case study question on is matter around us pure

Class 9 Science Case Study Questions Chapter 2 Is Matter Around Us Pure

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Case study Questions in Class 9 Science Chapter 2 are very important to solve for your exam. Class 9 Science Chapter 2 Case Study Questions have been prepared for the latest exam pattern. You can check your knowledge by solving  Class 9 Science Case Study Questions  Chapter 2 Is Matter Around Us Pure?

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In CBSE Class 9 Science Paper, Students will have to answer some questions based on Assertion and Reason. There will be a few questions based on case studies and passage-based as well. In that, a paragraph will be given, and then the MCQ questions based on it will be asked.

Is Matter Around Us Pure? Case Study Questions With Answers

Here, we have provided case-based/passage-based questions for Class 9 Science  Chapter 2 Is Matter Around Us Pure?

Case Study/Passage-Based Questions

Case Study 1: Akshita wants to separate the mixture of dyes constituting a sample of ink. She marked a line by the ink on the filter paper and placed the filter paper in a glass containing water as shown in the figure. The filter paper was removed when the water moved near the top of the filter paper.

(i) Identify the technique used by the Akshita. (a) Sedimentation (b) Filtration (c) Chromatography (d) Distillation

Answer: (c) Chromatography.

(ii) What would you expect to see, if the ink contains three different coloured components? (a) We will not see any band on the filter paper. (b) We would see three bands on the filter paper at various lengths. (c) We would see infinite bands on the filter paper. (d) We would see the single band on the filter paper.

Answer: (b) The components of the ink will travel with water and we would see three bands on the filter paper at various lengths.

(iii) An application where you can use this technique is: (a) To separate salt from sand (b) To separate the wheat from the husk (c) To separate oil from water (d) To separate drugs from the blood.

Answer: (d) To separate drugs from blood.

(iv) The above process is used for the separation of : (a) insoluble substances (b) single solute that dissolves in the soluble solvent. (c) solutes that dissolve in the same solvent. (d) solutes that dissolve in the different solvents.

Answer: (c) For the separation of those solutes that dissolve in the same solvent.

(v) What is chromatography? (a) It is an agricultural method to separate grains (b) A method to separate magnetic impurities from non-magnetic impurities

(c) The process of separating the suspended particles of an insoluble substance (d) Method of separating and identifying various components in a mixture, which are present in small trace quantities.

Answer: (d) Method of separating and identifying various components in a mixture, which are present in small trace quantities.

Case Study 2: A homogeneous mixture of two or more substances is called a true solution. it consists of solute and solvent. The particle size of the true solution is less than 1 nanometer. A suspension is a heterogeneous mixture in which the solute particle does not dissolve but remains suspended throughout the bulk of the medium. A colloid is a mixture that is actually heterogeneous but appears to be homogeneous as the particles are uniformly spread throughout the solution.

(i) which one of the following is most stable? 

A)True solution

B)Suspensions

D) both A and B

Answer: A)True solution

ii) which type of mixture can be separated by filtration? 

D)All of these

Answer: B)Suspensions

iii) which statement is incorrect about the Tyndall effect. *

A)True solution shows Tyndall effect

B)Suspensions show the Tyndall effect

C)Colloid show Tyndall effect

D)Both B and C show the Tyndall effect

Answer: A)True solution shows Tyndall effect

iv) Which is the correct order of stability of solution *

A) True < Colloid<Suspension

B)Colloid<Suspension<True

C)Colloid<True<Suspension

D)Suspension<Colloid<True

Answer: D)Suspension

Case Study 3:

Matter can be classified into two categories: pure substances and mixtures. Pure substances are made up of a single type of particle and cannot be separated into other substances by physical methods. They have definite and constant properties. On the other hand, mixtures are made up of two or more substances that are physically combined and can be separated into their individual components. Mixtures can be further classified into homogeneous and heterogeneous mixtures. Homogeneous mixtures are uniform in composition, meaning the components are evenly distributed throughout the mixture. Heterogeneous mixtures, on the other hand, have non-uniform composition with visible different parts. It is important to understand the nature of matter around us and differentiate between pure substances and mixtures to comprehend their properties and behavior.

What is the main characteristic of a pure substance? a) Made up of two or more substances b) Cannot be separated into other substances c) Has non-uniform composition d) Components are evenly distributed Answer: b) Cannot be separated into other substances

Which of the following is an example of a pure substance? a) Air b) Saltwater c) Gold d) Soil Answer: c) Gold

How are mixtures different from pure substances? a) Mixtures have definite and constant properties b) Mixtures are made up of a single type of particle c) Mixtures cannot be separated into other substances d) Mixtures are physically combined and can be separated Answer: d) Mixtures are physically combined and can be separated

Which type of mixture has a non-uniform composition? a) Homogeneous mixture b) Heterogeneous mixture Answer: b) Heterogeneous mixture

What is the primary reason for understanding the nature of matter around us? a) To separate mixtures into pure substances b) To comprehend the properties and behavior of matter c) To classify mixtures into homogeneous and heterogeneous d) To identify the components in pure substances Answer: b) To comprehend the properties and behavior of matter

Hope the information shed above regarding Case Study and Passage Based Questions for Class 9 Science Chapter 2 Is Matter Around Us Pure? with Answers Pdf free download has been useful to an extent. If you have any other queries about CBSE Class 9 Science Is Matter Around Us Pure? Case Study and Passage-Based Questions with Answers, feel free to comment below so that we can revert back to us at the earliest possible By Team Study Rate

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• Is Matter Around Us Pure Class 9 Case Study Questions Science Chapter 2

Last Updated on September 1, 2024 by XAM CONTENT

Hello students, we are providing case study questions for class 9 science. Case study questions are the new question format that is introduced in CBSE board. The resources for case study questions are very less. So, to help students we have created chapterwise case study questions for class 9 science. In this article, you will find case study questions for cbse class 9 science chapter 2 Is Matter Around Us Pure.

Table of Contents

Case Study Questions on Is Matter Around Us Pure

Question 1:

A group of students took an old shoe box and covered it with a black paper from all sides. They fixed a source of light (a torch) at one end of the box by making a hole in it and made another hole on the other side to view the light. They placed a milk sample contained in a tumbler in the box as shown in the figure below. They were amazed to see that milk taken in the tumbler was illuminated. They tried the same activity by taking a salt solution but found that light simply passed through it.

Read the given passage carefully and give the answer of the following questions:

Q 1. Explain why the milk sample was illuminated? Name the phenomenon involved.

Q2. Same results were not observed with a salt solution. Explain.

Q 3. Can you suggest two more solutions which would show the same effect as shown by the milk solution?

Q 4. Give one example of above phenomenon observed in our surroundings.

• Because milk is a colloidal solution and would show Tyndall effect.
• Salt solution is a true solution and would not scatter light.
• Soap solution and ink solution.
• Tyndall effect is observed when sunlight passes through the canopy of a dense forest.

Case study questions for other chapters of class 9 science is given below.

• Work and Energy Class 9 Case Study Questions Science Chapter 10
• Gravitation Class 9 Case Study Questions Science Chapter 9
• Force and Laws of Motion Class 9 Case Study Questions Science Chapter 8
• Motion Class 9 Case Study Questions Science Chapter 7
• Tissues Class 9 Case Study Questions Science Chapter 6

The Fundamental Unit of Life Class 9 Case Study Questions Science Chapter 5

Matter in our surroundings class 9 case study questions science chapter 1.

We hope the given case study questions for Is Matter Around Us Pure Class 9 helps you in your learning.

Helpful Links for CBSE Class 9 Science Preparation

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• Download Case Study Question Bank for CBSE Class 9 Science
• Download Numerical Problems for CBSE Class 9 Physics
• Download Important MCQs for CBSE Class 9 Physics

Topics from which case study questions may be asked

• Separation Techniques
• Concentration of Solutions
• Physical and Chemical Change
• Experiments and Observations

This chapter deals with the basic understanding of mixtures, solutions, separation techniques, physical change and chemical change. case study questions based on above topics may be asked.

Frequently Asked Questions (FAQs) on Is Matter Around Us Pure Case Study Questions

Q1: what are case study questions for cbse examinations.

A1: Case study questions in CBSE examinations typically involve scenarios or real-life examples, requiring students to apply their understanding of concepts to solve problems or analyze situations.

Q2: Why are case study questions important for understanding class 9 science chapters?

A2: Case study questions provide a practical context for students to apply theoretical knowledge to real-world situations, fostering deeper understanding and critical thinking skills.

Q3: How should students approach answering case study questions for CBSE?

A3: Students should carefully read the case study, identify the key issues or problems presented, analyze the information provided, apply relevant concepts and principles of chemical reactions and equations, and formulate well-supported solutions or responses.

Q4: Are there any resources available online for students to practice case study questions on class 9 science chapters for CBSE exams?

A4: Yes, several educational websites offer case study questions for CBSE students preparing for science examinations. We also offer a collection of case study questions for all classes and subject on our website. Visit our website to access these questions and enhance your learning experience. If you need more case study questions for your preparation, then you visit Physics Gurukul website.

Q5: How can students effectively prepare for case study questions on “Is Matter Around Us Pure” for CBSE exams?

A5: Effective preparation strategies include regular revision of concepts, solving practice questions, analyzing case studies from previous exams, seeking clarification on doubts, and consulting with teachers or peers for guidance and support.

Q6: How can teachers incorporate case study questions on “Is Matter Around Us Pure” class 9 science into classroom teaching?

A6: Teachers can integrate case studies into lesson plans, group discussions, or interactive activities to engage students in active learning, promote problem-solving skills, and facilitate a deeper understanding of “Is Matter Around Us Pure”.

Q7: What is meant by a substance?

A7: A material that consists of a single type of particles is known as pure substance. All constituent particles of pure substance have the same chemical nature.

Q8: List the points of differences between homogeneous and heterogeneous mixtures

A8: A homogeneous mixture is a mixture having a uniform composition throughout the mixture. For example: Salt in water, sugar in water, copper sulphate in water. A heterogeneous mixture is a mixture having a non-uniform composition throughout the mixture. For example: Sodium chloride and iron fillings, salt and sulphur, oil and water.

Q9: How can we check the purity of a substance?

A9: The purity of a substance can be checked by its melting point and boiling point. A pure substance has a fixed melting point or boiling point at constant pressure.

Q10: Define element.

A10: An element is a basic form of matter that cannot be broken down into simpler substances by chemical reaction. An element consists of only one kind of atom.

Q11: Define compound.

A11: A compound is a substance made up of two or more elements chemically combined with one another. A compound always contains a definite proportion of the elements by mass.

Q12: Name the three states of matter.

A12: The three states of matter are solid, liquid and gas.

Q13: Name the metal which is liquid at room temperature.

A13: Mercury

Q14: How will you separate a mixture of mercury, kerosene and water?

A14: The mixture of mercury, kerosene and water is taken in a separating funnel. Separating funnel is used to separate two immiscible liquids. The principle is that immiscible liquids separate out in layers depending on their densities. Mercury being the heaviest from the bottom layer, water form the middle layer and kerosene form the top layer. On opening the tap, mercury will run out first, followed by water and kerosene at the end

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Case Study Questions of Chapter 2 Is Matter Around Us Pure? PDF Download

Case study Questions on Class 9 Science Chapter 2 are very important to solve for your exam. Class 9 Science Chapter 2 Case Study Questions have been prepared for the latest exam pattern. You can check your knowledge by solving case study-based questions for Class 9 Science Chapter 2 Is Matter Around Us Pure?

