What is Elements Compounds Mixtures Exercises in Class 8 Science NCERT?

The Class 8 Science NCERT Chapter 8 — Nature of Matter: Elements, Compounds and Mixtures exercise section tests students on all the key concepts covered in the chapter, including NCERT exercises, element questions, compound questions, mixture questions, competency-based questions. It includes multi…

What does the NCERT Class 8 Science Nature of Matter: Elements, Compounds and Mixtures exercise section cover?

The Class 8 Science NCERT Chapter 8 u2014 Nature of Matter: Elements, Compounds and Mixtures exercise section tests students on all the key concepts covered in the chapter, including NCERT exercises, element questions, compound questions, mixture questions, competency-based questions. It includes multiple-choice questions (MCQs), assertion-reason questions, short-answer questions, long-answer questions, and competency-based questions that align with the NCERT Curiosity textbook. Working through these exercises helps Class 8 students reinforce their conceptual understanding, prepare for classroom assessments, and build exam readiness for CBSE school tests. Each question links back to a specific section of the chapter so students can revise the theory alongside the practice.

How should Class 8 students approach the Nature of Matter: Elements, Compounds and Mixtures exercises?

Class 8 students should approach the Nature of Matter: Elements, Compounds and Mixtures exercises by first revising the main theory and definitions from each part of the chapter, especially around NCERT exercises and element questions. Start with the MCQs and assertion-reason questions to quickly test recall, then attempt the short-answer questions that need a one or two-line explanation, and finally tackle the long-answer and competency-based questions that require applying concepts to new situations. Write neat diagrams wherever the question involves a process, cycle, or setup, and always use NCERT-style vocabulary in your answers to match CBSE marking schemes.

Are these Nature of Matter: Elements, Compounds and Mixtures questions competency-based as per NEP 2020?

Yes, the Nature of Matter: Elements, Compounds and Mixtures exercise set follows the NEP 2020 competency-based education (CBE) framework used by CBSE and NCERT for Class 8 Science. Instead of only asking students to recall definitions, many questions are scenario-based and require applying the concept to real-life situations, analysing data, or evaluating claims. This matches Bloom's Taxonomy levels L3 (Apply), L4 (Analyse), and L5 (Evaluate), going beyond rote learning. Students practising these questions build the higher-order thinking skills that modern CBSE school exams increasingly assess, and also prepare well for competitive foundation tests in later years.

Which NCERT Curiosity sections are tested in Chapter 8 exercises?

The Chapter 8 u2014 Nature of Matter: Elements, Compounds and Mixtures exercise set systematically tests every major section of the NCERT Curiosity Class 8 Science textbook for this chapter. Topics covered include NCERT exercises, element questions, compound questions, mixture questions, competency-based questions. Every in-text question, activity-linked question, and end-of-chapter question from the Curiosity book is represented, so students can be confident that completing this exercise set gives them full coverage of the NCERT syllabus. Teachers also frequently pick questions from these sections for school unit tests and half-yearly exams, making thorough practice essential for strong performance.

How do assertion-reason questions work in this Class 8 Science chapter?

Assertion-reason questions in the Class 8 Science Nature of Matter: Elements, Compounds and Mixtures exercise set present two statements u2014 an Assertion (A) and a Reason (R) u2014 and ask students to judge whether each is true and whether R correctly explains A. Students pick from four standard options: both true with R explaining A, both true but R not explaining A, A true and R false, or A false. This format tests whether Class 8 learners genuinely understand the cause-and-effect relationships behind NCERT exercises, not just surface facts. Mastering this format is valuable because CBSE Class 10 board exams use the same pattern.

What is the best revision strategy before attempting these exercises?

The best revision strategy before attempting Nature of Matter: Elements, Compounds and Mixtures exercises is to read through all theory parts of NCERT Curiosity Chapter 8 once, write down the key terms such as NCERT exercises, element questions, compound questions, mixture questions, competency-based questions in your own words, and then re-do all activities mentally to understand the underlying concept. Next, make a one-page mind map linking the main ideas. Only then attempt the exercise questions u2014 first without looking back, then self-correcting. This active-recall approach builds much stronger long-term memory than repeatedly re-reading the textbook, and is widely recommended by CBSE teachers for Class 8 Science preparation.

