CBSE Class 7 Science Chapter 04 The World Of Metals And Non Metals MCQs Set 02

Science Objective Questions and Answers: Chapter 04 The World Of Metals And Non Metals

Access targeted multiple-choice questions for Chapter 04 The World Of Metals And Non Metals designed to align with the latest CBSE academic syllabus for Class 7 Science. These objective practice sets help students evaluate their conceptual understanding and improve exam readiness.

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Question: When Sudarshan uncle shapes heated iron into an axe by beating it with a hammer, which property of metals allows this process to work effectively?
A. Ductility, which enables the metal to be drawn into wires
B. Malleability, which permits the metal to be flattened into sheets and shaped without breaking
C. Sonority, which produces a ringing sound when struck
D. Conduction of heat, which allows the metal to retain warmth from the furnace
Show Answer & Explanation

Answer: (B) Malleability, which permits the metal to be flattened into sheets and shaped without breaking

Explanation:
Malleability is the property that allows metals to be beaten or hammered into flat sheets and various shapes without breaking apart. The chapter explicitly describes this when Anandi expresses amazement that iron can be beaten into a flat shape, and Sudarshan explains he is shaping it into an axe through beating—a direct demonstration of malleability at work.

Question: What key distinction emerges from Activity 4.1 when materials are struck with a hammer?
A. Metals and non-metals differ in their ability to produce sound when hammered
B. Metals flatten while non-metals always break, revealing a fundamental difference in how these materials respond to force
C. All materials become harder after being struck with a hammer
D. Both metals and non-metals flatten equally well, but metals are more lustrous
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Answer: (B) Metals flatten while non-metals always break, revealing a fundamental difference in how these materials respond to force

Explanation:
Activity 4.1 demonstrates that copper, aluminium, and iron (metals) flatten when beaten, whereas coal and sulfur (non-metals) break into pieces. This contrasting behaviour is a key way to distinguish between the two categories of materials based on their physical response to mechanical force.

Question: In Activity 4.5, why does the iron nail in bottle A remain free of brown deposits after 8–10 days?
A. Water is completely absent, but this alone is insufficient to prevent rust formation
B. Both water and air must be present together; dry air alone cannot cause rust to develop
C. The silica gel has transformed the iron's chemical composition
D. The iron nail oxidises but the deposits wash away in the dry environment
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Answer: (B) Both water and air must be present together; dry air alone cannot cause rust to develop

Explanation:
The experiment shows that brown deposits (rust) form only when both water and air are present together (bottle C), not when either is present alone. In bottle A, despite the presence of air, the absence of water—ensured by the silica gel—prevents any rust formation. This proves that moist air, not dry air alone, is responsible for rusting.

Question: When magnesium burns in air during Activity 4.6, the white powder produced (magnesium oxide) reacts with water to form a solution that turns red litmus paper blue. What does this observation reveal?
A. Metal oxides are acidic in nature and change the colour of indicators
B. Metal oxides are basic in nature, displaying properties different from non-metal oxides
C. The reaction between magnesium and oxygen is reversible
D. Magnesium oxide is identical in behaviour to sulfur dioxide
Show Answer & Explanation

Answer: (B) Metal oxides are basic in nature, displaying properties different from non-metal oxides

Explanation:
The chapter states that generally, oxides of metals are basic in nature. The fact that the magnesium oxide solution turns red litmus blue is a characteristic property of basic substances. This contrasts sharply with non-metal oxides like sulfur dioxide, which form acidic solutions that turn blue litmus red.

Question: When sulfur burns in air (Activity 4.7) and the resulting gas dissolves in water, the solution becomes acidic. How does this compare to the behaviour of metals when they burn?
A. Both metals and non-metals produce acidic oxides when they react with oxygen
B. Metals produce basic oxides while non-metals produce acidic oxides—a fundamental difference in reactivity
C. Metals do not react with oxygen, while non-metals always do
D. Both produce similar oxides but with different physical properties like colour
Show Answer & Explanation

Answer: (B) Metals produce basic oxides while non-metals produce acidic oxides—a fundamental difference in reactivity

Explanation:
• Metal oxides (like magnesium oxide) are basic in nature
• Non-metal oxides (like sulfur dioxide) are acidic in nature
• This difference in the chemical nature of their oxides is one of the key distinctions between metals and non-metals discussed throughout the chapter.

