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Practice Class 9 Science Chapter 2 – Is Matter Around Us Pure? with 5 NCERT-based MCQs on solutions, solute, solvent, concentration, suspensions, colloids and the Tyndall effect.
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Chapter Information
Subject: Science
Class: 9
Chapter: Is Matter Around Us Pure?
Question Type: Multiple Choice Questions (MCQs)
Practice Set: 10
Difficulty Level: Moderate
Based On: NCERT Syllabus
Introduction
A mixture contains two or more substances that are physically combined. Mixtures can be classified into different types depending on the size of their particles and their properties.
A solution is a homogeneous mixture in which a substance called the solute dissolves in another substance called the solvent. Suspensions and colloids are other important types of mixtures with different characteristics.
This Practice Set 10 focuses on solutions, solute, solvent, concentration, suspensions, colloids and the Tyndall effect.
What You Will Learn
✔ Solute and solvent
✔ Solutions and their properties
✔ Concentration of a solution
✔ Suspensions
✔ Colloids
✔ Tyndall effect
✔ Difference between solutions, colloids and suspensions
Why This Topic Is Important
Understanding different types of mixtures is an important part of Is Matter Around Us Pure? Students need to identify whether a mixture is a solution, suspension or colloid based on its properties.
These concepts are useful for answering questions related to particle size, visibility, stability, filtration and scattering of light.
5 MCQs with Answers and Detailed Solutions
Q1. In a solution of sugar in water, which substance acts as the solvent?
A) Sugar
B) Water
C) Both sugar and water
D) Neither sugar nor water
Answer: B) Water
Detailed Solution
In a solution, the substance that dissolves the solute is called the solvent.
In a sugar solution, sugar is the solute because it gets dissolved, while water is the solvent because it dissolves the sugar.
Therefore, water acts as the solvent.
Exam Tip
Remember:
Sugar + Water → Sugar = Solute, Water = Solvent
Q2. Which of the following is a characteristic property of a suspension?
A) Its particles cannot be seen even with a microscope
B) Its particles settle down when left undisturbed
C) It is always transparent
D) Its particles never scatter light
Answer: B) Its particles settle down when left undisturbed
Detailed Solution
A suspension is a heterogeneous mixture containing sufficiently large insoluble particles.
The particles of a suspension can generally be seen and settle down when the suspension is left undisturbed. They can also be separated from the mixture by filtration.
Therefore, the correct answer is B) Its particles settle down when left undisturbed.
Exam Tip
Remember the key feature:
Suspension → particles settle down on standing.
Q3. Which phenomenon is observed when a beam of light becomes visible after passing through a colloidal solution?
A) Sedimentation
B) Filtration
C) Tyndall effect
D) Evaporation
Answer: C) Tyndall effect
Detailed Solution
The scattering of a beam of light by colloidal particles is known as the Tyndall effect.
Because colloidal particles are large enough to scatter light, the path of the light beam becomes visible when it passes through a colloid.
For example, the path of a beam of sunlight entering a dusty room may become visible due to scattering by suspended particles.
Therefore, the correct answer is C) Tyndall effect.
Exam Tip
Remember:
Scattering of light by colloidal particles → Tyndall effect
Q4. Which of the following is a homogeneous mixture?
A) Sand and water
B) Oil and water
C) Salt solution
D) Soil
Answer: C) Salt solution
Detailed Solution
A homogeneous mixture has a uniform composition throughout.
When salt dissolves completely in water, the salt particles are uniformly distributed throughout the solution. Therefore, salt solution is a homogeneous mixture.
Sand and water, oil and water, and soil are heterogeneous mixtures because their components are not uniformly distributed.
Therefore, the correct answer is C) Salt solution.
Exam Tip
Remember:
Completely dissolved substance + solvent → usually a homogeneous solution.
Q5. What happens to the concentration of a solution when more solvent is added to it while the amount of solute remains unchanged?
A) It increases
B) It decreases
C) It remains exactly the same
D) The solute disappears
Answer: B) It decreases
Detailed Solution
The concentration of a solution depends on the amount of solute present in a given amount of solution.
When more solvent is added while the amount of solute remains unchanged, the solute becomes more diluted. Therefore, the concentration decreases.
For example, if water is added to a concentrated salt solution, the amount of salt remains the same but it becomes distributed in a larger quantity of solution.
Therefore, the correct answer is B) It decreases.
