Class 9 Science Chapter 2 Is Matter Around Us Pure

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Practice Class 9 Science Chapter 2 – Is Matter Around Us Pure? with 5 NCERT-based MCQs on separation techniques, pure substances, mixtures, solutions, colloids, suspensions and classification of matter.

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Chapter Information

Subject: Science

Class: 9

Chapter: Is Matter Around Us Pure?

Question Type: Multiple Choice Questions (MCQs)

Practice Set: 15

Difficulty Level: Moderate to Advanced

Based On: NCERT Syllabus

Introduction

The classification and separation of matter are important concepts in Is Matter Around Us Pure? Matter can be classified into pure substances and mixtures. Pure substances include elements and compounds, while mixtures can be homogeneous or heterogeneous.

Different mixtures can be separated using suitable physical techniques based on properties such as solubility, boiling point, density, particle size and sublimation.

This final Practice Set 15 brings together important concepts from the chapter and focuses on application-based questions involving mixtures, solutions, colloids, suspensions and separation techniques.

What You Will Learn

✔ Classification of matter

✔ Elements and compounds

✔ Solutions

✔ Colloids and suspensions

✔ Separation techniques

✔ Physical properties used for separation

✔ Application of separation methods

✔ Difference between pure substances and mixtures

Why This Topic Is Important

A strong understanding of this chapter requires students to connect the properties of different substances with the appropriate method of separation.

Application-based questions often require students to identify the type of mixture, determine the physical property involved, and select the most suitable separation technique.

5 MCQs with Answers and Detailed Solutions

Q1. A mixture contains iron filings, sand and common salt. Which sequence of methods can be used to separate all three components?

A) Filtration → evaporation → magnet
B) Magnet → dissolve in water and filter → evaporation
C) Evaporation → magnet → filtration
D) Sublimation → filtration → centrifugation

Answer: B) Magnet → dissolve in water and filter → evaporation

Detailed Solution

The mixture contains:

• Iron filings
• Sand
• Common salt

First, a magnet can be used to remove the iron filings because iron is attracted to a magnet.

The remaining mixture contains sand and salt. Add water so that the salt dissolves while sand remains insoluble.

Next, filtration separates the sand from the salt solution.

Finally, evaporation removes the water and leaves the common salt behind.

Therefore, the correct sequence is:

Magnet → Dissolution in water → Filtration → Evaporation

Hence, the correct answer is B.

Exam Tip

For a mixture containing iron + insoluble solid + soluble solid, think:

Magnet → Dissolve → Filter → Evaporate

Q2. Which combination correctly matches the mixture with its separation method?

A) Cream from milk → Chromatography
B) Coloured components of ink → Centrifugation
C) Ammonium chloride and common salt → Sublimation
D) Salt from salt solution → Filtration

Answer: C) Ammonium chloride and common salt → Sublimation

Detailed Solution

Let’s check the options:

• Cream from milk → Centrifugation, not chromatography.
• Coloured components of ink → Chromatography, not centrifugation.
• Ammonium chloride and common salt → Sublimation, because ammonium chloride sublimes.
• Salt from salt solution → Evaporation or crystallisation, not ordinary filtration.

Therefore, only option C is correctly matched.

Exam Tip

Learn these common pairs:

Cream + milk → Centrifugation

Ink dyes → Chromatography

Ammonium chloride + salt → Sublimation

Salt solution → Evaporation/Crystallisation

Q3. Which statement correctly distinguishes a colloid from a true solution?

A) Colloidal particles always settle rapidly
B) Colloids can scatter light, while true solutions generally do not show the Tyndall effect
C) True solutions can always be separated by ordinary filtration
D) Colloids contain no particles

Answer: B) Colloids can scatter light, while true solutions generally do not show the Tyndall effect

Detailed Solution

A colloid contains particles that are larger than those in a true solution. These particles can scatter light, producing the Tyndall effect.

In a true solution, the particles are extremely small and generally do not scatter light sufficiently to make the path of a light beam visible.

Colloidal particles also generally do not settle down like suspension particles.

Therefore, the correct answer is B.

Exam Tip

Remember:

Colloid → Tyndall effect

Suspension → particles settle

True solution → no Tyndall effect under ordinary observation

Q4. Which statement about a compound is correct?

A) Its composition can vary freely
B) Its components retain all their original properties
C) It is formed by chemical combination of elements in a fixed proportion
D) It can always be separated by physical methods

Answer: C) It is formed by chemical combination of elements in a fixed proportion

Detailed Solution

A compound is a pure substance formed when two or more elements combine chemically in a fixed proportion.

The resulting compound has properties different from those of its constituent elements.

For example, hydrogen and oxygen combine chemically to form water, which has properties different from both hydrogen and oxygen.

Therefore, the correct answer is C.

Exam Tip

Remember:

Compound = Chemical combination + Fixed proportion + New properties

Q5. A student wants to separate a mixture of two miscible liquids having close boiling points. Which method is most suitable?

