NCERT Solutions for Class 7 Science (Curiosity) Chapter 4: The World of Metals and Non-metals (NCERT 2026–27)

These Class 7 Science Curiosity Chapter 4 solutions cover The World of Metals and Non-metals from the new NCF-2023 textbook (2026–27). The chapter explores the typical physical properties of metals — malleability, ductility, sonority and conduction of heat and electricity — and how metals and non-metals behave in the presence of air and water. Every question of the end-of-chapter exercise, “Let Us Enhance Our Learning”, is reproduced verbatim and solved step by step below.

Class: 7 Subject: Science Book: Curiosity Chapter: 4 Exercise: Let Us Enhance Our Learning Session: 2026–27
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Class 7 Science Curiosity Chapter 4 Solutions – Overview

Chapter 4 of Curiosity, The World of Metals and Non-metals, begins with a visit to an ironsmith’s workshop and uses everyday materials — copper, aluminium, an iron nail, coal, sulfur and a block of wood — to discover what makes a metal a metal. Through simple activities, you learn that metals are usually lustrous, hard, malleable, ductile, sonorous and good conductors of heat and electricity, while samples such as coal and the non-metal sulfur are generally dull, brittle and poor conductors. The chapter then studies how metals react with air and water: iron forms a brown deposit called rust only in the presence of both air and water (rusting and the wider process of corrosion), metal oxides like magnesium oxide are basic, while non-metal oxides like the one formed from sulfur are acidic. It closes by showing why non-metals such as oxygen, carbon, nitrogen, chlorine and iodine are essential in everyday life.

Metals and non-metals classify elements. Sulfur and carbon are elements; coal is a carbon-rich mixture, and wood, plastic and glass are materials rather than non-metal elements. Properties described here are general trends: graphite, a form of carbon, conducts electricity.

Key Concepts & Definitions

Metallic lustre: the shine shown by metals such as copper, aluminium and iron in their pure, fresh state.

Malleability: the property by which materials can be beaten into thin sheets. Most metals are malleable; gold and silver are the most malleable.

Ductility: the property by which materials can be drawn into wires. Metals like copper and aluminium are ductile; gold is the most ductile.

Brittle: materials such as coal and sulfur that break into pieces on hammering instead of flattening.

Sonority: the property of metals by which they produce a ringing sound; such metals are said to be sonorous.

Conduction: the transfer of heat (or electricity) through a material. Metals are good conductors of heat and electricity; non-metals are generally poor conductors.

Rusting & corrosion: rust is the brown deposit formed on iron in the presence of both air and water. The gradual deterioration of any metal surface by air, water or other substances is called corrosion.

Metal vs non-metal oxides: many metal oxides, such as magnesium oxide, are basic; many non-metal oxides, such as sulfur dioxide, are acidic. Exceptions exist: aluminium oxide reacts with both acids and bases, while carbon monoxide is neutral.

“Let Us Enhance Our Learning” — NCERT Solutions

Original explanations for Questions 1–12 on pages 55–56 of NCERT Curiosity, Reprint 2026–27, with completed diagrams and additional ClearStudy practice.

1. Which metal is commonly used to make food packaging materials as it is cheaper, and its thin sheets can be folded easily into any shape? (i) Aluminium   (ii) Copper   (iii) Iron   (iv) Gold

ANSWER (i) Aluminium. Aluminium is cheap, light and highly malleable, so it can be rolled into very thin foil and folded into any shape. This is why aluminium foil is widely used to wrap and pack food items.

2. Which of the following metal catches fire when it comes in contact with water? (i) Copper   (ii) Aluminium   (iii) Zinc   (iv) Sodium

ANSWER (iv) Sodium. Sodium reacts vigorously with water (and air) and releases a large amount of heat, which can make it catch fire. For this reason sodium is stored in kerosene to keep it away from air and moisture.