In CBSE Class 9 Science Paper, Students will have to answer some questions based on Assertion and Reason. There will be a few questions based on case studies and passage-based as well. In that, a paragraph will be given, and then the MCQ questions based on it will be asked.

Is Matter Around Us Pure? Case Study Questions With answers

Here, we have provided case-based/passage-based questions for Class 9 Science  Chapter 2 Is Matter Around Us Pure?

Case Study/Passage-Based Questions

Question 1:

Akshita wants to separate the mixture of dyes constituting a sample of ink. She marked a line by the ink on the filter paper and placed the filter paper in a glass containing water as shown in the figure. The filter paper was removed when the water moved near the top of the filter paper.

(i) Identify the technique used by the Akshita. (a) Sedimentation (b) Filtration (c) Chromatography (d) Distillation

Answer: (c) Chromatography.

(ii) What would you expect to see, if the ink contains three different coloured components? (a) We will not see any band on the filter paper. (b) We would see three bands on the filter paper at various lengths. (c) We would see infinite bands on the filter paper. (d) We would see the single band on the filter paper.

Answer: (b) The components of the ink will travel with water and we would see three bands on the filter paper at various lengths.

(iii) An application where you can use this technique is: (a) To separate salt from sand (b) To separate the wheat from the husk (c) To separate oil from water (d) To separate drugs from the blood.

Answer: (d) To separate drugs from blood.

(iv) The above process is used for the separation of : (a) insoluble substances (b) single solute that dissolves in the soluble solvent. (c) solutes that dissolve in the same solvent. (d) solutes that dissolve in the different solvents.

Answer: (c) For the separation of those solutes that dissolve in the same solvent.

(v) What is chromatography? (a) It is an agricultural method to separate grains (b) A method to separate magnetic impurities from non-magnetic impurities

(c) The process of separating the suspended particles of an insoluble substance (d) Method of separating and identifying various components in a mixture, which are present in small trace quantities.

Answer: (d) Method of separating and identifying various components in a mixture, which are present in small trace quantities.

Question 2:

A homogeneous mixture of two or more substances is called a true solution. it consists of solute and solvent. The particle size of the true solution is less than 1 nanometer. A suspension is a heterogeneous mixture in which the solute particle does not dissolve but remains suspended throughout the bulk of the medium. A colloid is a mixture that is actually heterogeneous but appears to be homogeneous as the particles are uniformly spread throughout the solution.

(i) which one of the following is most stable? 

A)True solution

B)Suspensions

D) both A and B

Answer: A)True solution

ii) which type of mixture can be separated by filtration? 

D)All of these

Answer: B)Suspensions

iii) which statement is incorrect about the Tyndall effect. *

A)True solution shows Tyndall effect

B)Suspensions show the Tyndall effect

C)Colloid show Tyndall effect

D)Both B and C show the Tyndall effect

Answer: A)True solution shows Tyndall effect

iv) Which is the correct order of stability of solution *

A) True < Colloid<Suspension

B)Colloid<Suspension<True

C)Colloid<True<Suspension

D)Suspension<Colloid<True

Answer: D)Suspension

Hope the information shed above regarding Case Study and Passage Based Questions for Class 9 Science Chapter 2 Is Matter Around Us Pure? with Answers Pdf free download has been useful to an extent. If you have any other queries about CBSE Class 9 Science Is Matter Around Us Pure? Case Study and Passage Based Questions with Answers, feel free to comment below so that we can revert back to us at the earliest possible

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Class 9th Science - Is Matter Around Us Pure Case Study Questions and Answers 2022 - 2023

By QB365 on 09 Sep, 2022

QB365 provides a detailed and simple solution for every Possible Case Study Questions in Class 9th Science Subject - Is Matter Around Us Pure, CBSE. It will help Students to get more practice questions, Students can Practice these question papers in addition to score best marks.

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Is matter around us pure case study questions with answer key.

9th Standard CBSE

Final Semester - June 2015

(ii) What would you expect to see, if the ink contains three different coloured components? (a) We will not see any band on the filter paper. (b) We would see three bands on the filter paper at various lengths. (c) We would see infinite bands on the filter paper. (d) We would see single band on the filter paper. iii) Give one application where you can use this technique. (a) To separate salt from sand (b) To separate wheat from husk (c) To separate oil from water (d) To separate drugs from blood. (iv) For the separation of what kind of substances is the above process used ? (a) For the separation of insoluble substances (b) For the separation of single solute that dissolves in single solvent. (c) For the separation of those solutes that dissolve in the same solvent. (d) For the separation of those solutes that dissolve in the different solvents. (v) What is chromatography ? (a) It is an agricultural method to separate grains (b) A method to separate magnetic impurities from non-magnetic impurities (c) The process of separating the suspended particles of an insoluble substance (d) Method of separating and identifying various components in a mixture, which are present in small trace quantities.

(ii) Oil from water.

(iii) Sodium chloride from its solution in water.

(iv) Camphor from salt.

(v) Cream from milk

(ii) Which type of substance can be separated by this method ? (a) Any solvent from its non-volatile solute. (b) The volatile solvent from its non-volatile solute. (c) The non-volatile solvent from its non-volatile solute. (d) The volatile solvent from its volatile solute. (iii) What can we interpret about the nature of ink ?

(iv) Name the component which gets evaporated. ( a) Heating leads to the evaporation of water. (b) Heating leads to the evaporation of dyes. (c) Heating leads to the filtration of water. (d) Heating leads to the distillation of dyes. (v) Define the process shown in the diagram (a) It is the process of conversion of a liquid into its vapours. (b) It is a process of separating insoluble component by filtering the solution (c) It is a process that separates a pure solid in the form of its crystals (d) It is a technique to separate two miscible liquids

(ii) One of the following does not undergo sublimation. This one is :

(iii) The conversion of a solid into vapours without passing through the liquid state is called : 

(iv) When heat is constantly supplied by a burner to boiling water, then the temperature of water during vaporisation :

(v) During summer days, water kept in an earthen pot (pitcher) becomes cool because of the phenomenon of :

*****************************************

Is matter around us pure case study questions with answer key answer keys.

(i) (c) Chromatography (ii) (b) We would see three bands on the filter paper at various lengths. (iii) (d) To separate drugs from blood. (iv) (c) For the separation of those solutes that dissolve in the same solvent. (v) (d) Method of separating and identifying various components in a mixture, which are present in small trace quantities.

(i) (b) Sedimentation and Decantation. (ii) (c) Separating funnel (iii) (d) Evaporation (iv) (c) Sublimation (v) (d) Centrifugation.

(i) (a) Boiling (ii) (b) The volatile solvent from its non-volatile solute. (iii) (d) Ink is a mixture of dyes in water. (iv) (a) Heating leads to the evaporation of water. (v) (a) It is the process of conversion of a liquid into its vapours.

(i) (c) sublimation (ii) (b) sodium chloride (iii) (c) sublimation (iv) (d) does not rise at all (v) (d) evaporation.

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Class 9 Science Chapter 2 Case Based Questions - Is Matter Around Us Pure??

(I) Read the given passage and answer the questions that follow based on the passage and related studied concepts. A pure substance consist of single type of particles. Mixture consist of more than one kind of pure form of matter. Mixtures can be separated by physical methods but pure substances especially compounds cannot be separated into chemical constituents by physical methods. Pure substance has same composition throughout. Soil and soft drinks are mixtures. Mixtures can be separated by various methods depending upon nature of substance present in it. Solution is a homogeneous mixture.

Q1: Name the process by which pure NaCl can be obtained from salt solution. Ans: Crystallisation

Q2: What are alloys-compounds or mixtures? Ans:  Alloys are homogeneous mixtures of two or more metals or a metal and a non-metal e.g. Brass is alloy of Cu and Zn

Q3: What is size of particles in solution? Ans: The size of particles in solutions are less than 1nm (10 –9 m).

Q4: What is solute and solvent in cold drinks? Ans: CO 2  gas, sugar, preservative are solute and water is solvent in cold drinks.

Q2: How can gases be separated that are present in air? Ans:  By fractional distillation of liquid air.

Q3: If sample of urea has melting point 129°C, then: (a)  It is impure (b) It is pure (c)  It can not be predicted (d) The compound is not urea Ans: (a) It is impure

Q4: Which of the following will have boiling point 100°C? (a) Distilled water (b) Sea water (c) River water (d) Well water Ans: (a) Distilled water will have boiling point 100°C.

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Important Questions for CBSE Class 9 Science Chapter 2 - Is Matter Around Us Pure

• Class 9 Important Question
• Chapter 2: Is Matter Around Us Pure

CBSE Class 9 Science Chapter-2 Important Questions - Free PDF Download

This chapter contains important questions for CBSE Class 9 Science Chapter 2 - Is Matter Around Us Pure in the form of free to download review notes. These questions will undoubtedly aid students in improving their understanding of Chapter 2 of Class 9 Science. Both homogeneous and heterogeneous states of mixtures are covered in Class 9 Science Chapter 2. In this chapter, students will also learn about matter and consider whether the surrounding stuff is pure.

Vedantu is a platform that provides free CBSE Solutions (NCERT) and other study materials for students. You can download Class 9 Science and Class 9 Maths NCERT Solutions to help you to revise the complete syllabus and score more marks in your examinations.

Download CBSE Class 9 Science Important Questions 2024-25 PDF

Also, check CBSE Class 9 Science Important Questions for other chapters:

Study Important Questions for Class 9 Science Chapter 2 Is Matter Around Us Pure

Very Short Answer Questions (1 Mark)

1. Try segregating the things around you as pure substances or mixtures.

Ans: Try mixing soil and water then separate them. Where soil is a mixture as it is the mix of more than one substance. And water is a pure substance because it’s made up of one kind of substance.

2. Classify each of the following as a homogeneous or heterogeneous mixture. soda water, wood, air, soil, vinegar, filtered tea.

Ans: Classification of the given into homogeneous or heterogeneous is enlisted below.

3. How would you confirm that a colorless liquid given to you is pure water?

Ans: Under the  atmospheric pressure one, the boiling point of water is \[{{100}^{{}^\text{o}}}C\]. and freezing point is \[{{0}^{{}^\text{o}}}C\]. When we boil the given colorless liquid, if it boils at \[{{100}^{{}^\text{o}}}C\]then it is pure water. If not boiling at \[{{100}^{{}^\text{o}}}C\] temperature, then there will be impurities mixed with it, hence not pure water.

4. Which of the following materials fall in the category of a “pure substance”?

d) Hydrochloric acid

e) Calcium oxide

Ans: Pure substances: ice, iron, hydrochloric acid, calcium oxide, mercury.

5. Identify the solutions among the following mixtures.

b) Sea water

e) Soda water.

Ans: Solutions: seawater, air, soda water.

6. Which of the following will show the “Tyndall effect”?

a) Salt solution

c) Copper sulfate solution

d) Starch solution.

Ans: (b)Milk and (d)starch solution 

7. Classify the following into elements, compounds, and mixtures.

c) Sugar solution

e) Calcium carbonate

l) Carbon dioxide

m) Blood 

Ans: Classification of the given into elements, compounds, and mixtures are enlisted below.

