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Practice Class 9 Science Chapter 2 – Is Matter Around Us Pure? with 5 NCERT-based MCQs on solutions, solubility, saturated and unsaturated solutions, concentration and the effect of temperature on solubility.
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Chapter Information
Subject: Science
Class: 9
Chapter: Is Matter Around Us Pure?
Question Type: Multiple Choice Questions (MCQs)
Practice Set: 2
Difficulty Level: Easy to Moderate
Based On: NCERT Syllabus
Introduction
A solution is a homogeneous mixture formed when one or more substances dissolve in another substance. The amount of solute present in a solution and its ability to dissolve are important properties of solutions.
In this Practice Set 2, we focus on solubility, saturated and unsaturated solutions, concentration of solutions and the effect of temperature on solubility.
These concepts are important for understanding how solutions behave under different conditions.
What You Will Learn
✔ Meaning of solubility
✔ Saturated solutions
✔ Unsaturated solutions
✔ Concentration of a solution
✔ Effect of temperature on solubility
✔ Solute and solvent
✔ Basic properties of solutions
Why This Topic Is Important
Solutions are commonly encountered in everyday life, such as sugar dissolved in water or salt dissolved in water.
Understanding solubility and concentration helps students explain why different amounts of substances can dissolve in a solvent and how conditions such as temperature can affect the amount of solute that dissolves.
These concepts are also useful for solving numerical and conceptual questions based on solutions.
5 MCQs with Answers and Detailed Solutions
Q1. What is meant by the solubility of a substance?
A) The amount of solvent present in a solution
B) The maximum amount of solute that can dissolve in a given amount of solvent at a specified temperature
C) The total mass of a solution
D) The amount of solvent that evaporates
Answer: B) The maximum amount of solute that can dissolve in a given amount of solvent at a specified temperature
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.
For example, water can dissolve only a certain maximum amount of salt at a particular temperature.
When this maximum amount has dissolved, the solution becomes saturated.
Exam Tip
Remember the key words: maximum amount of solute + given amount of solvent + specified temperature.
Q2. A solution that contains the maximum amount of solute that can dissolve at a given temperature is called:
A) Unsaturated solution
B) Dilute solution
C) Saturated solution
D) Suspension
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, it will not dissolve under the same conditions and may remain undissolved.
Exam Tip
Saturated = maximum solute dissolved at the given temperature.
Q3. Which statement correctly describes an unsaturated solution?
A) It cannot dissolve any more solute at the given temperature.
B) It contains no solvent.
C) It can dissolve more solute at the given temperature.
D) It always contains an equal amount of solute and solvent.
Answer: C) It can dissolve more solute at the given temperature.
Detailed Solution
An unsaturated solution contains less solute than the maximum amount that can dissolve in the solvent at a particular temperature.
Therefore, more solute can still dissolve in an unsaturated solution under the same conditions.
Exam Tip
Unsaturated = more solute can still dissolve.
Q4. Which factor can affect the solubility of many solid substances in water?
A) Temperature
B) Shape of the container only
C) Colour of the solute
D) Colour of the solvent
Answer: A) Temperature
Detailed Solution
The solubility of many solid substances in water changes with temperature.
For many solids, solubility increases when temperature increases, although the exact effect depends on the substance.
Therefore, temperature is an important factor affecting the solubility of solids.
Exam Tip
Do not assume that temperature affects every substance in exactly the same way. The effect depends on the nature of the solute.
Q5. Which statement about concentration is correct?
A) Concentration describes the amount of solute present in a given amount of solution.
B) Concentration is always equal to the mass of solvent.
C) Concentration does not depend on the amount of solute.
D) Concentration can only be expressed for pure substances.
Answer: A) Concentration describes the amount of solute present in a given amount of solution.
Detailed Solution
The concentration of a solution indicates how much solute is present in a given amount of solution.
A solution containing a relatively larger amount of solute is more concentrated than a solution containing a smaller amount of the same solute under comparable conditions.
Concentration can be expressed in different ways depending on the quantities being considered.
Exam Tip
For concentration questions, focus on the relationship between the amount of solute and the amount of solution.
