Download CBSE MCQs for Class 8 Science: Chapter 08 Nature Of Matter Elements, Compounds, And Mixtures
Review structured MCQ sets for Class 8 Science Chapter 08 Nature Of Matter Elements, Compounds, And Mixtures. Built according to official CBSE guidelines, these downloadable questions support daily revision and core concept reinforcement.
Chapter-wise Objective Questions: Chapter 08 Nature Of Matter Elements, Compounds, And Mixtures
Access the complete set of multiple-choice questions for Chapter 08 Nature Of Matter Elements, Compounds, And Mixtures below. This focused format allows students to isolate specific topics for thorough review and uninterrupted practice alongside official CBSE textbooks.
A. Water is a mixture of hydrogen and oxygen that can be physically separated
B. Water is a compound whose constituent elements have entirely different properties from water itself
C. Water is an element that can be broken into simpler components through physical processes
D. Water is a pure substance that cannot be divided into any smaller units
Show Answer & Explanation
Answer: (B) Water is a compound whose constituent elements have entirely different properties from water itself
Explanation:
The activity demonstrates that water breaks down into hydrogen (which burns with a pop sound) and oxygen (which makes a flame burn brighter)—two elements with properties completely different from water. This shows water is a compound where elements combine chemically in fixed ratios, not a mixture where components retain their individual properties or an element that cannot be further decomposed.
A. Mixtures always contain magnetic materials, whereas compounds are never magnetic
B. In a mixture, individual components retain their original properties; in a compound, new properties emerge through chemical combination
C. Heating always destroys the magnetic properties of any substance
D. Elements lose their characteristic properties when combined in any form
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Answer: (B) In a mixture, individual components retain their original properties; in a compound, new properties emerge through chemical combination
Explanation:
• Sample A retains iron's magnetic property because components in a mixture stay separate
• Sample B shows that heating caused iron and sulfur to chemically combine into iron sulfide
• The resulting compound has entirely new properties—it is not attracted to magnets
• This exemplifies how compounds have different properties than their constituent elements
A. It proves that air contains only water vapour and no gases
B. It provides evidence that carbon dioxide, a gas component of air, reacts chemically with calcium hydroxide to form a visible precipitate
C. It shows that air is entirely composed of inert gases that do not participate in reactions
D. It indicates that water vapour in air undergoes a chemical change to produce white particles
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Answer: (B) It provides evidence that carbon dioxide, a gas component of air, reacts chemically with calcium hydroxide to form a visible precipitate
Explanation:
The lime water turns milky due to carbon dioxide in the air reacting with calcium hydroxide to produce calcium carbonate—the white precipitate. This demonstrates that air contains carbon dioxide and is a mixture of different gases, as stated in section 8.1.1.
A. Compounds and mixtures are made by arranging elements in different physical configurations
B. All matter—whether compounds or mixtures—is ultimately composed of elements combined in various ways
C. Elements only form compounds; they never exist in mixtures
D. Compounds are made from elements, but mixtures are made from other substances
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Answer: (B) All matter—whether compounds or mixtures—is ultimately composed of elements combined in various ways
Explanation:
This concept means that both compounds (where elements chemically combine in fixed ratios) and mixtures (where elements or compounds combine without chemical bonding) are fundamentally composed of elements. Elements are the simplest substances that cannot be broken down further, making them the foundation of all matter.
A. Sugar is an element composed only of carbon
B. Sugar contains the elements hydrogen and oxygen in addition to carbon
C. Sugar is a mixture of carbon, water, and other substances
D. Sugar is pure hydrogen and oxygen that burn to leave charcoal
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Answer: (B) Sugar contains the elements hydrogen and oxygen in addition to carbon
Explanation:
The water droplets that form during sugar's decomposition come from the sugar itself, not from air. Since water contains hydrogen and oxygen, the presence of water in the products proves that sugar contains these elements along with carbon (the black residue). This demonstrates sugar is a compound of carbon, hydrogen, and oxygen.
A. It explains why air is uniform and cannot be separated into components
B. It shows that the different gases in air retain their individual properties even when mixed together
C. It proves that air is a compound rather than a mixture
D. It indicates that air would change composition if any oxygen were removed
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Answer: (B) It shows that the different gases in air retain their individual properties even when mixed together
Explanation:
Each component gas in air maintains its characteristic properties—nitrogen remains inert, oxygen supports combustion—even though they are mixed together. This retention of individual properties is a defining characteristic of mixtures, contrasting with compounds where elements lose their original properties upon chemical combination.
