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Practice Class 9 Science Chapter 2 – Is Matter Around Us Pure? with 5 NCERT-based MCQs on pure substances, mixtures, homogeneous and heterogeneous mixtures, solutions, solute and solvent, with answers and detailed explanations.
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Chapter Information
Subject: Science
Class: 9
Chapter: Is Matter Around Us Pure?
Question Type: Multiple Choice Questions (MCQs)
Practice Set: 1
Difficulty Level: Easy to Moderate
Based On: NCERT Syllabus
Introduction
Everything around us is made up of matter, but all matter is not necessarily pure. Some substances contain only one kind of particles, while others contain two or more substances mixed together.
In this chapter, students learn about pure substances, mixtures, solutions, solutes, solvents, homogeneous mixtures and heterogeneous mixtures.
This Practice Set 1 focuses on the basic concepts needed to understand how matter can be classified as a pure substance or a mixture.
What You Will Learn
✔ Meaning of a pure substance
✔ Meaning of a mixture
✔ Homogeneous mixtures
✔ Heterogeneous mixtures
✔ Solutions
✔ Solute and solvent
✔ Difference between pure substances and mixtures
✔ Basic classification of matter
Why This Topic Is Important
The concepts of pure substances and mixtures are fundamental to understanding the composition of matter.
Many substances we encounter in everyday life, such as air, salt solution, soil and milk, contain more than one component. Understanding their classification helps students identify whether a substance is pure or a mixture.
These basic concepts also help students understand the later topics of the chapter, including suspensions, colloids and separation techniques.
5 MCQs with Answers and Detailed Solutions
Q1. Which of the following is an example of a pure substance?
A) Air
B) Soil
C) Copper
D) Salt solution
Answer: C) Copper
Detailed Solution
A pure substance contains only one kind of particles and has a fixed composition.
Copper is an element and consists of only one type of atom. Therefore, copper is considered a pure substance.
Air, soil and salt solution contain more than one component and are therefore mixtures.
Exam Tip
Remember that elements and compounds are pure substances, while mixtures contain two or more substances.
Q2. Which of the following is a homogeneous mixture?
A) Soil
B) Sand and water
C) Salt solution
D) Oil and water
Answer: C) Salt solution
Detailed Solution
A homogeneous mixture has a uniform composition throughout the mixture.
When salt dissolves completely in water, the salt particles are distributed uniformly throughout the solution. Therefore, salt solution is a homogeneous mixture.
Soil, sand and water, and oil and water have non-uniform compositions and are examples of heterogeneous mixtures.
Exam Tip
The key word for a homogeneous mixture is “uniform composition.”
Q3. In a salt solution, what is the role of water?
A) Solute
B) Solvent
C) Mixture
D) Suspension
Answer: B) Solvent
Detailed Solution
A solution is a homogeneous mixture of two or more components.
The component that gets dissolved is called the solute, while the component in which the solute dissolves is called the solvent.
In a salt solution:
- Salt → Solute
- Water → Solvent
Therefore, water acts as the solvent.
Exam Tip
Remember: Solute dissolves; solvent does the dissolving.
Q4. Which statement correctly describes a heterogeneous mixture?
A) It has a uniform composition throughout.
B) It contains only one type of particle.
C) Its components are not uniformly distributed.
D) It always has a fixed composition.
Answer: C) Its components are not uniformly distributed.
Detailed Solution
A heterogeneous mixture does not have a uniform composition throughout.
Its different components are not evenly distributed and may sometimes be distinguished from one another.
For example, soil contains different components such as sand, clay, organic matter and small rocks.
Therefore, a heterogeneous mixture has a non-uniform composition.
Exam Tip
If the composition is not uniform throughout, think heterogeneous mixture.
Q5. Which of the following correctly represents the relationship between a solute and a solvent?
A) Solute dissolves the solvent.
B) Solvent is always present in solid form.
C) Solute is dissolved in the solvent.
D) Solute and solvent are always present in equal amounts.
Answer: C) Solute is dissolved in the solvent.
Detailed Solution
A solution contains a solute and a solvent.
The solute is the component that gets dissolved, whereas the solvent is the component in which the solute dissolves.
For example, in a sugar solution:
- Sugar → Solute
- Water → Solvent
The solute and solvent do not have to be present in equal amounts.
Exam Tip
In a solution, the solute is dissolved in the solvent.
Important Formulas & Concepts
This part of the chapter mainly focuses on scientific concepts rather than mathematical formulas.
