iron metal

Answer: C — Wood and plastic are poor conductors of heat, so they protect hands from burns, while metal handles would conduct heat and burn hands.

Q4. What is the property by which metals can be drawn into wires?

  • A. Malleability
  • B. Ductility ✓
  • C. Sonority
  • D. Conduction

Answer: B — Ductility is the specific property that allows metals to be stretched and drawn into wires used in electrical fittings and instruments like sitar.

Q5. In Activity 4.3, why did the metal spoon get hotter than the wooden spoon?

  • A. Metal spoons are darker in colour
  • B. Metals are good conductors of heat while wood is a poor conductor ✓
  • C. Wooden spoons are never immersed in water
  • D. Wood absorbs water and becomes cold

Answer: B — Metals conduct heat rapidly from hot water through the spoon, while wood conducts heat poorly, remaining cooler longer.

Q6. Why does Sudarshan heat iron before beating it into an axe?

  • A. To make it harder
  • B. To make it more malleable and easier to shape ✓
  • C. To prevent rust formation
  • D. To increase its weight

Answer: B — Heating iron increases its malleability, making it easier to beat and shape into desired forms like axes and tools without breaking.

Q7. Which of the following materials would make the bulb glow in an electrical tester circuit?

  • A. Rubber eraser and nylon rope
  • B. Coal and wooden block
  • C. Copper wire and iron nail ✓
  • D. Sulfur lump and stone

Answer: C — Copper and iron are metals that are good conductors of electricity and allow current to flow, making the bulb glow in the tester.

Q8. A suspension bridge uses steel wire ropes instead of wooden ropes because steel is—

  • A. Lighter in weight
  • B. More flexible than wood
  • C. Ductile and strong enough to support heavy loads ✓
  • D. Cheaper than wood

Answer: C — Steel is ductile (can be drawn into wires) and strong, making it capable of supporting the heavy loads of bridges and cranes.

Q9. Why did Sudarshan need to use coal in his furnace to heat the iron?

  • A. Coal is a non-metal and cannot conduct heat
  • B. Coal burns and produces heat required to make iron malleable for shaping ✓
  • C. Coal prevents iron from rusting
  • D. Coal is cheaper than other heating materials

Answer: B — Coal burns to produce high heat that makes iron hot and malleable, allowing the ironsmith to beat and shape it into useful tools and utensils.

Q10. An iron nail develops a brown deposit when left in the open for several days because—

  • A. It comes into contact with dry air only
  • B. It comes into contact with water only
  • C. It comes into contact with both air and water together ✓
  • D. It is heated by sunlight during the day

Answer: C — Rust forms only when iron is exposed to both oxygen in air and water (moisture) simultaneously; either one alone does not cause rusting.

Flashcards

What is malleability?

The property of metals by which they can be beaten into thin sheets without breaking.

Define ductility with an example.

The property of metals to be drawn into wires; copper wires in electrical fittings show ductility.

What is sonority?

The property of metals to produce a ringing sound when struck or dropped.

Why are cooking vessel handles made of wood instead of metal?

Wood is a poor conductor of heat, so it protects hands from burns while metal vessel conducts heat.

Why does an electrician wear rubber gloves?

Rubber is a poor conductor of electricity and prevents electric shock by not allowing current to flow.

What is the difference between a conductor and an insulator?

A conductor allows heat or electricity to flow through it easily; an insulator prevents or slows down this flow.

Name one metal that is liquid at room temperature.

Mercury is the only metal that is liquid at room temperature and is used in thermometers.

What conditions cause iron to rust?

Iron rusts when it comes into contact with both air and water together, not just one alone.

What is the brown deposit that forms on iron objects called?

The brown deposit is called rust, which forms due to corrosion of iron in presence of air and moisture.

Which metal is the most malleable and ductile?

Gold is the most malleable and ductile metal; one gram can be drawn into 2 kilometre-long wire.