8. Which of the following are chemical changes?

(a) Growth of a plant

(b) Rusting of iron

(c) Mixing of iron filings and sand

(d) Cooking of food

(e) Digestion of food

(f) Freezing of water

(g) Burning of a candle.

Ans: Chemical changes: rusting of iron, cooking of food, digestion of food, burning of a candle.

9. Which of the following solutions scatter light?

(a) colloidal solution

(b) suspension

(d) none 

Ans: (c) both

10. Which of the following methods would you use to separate cream from milk?

(a) fractional distillation

(b) distillation

(c) centrifugation

(d) filtration

Ans: (c) Centrifugation

11. Cooking of food and digestion of food:

(a) are both physical processes, (b) are both chemical processes, (c) cooking is physical whereas digestion is chemical.

(d) Cooking is chemical whereas digestion physical 

Ans: (b) Are both chemical processes

12. Mercury and Bromine are both

(a) liquid at room temperature

(b) solid at room temperature

(c) gases at room temperature

(d) both (a) and (b)

Ans: (a) liquid at room temperature

13. Blood and seawater are:

(a) both mixtures

(b) both are compound

(c) blood is a mixture whereas seawater is a compound, (d) blood is a compound and seawater is a mixture , ans: (a) both mixtures.

14. Sol and Gel are examples of examples of

(a) Solid-solid colloids

(b) Sol is a solid-liquid colloid and Gel is a liquid-solid colloid

(c) Sol is a solid-solid colloid and Gel is a solid-liquid colloid

(d) Sol is a liquid-solid colloid and Gel is a solid-liquid colloid

Ans: (b) Sol is a solid-liquid colloid and Gel is a liquid-solid colloid

15. In a water-sugar solution:

(a) water is solute and sugar is solvent

(b) water is solvent and sugar is solute

(c) water is solute and water is also solute

(d) none of these

16. boron and carbon:.

(a) are metalloids

(b) boron is metalloid and carbon is non-metal

(c) boron is metallic and carbon is a metal

(d) boron is non-metal and carbon are a metalloid

Ans: (a) are metalloids

Short Answer Questions (2 Marks)

1. What is meant by a substance?

Ans: Substance will have similar chemical properties and can be defined as that kind of matter where constituent particles cannot be separated from each other by any physical process. 

2. How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than \[{{25}^{{}^\text{o}}}C\] ), which are miscible with each other?

Ans: We can use the distillation technique to separate a mixture containing kerosene and petrol since the difference in their boiling points is more than \[{{25}^{{}^\text{o}}}C\].

3. Name the technique to separate

(i) Butter from curd

Ans: Centrifugation method.

(ii) Salt from sea-water

Ans: Evaporation method.

(iii) Camphor from salt

Ans: Sublimation method.

4. What type of mixtures are separated by the technique of crystallization?

Ans: From liquid solutions of impure samples, pure solid crystals can be separated. This method is known as crystallization. 

Example: Pure sugar from impure sugar, salt from seawater.

5. What is a mixture? What are its various types?

Ans: A mixture is constituted by more than one element or compound or both mixed in any proportion. They are of two types:

(a) Homogenous mixture

(b) Heterogeneous mixture

6. Define solute, solvent, and solution?

Ans: Solute: It is the substance of the solution which is being added to the solvent.

Solvent: It dissolves the solute. The component of the solution to which the solute is added.

Solution: It is homogeneous, constituted by solute and solvent.

7. What is a solution? What are the properties of the solution?

Ans: A solution is a homogenous mixture of two or more substances. The various properties of the solution are: -

The particles of a solution cannot be seen by naked eyes because they are smaller than $1$ nm.

When the beam of light passes through a solution, it does not scatter.

Filtration cannot be used to separate the components of a solution from each other. 

8. Differentiate between elements and compounds.

Ans: The difference between elements and compounds is enlisted below.

9. What is the Tyndall effect? Which kinds of solutions show it?

Ans: Tyndall effect is a process in which the scattering of beams of light takes place in particles of a colloid when that is directed towards them. Heterogeneous mixtures like Suspension solution and colloidal solution show the Tyndall effect.

10. Differentiate between homogeneous and heterogeneous mixture?

Ans: The difference between homogeneous and heterogeneous mixtures are listed below.

11. What is centrifugation? Where it is used?

Ans: Centrifugation is a technique used for the separation of suspended particles of a substance from liquid and is based upon the principle that denser particles stay at the bottom and lighter particles stay at the top when rotated at a high speed in a centrifuge application . It is used in separate butter from milk, also in washing machines for squeezing out water from clothes.

12. What is a suspension? What are the properties of suspension?

Ans: A suspension is a heterogeneous mixture in which the solute particles do 

not dissolve in the solvent but remain suspended throughout the bulk of the medium. The suspension particle size is large enough to be visible from naked eyes.

Properties of suspension:

The particles are large so can be seen by naked eyes.

They scatter a beam of light passing through it.

When particles are left undisturbed, they settle down.

Short Answer Questions (3 Marks)

1. How are sol, solution, and suspension different from each other?

Ans: The difference between sol, solution, and suspension are enlisted below.

2. To make a saturated solution, $36$ g of sodium chloride is dissolved in \[100\] g of water at \[293\] K. Find its concentration at this temperature.

Ans: In the problem, it is given that to make a saturated solution, $36$ g of sodium chloride is dissolved in \[100\] g of water at \[293\] K. 

Mass of sodium chloride (solute) is $36$ g 

Mass of water (solvent) is \[100\] g

Mass of solution is the sum of solute and solvent 

\[\Rightarrow 36+100=136\]

Therefore, concentration percentage \[=\dfrac{mass\text{ }of\text{ }solute}{mass\text{ }of\text{ }solution}\times 100\]

$=\dfrac{36}{136}\times 100$

3. Classify the following as chemical or physical changes:

cutting of trees

melting of butter in a pan

rusting of almirah

boiling of water to form steam

the passing of electric current through water and the water breaking    down into hydrogen and oxygen gases

dissolving common salt in water

Making a fruit salad with raw fruits burning of paper and wood.

Ans: When the chemical properties of a substance change then it’s called a chemical change.

Chemical change: rusting of almirah, passing of electric current, through water and the water breaking down into hydrogen and oxygen gases, burning of paper and wood.

Physical properties of a substance such as a shape, size, color, state change then it’s called a physical change.

Physical change: cutting of trees, melting of butter in a pan, boiling of water to form steam, dissolving common salt in water, making a fruit salad with raw fruits.

4. Which separation techniques will you apply for the separation of the following?

a) Sodium chloride from its solution in water.

Ans: Evaporation method

b) Ammonium chloride from a mixture containing sodium chloride and 

Ammonium chloride., ans: sublimation method, c) small pieces of metal in the engine oil of a car..

Ans: Filtration method

d) Different pigments from an extract of flower petals.

Ans: chromatography.

e) Butter from curd.

Ans: Centrifugation method

f) Oil from water.

Ans: by using separating funnel.

g) Tea leaves from tea.

Ans: Filtration by using a strainer

h) Iron pins from sand.

Ans: magnetic separation.

i) Wheat grains from husk.

Ans: Winnowing method

j) Fine mud particles suspended in water.

5. write the steps you would use for making tea. use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate, and residue..

Ans: First, take the required amount of water as a solvent in a pan, and after boiling it add a little amount of sugar which is solute to the solvent. The solute will dissolve completely in the solvent forming the true solution, then add tea leaves that are insoluble along with another soluble liquid milk. After boiling the solution use the method of filtration with a sieve so that the filtrate obtained is tea while the residue has tea leaves that can be thrown away.

6. Pragya tested the solubility of three different substances at different temperatures and collected the data as given below(results are given in the following table, as grams of substance dissolved in $100$ grams of water to form a saturated solution)

a) What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in \[50\] grams of water at $313$ K?

Ans: At temperature $313$ K the amount of potassium nitrate required was $62$ g in $100$ ml of water.

Therefore, in \[50\] g water we will need to dissolve $62\times \dfrac{50}{100}=31$ g potassium nitrate.

b) Pragya makes a saturated solution of potassium chloride in water at $353$ K and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.

Ans: at $353$ k saturated solution preparation needs \[54\] g potassium nitrate and at room temperature (\[293\]k) saturation solution formation occurs with \[35\] g potassium nitrate hence \[5435=19\] g potassium nitrate will precipitate out as undissolved salt..

c) Find the solubility of each salt at \[293\] K. Which salt has the highest solubility at this temperature?

Ans: Solubilities are (in \[100\] mg of water) \[32,36,35,37\] respectively for the mentioned salts and the highest solubility is of ammonium chloride at this temperature.

d) What is the effect of change of temperature on the solubility of a salt?

Ans: Solubility of salts is directly proportional to the temperature i.e., if temperature increases then solubility will also increase, and if the temperature decreases then solubility will also decrease.

7. Explain the following examples.

(a) Saturated solution

Ans: It is a solution in which no more solute particles can be dissolved at a particular temperature.

(b) Pure substance

Ans: It is a substance that has a fixed composition and is made up of only one type of particle.

(c) Colloid

Ans: It is a substance that has a fixed composition and is made up of only one type of particle. It is a  kind of heterogeneous mixture/solution in which particle size is between $1$ nm and $1000$ nm that is intermediate between true solution and suspensions. Colloids have dispersion medium and dispersed phases.

(d) Suspension

Ans: It is a  kind of heterogeneous mixture, in which insoluble solid particles remain suspended in the medium and dispersion particles are visible to the bare eyes.

8. Write a method to separate different gases from the air.

Ans: Air is a homogeneous mixture of various gases.

Fractional distillation can be used to separate its various components.

(a) First, compress air by increasing the pressure and cool the air by decreasing the temperature.

(b) The obtained air is liquid air; now allow the liquid air to warm up slowly in a fractional distillation column.

(c) The various gases separate from each other according to their boiling points at various heights of the fractionating column.

9. What is a colloid? What are its various properties?

Ans: The heterogeneous mixture of substances are colloids, in which the particle size is too small and cannot be seen by naked eyes.

(1) It is a heterogeneous mixture but appears homogeneous.

(2) The size of particles is too small so cannot be seen by naked eyes.

(3) They make its path visible by scattering the beam of light passing through it.

(4) When the colloid is left undisturbed, the particles of it do not settle down.

10. A solution contains $60$ g of $NaCl$ in $400$ g of water. Calculate the concentration in terms of mass-by-mass percentage of the solution.

Ans: In the problem, it is given that, A solution contains $60$ g of $NaCl$ in 400g of water. 

Mass of solute ($NaCl$) is $60$ g

Mass of solvent (water) is $400$ g

Mass of solution $=$ Mass of solute $+$ Mass of solvent

$\Rightarrow 60+400=460$ g

Mass percentage of the solution is the percentage of the ratio of the mass of solute to the mass of solution.

\[\Rightarrow \dfrac{60}{460}\times 100=\dfrac{300}{23}~~\]

\[=13.4\%\]

11. Differentiate between metals and non-metal based upon the various properties that they show.

Ans : the difference between metals and non-metal based upon the various properties are enlisted below..

12. Differentiate between mixtures and compounds by giving appropriate examples?

Ans : differences between mixtures and compounds are enlisted below..