Question: Based on the chapter's discussion of different non-metals, why is phosphorus stored in water while sulfur can safely remain in open contact with water?
A. Sulfur is denser and sinks to the bottom, preventing reaction with air
B. Phosphorus catches fire when exposed to atmospheric air, so water prevents this hazard, whereas sulfur shows no reaction with water
C. Water reacts with phosphorus but not with sulfur, making storage different for each
D. Both non-metals require water storage, but the chapter only mentions phosphorus for emphasis
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Answer: (B) Phosphorus catches fire when exposed to atmospheric air, so water prevents this hazard, whereas sulfur shows no reaction with water

Explanation:
The chapter clearly states that phosphorus catches fire when exposed to atmospheric air and is therefore stored in water to prevent exposure to moisture and air. In contrast, Activity 4.8 shows that sulfur placed in water produces no reaction, so water storage is unnecessary. This difference reflects the distinct chemical reactivity of different non-metals.

Question: In the context of electrical safety, why do plastic and rubber materials protect electricians from electric shock?
A. They absorb electricity and neutralise its effects safely
B. They are poor conductors of electricity and prevent electrical current from flowing through the body
C. They are metals with special insulating coatings
D. They conduct electricity slowly, giving the body time to adjust
Show Answer & Explanation

Answer: (B) They are poor conductors of electricity and prevent electrical current from flowing through the body

Explanation:
The chapter explains that plastic coverings on screwdrivers and rubber gloves protect electricians because these materials are poor conductors of electricity. Since they do not allow electricity to pass through them easily, they prevent electrical current from reaching the electrician's body, thereby preventing electric shock.

Question: When an iron nail is placed in bottle B with only water (covered with oil to prevent air contact) during Activity 4.5, what does the absence of rust deposits after 8–10 days specifically indicate?
A. Water alone, without air, is insufficient to produce rust
B. Water is more important than air in causing rust formation
C. The oil layer completely prevents all chemical reactions with the nail
D. Rust requires three conditions: water, air, and salt from the environment
Show Answer & Explanation

Answer: (A) Water alone, without air, is insufficient to produce rust

Explanation:
Bottle B demonstrates that even with prolonged contact with water, rust does not form if air is excluded. This shows that water alone is not the sole cause of rust. The rust formation requires both conditions—water and air together—as proven by the brown deposits appearing only in bottle C where both are present.

Question: How would a material need to be classified if it flattens when hammered but does not conduct electricity?
A. It must be a metal because all metals are malleable
B. It cannot exist because all malleable materials conduct electricity
C. It would be difficult to classify definitively based on these two properties alone, as metals typically show both traits but exceptions exist
D. It must be a non-metal because non-metals can sometimes flatten
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Answer: (C) It would be difficult to classify definitively based on these two properties alone, as metals typically show both traits but exceptions exist

Explanation:
While the chapter establishes that metals are generally both malleable and good conductors of electricity, and non-metals are typically neither, the existence of exceptional metals (like sodium and potassium, which are soft) and the note about mercury being liquid suggest that individual properties do not always align perfectly. A material showing one characteristic but not another would require consideration of additional properties before final classification.

Question: What is the most direct reason that gold and silver are described as the most malleable metals in the chapter?
A. They are the rarest metals found on Earth
B. They can be beaten into extremely thin sheets more readily than other metals, making them suitable for applications like decorative foil
C. They conduct electricity better than all other metals
D. They do not rust or corrode like iron does
Show Answer & Explanation

Answer: (B) They can be beaten into extremely thin sheets more readily than other metals, making them suitable for applications like decorative foil

Explanation:
The chapter defines malleability as the property by which materials can be beaten into thin sheets. Gold and silver are highlighted as the most malleable because they can be worked into thinner sheets more easily than other metals. The text mentions seeing thin silver foil on sweets and suggests gold can similarly be worked into very fine foils, demonstrating their exceptional malleability.

