Welcome To My School Study
Practice Class 9 Science Chapter 2 – Is Matter Around Us Pure? with 5 NCERT-based MCQs on colloids, Tyndall effect, dispersed phase, dispersion medium, emulsions and the classification of colloidal mixtures.
Do You Know
Chapter Information
Subject: Science
Class: 9
Chapter: Is Matter Around Us Pure?
Question Type: Multiple Choice Questions (MCQs)
Practice Set: 6
Difficulty Level: Moderate
Based On: NCERT Syllabus
Introduction
Colloids are mixtures in which very small particles of one substance are distributed throughout another substance. Although colloidal particles are not usually visible individually, they can scatter light and remain dispersed for a long time.
Different types of colloids are classified according to the physical states of their dispersed phase and dispersion medium. Examples include emulsions, aerosols and foams.
This Practice Set 6 focuses on types of colloids, emulsions, aerosols, foams, dispersed phase and dispersion medium.
What You Will Learn
✔ Types of colloids
✔ Dispersed phase
✔ Dispersion medium
✔ Emulsions
✔ Aerosols
✔ Foams
✔ Examples of colloids
✔ Classification of colloidal mixtures
Why This Topic Is Important
Different colloids are present in everyday life. Milk, fog, smoke, shaving cream and butter are familiar examples of colloidal systems.
Understanding their types helps students identify the dispersed phase and dispersion medium and answer classification-based questions from the chapter.
5 MCQs with Answers and Detailed Solutions
Q1. Milk is an example of which type of colloid?
A) Aerosol
B) Emulsion
C) Foam
D) Solid sol
Answer: B) Emulsion
Detailed Solution
Milk is an emulsion, a type of colloid in which one liquid is dispersed in another liquid.
In milk, tiny droplets of fat are dispersed throughout a water-based medium. Therefore, milk is classified as an emulsion.
Exam Tip
Remember: Liquid dispersed in liquid → Emulsion.
Q2. Fog is an example of which type of colloid?
A) Aerosol
B) Emulsion
C) Foam
D) Gel
Answer: A) Aerosol
Detailed Solution
Fog consists of tiny liquid water droplets dispersed in air.
When a liquid is dispersed in a gas, the colloid is called an aerosol.
Therefore, fog is an example of an aerosol.
Exam Tip
Remember: Fog = liquid droplets + air = aerosol.
Q3. Smoke is classified as which type of colloid?
A) Emulsion
B) Aerosol
C) Foam
D) Gel
Answer: B) Aerosol
Detailed Solution
Smoke contains very small solid particles dispersed in a gas, usually air.
A colloid in which solid or liquid particles are dispersed in a gas is called an aerosol.
Therefore, smoke is an aerosol.
Exam Tip
Remember: Smoke = solid particles dispersed in air.
Q4. Which of the following is an example of a foam?
A) Milk
B) Fog
C) Shaving cream
D) Smoke
Answer: C) Shaving cream
Detailed Solution
Shaving cream is a foam in which gas is dispersed in a liquid or semi-solid medium.
Other common examples of foams include soap lather and whipped cream.
Milk is an emulsion, while fog and smoke are aerosols.
Exam Tip
Think foam = gas dispersed in a liquid or solid medium.
Q5. Which pair is correctly matched?
A) Milk → Aerosol
B) Fog → Emulsion
C) Smoke → Aerosol
D) Shaving cream → Emulsion
Answer: C) Smoke → Aerosol
Detailed Solution
Smoke consists of solid particles dispersed in air, so it is classified as an aerosol.
The other pairs are incorrect:
- Milk → Emulsion
- Fog → Aerosol
- Shaving cream → Foam
Correct identification of examples is useful for classification-based MCQs.
Exam Tip
Learn the common examples together: milk → emulsion, fog → aerosol, smoke → aerosol, shaving cream → foam.
Important Formulas & Concepts
This topic does not involve a mathematical formula. The following classification concepts are important.
1. Emulsion
An emulsion is a colloid in which one liquid is dispersed in another liquid.
Example: Milk.
2. Aerosol
An aerosol is a colloidal system in which solid or liquid particles are dispersed in a gas.
Examples: Smoke and fog.
3. Foam
A foam contains gas dispersed in a liquid or solid medium.
Examples: Shaving cream and soap lather.
4. Dispersed Phase
The component present as small particles in a colloid is called the dispersed phase.
5. Dispersion Medium
The component throughout which the dispersed particles are distributed is called the dispersion medium.
6. Important Examples
Milk → Emulsion
Fog → Aerosol
Smoke → Aerosol
Shaving cream → Foam
Related Practice Questions
Q1. Why is milk called an emulsion?