3. State with reason(s) whether the following statements are True [T] or False [F]. (i) Aluminium and copper are examples of non-metals used for making utensils and statues. [ ] (ii) Metals form oxides when combined with oxygen, the solution of which turns blue litmus paper to red. [ ] (iii) Oxygen is a non-metal essential for respiration. [ ] (iv) Copper vessels are used for boiling water because they are good conductors of electricity. [ ]

ANSWER (i) False [F]. Aluminium and copper are metals, not non-metals. They are indeed used for making utensils and statues, but the statement wrongly calls them non-metals. (ii) False [F]. Metals do form oxides with oxygen, but metal oxides are basic in nature. Their solution turns red litmus paper to blue, not blue litmus to red. (iii) True [T]. Oxygen is a non-metal, and humans and many other organisms need it for aerobic respiration. Some microorganisms can live without oxygen; the statement is used here in the textbook’s aerobic-respiration context. (iv) False [F]. Copper vessels are used for boiling water because copper is a good conductor of heat, not because it conducts electricity. The reason given is wrong.

4. Why are only a few metals suitable for making jewellery?

ANSWERJewellery materials need an attractive appearance, workability and suitable resistance to corrosion. Gold is lustrous, highly malleable and ductile, and very resistant to corrosion; silver is also readily shaped and attractive.Silver can develop a black tarnish, as the textbook notes, so it is incorrect to say that it never discolours. Jewellery often uses alloys to improve hardness and durability. “Rust” specifically refers to corrosion of iron.

5. Match the uses of metals and non-metals given in Column I with the jumbled names of metals and non-metals given in Column II.

ANSWER Each jumbled name in Column II is first unscrambled, then matched to its correct use:
Column I (use)Column II (unscrambled)Match
(i) Used in electrical wiring(c) P E P O R C → Copper(i) → (c)
(ii) Most malleable and ductile(e) O G D L → Gold(ii) → (e)
(iii) Living organisms cannot survive without it.(a) E N X Y G O → Oxygen(iii) → (a)
(iv) Plants grow healthy when fertilisers containing it are added to the soil.(d) T E N G O I N R → Nitrogen(iv) → (d)
(v) Used in water purification(b) N E C O H I R L → Chlorine(v) → (b)
So: (i)→(c) Copper, (ii)→(e) Gold, (iii)→(a) Oxygen, (iv)→(d) Nitrogen, (v)→(b) Chlorine.

6. What happens when oxygen reacts with magnesium and sulfur. What are the main differences in the nature of products formed?

ANSWERMagnesium + oxygen → magnesium oxide: magnesium burns with a dazzling white light and leaves white MgO ash. Adding water produces a weakly soluble basic mixture containing magnesium hydroxide; it turns red litmus blue.Sulfur + oxygen → sulfur dioxide: sulfur forms a gas that gives an acidic solution in water, described at this level as sulfurous acid; it turns blue litmus red.The key contrast is basic magnesium oxide versus acidic sulfur dioxide. These are general trends, not rules without exceptions. Burning demonstrations belong with the teacher: sulfur fumes are harmful and burning magnesium is intensely bright.

7. Complete the following flow chart: ?  → Air → Heat → Ash → (+ Water) → ? → Add blue and red litmus solutions separately → Change in blue litmus solution = ? ; Change in red litmus solution = Blue

ANSWERThe blanks are magnesium ribbon, basic mixture obtained by adding water to magnesium oxide, and no change (blue remains blue). The textbook calls the liquid a solution of magnesium oxide; more precisely, MgO reacts with water to form sparingly soluble magnesium hydroxide.Magnesium burns in oxygen in the air to give white ash. The mixture after adding water turns red litmus blue and leaves blue litmus unchanged. Test separate portions with the two indicators.
Magnesium ribbon burns in air to give magnesium oxide ash; adding water gives a basic mixture. Blue litmus stays blue and red litmus turns blue.
Question 7: completed flowchart. Magnesium burning is a teacher demonstration. Tap to view at full size.