Important Board Questions

What is malleability? Give one example. [1 mark]

Define as ability to be beaten into sheets. Example: copper foil, aluminium foil, or gold foil used for wrapping food or sweets.

Explain why metal cooking vessels have wooden or plastic handles. What property of materials is involved? [2 marks]

Metals conduct heat (good conductors), wood and plastic do not conduct heat (poor conductors). This protects hands from burns.

In Activity 4.1, why did the copper piece flatten when hammered but the coal lump broke into pieces? Name the properties involved. [3 marks]

Copper is malleable (flattens when beaten). Coal is brittle (breaks into pieces when beaten). Explain that metals are malleable while non-metals are brittle and cannot be shaped by beating.

Describe Activity 4.3 to show that metals are good conductors of heat. What can you conclude about using metals for cooking vessels? Draw and label a diagram of the experimental setup. [5 marks]

Diagram: glass tumbler with hot water, metal spoon and wooden spoon immersed. Observation: metal spoon becomes hotter. Conclusion: metals conduct heat quickly, so they are suitable for cooking. Wood is poor conductor, making handles safe.

Assertion-Reason Questions for The World of Metals and Non-Metals

Q1. Assertion (A):

Metals can be beaten into thin sheets without breaking.

Reason (R):

This property of metals is called malleability, which is shown by metals like copper, aluminium, and iron.

Answer: A — Both A and R are true, and R is the correct explanation of A — Both the assertion and reason are true, and the reason correctly explains why metals can be beaten into thin sheets. Malleability is the defining property that enables this behavior, as demonstrated in the chapter with examples of silver foil and aluminium foil.

Q2. Assertion (A):

Coal and sulfur are brittle materials.

Reason (R):

Brittle materials can be drawn into wires just like metals.

Answer: C — A is true but R is false — The assertion is true—coal and sulfur break into pieces when hammered, making them brittle. However, the reason is false because brittleness has nothing to do with being able to be drawn into wires (ductility). Brittle materials cannot be drawn into wires; ductility is a property of metals.

Q3. Assertion (A):

Gold is the most malleable and most ductile metal.

Reason (R):

Gold can be beaten into thin sheets and one gram can be drawn into a 2-kilometre-long wire.

Answer: A — Both A and R are true, and R is the correct explanation of A — Both the assertion and reason are true. The chapter explicitly states that gold is the most malleable metal (can be beaten into sheets) and gives the specific example of ductility that one gram of gold can be drawn into a 2-kilometre-long wire, supporting both claims.

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Case-Based Questions (CBQ) for The World of Metals and Non-Metals

Case Study:

A school science fair project involves testing different materials to understand their properties. Students collected four samples: a copper wire, a piece of iron nail, a lump of coal, and a block of wood. They performed three tests: (1) observing the appearance for lustre, (2) attempting to hammer each material, and (3) dropping each from a height to hear the sound produced. The results showed that copper and iron became flat when hammered, coal broke into pieces, wood remained unchanged, and only copper and iron produced ringing sounds.

Q1. Which materials demonstrated metallic lustre in the appearance test?

  • A. Only copper and iron ✓
  • B. Only coal and wood
  • C. All four materials equally
  • D. Only the materials that produced sound

Answer: A

Q2. What property is demonstrated by the copper and iron becoming flat when hammered?

  • A. Brittleness
  • B. Malleability ✓
  • C. Ductility
  • D. Sonority

Answer: B

Q3. The coal broke into pieces when hammered. This demonstrates which property?

  • A. Malleability
  • B. Ductility
  • C. Brittleness ✓
  • D. Metallic lustre

Answer: C

Q4. Based on the results, which materials are metals and which are non-metals?

  • A. Metals: copper and iron; Non-metals: coal and wood ✓
  • B. Metals: all four materials; Non-metals: none
  • C. Metals: copper only; Non-metals: iron, coal, and wood
  • D. Metals: coal and wood; Non-metals: copper and iron

Answer: A

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