13. Write a method to separate a mixture of salt and ammonium chloride?

Ans: A mixture of salt and ammonium chloride can be separated by the process of sublimation. In this process, the solid substance is directly converted into a gaseous state.  Since ammonium chloride changes directly from a solid into a gaseous state on heating and salt does not have that property, this principle can be used to the mixture of two.

The mixture of $N{{H}_{4}}Cl$ (ammonium chloride) and salt is taken in a china dish inside an inverted funnel.

The mixture is then heated using a burner and because $N{{H}_{4}}Cl$ sublimates thus it changes into vapors directly.

Salt settles into the inverted funnel as it is a non-sublimely substance.

Separation of $N{{H}_{4}}Cl$ salt by sublimation

14. What is crystallization? Where is it used? Why is this better than the simple evaporation technique?

Ans: Crystallization is the process of the transformation of solution into pure solid in the form of crystals. It is used to purify solids. For example, salt from seawater is purified using crystallization. It is a better technique than simple evaporation because:

Some solids may decompose or get charred on heating to dryness during evaporation.

Some of the impurities will remain dissolved in the solution.

15. What is chromatography? What are its various applications and underline the basic principle involved?

Ans: A technique used for the separation of those components whose solubility is different in the same solvent is chromatography. The basic principle in chromatography is that different solutes have different solubility in the same solvent.

Its various applications are:

It is used to separate different colors in dye .

It is used to separate pigments from natural colors.

It is used to separate drugs from the blood.

16. A solution of \[{{H}_{2}}S{{O}_{4}}\] acid is labeled is \[95\%\]. What is the mass of this that must be diluted with water to get \[5\]L of a solution containing \[10\] g of \[{{H}_{2}}S{{O}_{4}}\] per litre?

Ans: In the problem, it is given that, A solution of \[{{H}_{2}}S{{O}_{4}}\] acid is labeled is \[95\%\].

\[1\] L of the diluted solution must contain \[10\] g of \[{{H}_{2}}S{{O}_{4}}\]. Therefore, \[5\] L of the diluted solution must contain \[50\] g of \[{{H}_{2}}S{{O}_{4}}\].

The concentration of the acid in the bottle is \[95\%\] as per the problem.

This means that,

\[95\] g of \[{{H}_{2}}S{{O}_{4}}\] is present in \[100\] g of the acid solution .

\[50\] g of \[{{H}_{2}}S{{O}_{4}}\] will be present in \[\dfrac{\left( 50\times 100 \right)}{95}=52.64\] g of the solution.

Chemistry plays an important role in everyone's life, we might not know much about it but it is present in our everyday life, that is what this chapter tries to show where it indicates the different types of matters that are present everywhere around us. In this chapter, students will learn how matter is composed of and how it differs from various substances. Regular practice of Chapter 2 Class 9 Important Questions can help students improve, become through the concepts and topics, and be efficient during preparation or revision. Students must learn to utilize the material given to them to get more marks. In this article, we will also look at Class 9 Science Chapter 2 extra questions .

Important Questions for CBSE Class 9 Science Chapter 2 - Is Matter Around Us Pure - Benefits of Class 9th Science Chapter 2 Important Questions

It is vital that students understand the importance of this subject and what it holds for students of Class 9. By utilising the important questions and with a rigorous practice regime, students will be able to score the most out of their exams. These exams can be a little difficult without the right guidance but by using Vedantu’s important questions on Chapter 2, students will be able to study in a more structured manner. Following is the list of benefits:

Students can use Vedantu to use their time wisely, it helps boost their confidence after consistent practice and students can plan their preparation accordingly. 

It provides students with a structure with which they can study for their upcoming examinations. 

This is a fundamental chapter for students and plays a crucial role in upcoming grades. 

Students don’t have to worry about the relevance of these questions as they are all cross-checked and updated according to the latest CBSE guidelines and rules. So, the information in this article is genuine and reliable.

Topics Covered under CBSE Class 9 Chapter 2 ‘Is Matter Around Us Pure’ 

Following are the topics that are covered in CBSE Class 9 Chapter 2 ‘Is Matter Around Us Pure’:

Matter and its Types

Metals, Non-metals, and Metalloids

Mixture and its Types

Solution and its Types

Factors Affecting the Solubility

Concentration of Solution

Key Takeaways of CBSE Class 9 Science Chapter 2 Is Matter Around Us Pure 

Students here will learn some of the basic elements of constituents of matters. This will help them in their future grades as it sets the groundwork. Constant practice of the essential questions should help students to tackle any difficult questions in their final examinations. Some of the topics that these chapter covers are as follows:

Chemistry 

This subject is known as the central science subject that connects all the science subjects. This subject is very detailed and helps students understand the chemical constituents in different materials. it is connected to a lot of the physical subjects together such as Chemistry with Applied Science and Life Sciences such as Engineering and Medicine. Chemistry is defined as the study of the interaction, composition, and properties of matter.

Homogeneous and Heterogeneous Mixture 

These are two very different mixtures as in a homogeneous mixture, it has a uniform composure of its constituents where heterogeneous is a nonuniform composure of its constituents.

Tyndall Effect 

The scattering of a beam of light by particles of a solution when light is passed through it is known as the Tyndall effect. The solution where the size of the particle is very small.

Matter is defined as anything that possesses mass, occupies space, and the presence that can be felt by the five senses. Matter exists in three forms, namely, a solid, liquid, and gas. Solids are substances that possess a definite structure and a definite shape like sugar, iron, etc. Liquids are substances that have a definite volume but lack a definite form and take the shape of the vessel in which they are put — for example, mercury, milk, water, etc. Gases are substances that can neither possess a definite shape or definite volume like hydrogen, oxygen, nitrogen, etc.

The Difference Between Mixture and Compound 

This chapter takes a detailed look into the difference between mixture and compounds. The mixture is basically the elements or compounds that are mixed together in a heterogeneous way. It has a variable composition and also shows us the properties of constituent elements and the various ways in which they can be mixed. The examples are air, blood, and water. In a compound when the elements react, they form new compounds. This new substance formed shows new properties and examples of this are sodium chloride.

Crystallisation 

This is a very important process where we can separate the pure solid in the form of its crystals from its solutions. This is an important process when forming crystals. Unlike many processes where the solids may decompose because of the heat during the process of decomposition. In the process of evaporations, some solids stay intact.

Substance 

In this situation, it is physically impossible to separate the constituent particles from one another on one's own. Chemical or electrochemical procedures can be used to separate them because their chemical properties are similar. A material possesses particular qualities or attributes. Physical properties and chemical properties are the two main categories into which properties of matter can be divided. Melting point, boiling point, colour, aroma, and other physical attributes can be observed or quantified without affecting the content or identification of the substance. Chemical characteristics, such as combustibility, basicity, or acidity, are the chemical transformations that result in a distinctive response.

Chromatography 

This is a process where substances used for the separation of different substances have different solubility in the same solvent. It is used to separate different colours in the dye. It is used to separate different pigments from natural colours and separate drugs from the blood. There are various ways in which they can be separated and we will learn that in this chapter.

Colloid 

These are heterogeneous mixtures of substances whose particles are too small for the naked eye and cannot be seen. It appears homogeneous but is actually a heterogeneous mixture. The particles are too small for the naked eye to see. They scatter a beam of light through it and make its path invisible. The particles of the colloid do not settle down when left undisturbed. 

Important Questions on CBSE Class 9 Science Chapter 2 - Is Matter Around Us Pure 

To get a better understanding of Class 9 Science Chapter 2 important questions , let's look at how the various essential questions are framed and how they can be beneficial to students. Using the following questions should help students in the long term. 

1. What is chromatography? What are its various applications and underline the basic principles involved?

2. What is crystallisation? Why is crystallisation used? 

3. Why is crystallisation a better technique than the evaporation process?

4. Write a method to separate salt from sodium chloride.

5. Differentiate between mixture and compound by giving appropriate examples.

6. Differentiate between metals and non-metals based on the various metal properties they show.

7. What is a colloid? 

8. What are the various properties of a colloid? 

9. Write a different method to separate gas from the air?

10. Explain and give the example of the following: 

a. Saturated solution 

b.Pure substance 

c. Colloid 

d.Suspension

Tips to Study Science Better

Following are some tips that will help the students to study science in a better way:

Follow the concepts and study them properly. 

Try out the experiments under the guidance of someone elderly, which will help you to understand the topic better.

Practise solving the questions and answers, this will increase your chance of getting better results.

Practise with reliable notes for this chapter, you can refer to Is Matter Around Us Pure Class 9 Notes CBSE Science Chapter 2 (Free PDF Download) of Vedantu, this is quite reliable.

Conclusion 

The Situation in the Matter Around Us Pure, students have found pure important questions to be incredibly helpful. As you can see from this article, this chapter is very important for students to begin their study of chemistry because it essentially lays the foundation for subsequent grades. This article can help students make the most of their time, build their confidence after constant practice, and manage their study sessions effectively. Students might aspire for higher grades by working more hard toward their goals. These significant questions ensure that students understand the chapter's numerous concepts, and with continued practice, they will develop the skills necessary to answer the challenging questions on exams.

Important Related Links for CBSE Class 9 

FAQs on Important Questions for CBSE Class 9 Science Chapter 2 - Is Matter Around Us Pure

1. What are the major differences between a mixture and a compound?

Mixture: Elements or compounds just mix together to form a mixture. It has a variable composition and shows the properties of constituent elements. These constituent particles can be separated by physical methods. For example, air, blood, etc.

Compound: When elements chemically react, they form new compounds. Compounds have a fixed composition. The new substance formed shows new properties. The constituent elements can only be separated by chemical methods. For example, Sodium Chloride, Calcium Sulphate, etc.

2. What is crystallisation? Why is it an important process?

Crystallisation is a process by which we can separate a pure solid in the form of crystals from its solutions. It is an important process which is used to purify solids. It is a better technique than many processes like simple evaporation as some solids may decompose on heating during evaporation. In evaporation, some impurities still remain dissolved in the solutions.

3. Where can I find Important Questions for CBSE Class 9 Science Chapter 2 - Is Matter Around Us Pure?

Students can find a set of important questions for Class 9 Chapter 2 Is Matter Around Us Pure on Vedantu, a reliable online learning site. Vedantu caters to solve important questions chosen from the exam perspective. These questions are answered by subject matter experts who have immense subject knowledge and expertise. The material is available in the free PDF format and can be downloaded at students’ convenience for learning and during exam preparation.

4. What is meant by a substance?

Substance can be defined as the kind of matter where constituent particles cannot be separated from one another with the help of any physical process. Since they are similar in chemical properties, they can also be separated by chemical or electrochemical methods. Examples are diamond, water, sulphur, etc.

5. What is the saturated solution according to Chapter 2 of Class 9 Science?

A saturated solution is a solution in which no more solute can be added without increasing the temperature of a solution. It is stable at room temperature.  Students study more about saturated solutions in their science books for Class 9. They will understand the concept of pure substances and matter too. All definitions related to different types of solutions and substances are given in detail on Vedantu.

6. What is a mixture and a compound according to Chapter 2 of Class 9 Science ?

A mixture and a compound are different from each other in many ways. A mixture is not a pure substance but a compound is a pure substance. A mixture has different constituents and the properties of the constituents do not change in a mixture but the properties of all constituents will change in a compound. In a mixture, two or more substances can be mixed together in any ratio whereas in a compound two or more substances are mixed together in a fixed ratio.