What does the NCERT Class 8 Science Nature of Matter: Elements, Compounds and Mixtures exercise section cover?

The Class 8 Science NCERT Chapter 8 — Nature of Matter: Elements, Compounds and Mixtures exercise section tests students on all the key concepts covered in the chapter, including NCERT exercises, element questions, compound questions, mixture questions, competency-based questions. It includes multiple-choice questions (MCQs), assertion-reason questions, short-answer questions, long-answer questions, and competency-based questions that align with the NCERT Curiosity textbook. Working through these exercises helps Class 8 students reinforce their conceptual understanding, prepare for classroom assessments, and build exam readiness for CBSE school tests. Each question links back to a specific section of the chapter so students can revise the theory alongside the practice.

How should Class 8 students approach the Nature of Matter: Elements, Compounds and Mixtures exercises?

Class 8 students should approach the Nature of Matter: Elements, Compounds and Mixtures exercises by first revising the main theory and definitions from each part of the chapter, especially around NCERT exercises and element questions. Start with the MCQs and assertion-reason questions to quickly test recall, then attempt the short-answer questions that need a one or two-line explanation, and finally tackle the long-answer and competency-based questions that require applying concepts to new situations. Write neat diagrams wherever the question involves a process, cycle, or setup, and always use NCERT-style vocabulary in your answers to match CBSE marking schemes.

Are these Nature of Matter: Elements, Compounds and Mixtures questions competency-based as per NEP 2020?

Yes, the Nature of Matter: Elements, Compounds and Mixtures exercise set follows the NEP 2020 competency-based education (CBE) framework used by CBSE and NCERT for Class 8 Science. Instead of only asking students to recall definitions, many questions are scenario-based and require applying the concept to real-life situations, analysing data, or evaluating claims. This matches Bloom's Taxonomy levels L3 (Apply), L4 (Analyse), and L5 (Evaluate), going beyond rote learning. Students practising these questions build the higher-order thinking skills that modern CBSE school exams increasingly assess, and also prepare well for competitive foundation tests in later years.

Which NCERT Curiosity sections are tested in Chapter 8 exercises?

The Chapter 8 — Nature of Matter: Elements, Compounds and Mixtures exercise set systematically tests every major section of the NCERT Curiosity Class 8 Science textbook for this chapter. Topics covered include NCERT exercises, element questions, compound questions, mixture questions, competency-based questions. Every in-text question, activity-linked question, and end-of-chapter question from the Curiosity book is represented, so students can be confident that completing this exercise set gives them full coverage of the NCERT syllabus. Teachers also frequently pick questions from these sections for school unit tests and half-yearly exams, making thorough practice essential for strong performance.

How do assertion-reason questions work in this Class 8 Science chapter?

Assertion-reason questions in the Class 8 Science Nature of Matter: Elements, Compounds and Mixtures exercise set present two statements — an Assertion (A) and a Reason (R) — and ask students to judge whether each is true and whether R correctly explains A. Students pick from four standard options: both true with R explaining A, both true but R not explaining A, A true and R false, or A false. This format tests whether Class 8 learners genuinely understand the cause-and-effect relationships behind NCERT exercises, not just surface facts. Mastering this format is valuable because CBSE Class 10 board exams use the same pattern.

What is the best revision strategy before attempting these exercises?

The best revision strategy before attempting Nature of Matter: Elements, Compounds and Mixtures exercises is to read through all theory parts of NCERT Curiosity Chapter 8 once, write down the key terms such as NCERT exercises, element questions, compound questions, mixture questions, competency-based questions in your own words, and then re-do all activities mentally to understand the underlying concept. Next, make a one-page mind map linking the main ideas. Only then attempt the exercise questions — first without looking back, then self-correcting. This active-recall approach builds much stronger long-term memory than repeatedly re-reading the textbook, and is widely recommended by CBSE teachers for Class 8 Science preparation.

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Elements Compounds Mixtures — Exercises

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Chapter Summary

In Chapter 8 we learnt how chemists re-classify matter based on its composition, rather than its state.

Pure vs Impure

Pure substances have one kind of particle; mixtures contain two or more substances blended physically.

Elements

118 are known, 94 natural. Made of one kind of atom. Classified as metals, non-metals, metalloids.

