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Practice Class 9 Science Chapter 2 – Is Matter Around Us Pure? with 5 NCERT-based MCQs on separation of mixtures, distillation, fractional distillation, sublimation and suitable separation techniques.
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Chapter Information
Subject: Science
Class: 9
Chapter: Is Matter Around Us Pure?
Question Type: Multiple Choice Questions (MCQs)
Practice Set: 14
Difficulty Level: Moderate
Based On: NCERT Syllabus
Introduction
Different mixtures require different separation techniques. The most suitable method depends on the physical properties of the components, such as boiling point, solubility, particle size and sublimation properties.
Some mixtures can be separated by simple physical methods, while others require techniques such as distillation, fractional distillation and sublimation.
This Practice Set 14 focuses on important separation techniques and their applications.
What You Will Learn
✔ Distillation
✔ Fractional distillation
✔ Sublimation
✔ Separation based on boiling points
✔ Separation of miscible liquids
✔ Separation of sublimable substances
✔ Selection of suitable separation methods
Why This Topic Is Important
Knowing the correct separation technique is an important part of Is Matter Around Us Pure?
Students should understand why a particular method is suitable for a particular mixture. Questions based on boiling points, sublimation and separation of liquids are common in school examinations.
5 MCQs with Answers and Detailed Solutions
Q1. Which method is commonly used to separate two miscible liquids having sufficiently different boiling points?
A) Filtration
B) Distillation
C) Handpicking
D) Sedimentation
Answer: B) Distillation
Detailed Solution
Distillation is used to separate components of a mixture based on differences in their boiling points.
When two miscible liquids have sufficiently different boiling points, the liquid with the lower boiling point vaporises first and can then be condensed separately.
Therefore, distillation is a suitable method.
Exam Tip
Remember:
Miscible liquids + sufficiently different boiling points → Distillation
Q2. Which method is used to separate a mixture of ammonium chloride and common salt?
A) Filtration
B) Sublimation
C) Centrifugation
D) Decantation
Answer: B) Sublimation
Detailed Solution
Sublimation is the process in which a solid changes directly into vapour without passing through the liquid state.
Ammonium chloride is a sublimable substance, whereas common salt does not sublime under ordinary conditions.
Therefore, ammonium chloride can be separated from common salt by sublimation.
Exam Tip
Remember:
Ammonium chloride + common salt → Sublimation
Q3. Which technique is used to separate different components of petroleum?
A) Filtration
B) Fractional distillation
C) Evaporation
D) Sublimation
Answer: B) Fractional distillation
Detailed Solution
Petroleum is a mixture of several hydrocarbons with different boiling points.
Fractional distillation is used to separate components of a mixture of miscible liquids having relatively close boiling points.
It separates the components into different fractions according to their boiling ranges.
Therefore, the correct answer is B) Fractional distillation.
Exam Tip
Remember:
Petroleum → Fractional distillation
Q4. Which physical property is mainly used in distillation to separate liquids?
A) Difference in colour
B) Difference in boiling points
C) Difference in smell
D) Difference in taste
Answer: B) Difference in boiling points
Detailed Solution
Distillation depends mainly on the difference in boiling points of the components.
The component with the lower boiling point vaporises more readily. The vapour is then cooled and condensed to obtain the separated liquid.
Therefore, the correct answer is B) Difference in boiling points.
Exam Tip
Remember:
Distillation → Difference in boiling points
Q5. Which of the following mixtures can be separated by sublimation?
A) Sand and water
B) Salt and water
C) Ammonium chloride and common salt
D) Oil and water
Answer: C) Ammonium chloride and common salt
Detailed Solution
Sublimation is suitable when one component of a solid mixture can change directly from solid to vapour.
Ammonium chloride sublimes, while common salt does not under ordinary conditions.
Therefore, the mixture of ammonium chloride and common salt can be separated by sublimation.
Hence, the correct answer is C.
Exam Tip
For a solid mixture, ask:
Does one component sublime? → Sublimation may be suitable.
Important Concepts
1. Distillation
Distillation is a separation technique based mainly on differences in the boiling points of liquids.
It involves vaporisation followed by condensation.