7. Write down the important properties of a colloidal solution?

Colloidal solutions are heterogeneous mixtures. The size of particles in a colloidal solution varies between 1nm and 100 nm. The particles are very small in size and cannot be seen easily. If the particles are left undisturbed, the solutions remain stable. Students of Class 9 can understand the concept of colloidal solution in Chapter 2. Students should read Chapter 2 of Class 9 carefully to understand the definitions of important terms given in the chapter.

8. Water acts as a compound and not a mixture. Give reasons.

Water acts as a compound because it is made of two components oxygen and hydrogen. The two constituents can be separated through the process of electrolysis. The two constituents are combined together in a fixed ratio of 1:2. The ratio of hydrogen and oxygen is fixed and does not change. It is not easy to separate the constituents of water easily. They can only be separated by a special process only called electrolysis.

9. What are the important features of important questions of Chapter 2 of Class 9 Science from Vedantu?

Important questions for Chapter 2 of Class 9 Science available on Vedantu include questions that can help students to score high marks in exams. These important questions are available at free of cost on Vedantu(vedantu.com) and mobile app. Important questions can also help students to understand the concepts and gain in-depth knowledge of all the concepts given in the chapter. Students can prepare for their exams by practising all-important questions given in Vedantu because they are prepared by expert and experienced teachers and professionals.

CBSE Class 9 Science Important Questions

Cbse study materials.

NCERT Solutions for Class 6, 7, 8, 9, 10, 11 and 12

NCERT Solutions For Class 9 Science Chapter 2 Is Matter Around Us Pure

NCERT Solutions Class 9 Science Chapter 2 Is Matter Around Us Pure – Here are all the NCERT solutions for Class 9 Science Chapter 2. This solution contains questions, answers, images, step by step explanations of the complete Chapter 2 titled Is Matter Around Us Pure of Science taught in class 9. If you are a student of class 9 who is using NCERT Textbook to study Science, then you must come across Chapter 2 Is Matter Around Us Pure. After you have studied lesson, you must be looking for answers of its questions. Here you can get complete NCERT Solutions for Class 9 Science Chapter 2 Is Matter Around Us Pure in one place. For a better understanding of this chapter, you should also see Chapter 2 Is Matter Around Us Pure Class 9 notes , Science.

NCERT Solutions For Class 9 Science Chapter 2 Is Matter Around Us Pure

Topics and Sub Topics in Class 9 Science Chapter 2 Is Matter Around Us Pure:

• Is Matter Around Us Pure
• What is a Mixture?
• What is a Solution?
• Separating the Components of a Mixture
• Physical and Chemical Changes
• What are the Types of Pure Substances?

These solutions are part of NCERT Solutions for Class 9 Science . Here we have given Class 9 NCERT Science Text book Solutions for Chapter 2 Is Matter Around Us Pure.

IN-TEXT QUESTIONS SOLVED

NCERT Textbook for Class 9 Science – Page 15 Question 1. What is meant by a substance? Answer:  A pure substance consists of a single type of particles.

More Resources for Class 9 Science

NCERT Solutions

• NCERT Solutions Class 9 Science

Formulae Handbook for Class 9 Maths and Science Educational Loans in India

Class 9 Science NCERT Textbook Page 24 Question 1. How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C), which are miscible with each other? Answer:  A mixture of kerosene and petrol which are miscible with each other can be separated by distillation. Method

• Take a mixture in a distillation flask.
•  Fit it with a thermometer.
• Arrange the apparatus as shown in the figure.
• Heat the mixture slowly.
• Petrol vaporises first as it has lower boiling point. It condenses in the condenser and is collected from the condenser outlet.

Question 2. Name the technique to separate (i) butter from curd, (ii) salt from sea-water, (iii) camphor from salt. Answer:  (i) Centrifugation, (ii) Evaporation, (iii) Sublimation.

Question 3. What type of mixtures are separated by the technique of crystallisation? Answer:  Crystallisation technique is used to purify solid with some impurities in it. Example: Salt from sea-water.

NCERT Textbook Questions Page 24 Question 2. Classify the following as chemical or physical changes:

• cutting of trees,
• melting of butter in a pan,
• rusting of almirah,
• boiling of water to form steam,
• passing of electric current, through water and the water breaking down into hydrogen and oxygen gas,
• dissolving common salt in water,
• making a fruit salad with raw fruits and
• burning of paper and wood.

Question 3. Try segregating the things around you as pure substances or mixtures Answer:  Pure substances—Water, bread, sugar and gold. Mixtures—Steel, plastic, paper, talc, milk and air.

Questions From NCERT Textbook for Class 9 Science

Question 1. Which separation techniques will you apply for the separation of the following? (a) Sodium chloride from its solution in water. (b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride. (c) Small pieces of metal in the engine oil of a car. (d) Different pigments from an extract of flower petals. (e) Butter from curd. (f) Oil from water. (g) Tea leaves from tea. (h) Iron pins from sand. (i) Wheat grains from husk. (j) Fine mud particles suspended in water. Answer:  (a) Evaporation (b) Sublimation (c) Filtration (d) Chromatography (e) Centrifugation (f) Separating funnel (g) Filtration (h) Magnetic separation (i) Winnowing/ sedimentation (j) Decantation and filtration

Question 2. Write the steps you would use for making tea. Use the words, solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue. Answer:  1. Take a cup of water in a container as solvent and heat it. 2. Add sugar in it which is solute. Heat it till all sugar dissolves. 3. You get a solution of water and sugar. 4. Sugar is soluble in water completely. 5. Add half a tea-spoon of tea-leaves, it is insoluble in water. 6. Boil the content, add milk which is also soluble in water, boil again. 7. Filter the tea with the help of strainer, the tea collected in cup is filtrate and the tea leaves collected on the strainer is residue.

Question 4. Explain the following giving examples: (a) Saturated solution (b) Pure substance (c) Colloid (d) Suspension Answer:   (a) Saturated solution: In a given solvent when no more solute can dissolve further at a given temperature is called saturated solution. (b) Pure substance: A pure substance consists of a single type of particles. E.g., gold, silver. (c) Colloid: A colloid is a solution in which the size of solute particles are bigger than that of true solution. These particles cannot be seen with our naked eyes, they are stable, e.g., ink, blood. (d) Suspension: It is a heterogeneous mixture in which the solute particles are big enough to settle down, e.g., chalk-water, paints, etc.

Question 5. Classify each of the following as a homogeneous or heterogeneous mixture: soda water, wood, air. soil, vinegar, filtered tea. Answer:   Homogeneous: Soda water, vinegar, filtered tea. Heterogeneous: Wood, air, soil.

Question 6. How would, you confirm that a colourless liquid given to you is pure water? Answer:  By finding the boiling point of a given colourless liquid. If the liquid boils at 100°C at atmospheric pressure, then it is pure water. This is because pure substances have fixed melting and boiling point.

Question 7. Which of the following materials fall in the category of a “pure substance”? (a) Ice (b) Milk (c) Iron (d) Hydrochloric acid (e) Calcium oxide (f) Mercury (g) Back (h) Wood (i) Air. Answer:  Pure substances are: Ice, iron, hydrochloric acid, calcium oxide and mercury.

Question 8. Identify the solutions among the following mixtures. (a) Soil (b) Sea water (c) Air (d) Coal (e) Soda water. Answer:  Solutions are: Sea water soda water and air.

Question 9. Which of the following will show “Tyndall effect”? (a) Salt solution (b) Milk (c) Copper sulphate solution (d) Starch solution. Answer:  Milk and starch solution.

Question 10. Classify the following into elements, compounds and mixtures. (a) Sodium (b) Soil (c) Sugar solution (d) Silver (e) Calcium carbonate (f) Tin (g) Silicon (h) Coal (i) Air (j) Soap (k) Methane (l) Carbon dioxide (m) Blood Answer:  Elements – Compounds – Mixtures Sodium – Calcium carbonate –  Sugar solution Silver – Methane – Soil Tin – Carbon dioxide – Coal Silicon – Soap – Air ,Blood

Question 11. Which of the following are chemical changes? (a) Growth of a plant (b) Rusting of iron (c) Mixing of iron filings and sand (d) Cooking of food (e) Digestion of food (f) Freezing of water (g) Burning of a candle. Answer:  Chemical changes are: (a) Growth of a plant (b) Rusting of iron (c) Cooking of food (d) Digestion of food (e) Burning of a candle

NCERT Solutions for Class 9 Science Chapter 2 Is Matter Around Us Pure (Hindi Medium)

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NCERT Solutions For Class 9 Science Chapter 2 Multiple Choice Questions

Choose the correct option: 1. Fog, clouds are an example of (a) aerosol (b) colloid (c) suspension (d) emulsion 2. Sponge can be compressed, it is a (a) solid (b) liquid (c) gas (d) foam 3. An impure sample of potash alum can be purified by (a) evaporation (b) crystallisation (c) centrifugation (d) filtration 4. Chalk dissolved in water is an example of (a) true solution (b) colloid (c) suspension (d) saturated solution 5. 50 gm sugar is dissolved in a glass of water at 30°C. On heating this solution it will (a) crystallise (b) evaporate (4 become unsaturated (d) sugar will char 6. Which of the following shows tyndall effects? (a) salt solution (b) sugar solution (c) starch solution (d) copper sulphate solution 7. Pick up the odd one out. (a) brass ‘ (b) air (c) sand (d) graphite 8. Which of the following is liquid-liquid solution? (a) face-cream (b) emulsion (c) milk (d) all of these 9. To separate two miscible liquids by fractional distillation, it should have one of the following condition (a) should be miscible (b) should be immiscible (c) difference in the boiling point should be less than 25 K (d) none of these 10. To obtain toned and double toned milk from full-cream milk we can (a) filtrate it (b) sediment it (c) distillate it – (d) centrifuge it 11. The separation technique which involves the difference in their densities is (a) sublimation (b) separation by separating funnel (c) centrifugation (d) both (b) and (c) Answer:  1—(a). 2—(a), 3—(b), 4—(c), 5—(c), 6—(c), 7—(d), 8—(d), 9—(c), 10—(d), 11-(d).

NCERT Solutions For Class 9 Science Chapter 2 Very Short Answer Questions

Question 1. Define solvent. Answer:  The component of the solution that dissolves the other component in it is called the solvent.

Question 2. Define solute. Answer:  The component of the solution that is dissolved in the solvent is called solute.

Question 3. What is ‘tincture of iodine’? Answer:  A solution of iodine in alcohol is known as tincture of iodine. It has iodine (solid) as the solute and alcohol (liquid) as the solvent.

Question 4. What are alloys? Answer:  The homogeneous mixture of two or more metals or a metal and non-metal is called an alloy. E.g., steel is an alloy of iron and carbon.

Question 5. Give one example of gas in liquid solution. Answer:  Cold-drinks, carbon dioxide gas as solute is mixed with water as a solvent.

Question 6. How can a solution be dilute or concentrated? Answer:  The amount of solute dissolving in a solvent decides whether the solution is dilute or concentrated.

Question 7. What is “concentration of a solution”? Answer:  The concentration of a solution is the amount of solute present in a given amount of solution or the amount of solute dissolved in a given mass or volume of solvent.