8. You are provided with the following materials. Discuss which material would be your choice to make a pan that is most suitable for boiling water and why? Iron   copper   sulfur   coal   plastic   wood   cardboard

ANSWER The best choice is a metal — copper (or iron). A good pan for boiling water must be a good conductor of heat so that heat passes quickly to the water, and it must be hard and strong enough to hold its shape on a flame. Copper and iron are metals and meet both needs (copper is an especially good conductor of heat). The other materials are unsuitable: sulfur and coal are brittle and poor conductors; plastic, wood and cardboard are poor conductors of heat and would melt, burn or get spoilt on the flame. Hence a copper (or iron) pan is most suitable for boiling water.

9. You are provided with three iron nails, each dipped in oil, water and vinegar. Which iron nail will not rust, and why?

ANSWERThe expected answer is the nail fully covered by oil. A continuous oil layer limits contact with water and oxygen, protecting the iron.Ordinary water contains dissolved oxygen, so an unprotected nail can rust. Vinegar is an acidic water-based liquid that can corrode iron; visible brown rust may vary because acid can also dissolve rust. Do not equate every form of corrosion with the same brown deposit.

10. How do the different properties of metals and non-metals determine their uses in everyday life?

ANSWER Metals are used wherever their properties are useful: because they are malleable, thin sheets such as aluminium foil are used to wrap food; because they are ductile, copper and aluminium are drawn into wires for electrical fittings and ornaments; because they are good conductors of heat, they are used to make cooking vessels; because they conduct electricity, they are used in electrical wiring; their lustre and resistance to corrosion make gold and silver ideal for jewellery; and their sonority is used in bells and musical instruments. Non-metals are used for what their nature offers: oxygen is essential for respiration and burning, carbon is the building block of all life forms, nitrogen is used in fertilisers, chlorine is used to purify water and iodine is used as an antiseptic on wounds. Thus the choice of a metal or non-metal for any job depends directly on the property needed for that use.

11. One of the methods of protecting iron from getting rusted is to put a thin coating of zinc metal over it. Since sulfur does not react with water, can it be used for this purpose? Justify your answer.

ANSWERNo, sulfur is not a suitable substitute for zinc galvanisation. A sulfur layer is brittle and is not a durable, adherent protective coating; merely failing to react with water is not enough.Zinc forms a protective coating and can also protect iron electrochemically by corroding preferentially. Malleability alone is not the reason galvanisation works, and galvanising is not done by hammering zinc foil onto iron.

12. An ironsmith heats iron before making tools. Why is heating necessary in this process?

ANSWER Iron is hard and stiff at room temperature, so it is very difficult to bend or shape. When the ironsmith heats the iron until it becomes red hot, it becomes soft and more malleable. In this softened state the iron can be easily beaten with a hammer and shaped into tools such as axes, spades and tongs. So heating is necessary because it increases the malleability of iron and makes it easy to give the desired shape.

Reactive sodium, burning magnesium and burning sulfur are not home experiments. The teacher must handle reactive substances and use the textbook’s protective equipment and ventilation precautions.

Extra Practice Questions

These questions and MCQs are ClearStudy practice, separate from the NCERT exercise.

Short Answer Type Questions

Q1. Define malleability and give one example of a malleable metal.

ANSWERMalleability is the property by which a material can be beaten into thin sheets. Gold (and silver) are the most malleable metals; aluminium is another common example used as foil.

Q2. Why are the handles of cooking vessels often made of wood or plastic?

ANSWERWood and suitable heat-resistant plastics conduct heat slowly, so less heat reaches the hand than through a metal handle. Handles can still become hot near a flame or after prolonged heating; use an appropriate dry heat-resistant holder when needed.

Q3. What is rust, and under what conditions does it form on iron?

ANSWERRust is the brown deposit that forms on iron. It develops only when iron is in contact with both air and water (moist air); dry air alone or water alone does not cause rusting.

Q4. Why is sodium stored in kerosene?