Question: The Iron Pillar of Delhi has remained nearly rust-free for over 1600 years despite exposure to wind, rainfall, and intense weather. What does this historical fact primarily demonstrate about the relationship between materials and civilisation?
A. Iron was not used in ancient India because it rusts too easily
B. Ancient Indian metallurgists developed sophisticated knowledge and techniques to create iron structures that resist corrosion—showing how understanding material properties advances technology
C. The pillar must be made of a non-metal that is naturally rust-resistant
D. Modern iron is superior to ancient iron because it does not rust at all
Show Answer & Explanation

Answer: (B) Ancient Indian metallurgists developed sophisticated knowledge and techniques to create iron structures that resist corrosion—showing how understanding material properties advances technology

Explanation:
The "Fascinating Facts" section on the Iron Pillar emphasises that despite centuries of exposure to harsh conditions, it has barely any rust because it was made in a way that resists rusting. This demonstrates that ancient Indian metallurgists possessed advanced knowledge of metals and corrosion prevention, illustrating how understanding material properties is central to technological progress and civilisation's development.

Question: Why would carbon be considered essential for all living organisms while copper, despite being a useful metal, is not equally essential to every living thing?
A. Carbon is a metal and metals are more abundant in organisms than non-metals
B. Carbon is the fundamental building block of proteins, fats, and carbohydrates necessary for life, whereas copper serves specific industrial and biological roles but organisms can function without it
C. Copper is harmful to all living organisms, while carbon is universally beneficial
D. Both carbon and copper are equally essential; the chapter makes no distinction
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Answer: (B) Carbon is the fundamental building block of proteins, fats, and carbohydrates necessary for life, whereas copper serves specific industrial and biological roles but organisms can function without it

Explanation:
The chapter explicitly states that carbon is essential in everyday life because it is the building block of all life forms and is a key component of proteins, fats, and carbohydrates necessary for growth and energy. Copper, while important for various applications, is not described as essential for basic life processes. This illustrates that the essentiality of a substance depends on its role in biological systems.

Question: During the burning of magnesium ribbon in Activity 4.6, the metal undergoes a reaction with oxygen. Why might this process be considered irreversible based on the chapter's description?
A. The white powder can be heated again to recover the original magnesium metal
B. The white powder (magnesium oxide) is a new substance formed through reaction with oxygen, and the chapter does not discuss recovering pure magnesium from it
C. Magnesium burns at a temperature that prevents any chemical reaction
D. All reactions between metals and oxygen are reversible processes
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Answer: (B) The white powder (magnesium oxide) is a new substance formed through reaction with oxygen, and the chapter does not discuss recovering pure magnesium from it

Explanation:
The chapter describes the burning of magnesium as producing magnesium oxide—a new substance formed through a reaction. The chapter notes that this burning will be discussed further in the 'Changes Around Us' chapter, implying it is a significant chemical change. The text does not mention any process to reverse this and obtain the original magnesium, suggesting the process is irreversible under normal conditions.

Question: Which combination of properties would make a material ideal for use as a cooking vessel according to the principles outlined in the chapter?
A. Poor conductor of heat and high malleability to allow shaping
B. Good conductor of heat to transfer warmth to food, and sufficient hardness to withstand use
C. Non-lustrous appearance and brittleness for safety
D. Ductility and acoustic properties that produce pleasant sounds
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Answer: (B) Good conductor of heat to transfer warmth to food, and sufficient hardness to withstand use

Explanation:
The chapter explains that metals are good conductors of heat, which is why metal vessels are used for cooking to efficiently transfer heat to food. The vessels must also be hard and durable enough to withstand regular use and temperature changes. These properties combine to make metals ideal for cookware, whereas non-metals, being poor heat conductors, would be unsuitable for this purpose.

Question: In Activity 4.4, when different materials are tested in an electrical circuit, all materials that make the bulb glow are identified as metals. What does the pattern observed in this activity suggest about the relationship between a material's classification and its electrical properties?
A. All substances that conduct electricity are non-metals
B. The ability to conduct electricity is a characteristic property strongly associated with metals as a group, though exceptions may exist
C. Electrical conductivity has no relationship to whether a material is a metal or non-metal
D. Non-metals always conduct electricity better than metals do
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Answer: (B) The ability to conduct electricity is a characteristic property strongly associated with metals as a group, though exceptions may exist

Explanation:
The chapter observes that in Activity 4.4, all materials that make the bulb glow are metals, while sulfur, coal, wood, stone, eraser, and nylon rope do not. This establishes a clear pattern: metals are generally good conductors of electricity. The chapter emphasises that this is a characteristic property of metals and explains how it applies to practical safety measures with electricians. The qualification 'generally' and 'typically' in the chapter text suggests the possibility of exceptions while confirming the broad pattern.