Question 8. State the difference between aqueous and, non-aqueous solution. Answer:  Aqueous solutions have water as solvent and non-aqueous solutions do not haVe water as solvent.

Question 9. What is “solubility” of a solute? Answer:  The amount of the solute present in the saturated solution at the given temperature is called its solubility.

Question 10. What is saturated solution? Answer:  The maximum amount of solute dissolved in a solvent at given temperature is called saturated solution, where no more solute can dissolve further.

Question 11. What is unsaturated solution? Answer:  If the amount of solute contained in a solution is less than the saturation level, it is called an unsaturated solution.

Question 12. How can you convert saturated solution into unsaturated or vice-versa? Answer:  Saturated solution on heating becomes unsaturated and unsaturated solution on cooling becomes saturated.

Question 13. Why water is called universal solvent? Answer:  Water can dissolve large number of substances in it.

Question 14. What is Tyndall effect? Answer. The scattering of light by colloidal particles is known as Tyndall effect.

Question 15. How can we separate colloidal mixtures? Answer:  By centrifugation, in a centrifuge machine the colloidal solution is kept in a test tube, rotated very fast and due to centrifugal force the colloidal particles are separated.

Question 16. What is emulsion? Answer:  When both the dispersed phase and dispersing medium is liquid, it is called emulsion. E.g., milk, face cream.

Question 17. What is aerosol? Answer. When the solid or liquid is dispersed in a gas it is called aerosol. E.g., smoke, fog.

Question 18. What is the principle for separation of immiscible liquids? Answer:  The principle of separating immiscible liquids into layers depending on their densities. The less denser liquid collects at the top and more denser liquid at the bottom. ‘

Question 19. What is chromatography? Answer:  Chromatography is the technique used for separation of those solutes that dissolve in the same solvent.

Question 20. What is distillation? Answer:  Distillation is the separation technique of two miscible liquids that boils without decomposition and have sufficient difference in their boiling points.

Question 21. How can you separate two liquids that have less than 25 K difference of boiling points? Answer:  To separate a mixture of two or more miscible liquids for which the difference in boiling points is less than 25 K, is fractional distillation.

Question 22. What is condenser? Answer:  It is an apparatus used to convert gas into liquid by cooling it.

Question 23. What is crystallisation? Answer:  When a saturated solution is heated and allowed to cool slowly, crystal of the solute dissolved in the saturated solution are separated from it. It is used to purify solids.

NCERT Solutions For Class 9 Science Chapter 2 Short Answer Questions

Question 1. Why is mixture called impure substance? Answer:  Mixture consists of different components which retain their properties and can be easily separated by physical processes, hence it is called as impure substance.

Question 4. State the properties of a solution. Answer:  Properties of a solution are:

• A solution is a homogeneous mixture.
• Particles of a solution are smaller than 1 nm and cannot be seen by naked eyes.
• Do not scatter beam of light.
• Solute particles cannot be separated from the mixture by the process of filtration and thus, solution is stable.

Question 5. State the properties of a suspension. Answer:  Properties of a suspension

• Suspension is a heterogeneous mixture having particle size greater than 100 nm.
• The particles of a suspension can be seen by naked eyes.
• Particles can scatter a beam of light.
• It is unstable.

Question 6. What is a colloidal solution? Answer:  It is a heterogeneous solution which appears to be homogeneous, particles size is very small and so cannot be seen with naked eyes but it is stable. E.g., milk and blood.

Question 7. State the properties of colloidal solution. Answer:  Properties of colloidal solution.

•  It is a heterogeneous mixture having particle size between 1 nm to 100 nm.
• Size of particles is very small, cannot be seen with naked eyes.
• It scatters a beam of light.
• They are stable as the particles do not settle when left undisturbed.

Question 8. Give the applications of centrifugation. Answer:  Application of centrifugation are:

• Used in diagnostic laboratories for blood and urine test.
• Used in dairies and home to separate butter from cream.
• Used in a washing machines to squeeze out water from wet clothes.

Question 9. Give the applications of chromatography. Answer:  Applications of chromatography are

• To separate colours in a dye.
• To separate pigments from natural colours.
• To separate drugs from blood.

Question 10. Why is crystallisation better than evaporation? Answer:  Crystallisation is a process that separates a pure solid in the form of its crystals from a solution. Crystallisation is better than evaporation because during Evaporation

• Some solids decompose or some, like sugar may get charred on heating to dryness.
• Some impurities may remain dissolved in the solution even after filtration which on evaporation contaminates the solid.

Question 11. How will you separate a mixture of oil and water? Answer:  To separate a mixture of oil and water, we need a separating funnel as both are immiscible liquids. Pour the mixture in separating funnel and let the funnel stand undisturbed for sometime. So that separate layer of oil and water are formed. Open the stopcock of the separating funnel and pour out the lower layer of water carefully.

Question 15. Why is air considered as a mixture and not compound? Answer:  Air is considered as a mixture because it exhibits following properties:

• Each component present in air retains its properties.
• Each component can be separated by simple physical processes.
• The components do not have any fixed proportion. All gases are present in different amount. Example, in greener area—more oxygen and water vapour is present; near industrial area—air consists of lot of impurities and smoke suspended in it.

Question 16. How can you prove that water is a compound? Answer:  Water is a compound because if we pass electricity through it then at two different electrodes, we get two different gases i.e., oxygen and hydrogen during electrolysis of water. The ratio of oxygen: hydrogen is 1 : 2 by number of molecules.

• The properties of oxygen and hydrogen gases sire entirely different from that of liquid water.
• The ratio of oxygen: hydrogen combination is always constant i.e., 1: 2 by volume.
• To separate the components of water, we need electrolytic cell, and it is not a simple process.

Question 17. How can we convert saturated solution into unsaturated by heating? Answer:  Saturated solution is said to be saturated at a given temperature when there is no more scope of solute particles to dissolve /dissociate into water. It is because the solute particle has taken all the inter molecular space present in the solvent. On heating, the molecules of solvent gain kinetic energy, start vibrating and try to move away from each other thereby accommodating some more solute particle in this space and hence it becomes an unsaturated solution.

Question 18. What is the difference in fog and smoke? Answer:  Fog is a colloidal solution with liquid dispersed in gas. Smoke is a colloidal solution with solid dispersed in gas.

NCERT Solutions For Class 9 Science Chapter 2 Long Answer Type Questions

NCERT Solutions For Class 9 Science Chapter 2 Value-Based Questions

Question 1. Anil’s sister acddentally added some water into the bottle containing olive oil and she was afraid of the scolding. Anil helped his sister and separated the water from olive oil using bottle as separating funnel. (a) What is the principle of using and working of separating funnel? (b) Suggest two separation techniques used to separate liquid mixtures. (c) What value of Anil is seen in the above case? Answer:  (a) The principle of separating funnel is difference in the densities of two liquids. (b) Liquid mixtures can be separated by distillation and fractional distillation. (c) Anil showed the value of helping, caring and responsible behaviour.

Question 2. Preeti saw a labour entering into the sewage manhole immediately after removing the lid. She promptly stopped the labour from entering into the manhole and told him to wait for some time before he enters into it. (a) What will happen if the labour immediately enters into the manhole for cleaning) after removing the lid? (b) Name main gases that are released from the manhole. (c) What value of Preeti is seen in the above act? Answer:  (a) If the labour immediately enters the manhole on removing its lid he would die due to suffocation and inhalation of poisonous gases which are compressed and released by sewage. (b) Gases released from the sewage manhole are methane, carbon dioxide and hydrogen sulphide. (c) Preeti shows the value of moral responsible behaviour and aware citizen.

Question 3. Prasanna wanted to buy a deodorant from the shop. While buying a bottle he felt that it was slightly heavier than usual deodorant bottle that he purchased everytime. He read the weight mentioned on the bottle and told the shopkeeper to weigh the same. He found the bottle was heavy and on opening the deodorant bottle he found it half-filled with water. He complained the matter to the consumer authority. (a) Define density. (b) Apart from water what is the other substance that some shopkeepers add into the deodorant. (c) What value of Prasanna is reflected in this act? Answer:  (a) Density of any substance is defined to be the mass of the substance per unit volume. (b) One can add some cheap gases or compressed air in the deodorant bottles. (c) Prasanna showed the value of being having leadership quality, rightful, aware and responsible citizen.

Question 4. Rita’s father always got his vehicle checked for pollution control. He got it tested for the aerosol if released by his car. He also uses unleaded petrol and makes use of public transport wherever possible. He sparingly use his car. (a) What is aerosol? (b) What happens when smoke released from vehicle mixes with fog? (c) What are the values of Rita’s father is reflected here? Answer:  (a) When the solid or liquid is dispersed in a gas it is called aerosol e.g. smoke. (b) When smoke mixes with fog it forms smog. (c) Rita’s father is an aware citizen, environmentally concerned and dutiful.

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NCERT Solutions for Class 9 Science Chapter 2 Is Matter Around Us Pure

NCERT Solutions for Class 9 Science (chemistry) Chapter 2 Is Matter Around Us Pure are given below. In these solutions, we have answered all the intext and exercise questions provided in NCERT class 9 science textbook. Class 9 NCERT Solutions Science Chapter 2 provided in this article are strictly based on the CBSE syllabus and curriculum. Students can easily download these solutions in PDF format for free from our app.

Class 9 Science Chapter 2 Textbook Questions and Answers

Intext Questions Page No. 15

Questions 1: what do mean by a pure substance?

Answer:  A pure substance is the one that consists of a single type of particles, i.e., all constituent particles of the substance have the same chemical nature. Pure substances can be Classified as elements or compounds.

Question 2: List the points of differences between homogeneous and heterogeneous mixtures. 

Page No. 18

Question 1: Differentiate between homogeneous and heterogeneous mixtures with examples. 

Answer:  A homogeneous mixture is a mixture having a uniform composition throughout the mixture. For example, mixtures of salt in water, sugar in water, copper sulphate in water, iodine in alcohol, alloy, and air have uniform compositions throughout the mixtures.  

On the other hand, a heterogeneous mixture is a mixture having a non-uniform composition throughout the mixture. For example, composition of mixtures of sodium chloride and iron fillings, salt and sulphur, oil and water, chalk powder in water, wheat flour in water, milk and water are not uniform throughout the mixtures.  

Question 2: How are sol, solution and suspension different from each other? 

Answer:  Sol is a heterogeneous mixture. In this mixture, the solute particles are so small that they cannot be seen with the naked eye. Also, they seem to be spread uniformly throughout the mixture. The Tyndall effect is observed in this mixture. For example: milk of magnesia, mud 

Solution is a homogeneous mixture. In this mixture, the solute particles dissolve and spread uniformly throughout the mixture. The Tyndall effect is not observed in this mixture. 

For example: salt in water, sugar in water, iodine in alcohol, alloy  

Suspensions are heterogeneous mixtures. In this mixture, the solute particles are visible to the naked eye, and remain suspended throughout the bulk of the medium. The Tyndall effect is observed in this mixture. 

For example: chalk powder and water, wheat flour and water 

Question 3: To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature. 

PAGE NO. 24 (I)

Question 1: How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C), which are miscible with each other? 

Answer:   A mixture of two miscible liquids having a difference in their boiling points more than 25°C can be separated by the method of distillation. Thus, kerosene and petrol can be separated by distillation.

