CBSE Class 9 Science Chapter 5: Exploring Mixtures and their Separation — Assertion & Reason
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The following Assertion and Reason questions are based on Chapter 5: Exploring Mixtures and their Separation from the NCERT Class 9 Science textbook. 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): A sugar solution is a homogeneous mixture.
Reason (R): Dissolved sugar particles remain uniformly distributed throughout the solution.
Reason (R): Dissolved sugar particles remain uniformly distributed throughout the solution.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Uniform composition from one portion to another is the defining feature of a homogeneous mixture.
2
Assertion (A): A heterogeneous mixture does not have uniform composition throughout.
Reason (R): A suspension is a type of heterogeneous mixture.
Reason (R): A suspension is a type of heterogeneous mixture.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. Both statements are true, but naming one heterogeneous type does not explain the general lack of uniformity.
3
Assertion (A): A salt solution can be transparent and does not show a visible light path.
Reason (R): Its dispersed particles are larger than 1000 nm and settle on standing.
Reason (R): Its dispersed particles are larger than 1000 nm and settle on standing.
Answer: (c)
A is true, but R is false. Dissolved particles are extremely small, remain distributed, and do not settle.
4
Assertion (A): Milk is a true solution in which all dispersed particles are smaller than 1 nm.
Reason (R): Milk is a colloid and can scatter a beam of light.
Reason (R): Milk is a colloid and can scatter a beam of light.
Answer: (d)
A is false, but R is true. Milk contains colloidal particles rather than molecular-sized solute particles.
5
Assertion (A): Mass-by-mass percentage compares the mass of solute with the mass of the solution.
Reason (R): It is calculated as mass of solute divided by mass of solvent, multiplied by 100.
Reason (R): It is calculated as mass of solute divided by mass of solvent, multiplied by 100.
Answer: (c)
A is true, but R is false. The denominator must be the total mass of the solution, not merely the mass of the solvent.
6
Assertion (A): Volume-by-volume percentage uses the volume of solute and the total volume of solution.
Reason (R): Solubility is the maximum amount of solute that can dissolve under specified conditions.
Reason (R): Solubility is the maximum amount of solute that can dissolve under specified conditions.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. Both are correct concepts, but the solubility definition does not explain volume percentage.
7
Assertion (A): A saturated solution cannot dissolve more of a given solute at the specified temperature.
Reason (R): Every saturated solution must contain only a very small amount of solute and is therefore dilute.
Reason (R): Every saturated solution must contain only a very small amount of solute and is therefore dilute.
Answer: (c)
A is true, but R is false. Saturation depends on the solubility limit, not on whether the concentration is described as dilute or concentrated.
8
Assertion (A): The solubility of every substance is completely independent of temperature.
Reason (R): The solubility of many solid solutes in water changes when temperature changes.
Reason (R): The solubility of many solid solutes in water changes when temperature changes.
Answer: (d)
A is false, but R is true. Temperature is an important condition when specifying and comparing solubility.
9
Assertion (A): Crystallization can obtain a purer solid from its saturated solution.
Reason (R): On suitable cooling or solvent removal, excess dissolved substance separates as crystals while many impurities remain behind.
Reason (R): On suitable cooling or solvent removal, excess dissolved substance separates as crystals while many impurities remain behind.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Controlled crystal formation separates the desired solid more effectively than simple drying in many cases.
10
Assertion (A): Evaporation occurs at the surface, whereas boiling occurs throughout a liquid at its boiling point.
Reason (R): Distillation includes vaporisation followed by condensation.
Reason (R): Distillation includes vaporisation followed by condensation.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. Both statements are correct, but the description of distillation does not explain the evaporation-boiling distinction.
11
Assertion (A): Simple distillation can separate suitable miscible liquids with sufficiently different boiling points.
Reason (R): The more volatile component vaporises preferentially and is then condensed and collected.
Reason (R): The more volatile component vaporises preferentially and is then condensed and collected.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. The boiling-point difference enables preferential vaporisation and recovery of one liquid.
12
Assertion (A): Paper chromatography separates components because all of them move at exactly the same rate on paper.
Reason (R): Different components travel at different rates because of their differing interactions with the mobile and stationary phases.
Reason (R): Different components travel at different rates because of their differing interactions with the mobile and stationary phases.
Answer: (d)
A is false, but R is true. The different movement rates, not identical rates, produce separation.
13
Assertion (A): A separating funnel can separate two immiscible liquids.
Reason (R): The liquids form layers because of their immiscibility and different densities, allowing the lower layer to be drained first.
Reason (R): The liquids form layers because of their immiscibility and different densities, allowing the lower layer to be drained first.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Layer formation and controlled draining make the technique effective.
14
Assertion (A): Sublimation is the direct change of a solid into vapour without passing through the liquid state.
Reason (R): Deposition is the direct change of vapour back into a solid.
Reason (R): Deposition is the direct change of vapour back into a solid.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. Both definitions are correct, but deposition is the reverse process rather than the explanation for sublimation.
15
Assertion (A): Centrifugation can separate heavier suspended particles from a liquid.
Reason (R): Rapid spinning makes particles remain permanently and uniformly dispersed.
Reason (R): Rapid spinning makes particles remain permanently and uniformly dispersed.
Answer: (c)
A is true, but R is false. Spinning promotes separation according to density instead of preventing it.
16
Assertion (A): Suspension particles remain evenly distributed forever and cannot settle on standing.
Reason (R): Suspension particles are relatively large and commonly settle when the mixture is left undisturbed.
Reason (R): Suspension particles are relatively large and commonly settle when the mixture is left undisturbed.
Answer: (d)
A is false, but R is true. Settling is a characteristic difference between suspensions and stable colloidal dispersions.
17
Assertion (A): Coagulation helps remove fine suspended material from water.
Reason (R): A coagulant causes small particles to clump into larger aggregates that can settle more readily.
Reason (R): A coagulant causes small particles to clump into larger aggregates that can settle more readily.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Increasing the effective particle size promotes settling and subsequent removal.
18
Assertion (A): Colloids are heterogeneous mixtures even when they appear uniform to the naked eye.
Reason (R): Particles in a true solution are generally smaller than 1 nm.
Reason (R): Particles in a true solution are generally smaller than 1 nm.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. Both statements are true, but true-solution particle size does not explain the microscopic heterogeneity of colloids.
19
Assertion (A): Colloids and suspensions can show the Tyndall effect by scattering light.
Reason (R): A true salt solution scatters enough light to make the beam path clearly visible.
Reason (R): A true salt solution scatters enough light to make the beam path clearly visible.
Answer: (c)
A is true, but R is false. Particles in a true solution are too small to produce the visible Tyndall effect.
20
Assertion (A): Ordinary filtration can separate dissolved salt from a salt solution.
Reason (R): Dissolved particles pass through common filter paper with the solvent.
Reason (R): Dissolved particles pass through common filter paper with the solvent.
Answer: (d)
A is false, but R is true. A method such as evaporation, crystallization, or distillation is needed instead.
❓ Frequently Asked Questions
What is covered in CBSE Class 9 Science Chapter 5 Exploring Mixtures and their Separation?
This chapter covers all key topics from Exploring Mixtures and their Separation as per CBSE 2026-27 syllabus.
Is this Assertion & Reason useful for CBSE board exams?
Yes, designed for CBSE Class 9 board exam preparation covering the complete syllabus.
Are these CBSE Class 9 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 9 Science?
All chapters of CBSE Class 9 Science are covered at eBookPublisher with free Assertion & Reason for each chapter.
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