2. Fractional Distillation
Fractional distillation is used to separate a mixture of miscible liquids with close boiling points.
A fractionating column helps improve the separation.
3. Sublimation
Sublimation is the direct conversion of a solid into vapour without passing through the liquid state.
Examples of sublimable substances include:
- Ammonium chloride
- Camphor
- Naphthalene
4. Boiling Point
The boiling point is an important physical property used in the separation of liquids by distillation.
5. Choosing a Separation Method
The appropriate method depends on the physical properties of the components.
Examples:
- Ammonium chloride + common salt → Sublimation
- Miscible liquids with sufficiently different boiling points → Distillation
- Petroleum fractions → Fractional distillation
Related Practice Questions
Q1. What is distillation?
Q2. What is fractional distillation?
Q3. What is sublimation?
Q4. Why is fractional distillation used for petroleum?
Q5. Which physical property is important in distillation?
Mini Quiz Challenge
Try answering these questions within 60 seconds.
Q1. Which method is suitable for separating two miscible liquids with sufficiently different boiling points?
A) Distillation
B) Filtration
C) Sublimation
D) Sedimentation
Q2. Which substance can sublime?
A) Common salt
B) Sand
C) Ammonium chloride
D) Sugar
Q3. Petroleum is separated into different fractions by:
A) Evaporation
B) Fractional distillation
C) Filtration
D) Centrifugation
Q4. Distillation mainly depends on differences in:
A) Density
B) Boiling point
C) Colour
D) Particle shape
Q5. What happens during sublimation?
A) Solid changes directly into vapour
B) Liquid changes into solid
C) Gas changes into liquid
D) Solid changes directly into liquid
Exam Tips
✔ Learn the difference between distillation and fractional distillation.
✔ Remember that distillation mainly depends on boiling points.
✔ Learn common sublimable substances.
✔ Remember ammonium chloride + common salt → sublimation.
✔ Remember petroleum → fractional distillation.
✔ Always select a separation technique according to the physical properties of the components.
Quick Revision Notes
✔ Distillation: Separation based mainly on differences in boiling points.
✔ Fractional distillation: Used for miscible liquids with relatively close boiling points.
✔ Sublimation: Solid changes directly into vapour.
✔ Ammonium chloride: Sublimable substance.
✔ Petroleum: Separated into fractions by fractional distillation.
✔ Boiling point: Important property used in distillation.
✔ Separation method: Depends on physical properties of the components.
Common Mistakes Students Make
❌ Confusing distillation with filtration.
❌ Using simple distillation for every mixture of liquids.
❌ Forgetting that fractional distillation is used for miscible liquids with close boiling points.
❌ Thinking common salt sublimes under ordinary conditions.
❌ Confusing sublimation with melting.
Key Takeaways
✔ Distillation is useful for separating suitable mixtures of liquids based on differences in boiling points.
✔ Fractional distillation is used for separating miscible liquids with relatively close boiling points.
✔ Petroleum is separated into different fractions by fractional distillation.
✔ Sublimation can separate a sublimable solid from a non-sublimable solid.
✔ Ammonium chloride can be separated from common salt by sublimation.
✔ Selecting the correct separation method requires understanding the physical properties of the components.
FAQs
Q. What is distillation?
Answer:
Distillation is a separation technique that uses differences in boiling points. It involves vaporising a component and then condensing its vapour.
Q. What is fractional distillation?
Answer:
Fractional distillation is used to separate a mixture of miscible liquids having relatively close boiling points.
Q. What is sublimation?
Answer:
Sublimation is the direct conversion of a solid into vapour without passing through the liquid state.
Q. How can ammonium chloride be separated from common salt?
Answer:
The mixture can be separated by sublimation because ammonium chloride sublimes while common salt does not under ordinary conditions.
Q. How is petroleum separated into different components?
Answer:
Petroleum is separated into different fractions by fractional distillation based on differences in boiling ranges.
Conclusion
Class 9 Science Chapter 2 – Is Matter Around Us Pure? focuses on important separation techniques including distillation, fractional distillation and sublimation.
Understanding the physical properties used in these techniques helps students choose the appropriate method for separating different mixtures and answer application-based examination questions accurately.
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