A) Simple filtration
B) Fractional distillation
C) Sublimation
D) Sedimentation

Answer: B) Fractional distillation

Detailed Solution

When two liquids are miscible and have relatively close boiling points, simple distillation may not provide effective separation.

Fractional distillation uses a fractionating column to improve separation by repeated vaporisation and condensation.

Therefore, fractional distillation is the most suitable method.

Hence, the correct answer is B) Fractional distillation.

Exam Tip

Remember:

Miscible liquids + close boiling points → Fractional distillation

Important Concepts

1. Classification of Matter

Matter can be broadly classified as:

Matter → Pure substances + Mixtures

Pure substances include:

• Elements
• Compounds

Mixtures include:

• Homogeneous mixtures
• Heterogeneous mixtures

2. Solution

A solution is a homogeneous mixture containing a solute and a solvent.

3. Colloid

A colloid is a heterogeneous mixture containing intermediate-sized particles that can scatter light.

4. Suspension

A suspension is a heterogeneous mixture containing relatively large insoluble particles that can settle down when left undisturbed.

5. Separation Techniques

Different methods depend on different physical properties:

6. Compound vs Mixture

A compound is formed by chemical combination in a fixed proportion, while a mixture is formed by physical combination and may have variable composition.

Related Practice Questions

Q1. How can iron filings, sand and salt be separated?

Q2. Why is chromatography used for separating dyes?

Q3. How does a colloid differ from a true solution?

Q4. What is the difference between a compound and a mixture?

Q5. When is fractional distillation used?

Mini Quiz Challenge

Try answering these questions within 60 seconds.

Q1. Which method is used to separate iron filings from a mixture?

A) Filtration
B) Magnetic separation
C) Evaporation
D) Crystallisation

Q2. Which mixture can be separated by chromatography?

A) Sand and water
B) Salt and water
C) Coloured components of ink
D) Iron and sulphur

Q3. Which type of mixture shows the Tyndall effect?

A) True solution
B) Colloid
C) Pure substance
D) Element

Q4. Which is a pure substance?

A) Air
B) Soil
C) Copper
D) Salt solution

Q5. Which technique is suitable for separating miscible liquids with close boiling points?

A) Fractional distillation
B) Filtration
C) Handpicking
D) Sedimentation

Exam Tips

✔ Learn the classification of matter into pure substances and mixtures.

✔ Remember the difference between elements and compounds.

✔ Learn common separation techniques and their applications.

✔ Remember colloid → Tyndall effect.

✔ Remember suspension → particles settle down.

✔ Use fractional distillation for miscible liquids with close boiling points.

✔ Select a separation method according to the relevant physical property.

Quick Revision Notes

✔ Element: Pure substance made of one kind of atom.

✔ Compound: Pure substance formed by chemical combination of elements in a fixed proportion.

✔ Solution: Homogeneous mixture.

✔ Colloid: Heterogeneous mixture that can show the Tyndall effect.

✔ Suspension: Heterogeneous mixture whose particles can settle down.

✔ Chromatography: Separation of components based on different movement through a medium.

✔ Centrifugation: Separation based mainly on differences in density.

✔ Sublimation: Direct conversion of solid into vapour.

✔ Distillation: Separation based mainly on differences in boiling points.

✔ Fractional distillation: Used for miscible liquids with relatively close boiling points.

Common Mistakes Students Make

❌ Confusing compounds with mixtures.

❌ Using filtration to separate dissolved salt from water.

❌ Confusing colloids with suspensions.

❌ Forgetting the Tyndall effect of colloids.

❌ Using simple distillation when fractional distillation is more suitable.

❌ Choosing a separation method without considering the physical properties of the components.

Key Takeaways

✔ Matter can be classified into pure substances and mixtures.

✔ Pure substances include elements and compounds.

✔ Mixtures can be homogeneous or heterogeneous.

✔ Different separation methods depend on different physical properties.

✔ Colloids show the Tyndall effect.

✔ Suspensions contain particles that can settle down.

✔ Fractional distillation is useful for separating miscible liquids with close boiling points.

✔ Understanding the properties of substances helps in selecting the correct separation technique.

FAQs

Q. How can iron filings, sand and salt be separated?

Answer:

First, use a magnet to remove iron filings. Then dissolve the salt in water, filter the mixture to remove sand, and finally evaporate the water to recover the salt.

Q. What is the difference between a colloid and a suspension?

Answer:

Colloidal particles are intermediate in size and generally do not settle down on standing, while suspension particles are larger and can settle down when left undisturbed.

Q. Why does a colloid show the Tyndall effect?

Answer:

Colloidal particles are large enough to scatter light, making the path of a light beam visible.

Q. What is fractional distillation used for?

Answer:

Fractional distillation is used to separate miscible liquids having relatively close boiling points.

Q. What is the main difference between a compound and a mixture?

Answer:

In a compound, elements are chemically combined in a fixed proportion, whereas in a mixture, substances are physically combined and their proportions can vary.

Conclusion

Class 9 Science Chapter 2 – Is Matter Around Us Pure? brings together the major concepts of the chapter, including classification of matter, solutions, colloids, suspensions, compounds, mixtures and separation techniques.

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