Question: When Yashwant and Anandi observe Sudarshan beating a red-hot iron block to shape it into an axe, they witness the practical application of which metal property?
A. Ductility, which allows the metal to be drawn into wires
B. Malleability, which enables the metal to be flattened into sheets or reshaped by force
C. Sonority, which produces sound when struck
D. Corrosion resistance, which prevents damage from air and water
Show Answer & Explanation

Answer: (B) Malleability, which enables the metal to be flattened into sheets or reshaped by force

Explanation:
The chapter defines malleability as the property by which materials can be beaten into thin sheets or reshaped. Sudarshan's use of hammering to shape iron directly demonstrates this property in action.

Question: In Activity 4.1, objects made of copper, aluminium, and iron flatten when hammered, while coal and sulfur shatter into fragments. Based on this observation, which statement best explains the difference?
A. Metals are harder and therefore resist breaking when struck
B. Metals are malleable and can deform without breaking, while non-metals are brittle and fracture under impact
C. Metals conduct heat better than non-metals, which affects how they respond to force
D. Metals are denser than non-metals, making them more resistant to damage
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Answer: (B) Metals are malleable and can deform without breaking, while non-metals are brittle and fracture under impact

Explanation:
The chapter explains that malleability is the property allowing metals to be beaten into sheets without breaking, whereas brittle materials like coal and sulfur break into pieces. This contrasts malleable metals with non-metals that are brittle or neither malleable nor brittle.

Question: During Activity 4.5, iron nails are placed in three separate bottles under different conditions. In bottle B, where the iron nail is submerged in boiled water covered with oil, no rust forms after 8–10 days. What does this observation specifically demonstrate?
A. Iron does not rust when exposed to water alone
B. Both air and water together are essential for rust formation
C. Oil prevents rusting by blocking contact with water molecules
D. The iron nail quality determines whether rust develops
Show Answer & Explanation

Answer: (A) Iron does not rust when exposed to water alone

Explanation:
The chapter states that in bottle B, where water is present but air is excluded by the oil layer, no brown deposits develop. This directly indicates that water alone is insufficient for rust formation; moist air (both water and air) is required.

Question: Why would an electrician choose to wear rubber gloves and use tools with plastic or rubber handles when working with electrical equipment, according to the principles discussed in the chapter?
A. These materials are lighter and easier to handle than metal tools
B. These materials are poor conductors of electricity and therefore protect against electric shock
C. These materials prevent the tools from becoming magnetized during use
D. These materials do not react with oxygen or water in the air
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Answer: (B) These materials are poor conductors of electricity and therefore protect against electric shock

Explanation:
• Plastic and rubber are poor conductors of electricity
• They prevent electrical current from flowing through the electrician's body
• This protection is essential for safety when working with live electrical circuits

Question: When a magnesium ribbon burns in air during Activity 4.6, it produces a white powder (magnesium oxide) that, when mixed with water, turns red litmus paper blue. What can be inferred about metal oxides from this observation?
A. Metal oxides are always white in colour and dissolve easily in water
B. Metal oxides form basic solutions that can turn red litmus paper blue
C. Metal oxides are non-metallic substances that do not dissolve in water
D. Metal oxides react violently with water and release harmful gases
Show Answer & Explanation

Answer: (B) Metal oxides form basic solutions that can turn red litmus paper blue

Explanation:
The chapter explicitly states that magnesium oxide solution changes red litmus to blue, indicating a basic nature. It also notes that generally, oxides of metals are basic in nature, making this observation consistent with metal oxide behaviour.

