Short Intro

“Exploring Mixtures and Their Separation” chapter explains different types of mixtures, concentration of solutions, solubility, crystallization, distillation, chromatography, colloids, suspensions, and various separation techniques used in daily life and industries. This chapter is highly important for conceptual understanding and exam preparation. Complete step-by-step solutions are provided below in Unicode format for uploading on www.mymockmate.com.

Quick Information Box

Topic	Details
Chapter Name	Exploring Mixtures and Their Separation
Subject	Science
Grade	Class 9
Main Topics	Solutions, Colloids, Separation Techniques
Important Concepts	Distillation, Crystallization, Tyndall Effect
Exam Importance	Very High
Numerical Problems	Included

Concepts Used (Topics Covered)

• Homogeneous and heterogeneous mixtures
• Solutions, suspensions and colloids
• Concentration of solutions
• Solubility and saturated solutions
• Crystallization
• Distillation and fractional distillation
• Paper chromatography
• Separating funnel
• Sublimation
• Centrifugation
• Coagulation
• Tyndall effect

Important Formulas

Mass by Mass Percentage

$\%\,(m/m)=\frac{\text{Mass of solute}}{\text{Mass of solution}}\times100$%(m/m)=Mass of solutionMass of solute​×100

Mass by Volume Percentage

$\%\,(m/v)=\frac{\text{Mass of solute}}{\text{Volume of solution}}\times100$%(m/v)=Volume of solutionMass of solute​×100

Volume by Volume Percentage

$\%\,(v/v)=\frac{\text{Volume of solute}}{\text{Volume of solution}}\times100$%(v/v)=Volume of solutionVolume of solute​×100

Questions & Step-by-step Solutions with Explanation

Question 1

Correct classification of mixtures

Answer

Correct Option: (iv)

Explanation

• Muddy water → Heterogeneous
• Milk → Heterogeneous (colloid)
• Blood → Heterogeneous (colloid)
• Brass → Homogeneous alloy

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Question 2

Which mixtures show Tyndall Effect?

Answer

Correct Option: (iii) a and c

Explanation

• Air + dust particles → Shows Tyndall effect
• Starch + water → Colloid, shows Tyndall effect
• Copper sulfate solution → True solution, no Tyndall effect
• Acetone + water → Homogeneous solution, no Tyndall effect

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Question 3

Complete Table 5.2

Type	Properties	Examples
Solution	Small particles, transparent, does not scatter light	Salt solution, Brass
Suspension	Large particles, settles down, separable by filtration	Sand in water, Mud
Colloid	Medium particles, scatters light, does not settle	Milk, Smoke, Butter

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Question 4 (i)

Cake recipe concentration

Given

Sugar = 75 g
Flour = 420 g
Sodium hydrogencarbonate = 5 g

Total Mass

$420+75+5=500\,g$420+75+5=500g

Sugar concentration

$\frac{75}{500}\times100=15\%$50075​×100=15%

Flour concentration

$\frac{420}{500}\times100=84\%$500420​×100=84%

Sodium hydrogencarbonate concentration

$\frac{5}{500}\times100=1\%$5005​×100=1%

Answer

• Sugar = 15% m/m
• Flour = 84% m/m
• Sodium hydrogencarbonate = 1% m/m

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Question 4 (ii)

Brass alloy composition

Given

Copper = 70%

Total brass = 120 g

Copper quantity

$\frac{70}{100}\times120=84\,g$10070​×120=84g

Zinc quantity

$120-84=36\,g$120−84=36g

Answer

• Copper = 84 g
• Zinc = 36 g

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Question 5

Cooking oil and water separation

Answer

Yes, oil forms a separate upper layer because it is less dense than water.

Method Used

Separating funnel

Explanation

• Water settles at bottom
• Oil remains on top
• Open stopcock to separate water first

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Question 6

Assertion-Reason

Answer

Correct Option: (iii)

Explanation

Assertion is true because solutions do not scatter light.

Reason is false because solution particles are extremely small.