Important Formulas & Concepts
1. Solubility
Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a specified temperature.
2. Saturated Solution
A solution containing the maximum amount of dissolved solute at a particular temperature is called a saturated solution.
3. Unsaturated Solution
A solution containing less than the maximum possible amount of dissolved solute is called an unsaturated solution.
4. Concentration
Concentration indicates the amount of solute present in a given amount of solution.
For a mass-based expression:
Mass percentage of a solution =
(Mass of solute / Mass of solution) × 100
where:
Mass of solution = Mass of solute + Mass of solvent
5. Effect of Temperature
For many solid solutes, solubility in water increases with an increase in temperature, although the effect varies from substance to substance.
Related Practice Questions
Q1. What is solubility?
Q2. What is a saturated solution?
Q3. What is an unsaturated solution?
Q4. How does temperature affect the solubility of many solid substances?
Q5. What is meant by concentration of a solution?
Mini Quiz Challenge
Try answering these questions within 60 seconds.
Q1. A solution that can dissolve more solute at a given temperature is:
A) Saturated
B) Unsaturated
C) Pure
D) Heterogeneous
Q2. The maximum amount of solute that can dissolve in a given amount of solvent at a specified temperature is related to:
A) Density
B) Solubility
C) Filtration
D) Evaporation
Q3. Which factor can affect the solubility of many solid solutes in water?
A) Temperature
B) Colour
C) Shape of the beaker
D) Label on the container
Q4. Mass percentage of a solution is calculated using:
A) Mass of solvent / Mass of solute × 100
B) Mass of solution / Mass of solute × 100
C) Mass of solute / Mass of solution × 100
D) Mass of solute + Mass of solvent only
Q5. A saturated solution contains:
A) No solute
B) Less than the maximum amount of dissolved solute
C) The maximum amount of dissolved solute at a given temperature
D) Only solvent
Exam Tips
✔ Learn the difference between saturated and unsaturated solutions.
✔ Remember the definition of solubility carefully.
✔ Revise the mass percentage formula.
✔ Understand that temperature can affect the solubility of many solid substances.
✔ In numerical questions, first identify whether the question asks for mass of solute, mass of solution or mass percentage.
Quick Revision Notes
✔ Solubility: Maximum amount of solute that can dissolve in a given amount of solvent at a specified temperature.
✔ Saturated solution: Contains the maximum amount of dissolved solute at a given temperature.
✔ Unsaturated solution: Can dissolve more solute at the given temperature.
✔ Concentration: Indicates the amount of solute present in a given amount of solution.
✔ Mass percentage: (Mass of solute / Mass of solution) × 100.
✔ Mass of solution: Mass of solute + Mass of solvent.
✔ Temperature can affect the solubility of many solid substances.
Common Mistakes Students Make
❌ Confusing saturated and unsaturated solutions.
❌ Thinking that a saturated solution contains no undissolved solute under all circumstances.
❌ Forgetting that solubility is specified for a particular temperature.
❌ Using mass of solvent instead of mass of solution in the mass percentage formula.
❌ Assuming that temperature affects the solubility of all substances in exactly the same way.
Key Takeaways
✔ Solubility tells us the maximum amount of solute that can dissolve under specified conditions.
✔ A saturated solution contains the maximum dissolved solute at a given temperature.
✔ An unsaturated solution can dissolve more solute.
✔ Concentration describes the amount of solute in a given amount of solution.
✔ Mass percentage is an important way of expressing concentration.
✔ Temperature can affect the solubility of many solid substances.
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 the maximum amount that can dissolve at a particular temperature, so more solute can still dissolve.
Q. What is solubility?
Answer:
Solubility is the maximum amount of a solute that can dissolve in a given amount of solvent at a specified temperature.
Q. What is concentration?
Answer:
Concentration indicates the amount of solute present in a given amount of solution.
Q. How is mass percentage calculated?
Answer:
Mass percentage is calculated by dividing the mass of solute by the mass of solution and multiplying the result by 100.
Conclusion
Class 9 Science Chapter 2 – Is Matter Around Us Pure? focuses on important concepts related to solubility, saturated solutions, unsaturated solutions, concentration and the effect of temperature on solubility.
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