Exam Tip
Remember:
More solvent + same solute → dilution → concentration decreases.
Important Concepts
This topic mainly involves understanding the properties and classification of mixtures.
1. Solute
The substance that is dissolved in a solution is called the solute.
Example: Sugar in sugar solution.
2. Solvent
The substance in which the solute dissolves is called the solvent.
Example: Water in sugar solution.
3. Solution
A solution is a homogeneous mixture of two or more substances.
Its particles are very small and generally cannot be seen separately.
4. Suspension
A suspension is a heterogeneous mixture containing sufficiently large insoluble particles.
Its particles can settle down when the mixture is left undisturbed.
5. Colloid
A colloid is a heterogeneous mixture in which particles are intermediate in size between those of a true solution and a suspension.
Colloidal particles can scatter light and show the Tyndall effect.
6. Tyndall Effect
The scattering of light by colloidal particles is called the Tyndall effect.
Related Practice Questions
Q1. What is a solute?
Q2. What is a solvent?
Q3. What is the difference between a solution and a suspension?
Q4. What is the Tyndall effect?
Q5. Why does the concentration decrease when more solvent is added to a solution?
Mini Quiz Challenge
Try answering these questions within 60 seconds.
Q1. In a salt solution, salt is the:
A) Solvent
B) Solute
C) Suspension
D) Colloid
Q2. Which type of mixture has particles that settle down on standing?
A) Solution
B) Suspension
C) Pure substance
D) Homogeneous mixture
Q3. The Tyndall effect is associated mainly with:
A) Colloids
B) Pure water
C) Crystals
D) Metals
Q4. Which of the following is a homogeneous mixture?
A) Muddy water
B) Sand and water
C) Salt solution
D) Soil
Q5. Adding more solvent to a solution generally makes it:
A) More concentrated
B) More dilute
C) A pure substance
D) A suspension
Exam Tips
✔ Remember the difference between solute and solvent.
✔ A solution is a homogeneous mixture.
✔ Suspension particles can settle down on standing.
✔ Colloidal particles show the Tyndall effect.
✔ Adding more solvent generally decreases concentration.
✔ Learn the differences between solution, colloid and suspension.
Quick Revision Notes
✔ Solute: Substance that gets dissolved.
✔ Solvent: Substance that dissolves the solute.
✔ Solution: Homogeneous mixture of two or more substances.
✔ Suspension: Heterogeneous mixture with relatively large insoluble particles.
✔ Colloid: Mixture containing intermediate-sized particles.
✔ Tyndall Effect: Scattering of light by colloidal particles.
✔ Salt in water: Salt is the solute and water is the solvent.
✔ Adding solvent: Dilutes the solution and decreases its concentration.
Common Mistakes Students Make
❌ Confusing solute with solvent.
❌ Thinking that every mixture is homogeneous.
❌ Forgetting that suspension particles settle down when left undisturbed.
❌ Confusing the Tyndall effect with sedimentation.
❌ Thinking that adding more solvent increases concentration.
❌ Treating colloids as true solutions.
Key Takeaways
✔ A solution is a homogeneous mixture.
✔ The solute is dissolved in the solvent.
✔ Suspensions contain relatively large insoluble particles that can settle down.
✔ Colloids contain particles that can scatter light.
✔ The scattering of light by colloidal particles is called the Tyndall effect.
✔ Adding more solvent to a solution decreases its concentration.
✔ Understanding the properties of solutions, colloids and suspensions helps in identifying different types of mixtures.
FAQs
Q. What is a solute?
Answer:
A solute is the substance that dissolves in a solvent to form a solution.
Q. What is a solvent?
Answer:
A solvent is the substance in which the solute dissolves.
Q. Is a salt solution homogeneous?
Answer:
Yes. A salt solution is a homogeneous mixture when the salt has completely dissolved in water.
Q. What is the Tyndall effect?
Answer:
The Tyndall effect is the scattering of light by colloidal particles, which can make the path of a light beam visible.
Q. What happens when more solvent is added to a solution?
Answer:
The solution becomes more dilute, so its concentration decreases if the amount of solute remains unchanged.
Conclusion
Class 9 Science Chapter 2 – Is Matter Around Us Pure? focuses on important concepts related to solutions, solute, solvent, concentration, suspensions, colloids and the Tyndall effect.
Understanding the characteristics of different mixtures helps students identify whether a mixture is homogeneous or heterogeneous and select the correct concept for different examination questions.
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