Question: During Activity 4.7, when sulfur burns in air and the resulting gas dissolves in water, the solution formed is acidic in nature. How does this contrast with the behaviour observed when magnesium burns?
A. Both magnesium and sulfur produce basic oxides when burned in air
B. Magnesium produces a basic oxide while sulfur produces an acidic oxide when burned
C. Neither magnesium nor sulfur reacts with oxygen in the air
D. Sulfur does not actually burn in air, so no gas is produced
Show Answer & Explanation

Answer: (B) Magnesium produces a basic oxide while sulfur produces an acidic oxide when burned

Explanation:
The chapter demonstrates that magnesium oxide forms a basic solution (turns red litmus blue), while sulfur dioxide dissolves in water to form sulfurous acid (acidic). This directly illustrates the distinction: metal oxides are basic, non-metal oxides are acidic.

Question: Phosphorus is stored in water to prevent it from catching fire when exposed to air, yet sulfur can remain in open contact with water without reacting. What does this difference reveal about how non-metals vary in their chemical behaviour?
A. Phosphorus is a metal while sulfur is a non-metal
B. Non-metals show varying levels of reactivity; some are highly reactive with air while others are relatively unreactive with water
C. Water reacts with all non-metals to form acids
D. Phosphorus is more dense than sulfur and therefore less likely to be affected by air
Show Answer & Explanation

Answer: (B) Non-metals show varying levels of reactivity; some are highly reactive with air while others are relatively unreactive with water

Explanation:
Activity 4.8 shows sulfur has no reaction when placed in water, yet the chapter notes phosphorus catches fire in atmospheric air, requiring water storage. This demonstrates that non-metals do not behave uniformly—their reactivity depends on the specific substance and conditions.

Question: The Iron Pillar of Delhi, constructed over 1600 years ago, has remained largely rust-free despite exposure to wind, rainfall, and intense weather. What aspect of metalworking and material science does this historical artifact primarily illustrate?
A. Iron was not commonly used in ancient India due to its poor corrosion resistance
B. Advanced metallurgical techniques and knowledge of metal treatment existed in ancient India to resist rusting
C. The climate in Delhi naturally prevents iron from rusting regardless of manufacturing methods
D. Modern rust-prevention methods are more effective than any technique available in ancient times
Show Answer & Explanation

Answer: (B) Advanced metallurgical techniques and knowledge of metal treatment existed in ancient India to resist rusting

Explanation:
The chapter's 'Fascinating Facts' section states the pillar has been made in a way that resists rusting, indicating sophisticated metallurgical knowledge. This demonstrates that ancient Indian craftspeople possessed advanced understanding of metal technology and corrosion prevention.

Question: When materials are tested in Activity 4.4 using a simple electrical circuit tester, all materials that allow the bulb to glow are identified as metals, while sulfur, coal, wood, stone, and rubber do not conduct electricity. What does this consistent pattern reveal about the relationship between material classification and electrical properties?
A. Only metals can conduct electricity because they are shiny and hard
B. Metals are generally good conductors of electricity, which is one defining characteristic that distinguishes them from non-metals
C. Non-metals can conduct electricity better than metals but were not tested in the activity
D. Electrical conductivity has no connection to whether a substance is classified as a metal or non-metal
Show Answer & Explanation

Answer: (B) Metals are generally good conductors of electricity, which is one defining characteristic that distinguishes them from non-metals

Explanation:
The chapter explains that all materials making the bulb glow in Activity 4.4 are metals, and states that metals are good conductors of electricity while non-metals are poor conductors. This property serves as a reliable distinguishing feature between the two material categories.

Question: During an ironsmith's work, heating the iron before shaping it into tools is essential. Which combination of the iron's properties makes this heating necessary?
A. Heating reduces the metal's lustre, making it easier to work with
B. Heating increases malleability by allowing the metal to deform more easily under the hammer's force
C. Heating changes iron into a non-metal so it can be shaped more quickly
D. Heating is unnecessary; Sudarshan simply prefers working with hot metal
Show Answer & Explanation

Answer: (B) Heating increases malleability by allowing the metal to deform more easily under the hammer's force

Explanation:
The interaction between heating and malleability is shown when Sudarshan heats iron until red-hot before beating it. Heating increases the material's ability to deform without breaking, making the shaping process effective. This demonstrates why heating enhances the practical application of malleability in metalworking.

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