A. Sample A and Sample B are both mixtures with identical chemical properties
B. Sample A is a mixture where iron reacts but sulfur does not; Sample B is a compound with different reactive properties
C. Both samples are compounds that produce different gases based on the order of reaction
D. Sample B has a stronger smell because it was heated at higher temperatures
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Answer: (B) Sample A is a mixture where iron reacts but sulfur does not; Sample B is a compound with different reactive properties
Explanation:
In Sample A (mixture), iron reacts with acid to produce hydrogen gas while sulfur remains unreacted—showing that components in a mixture retain their separate identities. In Sample B (compound), iron and sulfur have chemically combined into iron sulfide, which reacts as a single substance to produce hydrogen sulfide. This demonstrates how compounds have properties entirely different from their constituent elements.
A. Stainless steel is transparent, while compounds are always opaque
B. The components of stainless steel can theoretically be separated by physical methods and retain their individual properties, whereas compound components cannot be separated physically
C. Stainless steel was created artificially, so it is not a true pure substance
D. Compounds only form when elements are heated, while alloys form at room temperature
Show Answer & Explanation
Answer: (B) The components of stainless steel can theoretically be separated by physical methods and retain their individual properties, whereas compound components cannot be separated physically
Explanation:
Stainless steel is a mixture—specifically an alloy—where its metallic components are dispersed uniformly but do not undergo chemical combination. The metals retain their individual properties and could be separated using appropriate physical techniques. Compounds like water, however, involve elements chemically bonded in fixed ratios, making separation by physical means impossible.
A. They would be correct because all uniform-looking substances are mixtures
B. Appearance alone does not determine whether something is a mixture or compound; sugar's behaviour under heating proves it is a compound
C. Sugar would be a mixture if it contained visible particles, but since it is uniform, it must be a compound
D. The distinction between mixtures and compounds does not matter for substances that are uniform
Show Answer & Explanation
Answer: (B) Appearance alone does not determine whether something is a mixture or compound; sugar's behaviour under heating proves it is a compound
Explanation:
When sugar is heated, it decomposes into simpler substances—water and carbon—proving that its constituent elements are chemically bonded in fixed ratios. This chemical decomposition is characteristic of compounds. A mixture, by contrast, would not decompose this way; its components would remain unchanged. Uniformity of appearance is not the defining criterion.
A. Gold is harder and more valuable than all compound minerals
B. Gold cannot be broken down into simpler substances by any chemical process, whereas compound minerals can be decomposed into their constituent elements
C. Gold is the only mineral that exists in nature without being combined with other elements
D. Compound minerals are stronger than gold but less useful in applications
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Answer: (B) Gold cannot be broken down into simpler substances by any chemical process, whereas compound minerals can be decomposed into their constituent elements
Explanation:
A pure element like gold consists of identical atoms of a single type and cannot be chemically decomposed into simpler substances. Compound minerals, such as calcite or quartz, are made of two or more elements bonded together and can be broken down into those elements through chemical reactions. This is the fundamental distinction between elements and compounds.
A. It proves that all elements must be either solid or liquid at room temperature
B. It shows that elements—like all pure substances—can exist in different physical states depending on conditions
C. It demonstrates that gaseous elements are less important than solid elements
D. It indicates that states of matter are not relevant to classifying substances as elements
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Answer: (B) It shows that elements—like all pure substances—can exist in different physical states depending on conditions
Explanation:
Elements, as pure substances, can exist in any physical state (solid, liquid, or gas) depending on temperature and pressure. The fact that most elements are solid but some are gaseous at room temperature illustrates that state of matter is a physical property that varies, not a defining feature of whether something is an element or not. This is distinct from the chemical nature of the substance.
A. Elements can only form one type of substance under any conditions
B. The arrangement and structure of atoms of an element determine the properties of the resulting substance
C. Graphene aerogel is not truly made from pure carbon but contains other elements
D. Different arrangements of the same element prove that element is actually a compound
Show Answer & Explanation
Answer: (B) The arrangement and structure of atoms of an element determine the properties of the resulting substance
Explanation:
Graphene aerogel, diamond, and graphite are all pure forms of carbon, yet they have vastly different properties because of how their carbon atoms are arranged. This demonstrates that even within a single element, structural differences produce substances with different characteristics. The chemical composition is identical, but the physical structure and arrangement of atoms determine observable properties.
A. Air is a mixture of gases that each retain their individual properties
B. Water is composed of hydrogen (a flammable gas) and oxygen (a gas that supports combustion), yet water extinguishes fire
C. Iron filings are attracted to a magnet before and after being mixed with sulfur
D. Sugar appears uniform, so it is likely a mixture of simple substances
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Answer: (B) Water is composed of hydrogen (a flammable gas) and oxygen (a gas that supports combustion), yet water extinguishes fire
Explanation:
Hydrogen burns readily, oxygen supports combustion, yet their compound—water—extinguishes fire. This dramatic reversal of properties exemplifies how compounds possess characteristics completely different from those of their elements. The chapter uses this specific example to emphasize why compounds cannot be treated as simple mixtures of elements.
