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Practice Class 9 Science Chapter 2 – Is Matter Around Us Pure? with 5 NCERT-based MCQs on saturated solutions, solubility, concentration, physical and chemical changes, pure substances and mixtures.
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Chapter Information
Subject: Science
Class: 9
Chapter: Is Matter Around Us Pure?
Question Type: Multiple Choice Questions (MCQs)
Practice Set: 11
Difficulty Level: Moderate
Based On: NCERT Syllabus
Introduction
The substances around us can be classified as pure substances or mixtures. A pure substance contains only one kind of particles, whereas a mixture contains two or more substances physically combined.
The properties of solutions also depend on factors such as the amount of solute, amount of solvent and temperature. A solution may be unsaturated or saturated depending on how much solute can dissolve in a given amount of solvent at a particular temperature.
This Practice Set 11 focuses on saturated and unsaturated solutions, solubility, concentration, pure substances, mixtures and physical and chemical changes.
What You Will Learn
✔ Saturated solutions
✔ Unsaturated solutions
✔ Solubility
✔ Concentration of solutions
✔ Pure substances
✔ Mixtures
✔ Physical changes
✔ Chemical changes
Why This Topic Is Important
Understanding the difference between pure substances and mixtures is fundamental to Chapter 2.
Students should also understand how solubility and concentration affect solutions and how physical and chemical changes differ. These concepts are frequently used in conceptual questions and examination-based MCQs.
5 MCQs with Answers and Detailed Solutions
Q1. A solution that contains the maximum amount of solute that can dissolve in a given amount of solvent at a particular temperature is called:
A) Dilute solution
B) Unsaturated solution
C) Saturated solution
D) Colloidal solution
Answer: C) Saturated solution
Detailed Solution
A saturated solution contains the maximum amount of solute that can dissolve in a given amount of solvent at a particular temperature.
If additional solute is added to a saturated solution under the same conditions, it generally remains undissolved.
Therefore, the correct answer is C) Saturated solution.
Exam Tip
Remember:
Maximum solute dissolved at a given temperature → Saturated solution
Q2. A solution that can dissolve more solute at a given temperature is called:
A) Saturated solution
B) Unsaturated solution
C) Suspension
D) Colloid
Answer: B) Unsaturated solution
Detailed Solution
An unsaturated solution contains less solute than the maximum amount that can dissolve at a particular temperature.
Therefore, it is capable of dissolving additional solute under the same conditions.
For example, if more sugar can still dissolve in a sugar-water solution at a given temperature, the solution is unsaturated.
Therefore, the correct answer is B) Unsaturated solution.
Exam Tip
Remember:
Can dissolve more solute → Unsaturated solution
Q3. The maximum amount of a substance that can dissolve in a given amount of solvent at a particular temperature is related to:
A) Solubility
B) Density only
C) Colour
D) Melting point only
Answer: A) Solubility
Detailed Solution
Solubility refers to the maximum amount of a solute that can dissolve in a given amount of solvent at a particular temperature to form a saturated solution.
The solubility of different substances can vary.
For example, different solids have different abilities to dissolve in water.
Therefore, the correct answer is A) Solubility.
Exam Tip
Remember:
Maximum amount that dissolves at a particular temperature → Solubility
Q4. Which of the following is a pure substance?
A) Air
B) Soil
C) Distilled water
D) Salt solution
Answer: C) Distilled water
Detailed Solution
A pure substance consists of only one kind of particles and has a fixed composition.
Distilled water is considered a pure substance because it consists essentially of only water molecules.
Air, soil and salt solution are mixtures because they contain more than one substance.
Therefore, the correct answer is C) Distilled water.
Exam Tip
Remember:
Pure substance → fixed composition and one kind of particles.
Q5. Which of the following represents a chemical change?
A) Melting of ice
B) Dissolving sugar in water
C) Cutting paper
D) Rusting of iron
Answer: D) Rusting of iron
Detailed Solution
A chemical change results in the formation of one or more new substances with different chemical properties.
When iron rusts, iron reacts with oxygen and moisture to form iron oxide, commonly called rust. A new substance is formed.
Melting ice, dissolving sugar in water and cutting paper are physical changes because no new substance is formed in these processes.
Therefore, the correct answer is D) Rusting of iron.