ANSWERSodium reacts vigorously with oxygen and water, releasing a lot of heat. Storing it in kerosene prevents its exposure to air and moisture, keeping it safe.

Q5. Give two reasons why metals are preferred for making electrical wires.

ANSWER(1) Metals such as copper and aluminium are good conductors of electricity, so current passes through them easily. (2) Metals are ductile, so they can be drawn into long, thin wires.

Long Answer Type Questions

Q1. Describe Activity 4.5 and explain what it tells us about the conditions needed for rusting.

ANSWERIn Activity 4.5, three clean iron nails are placed in three bottles. Bottle A has a nail with silica gel (dry air, no water) and is sealed; bottle B has a nail in boiled-and-cooled water covered with a layer of oil (water, no air); bottle C has a nail partly dipped in water and left open (both air and water). After 8–10 days, the nails in A and B show no brown deposit, while the nail in C develops rust. This shows that iron rusts only when both air and water are present together — dry air alone (A) or water without air (B) does not cause rusting. Hence moist air is responsible for the rusting of iron.
Three rusting tests: A has dry air and silica gel with no rust; B has boiled cooled water under oil in a sealed bottle with little oxygen and no rust; C has air and water and develops rust.
Activity 4.5: expected observations after 8–10 days. Record your own results; poor seals or oxygen left in bottle B can affect the result. Tap to view at full size.

Q2. Compare the general properties of metals and non-metals with suitable examples.

ANSWERMetals are generally lustrous (copper, aluminium, iron), hard, malleable (can be beaten into sheets), ductile (can be drawn into wires), sonorous (produce a ringing sound) and good conductors of heat and electricity. Their oxides are generally basic in nature. Samples such as coal and the non-metal sulfur are generally non-lustrous, soft and brittle, are neither malleable nor ductile, are not sonorous and are poor conductors of heat and electricity. Their oxides are generally acidic in nature. There are exceptions — sodium and potassium are soft metals and mercury is a liquid metal — but these general properties help us tell metals and non-metals apart and decide their uses.

Q3. Explain why non-metals, though less obvious in daily life than metals, are essential for living things.

ANSWERAlthough metals are more visible because of their lustre and strength, non-metals are vital to life. We breathe in oxygen, a non-metal, and cannot survive without it. Carbon is the building block of all life forms and a key component of proteins, fats and carbohydrates needed for growth and energy. Nitrogen is used to make fertilisers and is an essential nutrient for plant growth. Chlorine is commonly used to purify drinking water, and a solution of iodine is applied to wounds as an antiseptic. Thus non-metals quietly support respiration, food, agriculture, clean water and health, making them just as essential as metals.

MCQs & Assertion–Reason

1. The property by which a metal can be beaten into thin sheets is called:

(a) ductility    (b) sonority    (c) malleability    (d) conduction

2. Which of the following is the most ductile metal?

(a) iron    (b) gold    (c) copper    (d) aluminium

3. The metal that is liquid at room temperature is:

(a) sodium    (b) mercury    (c) zinc    (d) copper

4. Rust forms on iron when it is in contact with:

(a) dry air only    (b) water only    (c) both air and water    (d) kerosene

5. The oxide of a metal is generally:

(a) acidic    (b) basic    (c) neutral    (d) brittle

6. When sulfur burns in air and the gas is dissolved in water, the solution is:

(a) basic    (b) neutral    (c) acidic    (d) sonorous

7. Which of the following is a non-metal?

(a) copper    (b) aluminium    (c) sulfur    (d) iron

8. Coating iron with a thin layer of zinc to prevent rusting is called:

(a) galvanisation    (b) ductility    (c) corrosion    (d) sonority

9. The property of metals to produce a ringing sound is:

(a) malleability    (b) ductility    (c) sonority    (d) lustre

10. Which non-metal is commonly used in the purification of water?

(a) oxygen    (b) chlorine    (c) nitrogen    (d) carbon

Answer key: 1-(c), 2-(b), 3-(b), 4-(c), 5-(b), 6-(c), 7-(c), 8-(a), 9-(c), 10-(b).