1. Pure Substance
A pure substance contains only one kind of particles and has a fixed composition.
Examples: Copper, oxygen and distilled water.
2. Mixture
A mixture contains two or more substances physically combined in variable proportions.
3. Homogeneous Mixture
A mixture having a uniform composition throughout is called a homogeneous mixture.
Example: Salt solution.
4. Heterogeneous Mixture
A mixture having a non-uniform composition is called a heterogeneous mixture.
Examples: Soil, oil and water.
5. Solution
A solution is a homogeneous mixture of two or more components.
6. Solute
The substance that gets dissolved in a solution is called the solute.
7. Solvent
The substance in which the solute dissolves is called the solvent.
8. Basic Relationship
Solution = Solute + Solvent
Related Practice Questions
Q1. What is meant by a pure substance?
Q2. Give one example of a homogeneous mixture.
Q3. Give one example of a heterogeneous mixture.
Q4. What is the difference between a solute and a solvent?
Q5. Why is salt solution considered a homogeneous mixture?
Mini Quiz Challenge
Try answering these questions within 60 seconds.
Q1. Which one is a pure substance?
A) Air
B) Copper
C) Soil
D) Lemonade
Q2. Which one is a homogeneous mixture?
A) Soil
B) Salt solution
C) Sand and water
D) Oil and water
Q3. In a sugar solution, sugar is the:
A) Solvent
B) Solute
C) Suspension
D) Colloid
Q4. Which mixture has a non-uniform composition?
A) Homogeneous mixture
B) Pure substance
C) Heterogeneous mixture
D) Solution
Q5. Water in a salt solution generally acts as the:
A) Solute
B) Solvent
C) Residue
D) Suspension
Exam Tips
✔ Learn the definitions of pure substance, mixture, solution, solute and solvent.
✔ Remember the difference between homogeneous and heterogeneous mixtures.
✔ Learn common examples of pure substances and mixtures.
✔ Remember that in a salt solution, salt is the solute and water is the solvent.
✔ Focus on the terms uniform composition and non-uniform composition because they are commonly used in MCQs.
Quick Revision Notes
✔ Pure substance: Contains only one kind of particles and has a fixed composition.
✔ Mixture: Contains two or more substances.
✔ Homogeneous mixture: Uniform composition throughout.
✔ Heterogeneous mixture: Non-uniform composition.
✔ Solution: A homogeneous mixture.
✔ Solute: Substance that gets dissolved.
✔ Solvent: Substance in which the solute dissolves.
✔ Salt solution: Salt = solute, water = solvent.
✔ Soil: Example of a heterogeneous mixture.
✔ Air: Example of a homogeneous mixture of gases.
Common Mistakes Students Make
❌ Thinking every homogeneous mixture is a pure substance.
❌ Confusing solute with solvent.
❌ Thinking the solute is always present in a larger amount.
❌ Assuming that all mixtures have a non-uniform composition.
❌ Forgetting that a solution is a homogeneous mixture.
❌ Confusing salt with water in a salt solution.
❌ Thinking that a mixture has a fixed composition like a pure substance.
Key Takeaways
✔ Matter can exist as pure substances or mixtures.
✔ Pure substances have a fixed composition.
✔ Mixtures contain two or more components.
✔ Homogeneous mixtures have uniform composition.
✔ Heterogeneous mixtures have non-uniform composition.
✔ A solution is a homogeneous mixture.
✔ The dissolved component is called the solute.
✔ The component in which the solute dissolves is called the solvent.
✔ Salt solution is a common example of a homogeneous mixture.
FAQs
Q. What is a pure substance?
Answer:
A pure substance contains only one kind of particles and has a fixed composition.
Q. What is a mixture?
Answer:
A mixture is formed when two or more substances are physically combined in variable proportions.
Q. What is a homogeneous mixture?
Answer:
A homogeneous mixture has a uniform composition throughout its entire volume.
Q. What is a heterogeneous mixture?
Answer:
A heterogeneous mixture has a non-uniform composition, and its components may be distinguishable.
Q. What are solute and solvent?
Answer:
The substance that gets dissolved is called the solute, while the substance in which it dissolves is called the solvent.
Q. Is salt solution a pure substance?
Answer:
No. Salt solution is a homogeneous mixture because it contains salt and water uniformly mixed together.
Conclusion
Class 9 Science Chapter 2 – Is Matter Around Us Pure? covers the fundamental concepts of pure substances, mixtures, homogeneous mixtures, heterogeneous mixtures, solutions, solutes and solvents.
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