In this method, the mixture of kerosene and petrol is taken in a distillation flask with a thermometer fitted in it. We also need a beaker, a water condenser, and a Bunsen burner. The apparatus is arranged as shown in the above figure. Then, the mixture is heated slowly. The thermometer should be watched simultaneously. Kerosene will vaporize and condense in the water condenser. The condensed kerosene is collected from the condenser outlet, whereas petrol is left behind in the distillation flask.

Question 2: Name the technique to separate  (i) butter from curd (ii) salt from sea-water (iii) camphor from salt

Answer: (i) Butter can be separated from curd by centrifugation.

(ii) Salt can be separated from sea-water by evaporation.

(iii) Camphor can be separated from salt by sublimation.

Question 3: What type of mixtures is separated by the technique of crystallization? 

Answer:   By the technique of crystallization, pure solids are separated from impurities. For example, salt obtained from sea is separated from impurities; crystals of alum (Phitkari) are separated from impure samples.

PAGE NO 24(II)

Question 1: Classify the following as chemical or physical changes:

• Cutting of trees
• Melting of butter in a pan
• Rusting of almirah
• Boiling of water to form steam
• Passing of electric current through water and water breaking into hydrogen and oxygen gases.
• Dissolving common salt in water
• Making a fruit salad with raw fruits, and
• Burning of paper and wood

 Answer:  Cutting of trees → Physical change

Melting of butter in a pan → Physical change

Rusting of almirah → Chemical change

Boiling of water to form steam → Physical change

Passing of electric current through water, and water breaking down into hydrogen and oxygen gas → Chemical change

Dissolving common salt in water → Physical change

Making a fruit salad with raw fruits → Physical change

Burning of paper and wood → Chemical change

Question 2: Try segregating the things around you as pure substances or mixtures. 

Answer: Listed below are the classifications based on pure substances and mixtures:

Question 1: Which separation techniques will apply for the separation of the following?  (a) Sodium chloride from its solution in water. (b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride. (c) Small pieces of metal in the engine oil of a car. (d) Different pigments from an extract of flower petals. (e) Butter from curd. (f) Oil from water. (g) Tea leaves from tea. (h) Iron pins from sand. (i) Wheat grains from husk. (j) Fine mud particles suspended in water.

Answer:  (a) Sodium chloride from its solution in water → Evaporation

(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride → Sublimation

(c) Small pieces of metal in the engine oil of a car → Centrifugation or filtration or decantation

(d) Different pigments from an extract of flower petals → Chromatography

(e) Butter from curd → Centrifugation

(f) Oil from water → Using separating funnel

(g) Tea leaves from tea → Filtration

(h) Iron pins from sand → Magnetic separation

(i) Wheat grains from husk → Winnowing

(j) Fine mud particles suspended in water → Centrifugation

Question 2: Write the steps you would use for making tea. Use the words – solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.

Answer: 1. Take a cup of water in a container as solvent and heat it. 2. Add sugar in it which is solute. Heat it till all sugar dissolves. 3. You get a solution of water and sugar. 4. Sugar is soluble in water completely. 5. Add half a tea-spoon of tea-leaves, it is insoluble in water. 6. Boil the content, add milk which is also soluble in water, boil again. 7. Filter the tea with the help of strainer, the tea collected in cup is filtrate and the tea leaves collected on the strainer is residue.

Question 3: Pragya tested the solubility of three different substances at different temperatures and collected the data as given below (results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution).

(a) What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K?

(b) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.

(c) Find the solubility of each salt at 293 K. Which salt has the highest solubility at this temperature?

(d) What is the effect of change of temperature on the solubility of a salt?

Answer: (a) Mass of potassium nitrate required to produce a saturated solution in 100 g of water at 313 K = 62g

∴ Mass of potassium nitrate required to produce a saturated solution in 50 g of water = (62 × 50)/100 = 31 Hence 31 g of potassium nitrate is required.

(b) Some amount of dissolved Potassium Chloride will reappear as undissolved solid as solubility of solute decreases with the decrease of temperature.

(c) Solubility of each salt at 393 K are as follows:

• Potassium nitrate – 32 g
• Sodium chloride – 36 g
• Potassium chloride – 35 g
• Ammonium chloride – 37 g
• Ammonium chloride has the highest solubility at 293 K.

(d) Solubility of salt increases with the increase in temperature.

Question 4: Explain the following giving examples. (a) Saturated solution, (b) Pure substance, (c) Colloid, (d) Suspension.

Answer: (a) Saturated Solution: A solution in which no more of the solid (solute) can be dissolved at a given temperature is called a saturated solution. Suppose 50 gm of a solute is the maximum amount that can be dissolved in 100 gm water at 298 K. Then 150 gm of solution so obtained is the saturated solution at 298 K.

A saturated solution is a solution in which the maximum amount of solute has been dissolved at a given temperature. The solution cannot dissolve beyond that amount of solute at that temperature. Any more solute added will settle down at the bottom of the container as a precipitate. Suppose 500 g of a solvent can dissolve a maximum of 150 g of a particular solute at 40°C. Then, the solution obtained by dissolving 150 g of that solute in 500 g of that solvent at 300 K is said to be a saturated solution at 300 K.

Pure Substance: A pure substance consists of a single of matter or particles and cannot be separated into other kind of matter by any physical process. Pure substances always have the same colour, taste and texture at a given temperature and pressure. For example, pure water is always colourless, odorless and tasteless and boils at 373 K at normal atmospheric pressure.

Colloid: Colloid A colloid is a heterogeneous mixture. The size of the solutes in this mixture is so small that they cannot be seen individually with naked eyes, and seems to be distributed uniformly throughout the mixture. The solute particles do not settle down when the mixture is left undisturbed. This means that colloids are quite stable. Colloids cannot be separated by the process of filtration. They can be separated by centrifugation. Colloids show the Tyndall effect. For example, milk, butter, foam,fog, smoke, clouds.

Suspension: Suspension Suspensions are heterogeneous mixtures. The solute particles in this mixture remain suspended throughout the bulk of the medium. The particles can be seen with naked eyes. Suspension shows the Tyndall effect. The solute particles settle down when the mixture is left undisturbed. This means that suspensions are unstable. Suspensions can be separated by the method of filtration. For example, mixtures of chalk powder and water, wheat flour and water.

Question 5. Classify each of the following as a homogeneous or heterogeneous mixture: soda water, wood, air. soil, vinegar, filtered tea.

Answer:   Homogeneous:  Soda water, vinegar, filtered tea. Heterogeneous:  Wood, air, soil.

Question 6. How would, you confirm that a colourless liquid given to you is pure water?

Answer:  We can confirm if a colourless liquid is pure by setting it to boil. If it boils at 100°C it is said to be pure. But if there is a decrease or increase in the boiling point, we infer that water has added impurities hence not pure.

Question 7. Which of the following materials fall in the category of a “pure substance”? (a) Ice (b) Milk (c) Iron (d) Hydrochloric acid (e) Calcium oxide (f) Mercury (g) Back (h) Wood (i) Air.

Answer:  Following substances from the above-mentioned list are pure substances:

• Hydrochloric acid
• Calcium oxide

Question 8. Identify the solutions among the following mixtures. (a) Soil (b) Sea water (c) Air (d) Coal (e) Soda water.

Answer:  The following are the solutions from the above-mentioned list of mixture:

Question 9. Which of the following will show “Tyndall effect”? (a) Salt solution (b) Milk (c) Copper sulphate solution (d) Starch solution.

Answer:  Milk and starch solution will show the “Tyndall effect”.

Question 10. Classify the following into elements, compounds and mixtures. (a) Sodium (b) Soil (c) Sugar solution (d) Silver (e) Calcium carbonate (f) Tin (g) Silicon (h) Coal (i) Air (j) Soap (k) Methane (l) Carbon dioxide (m) Blood

Question 11. Which of the following are chemical changes? (a) Growth of a plant (b) Rusting of iron (c) Mixing of iron filings and sand (d) Cooking of food (e) Digestion of food (f) Freezing of water (g) Burning of a candle.

Answer:  Chemical changes are: (a) Growth of a plant (b) Rusting of iron (d) Cooking of food (e) Digestion of food (g) Burning of candle

Class 9 Science NCERT Solutions Chapter 2 Is Matter Around Us Pure

CBSE Class 9 Science NCERT Solutions Chapter 2 helps students to clear their doubts and to score good marks in the board exam. All the questions are solved by experts with a detailed explanation that will help students complete their assignments & homework. Having a good grasp over CBSE NCERT Solutions for Class 9 Science will further help the students in their preparation for board exams and other competitive exams such as NTSE, Olympiad, etc.

NCERT Solutions for Class 9 Science Chapter 2 PDF

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Is Matter Around Us Pure Class 9 Extra Questions Science Chapter 2

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Extra Questions for Class 9 Science Chapter 2 Is Matter Around Us Pure

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Is Matter Around Us Pure Class 9 Extra Questions Very Short Answer Questions

Question 1. How can you change a saturated solution to an unsaturated solution without adding any more solvent to it? Answer: By heating the saturated solution, it becomes unsaturated.

Question 2. Sucrose (sugar) crystals obtained from sugarcane and beetroot are mixed together. Will it be a pure substance or a mixture? Give reasons for the same. [NCERT Exemplar] Answer: It is a pure substance because chemical composition of sugar crystals is same irrespective of its source.

Question 3. Based on which factor a solution is said to be diluted, concentrated or saturated? Answer: A solution is said to be diluted, concentrated or saturated on the basis of the amount of solute dissolved in the solution.

Question 4. Identify solute and solvent in ‘tincture of iodine’. Answer: Iodine is the solute and alcohol is the solvent.

Question 5. What is mass per cent of a solution? Answer: It is defined as the mass in grams of the solute present in one hundred grams of a solution.

Question 6. What are the two components of a colloidal solution? Answer: The two components of a colloidal solution are dispersed phase and dispersing medium.

Question 7. In what respect does a true solution differ from a colloidal solution? Answer: A true solution is homogeneous whereas a colloidal solution is heterogeneous.

Question 8. Two liquids ‘A’ and ‘B’ are miscible with each other at room temperature. Which separation technique will you apply to separate the mixture of ‘A’ and ‘B’ if the difference in their boiling points is 27°C? Answer: We can separate two miscible liquids by fractional distillation, if both the liquids have difference in their boiling points. So, the mixture of liquids ‘A’ and ‘B’ can be separated by fractional distillation.

Question 9. Define crystallisation. Answer: It is a process that separates a pure solid in the form of its crystals from a solution.

Question 10. Why is crystallisation technique considered better than simple evaporation to purify solids? Answer: Crystallisation is considered better than simple evaporation because

• some solids decompose or get charred on heating to dryness.
• some impurities may remain dissolved in the solution even after filtration. On evaporation, these contaminate the solid.

Question 11. Why is water called universal solvent? Answer: Water is known as universal solvent because it has the ability to dissolve wide variety of substances.

Question 12. Which of the following are physical changes? Melting of iron metal, rusting of iron, bending of iron rod, drawing a wire of iron metal. Answer: Melting of iron metal, bending of iron rod and drawing a wire of iron metal are physical changes because there is no change in the chemical composition of iron, only its form is changing.

Question 13. Name two elements which exist in liquid state at room temperature. Answer: Gallium and mercury exist in liquid state at room temperature.