For each Assertion–Reason question, choose: (A) Both true and the Reason correctly explains the Assertion; (B) Both true but the Reason is not the correct explanation; (C) Assertion true, Reason false; (D) Assertion false, Reason true.

A-R 1. Assertion: Aluminium is used to make foil for wrapping food.

Reason: Aluminium is malleable and can be beaten into thin sheets.

A-R 2. Assertion: The handles of cooking vessels are often made of wood or plastic.

Reason: Wood and plastic are poor conductors of heat.

A-R 3. Assertion: Coal and sulfur are sonorous materials.

Reason: Coal and sulfur are not sonorous and give a dull sound rather than a metallic ring.

A-R 4. Assertion: An iron nail kept in oil does not rust easily.

Reason: Oil forms a layer that keeps air and moisture away from the iron surface.

A-R 5. Assertion: The oxide of sulfur dissolved in water turns blue litmus red.

Reason: Sulfur dioxide forms an acidic solution when it dissolves in water.

Answer key: 1-(A), 2-(A), 3-(D), 4-(A), 5-(A).

Quick Revision Summary

  • Metals and non-metals are differentiated on the basis of their properties.
  • Metals are generally lustrous, hard, malleable (beaten into sheets), ductile (drawn into wires) and sonorous; non-metals are usually dull and brittle.
  • Metals are good conductors of heat and electricity; non-metals are generally poor conductors.
  • Metal oxides are generally basic (turn red litmus blue); non-metal oxides are generally acidic (turn blue litmus red).
  • Iron rusts only in the presence of both air and water; the wider damage of metals by air/water is called corrosion. Rusting can be prevented by painting, oiling, greasing or galvanisation.
  • Some metals are exceptions: sodium and potassium are soft, mercury is a liquid metal. Non-metals like oxygen, carbon, nitrogen, chlorine and iodine are essential in everyday life.

Common Mistakes to Avoid

Watch out for these

  • Calling aluminium or copper a non-metal — they are metals widely used for utensils and statues.
  • Mixing up the oxides — metal oxides are basic (red litmus → blue), non-metal oxides are generally acidic (blue litmus → red).
  • Confusing malleability and ductility — malleable = beaten into sheets; ductile = drawn into wires.
  • Saying copper vessels boil water because they conduct electricity — it is because they conduct heat.
  • Thinking iron rusts in dry air or in water alone — both air and water are needed.
  • Assuming all metals are hard solids — sodium and potassium are soft, and mercury is liquid.

How to write a clear answer

Learn the five typical properties of metals — lustre, malleability, ductility, sonority and conduction of heat/electricity — with one clear example each, and always pair a property with its use (malleable → foil, ductile → wires, good conductor → cooking vessels). Remember the litmus rule: metal oxide → basic (red turns blue), non-metal oxide → acidic (blue turns red). For rusting questions, state firmly that both air and water are needed and name prevention methods (painting, oiling, greasing, galvanisation).

Frequently Asked Questions

What is Class 7 Science Curiosity Chapter 4 about?

Chapter 4, The World of Metals and Non-metals, explains the properties of metals (lustre, malleability, ductility, sonority and good conduction of heat and electricity) and non-metals, and how they react with air and water — including rusting of iron, corrosion, and the basic nature of metal oxides versus the acidic nature of non-metal oxides.

What is the name of the exercise in this chapter?

The end-of-chapter exercise is titled “Let Us Enhance Our Learning” and has 12 questions. All of them are reproduced verbatim and answered step by step on this page.

Under what conditions does iron rust?

Iron rusts only when it is in contact with both air and water (moist air). Dry air alone or water without dissolved air does not cause rusting, as shown by Activity 4.5 in the textbook.

Are these Class 7 Science Curiosity Chapter 4 solutions free?

Yes. All solutions are free and follow the official NCERT Curiosity Grade 7 textbook for session 2026–27.

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