Symbols

One- or two-letter abbreviations, often from Latin names (Na, Fe, Au, Pb).

Compounds

Two or more elements chemically combined in a fixed ratio. Properties differ from constituent elements.

Formulas & Subscripts

H₂O means 2 H + 1 O. Subscripts count atoms, not molecules.

Mixtures

Homogeneous (uniform) or heterogeneous (non-uniform); separable by physical methods.

Reactions

Combination (elements → compound) and decomposition (compound → simpler).

Separation Methods

Filtration, evaporation, distillation, decantation, sieving, magnetic, chromatography, centrifugation.

Key Terms

Matter

Pure substance

Mixture

Element

Compound

Atom

Molecule

Symbol

Formula

Subscript

Metal

Non-metal

Metalloid

Homogeneous

Heterogeneous

Combination

Decomposition

Filtration

Distillation

Evaporation

Chromatography

Centrifugation

NCERT Exercises — Solved

Q1.Differentiate between an element and a compound.

Element	Compound
Made of only one kind of atoms.	Made of two or more different elements.
Cannot be broken into simpler substances by chemistry.	Can be broken into elements by chemical methods (heating, electrolysis).
Examples: O₂, Fe, Au, C.	Examples: H₂O, CO₂, NaCl.
Shown by symbols.	Shown by formulas with subscripts.

Q2.Give examples of five elements, five compounds and five mixtures.

Elements: hydrogen (H₂), oxygen (O₂), iron (Fe), gold (Au), carbon (C).
Compounds: water (H₂O), carbon dioxide (CO₂), common salt (NaCl), glucose (C₆H₁₂O₆), methane (CH₄).
Mixtures: air, seawater, milk, brass, soil.

Q3.What is the difference between pure substances and impure substances?

Pure substance: Contains only one type of particle throughout. It has a fixed composition and definite properties (e.g., fixed melting/boiling point). Examples: distilled water, pure gold, oxygen gas.
Impure substance (mixture): Contains more than one substance in variable proportions. Each component keeps its own properties and can be separated by physical methods. Examples: muddy water, air, milk.

Q4.Match the following symbols with the correct element names.

Symbol	Name (mix)
Fe	Copper
Au	Iron
Na	Potassium
Cu	Sodium
K	Silver
Ag	Gold
Pb	Mercury
Hg	Lead

Correct matches:
Fe → Iron (ferrum) · Au → Gold (aurum) · Na → Sodium (natrium) · Cu → Copper (cuprum) · K → Potassium (kalium) · Ag → Silver (argentum) · Pb → Lead (plumbum) · Hg → Mercury (hydrargyrum).

Q5.Write the chemical formulas for: water, carbon dioxide, common salt, sugar (sucrose), methane.

Water: H₂O · Carbon dioxide: CO₂ · Common salt: NaCl · Sugar (sucrose): C₁₂H₂₂O₁₁ · Methane: CH₄.

Q6.Classify each of the following as element, compound, or mixture:
carbon dioxide, sand, seawater, magnesium oxide, muddy water, aluminium, gold, oxygen, rust, iron sulfide, glucose, air, water, fruit juice, nitrogen, sodium chloride, sulfur, hydrogen, baking soda.

Substance	Classification
Carbon dioxide (CO₂)	Compound
Sand	Mixture (mostly SiO₂ with impurities)
Seawater	Mixture (homogeneous solution)
Magnesium oxide (MgO)	Compound
Muddy water	Mixture (heterogeneous)
Aluminium (Al)	Element
Gold (Au)	Element
Oxygen (O₂)	Element
Rust (Fe₂O₃·xH₂O)	Compound
Iron sulfide (FeS)	Compound
Glucose (C₆H₁₂O₆)	Compound
Air	Mixture (homogeneous)
Water (H₂O)	Compound
Fruit juice	Mixture (heterogeneous)
Nitrogen (N₂)	Element
Sodium chloride (NaCl)	Compound
Sulfur (S)	Element
Hydrogen (H₂)	Element
Baking soda (NaHCO₃)	Compound

Q7.What new substance is formed when a mixture of iron filings and sulfur powder is heated? How is it different from the original mixture? Write the word equation.

