CBSE Class 8 Science Chapter 7: Particulate Nature of Matter — Assertion & Reason
CBSE Class 8 Science Assertion & Reason
Expert crafted · Instant PDF download · 2026-27
The following Assertion and Reason questions are based on Chapter 7: Particulate Nature of Matter from the NCERT Class 8 Science textbook Curiosity. Each question has four options — read both the Assertion (A) and Reason (R) carefully before selecting your answer.
How to attempt Assertion & Reason questions:
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is NOT the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is NOT the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Assertion & Reason Questions
1
Assertion (A): Grinding chalk into a fine powder is a physical change.
Reason (R): Grinding only reduces the size of chalk particles without changing chalk into a new substance.
Reason (R): Grinding only reduces the size of chalk particles without changing chalk into a new substance.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. During grinding, only the physical size of chalk particles reduces, but the substance remains chalk throughout.
2
Assertion (A): Matter is composed of extremely small particles called constituent particles.
Reason (R): When sugar dissolves in water, it can no longer be seen but can still be tasted.
Reason (R): When sugar dissolves in water, it can no longer be seen but can still be tasted.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. While both statements are true, R demonstrates evidence for particulate nature but doesn't explain what constituent particles are.
3
Assertion (A): The constituent particles of matter are held together by interparticle attractions.
Reason (R): These attractive forces are strongest in gases and weakest in solids.
Reason (R): These attractive forces are strongest in gases and weakest in solids.
Answer: (c)
A is true, but R is false. While constituent particles are held together by interparticle attractions, these forces are strongest in solids (not gases) and weakest in gases (not solids).
4
Assertion (A): Solids have a definite shape and volume.
Reason (R): In solids, particles are tightly packed with strong interparticle attractions that hold them in fixed positions.
Reason (R): In solids, particles are tightly packed with strong interparticle attractions that hold them in fixed positions.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. The tight packing and strong forces prevent particles from moving freely, giving solids their definite shape and volume.
5
Assertion (A): The melting point is the temperature at which a solid changes into a liquid.
Reason (R): At the melting point, particles vibrate so vigorously that interparticle forces strengthen and the solid becomes more rigid.
Reason (R): At the melting point, particles vibrate so vigorously that interparticle forces strengthen and the solid becomes more rigid.
Answer: (c)
A is true, but R is false. At the melting point, vigorous vibrations actually weaken (not strengthen) the interparticle forces, allowing particles to leave their fixed positions and the solid to become liquid.
6
Assertion (A): Liquids have no fixed shape but have a definite volume.
Reason (R): Particles in liquids can move freely within a limited space, and interparticle attractions are slightly weaker than in solids.
Reason (R): Particles in liquids can move freely within a limited space, and interparticle attractions are slightly weaker than in solids.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. The weaker forces allow particles to move and take the container's shape, but they remain close enough to maintain a definite volume.
7
Assertion (A): We can move our finger through water without permanently breaking it.
Reason (R): Interparticle attractions in liquids are stronger than in solids.
Reason (R): Interparticle attractions in liquids are stronger than in solids.
Answer: (c)
A is true, but R is false. We can move our finger through water because interparticle attractions in liquids are slightly weaker than in solids (not stronger), allowing temporary displacement of water particles.
8
Assertion (A): At the boiling point, vapour formation occurs very fast throughout the liquid.
Reason (R): Evaporation is a slow process that occurs only at the surface of a liquid at all temperatures.
Reason (R): Evaporation is a slow process that occurs only at the surface of a liquid at all temperatures.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. Both describe different processes—boiling (rapid, throughout) vs evaporation (slow, surface only)—rather than R explaining A.
9
Assertion (A): Gases have no fixed shape or volume.
Reason (R): In gases, interparticle attractions are negligible and particles move freely in all directions.
Reason (R): In gases, interparticle attractions are negligible and particles move freely in all directions.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Negligible attractive forces allow gas particles to move completely freely, spreading to fill any available space.
10
Assertion (A): Air in a syringe can be compressed by pushing the plunger.
Reason (R): Gas particles have very little space between them, making compression difficult.
Reason (R): Gas particles have very little space between them, making compression difficult.
Answer: (c)
A is true, but R is false. Air can be compressed precisely because gas particles have a LOT of space (not very little) between them in their natural state, which can be reduced by applying pressure.
11
Assertion (A): When sugar is dissolved in water, the water level may decrease slightly after dissolution.
Reason (R): Sugar particles occupy the interparticle spaces present between water particles.
Reason (R): Sugar particles occupy the interparticle spaces present between water particles.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Since the volume of solution is less than the sum of individual volumes, it indicates sugar particles are fitting into spaces between water particles.
12
Assertion (A): Sand does not dissolve in water when mixed.
Reason (R): Sand particles are held together by forces so strong that water particles cannot pull them apart.
Reason (R): Sand particles are held together by forces so strong that water particles cannot pull them apart.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Unlike sugar, the constituent particles of sand are held together by very strong forces that water particles cannot overcome.
13
Assertion (A): Despite close packing in solids, some interparticle space exists between particles.
Reason (R): The interparticle space in solids is filled with air.
Reason (R): The interparticle space in solids is filled with air.
Answer: (c)
A is true, but R is false. While some space does exist between particles in solids, it is NOT filled with air—these spaces contain nothing at all (vacuum).
14
Assertion (A): When potassium permanganate is added to water, the entire water turns uniformly pink after some time.
Reason (R): Water particles are in constant motion and spread the potassium permanganate particles throughout the liquid.
Reason (R): Water particles are in constant motion and spread the potassium permanganate particles throughout the liquid.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Moving water particles pull out and hit potassium permanganate particles, spreading them uniformly throughout the water.
15
Assertion (A): Potassium permanganate spreads fastest in hot water compared to cold water.
Reason (R): Particles move faster when heat is provided, increasing their thermal energy.
Reason (R): Particles move faster when heat is provided, increasing their thermal energy.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Higher temperature increases particle movement, causing faster mixing and spreading of potassium permanganate in hot water.
❓ Frequently Asked Questions
What is covered in CBSE Class 8 Science Chapter 7 Particulate Nature of Matter?
This chapter covers all key topics from Particulate Nature of Matter as per CBSE 2026-27 syllabus.
Is this Assertion & Reason useful for CBSE board exams?
Yes, designed for CBSE Class 8 board exam preparation covering the complete syllabus.
Are these CBSE Class 8 Science Assertion & Reason updated for 2026-27?
Yes, all content at eBookPublisher is updated as per the latest 2026-27 CBSE syllabus.
How many chapters are in CBSE Class 8 Science?
All chapters of CBSE Class 8 Science are covered at eBookPublisher with free Assertion & Reason for each chapter.
Can I study Particulate Nature of Matter online for free?
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