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Practice Class 9 Science Chapter 2 – Is Matter Around Us Pure? with 5 NCERT-based MCQs on separation techniques, evaporation, centrifugation, chromatography, crystallisation and the separation of components of 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: 9
Difficulty Level: Moderate
Based On: NCERT Syllabus
Introduction
Mixtures contain two or more substances that can often be separated using suitable physical methods. The choice of separation method depends on the physical properties of the components, such as solubility, boiling point, particle size and density.
Different techniques are useful for different types of mixtures. Evaporation, centrifugation, chromatography and crystallisation are important separation methods discussed in this chapter.
This Practice Set 9 focuses on these methods and their applications.
What You Will Learn
✔ Evaporation
✔ Centrifugation
✔ Chromatography
✔ Crystallisation
✔ Separation based on physical properties
✔ Separation of soluble substances
✔ Separation of components of mixtures
Why This Topic Is Important
Separation techniques are an important part of Is Matter Around Us Pure? because mixtures can often be separated into their components without changing their chemical identities.
Students should understand which method is suitable for a particular mixture and the physical property on which that method is based.
5 MCQs with Answers and Detailed Solutions
Q1. Which method is commonly used to separate a soluble solid from a solution by removing the solvent?
A) Filtration
B) Evaporation
C) Sedimentation
D) Handpicking
Answer: B) Evaporation
Detailed Solution
Evaporation is used to remove the solvent from a solution.
For example, common salt can be obtained from salt solution by evaporating the water. As water changes into vapour, the dissolved salt remains behind.
Therefore, evaporation is suitable for recovering a soluble solid from a solution when the solvent can be removed by heating.
Exam Tip
Remember: Soluble solid + solution → Evaporation when the solvent needs to be removed.
Q2. Which separation technique is used to separate cream from milk?
A) Filtration
B) Centrifugation
C) Sublimation
D) Chromatography
Answer: B) Centrifugation
Detailed Solution
Centrifugation separates components of a mixture based mainly on differences in density by rapidly rotating the mixture.
It is commonly used to separate cream from milk. The denser and less dense components move differently during centrifugation, allowing separation.
Exam Tip
Remember the common application:
Milk → Cream → Centrifugation
Q3. Which technique is commonly used to separate different coloured components present in a mixture of dyes?
A) Chromatography
B) Filtration
C) Sedimentation
D) Decantation
Answer: A) Chromatography
Detailed Solution
Chromatography is a separation technique used to separate different components of a mixture based on differences in their movement through a medium.
It is commonly used to separate different coloured components present in dyes or inks.
Different components travel at different rates, allowing them to be separated.
Exam Tip
For coloured dyes or ink, think of chromatography.
Q4. Which method is commonly used to obtain pure crystals of a solid substance from its solution?
A) Crystallisation
B) Filtration only
C) Sedimentation
D) Decantation
Answer: A) Crystallisation
Detailed Solution
Crystallisation is used to obtain a pure solid in the form of crystals from a solution.
It is useful when a solid is dissolved in a suitable solvent and needs to be obtained in a purer crystalline form.
The process involves preparing a suitable solution and allowing crystals to form under controlled conditions.
Exam Tip
Remember:
Pure solid crystals from a solution → Crystallisation
Q5. Which property is mainly used in centrifugation to separate components of a mixture?
A) Colour
B) Density
C) Smell
D) Taste
Answer: B) Density
Detailed Solution
Centrifugation uses rapid rotation to separate particles or components according to their density.
Denser components tend to move outward and settle more strongly than less dense components during the process.
Therefore, density is an important physical property involved in centrifugation.
Exam Tip
Remember: Centrifugation → difference in density.
Important Formulas & Concepts
This topic mainly involves separation principles rather than mathematical formulas.
1. Evaporation
Evaporation removes the solvent from a solution, leaving behind the dissolved substance.
Example: Obtaining salt from salt solution.
2. Centrifugation
Centrifugation uses rapid rotation to separate components based mainly on differences in density.
Example: Separating cream from milk.
3. Chromatography
Chromatography separates components based on their different rates of movement through a medium.
Example: Separating coloured components of ink.
4. Crystallisation
Crystallisation is used to obtain a pure solid in the form of crystals from a solution.
5. Separation Principle
Different separation methods depend on differences in physical properties such as:
- Solubility
- Density
- Boiling point
- Particle size
- Movement through a medium
Related Practice Questions
Q1. How can salt be obtained from salt solution?
Q2. What is centrifugation?
Q3. How does chromatography separate components?
Q4. What is crystallisation?
Q5. Which physical property is important in centrifugation?
Mini Quiz Challenge
Try answering these questions within 60 seconds.
Q1. Which method is used to obtain salt from salt solution?
A) Evaporation
B) Filtration
C) Chromatography
D) Centrifugation
Q2. Cream can be separated from milk by:
A) Crystallisation
B) Centrifugation
C) Sublimation
D) Filtration
Q3. Which method is suitable for separating different coloured dyes?
A) Sedimentation
B) Chromatography
C) Decantation
D) Evaporation
Q4. Which method is used to obtain pure crystals from a solution?
A) Crystallisation
B) Filtration
C) Handpicking
D) Centrifugation
Q5. Centrifugation mainly makes use of differences in:
A) Colour
B) Density
C) Taste
D) Odour
Exam Tips
✔ Learn the common applications of each separation technique.
✔ Remember salt solution → evaporation.
✔ Remember cream from milk → centrifugation.
✔ Remember coloured dyes → chromatography.
✔ Remember pure crystals → crystallisation.
✔ Understand that separation methods depend on differences in physical properties.
Quick Revision Notes
✔ Evaporation: Removes solvent from a solution.
✔ Centrifugation: Separates components using rapid rotation and differences in density.
✔ Chromatography: Separates components based on differences in their movement through a medium.
✔ Crystallisation: Used to obtain pure crystals of a solid.
✔ Salt from salt solution: Evaporation.
✔ Cream from milk: Centrifugation.
✔ Dyes from ink: Chromatography.
✔ Pure crystals: Crystallisation.
Common Mistakes Students Make
❌ Choosing filtration to separate dissolved salt from water.
❌ Confusing centrifugation with filtration.
❌ Using evaporation when the question specifically asks for pure crystals.
❌ Forgetting the use of chromatography for separating coloured components.
❌ Thinking all separation methods work on the same physical property.
Key Takeaways
✔ Mixtures can often be separated using physical methods.
✔ Evaporation can recover a soluble solid from a solution.
✔ Centrifugation is useful for separating components with differences in density.
✔ Chromatography can separate different components of dyes and inks.
✔ Crystallisation is useful for obtaining pure crystals.
✔ The correct separation technique depends on the physical properties of the components.
FAQs
Q. How is salt obtained from salt solution?
Answer:
Salt can be obtained by evaporating the water from the salt solution.
Q. Which method is used to separate cream from milk?
Answer:
Centrifugation is used to separate cream from milk.
Q. What is chromatography?
Answer:
Chromatography is a separation technique in which components of a mixture move at different rates through a suitable medium.
Q. What is crystallisation?
Answer:
Crystallisation is a method used to obtain a pure solid in the form of crystals from a solution.
Q. Why are different separation methods used?
Answer:
Different methods are used because components of mixtures have different physical properties such as solubility, density, boiling point and particle size.
Conclusion
Class 9 Science Chapter 2 – Is Matter Around Us Pure? focuses on important separation techniques including evaporation, centrifugation, chromatography and crystallisation.
Understanding the principle and application of each technique helps students select the correct method for separating different mixtures and prepares them for conceptual and application-based examination questions.
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