A. Air is only the gaseous elements and compounds; suspended particles like dust are separate from air's composition
B. Pollutants are heavier than air and always settle before other components
C. Dust is an element that should not be present in any atmosphere
D. The classification of something as part of air depends solely on whether it is visible
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Answer: (A) Air is only the gaseous elements and compounds; suspended particles like dust are separate from air's composition
Explanation:
Air is defined as a uniform mixture of specific gases (nitrogen, oxygen, argon, carbon dioxide, water vapour) and carbon dioxide. Dust particles are physical matter suspended in air but not part of air's actual composition—they are contaminants or pollutants. This distinction shows that the composition of a mixture is defined by its intended or primary components, not by everything physically present in a space.
A. Brass and bronze are compounds, so they are more artistic than pure elements
B. These alloys are mixtures that can be melted and molded, yet they have properties like strength and durability superior to their pure component metals
C. Brass and bronze are elements that have been shaped into art for centuries
D. They are chosen because they are more uniform in appearance than other metals
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Answer: (B) These alloys are mixtures that can be melted and molded, yet they have properties like strength and durability superior to their pure component metals
Explanation:
Brass (copper and zinc) and bronze (copper and tin) are alloys—uniform mixtures of metals. The chapter explains that engineers and material scientists design alloys to achieve properties superior to those of pure metals: they are stronger and more durable than pure copper or tin alone. This makes them ideal for art that must be both visually attractive and structurally sound.
A. All physical separations are equally effective for separating all substances
B. Physical methods separate mixtures and dissolved compounds from solvents, but cannot separate the elements within a compound
C. Compounds are easier to separate than mixtures because they have stronger bonds
D. Sodium chloride is not a true compound because it can be separated from water
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Answer: (B) Physical methods separate mixtures and dissolved compounds from solvents, but cannot separate the elements within a compound
Explanation:
Salt dissolving in water creates a mixture (salt solution) that can be separated by physical evaporation. However, within sodium chloride itself, sodium and chlorine are chemically bonded and cannot be separated by physical processes—only by chemical reactions. This distinction is fundamental: physical methods separate mixtures, but cannot break the chemical bonds within compounds.
A. Stirring prevents the solution from cooling and affecting the reaction
B. Stirring ensures that lime water remains in contact with the carbon dioxide in the air, allowing the reaction to occur throughout the solution
C. Stirring removes impurities that would otherwise prevent the milky appearance
D. Stirring is only done for safety and does not affect the chemical reaction
Show Answer & Explanation
Answer: (B) Stirring ensures that lime water remains in contact with the carbon dioxide in the air, allowing the reaction to occur throughout the solution
Explanation:
Carbon dioxide from the air dissolves and reacts with calcium hydroxide (lime water) to form calcium carbonate, the white precipitate that makes the solution milky. Stirring helps distribute the lime water and expose more of it to the air's carbon dioxide, allowing the reaction to proceed more completely and noticeably. Without stirring, the reaction might be slow or localized to the surface.
A. Stainless steel must be a mixture because mixtures are always uniform in appearance
B. Stainless steel is a compound, but the chapter incorrectly classifies it as a mixture
C. The individual metallic components of stainless steel do not chemically bond in fixed ratios and retain their metallic properties; they are dispersed uniformly but remain separate
D. Uniformity of appearance determines whether something is a mixture or compound, and stainless steel appears uniform, so it is a mixture
Show Answer & Explanation
Answer: (C) The individual metallic components of stainless steel do not chemically bond in fixed ratios and retain their metallic properties; they are dispersed uniformly but remain separate
Explanation:
Uniform appearance alone does not determine if a substance is a compound. Stainless steel contains iron, nickel, chromium, and carbon dispersed uniformly, but these elements do not undergo chemical combination in fixed ratios. Each component retains its metallic nature, and in principle, they could be separated (though with difficulty). This dispersed but separate nature makes it a mixture (specifically, an alloy), not a compound where elements chemically bond to form a new substance with new properties.