Q2. Why is fog classified as an aerosol?
Q3. Why is smoke an aerosol?
Q4. What is a foam?
Q5. What are dispersed phase and dispersion medium?
Mini Quiz Challenge
Try answering these questions within 60 seconds.
Q1. Milk is an example of:
A) Aerosol
B) Emulsion
C) Foam
D) Suspension
Q2. Fog contains tiny water droplets dispersed in:
A) Water
B) Soil
C) Air
D) Oil
Q3. Smoke contains solid particles dispersed in:
A) Water
B) Air
C) Milk
D) Oil
Q4. Which one is an example of foam?
A) Shaving cream
B) Fog
C) Milk
D) Smoke
Q5. Which pair is correctly matched?
A) Milk → Aerosol
B) Fog → Emulsion
C) Smoke → Aerosol
D) Shaving cream → Emulsion
Exam Tips
✔ Learn the common examples of different types of colloids.
✔ Remember milk → emulsion.
✔ Remember fog and smoke → aerosols.
✔ Remember shaving cream → foam.
✔ Understand the difference between dispersed phase and dispersion medium.
✔ In classification questions, first identify the physical state of the dispersed phase and the medium.
Quick Revision Notes
✔ Emulsion: Liquid dispersed in another liquid.
✔ Milk: Common example of an emulsion.
✔ Aerosol: Solid or liquid particles dispersed in a gas.
✔ Fog: Liquid droplets dispersed in air.
✔ Smoke: Solid particles dispersed in air.
✔ Foam: Gas dispersed in a liquid or solid medium.
✔ Shaving cream: Common example of foam.
✔ Dispersed phase: Particles being distributed.
✔ Dispersion medium: Medium throughout which particles are distributed.
Common Mistakes Students Make
❌ Confusing milk with an aerosol.
❌ Confusing fog with an emulsion.
❌ Forgetting that smoke contains solid particles dispersed in air.
❌ Thinking all colloids are emulsions.
❌ Confusing dispersed phase with dispersion medium.
❌ Assuming that every gas-containing colloid is necessarily a foam.
Key Takeaways
✔ Colloids can be classified according to their dispersed phase and dispersion medium.
✔ Milk is an emulsion.
✔ Fog is an aerosol.
✔ Smoke is an aerosol.
✔ Shaving cream is a foam.
✔ The dispersed phase consists of the distributed particles.
✔ The dispersion medium is the medium in which those particles are distributed.
FAQs
Q. What type of colloid is milk?
Answer:
Milk is an emulsion, in which liquid fat droplets are dispersed in a water-based medium.
Q. Why is fog an aerosol?
Answer:
Fog contains tiny liquid water droplets dispersed in air, so it is classified as an aerosol.
Q. Why is smoke an aerosol?
Answer:
Smoke contains tiny solid particles dispersed in air, making it an aerosol.
Q. What is a foam?
Answer:
A foam is a colloidal system in which gas is dispersed in a liquid or solid medium.
Q. What is the difference between dispersed phase and dispersion medium?
Answer:
The dispersed phase is present as small particles, while the dispersion medium is the substance throughout which those particles are distributed.
Conclusion
Class 9 Science Chapter 2 – Is Matter Around Us Pure? focuses on the classification of colloids and important examples such as emulsions, aerosols and foams.
Learning these examples and understanding the dispersed phase and dispersion medium makes it easier to solve classification-based questions from the chapter.
Related Links
- Class 9 History Chapter 2 Socialism in Europe and Russian Revolution part-1
- Class 9 English Chapter 2 The Pot Maker part-2
- Class 9 Maths Chapter 4 Linear Equations in Two Variables part-10
- Class 9 Science Chapter 2 Is Matter Around Us Pure part-5
- Class 9 Social Science Chapter 1: The French Revolution part-18
- Class 9 English Chapter 2 The Pot Maker part-1
- Class 9 Maths Chapter 4 Linear Equations in Two Variables part-9
- Class 9 Science Chapter 2 Is Matter Around Us Pure part-4
- Class 9 Social Science Chapter 1: The French Revolution part-17
- Class 9 Maths Chapter 4 Linear Equations in Two Variables part-8
- Class 9 Science Chapter 2 Is Matter Around Us Pure PART-3
Latest Posts
- Class 9 English Chapter 2 The Pot Maker
- Class 8 English Chapter 2 A Concrete Example
- Class 10 English Chapter 2 Nelson Mandela: Long Walk to Freedom
- Class 7 English Chapter 2 The Wise Man
- Class 10 Science Chapter 2 Acids, Bases and Salts
Join Our Other Communities
Instagram , Youtube , Facebook