Exam Tip
Remember:
Formation of a new substance → Chemical change
Important Concepts
1. Saturated Solution
A saturated solution contains the maximum amount of solute that can dissolve in a given amount of solvent at a particular temperature.
2. Unsaturated Solution
An unsaturated solution contains less solute than its maximum dissolving capacity and can dissolve more solute.
3. Solubility
Solubility is the amount of solute that can dissolve in a given amount of solvent at a particular temperature to form a saturated solution.
4. Pure Substance
A pure substance consists of only one kind of particles and has a fixed composition.
Examples include:
- Oxygen
- Copper
- Distilled water
5. Mixture
A mixture contains two or more substances physically combined.
Examples include:
- Air
- Soil
- Salt solution
6. Physical and Chemical Changes
A physical change generally does not produce a new substance.
A chemical change results in the formation of one or more new substances.
Related Practice Questions
Q1. What is a saturated solution?
Q2. What is an unsaturated solution?
Q3. What is meant by solubility?
Q4. How is a pure substance different from a mixture?
Q5. What is the difference between a physical and chemical change?
Mini Quiz Challenge
Try answering these questions within 60 seconds.
Q1. A solution that can dissolve additional solute is:
A) Saturated
B) Unsaturated
C) Colloidal
D) Suspension
Q2. The maximum amount of solute that can dissolve in a solvent at a particular temperature is related to:
A) Solubility
B) Density
C) Colour
D) Volume only
Q3. Which is a pure substance?
A) Air
B) Soil
C) Copper
D) Lemonade
Q4. Which process forms a new substance?
A) Melting wax
B) Cutting wood
C) Rusting iron
D) Dissolving salt
Q5. A saturated solution contains:
A) No solute
B) Maximum dissolved solute at a given temperature
C) Only solvent
D) Only undissolved solute
Exam Tips
✔ Learn the definitions of saturated and unsaturated solutions.
✔ Remember that solubility depends on the substance, solvent and temperature.
✔ A pure substance has a fixed composition.
✔ Air and soil are examples of mixtures.
✔ Formation of a new substance indicates a chemical change.
✔ Melting and dissolving are generally physical changes when no new substance is formed.
Quick Revision Notes
✔ Saturated solution: Contains maximum dissolved solute at a particular temperature.
✔ Unsaturated solution: Can dissolve more solute at the same temperature.
✔ Solubility: Maximum amount of solute that can dissolve in a given amount of solvent at a particular temperature.
✔ Pure substance: Contains only one kind of particles.
✔ Mixture: Contains two or more substances.
✔ Physical change: No new substance is formed.
✔ Chemical change: One or more new substances are formed.
✔ Rusting of iron: Chemical change.
Common Mistakes Students Make
❌ Thinking every solution is saturated.
❌ Confusing solubility with concentration.
❌ Considering air a pure substance.
❌ Thinking every change in appearance is a chemical change.
❌ Forgetting that a chemical change involves the formation of a new substance.
Key Takeaways
✔ A saturated solution contains the maximum amount of dissolved solute at a particular temperature.
✔ An unsaturated solution can dissolve additional solute.
✔ Solubility describes the dissolving capacity of a solute in a solvent under specified conditions.
✔ Pure substances have fixed composition.
✔ Mixtures contain two or more substances.
✔ Physical changes do not form new substances, while chemical changes do.
✔ Rusting of iron is an example of a chemical change.
FAQs
Q. What is a saturated solution?
Answer:
A saturated solution contains the maximum amount of solute that can dissolve in a given amount of solvent at a particular temperature.
Q. What is an unsaturated solution?
Answer:
An unsaturated solution contains less solute than its maximum dissolving capacity and can dissolve more solute at that temperature.
Q. What is solubility?
Answer:
Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a particular temperature.
Q. Is distilled water a pure substance?
Answer:
Yes. Distilled water is considered a pure substance because it has essentially one kind of constituent, water molecules.
Q. Why is rusting a chemical change?
Answer:
Rusting is a chemical change because iron reacts with oxygen and moisture to form a new substance called rust.
Conclusion
Class 9 Science Chapter 2 – Is Matter Around Us Pure? covers important concepts related to saturated and unsaturated solutions, solubility, pure substances, mixtures and physical and chemical changes.
A clear understanding of these concepts helps students distinguish different types of substances and solutions and answer conceptual questions accurately in examinations.
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