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Question 7

Separation techniques

Mixture	Method	Reason
Mud from muddy water	Filtration	Insoluble particles
Plasma from blood	Centrifugation	Density difference
Naphthalene and sand	Sublimation	Naphthalene sublimes
Chalk powder and salt	Dissolve + filtration + evaporation	Salt dissolves
Salt and water	Evaporation	Water evaporates
Oil and water	Separating funnel	Immiscible liquids
Flower pigments	Chromatography	Different movement rates

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Question 8

Separation of miscible liquids A and B

Given

• Boiling point of A = 60°C
• Boiling point of B = 90°C

Answer

Distillation method is used.

Explanation

Difference in boiling points is 30°C which is greater than 25°C.

Liquid A vaporises first and condenses separately.

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Question 9

Comparison

Process	Purpose
Evaporation	Obtain dissolved solid
Crystallization	Obtain pure crystals
Distillation	Separate liquids and recover solvent

Preferred Situations

• Evaporation → Salt from seawater
• Crystallization → Pure copper sulfate crystals
• Distillation → Acetone-water separation

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Question 10

Blood as colloid

(i) If blood behaved like suspension

Blood cells would settle down causing blockage and improper circulation.

(ii) Components

• Dispersed phase → Blood cells
• Dispersion medium → Plasma

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Question 11

Correct sequence of techniques

Answer

1. Sublimation
2. Dissolution and filtration
3. Evaporation/crystallization

Explanation

• Naphthalene separated first by sublimation
• Salt dissolved in water
• Sand filtered out
• Salt recovered by evaporation

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Question 12

Why is distillation effective for water and acetone?

Answer

Because their boiling points differ greatly.

• Acetone boils at 56°C
• Water boils at 100°C

Acetone vaporises first and gets condensed separately.

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Question 13 (i)

Potassium nitrate required

Given

Solubility at 40°C:
62 g per 100 g water

For 50 g water:
$\frac{62}{100}\times50=31\,g$10062​×50=31g

Answer

31 g potassium nitrate

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Question 13 (ii)

Observation on cooling

Answer

Potassium chloride crystals will separate out because solubility decreases on cooling.

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Question 13 (iii)

Effect of temperature

Answer

Solubility generally increases with temperature.

Potassium nitrate shows maximum increase in solubility.

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Question 14 (i)

Concentration of sugar solutions

Student A

$\frac{20}{100}\times100=20\%$10020​×100=20%

Student B

$\frac{20}{120}\times100\approx16.67\%$12020​×100≈16.67%

Student C

$\frac{30}{110}\times100\approx27.27\%$11030​×100≈27.27%

Answer

• A = 20%
• B = 16.67%
• C = 27.27%

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Question 14 (ii)

Most concentrated solution

Answer

Student C’s solution is most concentrated because it has highest percentage of sugar.

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Question 15

(i) Technique S

Answer

Distillation

(ii) Apparatus labels

• A → Thermometer
• B → Condenser
• C → Receiver flask

(iii) Mixtures separated

Answer

• Water–acetone
• Alcohol–chloroform

Because their boiling points are sufficiently different.

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Common Mistakes

• Confusing colloids with solutions
• Writing filtration instead of distillation
• Using wrong percentage formula
• Forgetting boiling point differences
• Confusing sublimation with evaporation

Exam Tips

• Learn all separation methods with examples.
• Practice numerical problems on concentration.
• Revise Tyndall effect carefully.
• Remember examples of colloids and suspensions.
• Draw labelled diagrams for distillation and separating funnel.

Practice MCQs

1. Which mixture shows Tyndall effect?

A. Sugar solution
B. Salt solution
C. Milk
D. Acetone and water

Answer

C. Milk

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2. Which process separates acetone and water?

A. Filtration
B. Distillation
C. Sublimation
D. Sedimentation

Answer

B. Distillation

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3. Which substance sublimes?

A. Sand
B. Salt
C. Camphor
D. Chalk powder

Answer

C. Camphor

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4. Which method separates plasma from blood?

A. Filtration
B. Distillation
C. Centrifugation
D. Evaporation

Answer

C. Centrifugation

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FAQ Section

Q1. What is a homogeneous mixture?

A mixture having uniform composition throughout.

Q2. What is Tyndall effect?

Scattering of light by colloidal particles.

Q3. Which method separates immiscible liquids?

Separating funnel method.

Q4. What is sublimation?

Direct conversion of solid into vapour without becoming liquid.

Q5. Why is distillation used?

To separate miscible liquids with different boiling points.

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