On strong heating, iron (Fe) and sulfur (S) chemically combine to form a new compound called iron sulfide (FeS).
Word equation: Iron + Sulfur → Iron sulfide.
Symbolically: Fe + S → FeS.

How it differs from the original mixture:

In the original mixture, a magnet could still pull out the iron and the two substances kept their own properties.
In the new compound FeS, the iron has lost its magnetism — a magnet no longer removes it.
The mixture showed yellow sulfur grains and grey iron; FeS is a uniform black solid.
The compound has a fixed composition (by mass); the original mixture could be made in any ratio.

Q8.Is it possible for a substance to be classified as both an element and a compound? Explain why or why not.

No, a substance cannot be both at the same time. The two definitions are mutually exclusive:

An element is made of a single kind of atom only.
A compound is made of atoms of two or more different elements bonded chemically.

If a substance has only one kind of atom, it is an element (e.g., O₂, even though it contains 2 atoms, they are both oxygen). The moment a second kind of atom enters chemically, it becomes a compound (e.g., CO₂). Therefore, the same pure substance cannot belong to both categories — its atomic composition decides which one it is.

Q9.How would our daily lives be changed if water were not a compound but merely a mixture of hydrogen and oxygen?

Life as we know it would be impossible. If water were just a mixture:

It would not be a liquid at room temperature. H₂ and O₂ are both gases that boil far below 0 °C. So "water" would be a gas — no rivers, no lakes, no oceans.
It would not put out fires. Hydrogen burns and oxygen supports burning. A spark would cause it to explode rather than extinguish flames.
Proportions would vary. Drinking water from different sources would have different H : O ratios, making it unreliable.
Living cells could not form. Cells rely on H₂O's unique bonded structure to dissolve nutrients and carry signals.
Weather, rain and climate would not exist, because there would be no liquid water to evaporate and condense.

The chemical bonding in H₂O gives water totally new, life-friendly properties (liquid state, surface tension, high heat capacity) that neither hydrogen nor oxygen gases possess.

Q10.Analyse Fig. 8.24 (an experiment where a metal ribbon is burnt in air producing a white powder and a gas is evolved when the powder is added to dilute acid). Identify Gas A and write the word equation of the chemical reaction shown.

The burning of the metal ribbon (magnesium) in air produces magnesium oxide:
Word equation 1: Magnesium + Oxygen → Magnesium oxide.
2 Mg + O₂ → 2 MgO.

When magnesium oxide is added to dilute hydrochloric acid, it reacts to give magnesium chloride and water. If, instead, the unburnt magnesium ribbon is added to dilute acid, the gas evolved is hydrogen (H₂).
Word equation 2 (metal + acid): Magnesium + Hydrochloric acid → Magnesium chloride + Hydrogen.
Mg + 2 HCl → MgCl₂ + H₂↑.
Hence Gas A is hydrogen (H₂). It can be confirmed by a lighted splinter — hydrogen burns with a "pop" sound.

Q11.Write the names of any two compounds made only from non-metals, and mention two uses of each.

1. Water (H₂O) — made of H and O (both non-metals).

Drinking and cooking — the universal solvent for our bodies.
Generation of hydroelectric power and irrigation for agriculture.

2. Carbon dioxide (CO₂) — made of C and O (both non-metals).

Used by green plants for photosynthesis to make food.
Used in fire extinguishers and to make fizzy soft drinks.

(Other valid examples: ammonia NH₃ — fertilisers, cleaners; methane CH₄ — cooking gas, fuel.)

Q12.How can gold be classified as both a mineral and a metal?

The words "mineral" and "metal" answer two different questions.

Mineral is a geological term: a naturally occurring solid substance, usually found in rocks or ores. Gold occurs naturally as nuggets and flakes inside rocks in the Earth's crust — so it is a mineral.
Metal is a chemical term: an element that is lustrous, malleable, ductile, and a good conductor of heat and electricity. Gold shows all these properties — so it is a metal (in fact, one of the most unreactive metals).

So "mineral" describes where and how we find gold in nature; "metal" describes the kind of element it is chemically. Both labels can apply to the same substance at the same time, because they describe different aspects. Many, but not all, minerals are metals (e.g., sulphur is a non-metallic mineral).

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