A. Water is an element because it produces only one type of gas
B. Water is a compound made of hydrogen and oxygen because it breaks down into two distinct substances with different properties
C. Water is a mixture because the gases produced have different burning characteristics
D. Water is a pure substance that cannot be separated into anything simpler
Show Answer & Explanation
Answer: (B) Water is a compound made of hydrogen and oxygen because it breaks down into two distinct substances with different properties
Explanation:
The chapter describes how passing electricity through water yields hydrogen gas (which makes a 'pop' sound with a burning splinter) and oxygen gas (which makes a flame glow brighter). Since water breaks down into two different elements with contrasting chemical properties, this demonstrates water is a compound formed by chemical bonding of hydrogen and oxygen, not a simple element or mixture.
A. The heating process removed all the iron from the mixture
B. A new substance with entirely different properties was formed through chemical combination of the elements
C. The sulfur absorbed the magnetic properties of the iron
D. The magnet became weaker and could no longer attract iron
Show Answer & Explanation
Answer: (B) A new substance with entirely different properties was formed through chemical combination of the elements
Explanation:
Sample A retains the magnetic property of iron because the elements remain physically separate—they haven't chemically reacted. When heated, iron and sulfur combine chemically to form iron sulfide, a compound with completely different properties. The loss of magnetism in Sample B demonstrates that the individual elements no longer exist as separate substances but have transformed into a new material through chemical bonding.
A. Sugar is a pure element that only releases water when heated
B. Sugar is a mixture of carbon and water that separates when heated
C. Sugar is a compound containing the elements carbon, hydrogen, and oxygen
D. Sugar is a mixture of water and charcoal in fixed proportions
Show Answer & Explanation
Answer: (C) Sugar is a compound containing the elements carbon, hydrogen, and oxygen
Explanation:
• The production of water droplets indicates presence of hydrogen and oxygen
• The black charcoal residue indicates presence of carbon
• Since heating causes sugar to decompose into these substances with the loss of the original sugar properties, sugar must be a compound made from these three elements chemically bonded together, not a physical mixture.
A. To show that air contains only gases and no solid matter
B. To distinguish between the stable gaseous components that make air a mixture and the pollutants that are present but not considered part of air's composition
C. To prove that air is a compound rather than a mixture
D. To explain why dust particles are essential components of air
Show Answer & Explanation
Answer: (B) To distinguish between the stable gaseous components that make air a mixture and the pollutants that are present but not considered part of air's composition
Explanation:
The chapter carefully separates the discussion of air's main components (nitrogen, oxygen, carbon dioxide) from dust particles, explicitly stating that dust "is not an integral part of the air and is considered pollutants." This distinction shows that air's classification as a uniform mixture refers to its gaseous components that intentionally combine, while dust represents unwanted contaminants suspended in air but not part of air's defined composition.
A. Elements lose their identity when dissolved in water
B. Compounds have completely different properties from their constituent elements
C. Mixtures are always less useful than their individual components
D. Elements can only combine in equal numbers of atoms
Show Answer & Explanation
Answer: (B) Compounds have completely different properties from their constituent elements
Explanation:
The dramatic change from a dangerous, reactive metal and a poisonous gas to a harmless, beneficial substance demonstrates that compounds formed through chemical bonding possess entirely new properties distinct from those of their component elements. This principle is central to understanding why compounds cannot be considered simple mixtures of elements.
A. Stainless steel only appears uniform but is actually visible as separate metals if magnified
B. The components of stainless steel retain their individual properties and can theoretically be separated by physical means, unlike compounds where elements are chemically bonded
C. Compounds must contain only two elements, while stainless steel contains four
D. Stainless steel becomes a compound only after it rusts or corrodes
Show Answer & Explanation
Answer: (B) The components of stainless steel retain their individual properties and can theoretically be separated by physical means, unlike compounds where elements are chemically bonded
Explanation:
Even though stainless steel looks uniform to the eye, it remains a physical mixture where the metallic components retain their distinct properties but are distributed evenly. In compounds like sodium chloride or water, the elements are chemically bonded in fixed ratios and cannot be separated by physical means. Uniformity of appearance alone does not make something a compound—the key difference lies in whether elements are chemically bonded or physically mixed.
A. As an element because it contains only carbon atoms
B. As a compound because it has unique properties different from regular carbon
C. As a mixture of different forms of carbon
D. As a pure substance made from one element that exhibits special structural properties
Show Answer & Explanation
Answer: (D) As a pure substance made from one element that exhibits special structural properties
Explanation:
Graphene aerogel is a pure substance consisting solely of carbon atoms (the element), but arranged in a unique three-dimensional structure that creates its extraordinary properties. This shows that a single element can form different substances with vastly different characteristics depending on how its atoms are arranged. It is neither a compound (which requires multiple elements) nor a mixture (which combines multiple substances)—it is a pure elemental substance with engineered structure.
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Chapter 08 Nature Of Matter Elements, Compounds, And Mixtures Objective Questions & Solutions for Class 8 Science
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