Question 14. An unknown substance ‘A’ on thermal decomposition produces ‘B’ and ‘C’. What is ‘A’—an element, a compound or a mixture? Answer: Unknown substance ‘A’ should be a compound because elements and mixture do not decompose.

Question 15. Identify the elements from the following substances: sulphur, brine, hydrochloric acid, water, neon, paper, sugar. Answer: The elements are sulphur and neon.

Is Matter Around Us Pure Class 9 Extra Questions Short Answer Questions-I

Question 1. ‘Sea water can be classified as homogeneous as well as heterogeneous mixture.’ Comment. [NCERT Exemplar] Answer: Sea water is a mixture of salts and water which cannot be separated except by evaporation. Therefore, sea water is considered homogeneous. Sea water also contains mud, decayed plant, etc., other than salts and water, so it is heterogeneous also.

Question 2. Why is it not possible to distinguish particles of a solute from the solvent in solution? Answer: A true solution is homogeneous in nature. The solute and solvent particles are very small. They cannot be distinguished even under a microscope.

Question 3. Explain why particles of a colloidal solution do not settle down when left undisturbed, while in the case of a suspension they do. [NCERT Exemplar] Answer: Particle size in a suspension is larger than those in a colloidal solution. Also molecular interaction in a suspension is not strong enough to keep the particles suspended and hence they settle down.

Question 4. Identify colloids and true solutions from the following: Pond water, fog, aluminium paint, vinegar and glucose solution. Answer: True solutions are vinegar and glucose solution. Colloids are fog, aluminium paint.

Question 5. Give two examples each for

• Aerosol: Clouds, smoke
• Emulsion: Milk, face cream.

Question 6. Smoke and fog both are aerosols. In what way are they different? [NCERT Exemplar] Answer: Both fog and smoke have gas as the dispersion medium. The only difference is that the dispersed phase in fog is liquid and in smoke it is a solid.

Question 7. What do you understand by the term distillation? Give its one application. Answer: Distillation is a process of boiling a liquid and then condensing the vapour obtained into a liquid. This process is used to obtain wines from the sugarcane juice.

Question 8. While diluting a solution of salt in water, a student by mistake added acetone (boiling point 56°C). What technique can be employed to get back the acetone? Justify your choice. [NCERTExemplar] Answer: Distillation is used to get back acetone. We know that boiling point of water is 100°C and since acetone is more volatile it will separate out first.

Question 9. Define chromatography and give its one application. Answer: Chromatography is a technique used for the separation of a mixture of solutes brought about by distribution of dissolved material between two immiscible phases, one of which is mobile phase and the other part is stationary phase. It is useful in forensic science to detect and identify trace amounts of substances in the contents of bladder or stomach.

Question 10. Rain water stored in a tank contains sand grains, unfiltrable clay particles, calcium carbonate, salt, pieces of paper and some air bubbles. Select from amongst these one example each of a solvent, a solute, a colloid and a suspension. Answer: Solvent – water Solute – salt Colloid – air bubbles Suspension – clay particles.

Question 11. Classify the following as physical or chemical properties: (a) The composition of a sample of steel is 98% iron, 1.5% carbon and 0.5% other elements. (b) Zinc dissolves in hydrochloric acid with the evolution of hydrogen gas. (c) Metallic sodium is soft enough to be cut with a knife. (d) Most metal oxides form alkalis on interacting with water. [NCERT Exemplar] Answer: Physical properties—(a) and (c) Chemical properties—(b) and (d)

Question 12. Give two points of differences between an element and a compound. Answer:

Question 13. Which of the following are not compounds? (a) Chlorine gas (b) Potassium chloride (c) Iron (d) Iron sulphide (e) Aluminium (f) Iodine (g) Carbon (h) Carbon monoxide (i) Sulphur powder Answer: Chlorine gas, iron, aluminium, iodine, carbon, sulphur powder.

Question 14. Is water an element or a compound? Give reason in support of your statement Answer: Water is a compound because of the following reasons:

• It is composed of two different elements, hydrogen and oxygen which cannot be separated by physical methods. They can be separated only by electrolysis.
• The physical and chemical properties of hydrogen and oxygen are entirely different from the properties of water.

Is Matter Around Us Pure Class 9 Extra Questions Short Answer Questions-II

Question 1. Identify the dispersed phase and dispersing medium in the following colloids. (a) Fog (b) Cheese (c) Coloured gemstone Answer: (a) Fog—liquid, gas (b) Cheese—liquid, solid (c) Coloured gemstone—solid, solid

Question 2. Describe any three properties of colloid. Answer:

• It is a heterogenous mixture.
• Size of particles is too small to be seen by naked eye.
• They scatter light passing through them making its path visible.
• They do not settle down when left undisturbed.
• They cannot be separated by the process of filtration, (any three points)

• Pour the mixture of kerosene oil and water in separating funnel as shown in figure.
• Let it stand undisturbed for sometime so that separate layers of oil and water are formed.
• Open the stopcock of the separating funnel and pour out the lower layer of water carefully.
• Close the stopcock of the separating funnel as the oil reaches the stopcock.

Question 4. What would you observe when (a) a saturated solution of potassium chloride prepared at 60°C is allowed to cool at room temperature? (b) an aqueous sugar solution is heated to dryness? (c) a mixture of iron filings and sulphur powder is heated strongly? [NCERT Exemplar] Answer: (a) Solid potassium chloride will separate out. (b) Initially the water will evaporate and then sugar will get charred. (c) Iron sulphide will be formed.

Question 5. Suggest separation technique (s) one would need to employ to separate the following mixtures: (a) Mercury and water (b) Potassium chloride and ammonium chloride (c) Common salt, water and sand (d) Kerosene oil, water and salt. [NCERT Exemplar] Answer: (a) Separation by using separating funnel (b) Sublimation (c) Filtration to separate sand followed by evaporation/distillation (d) Separation by using separating funnel to separate kerosene oil followed by evaporation or distillation.

Question 6. Name the process associated with the following: (a) Dry ice is kept at room temperature and at one atmospheric pressure. (b) A potassium permanganate crystal is in a beaker and water is poured into the beaker with stirring. (c) An acetone bottle is left open and the bottle becomes empty. (d) Milk is churned to separate cream from it. (e) Settling of sand when a mixture of sand and water is left undisturbed for some time. (f) Fine beam of light entering through a small hole in a dark room, illuminates the particles in its paths. [NCERT Exemplar] Answer: (a) Sublimation (b) Dissolution/diffusion (c) Evaporation/diffusion (d) Centrifugation (e) Sedimentation (f) Scattering of light (Tyndall effect).

Question 7. On heating, calcium carbonate gets converted into calcium oxide and carbon dioxide. (a) Is this a physical or a chemical change? (b) Can you prepare one acidic and one basic solution by using the products formed in the above process? If so, write the chemical equation involved. [NCERT Exemplar] Answer: (a) Chemical change. (b) Acidic and basic solutions can be prepared by dissolving the products of the above process in water. CaO + H 2 O → Ca(OH) 2 (basic solution) CO 2 + H 2 O → H 2 CO 3 (acidic solution)

Question 8. Non-metals are usually poor conductors of heat and electricity. They are non-lustrous, non-sonorous, non-malleable and are coloured. (a) Name a lustrous non-metal. (b) Name a non-metal which exists as a liquid at room temperature. (c) The allotropic form of a non-metal is a good conductor of electricity. Name the allotrope. (d) Name a non-metal which is known to form the largest number of compounds. (e) Name a non-metal other than carbon which shows allotropy. (f) Name a non-metal which is required for combustion. [NCERT Exemplar] Answer: (a) Iodine (b) Bromine (c) Graphite (d) Carbon (e) Sulphur (f) Oxygen

Question 9. Classify the following into metals, non-metals and metalloids: (i) Germanium (ii) Boron (iii) Diamond (iv) Iodine (v) Copper (vi) Helium. Answer: Metal – Copper Non-metals – Diamond, iodine and helium Metalloids – Germanium, boron.

Question 10. Classify the following into elements, compounds and mixtures. (i) Pure sand (ii) Air (iii) Ammonia gas (iv) Ice (v) Glass (vi) CaO. Answer: Elements – Nil Compounds – Pure sand, Ice, CaO, Ammonia gas Mixture – Air, Glass.

Is Matter Around Us Pure Class 9 Extra Questions Long Answer Questions

Question 4. Distinguish between compounds and mixtures. Answer:

Question 8. You are provided with a mixture containing sand, iron filings, ammonium chloride and sodium chloride. Describe the procedures you would use to separate these constituents from the mixture. [NCERT Exemplar] Answer:

• Removing iron filings from the mixture by magnetic separation. Take the mixture in a petri dish and roll a bar magnet over it. Iron filings will get attach to the magnet and thus separate from the mixture.
• Removing ammonium chloride by sublimation Transfer the remaining mixture into China dish and heat it. On heating, ammonium chloride sublimes and solidifies on condensation. The mixture containing sand and sodium chloride left behind in the China dish.
• Removing sand by filtration Make a solution of sand and sodium chloride in water. Filter the solution. Sodium chloride will dissolve in water and sand is left as residue on the filter paper.
• Evaporate the filtrate to dryness to get sodium chloride or by crystallisation.

Question 9. Classify each of the following as a physical or a chemical change. Give reasons. (a) Drying of a shirt in the sun. (b) Rising of hot air over a radiator. (c) Burning of kerosene in a lantern. (d) Change in the colour of black tea on adding lemon juice to it. (e) Churning of milk cream to get butter. [NCERT Exemplar] Answer: (a) It is a physical change because water is converted from its liquid state to gaseous state because of the sun’s heat. (b) It is a physical change because water in the radiator is converted from a liquid state to gaseous state. (c) It is a chemical change because combustion of kerosene occurs and new products are formed. (d) It is a chemical change because there is a reaction between the citric acid in the lemon and the compounds of tea resulting in formation of new products. (e) It is a physical change because the cream suspended in the milk is separated by churning.

Question 11. Iron filings and sulphur were mixed together and divided into two parts ‘A’ and ‘S’. Part ‘A’ was heated strongly while Part ‘S’ was not heated. Dilute hydrochloric acid was added to both the parts and evolution of gas was seen in both the cases. How will you identify the gases evolved? [NCERT Exemplar] Answer: Part A \(\mathrm{Fe}(s)+\mathrm{S}(s) \quad \stackrel{\mathrm{Heat}}{\longrightarrow} \quad \mathrm{FeS}(s)\) FeS(s) + 2HCl(aq) → FeCl 2 (aq) + H 2 S(g)

Part B Fe(i) + S(s) → Mixture of iron filings and sulphur When dilute HCl is added to it Fe(s) + S(s) + 2HCl(aq) → FeCl 2 (aq) + H 2 (g) Sulphur remains unreacted. H 2 S gas formed has a foul smell and on passing through lead acetate solution, it turns the solution black. Hydrogen gas burns with a pop sound.

Numericals Question 1. 0.5 g of salt is dissolved in 25 g of water. Calculate the percentage amount of the salt in the solution. Solution: Mass of salt present = 0.5 g Mass of water present in solution = 25 g ∴ Percentage amount of the salt = \(\frac{0.5}{0.5+25} \times 100\) = 1.96%

Question 8. How much water should be mixed with 12 mL of alcohol so as to obtain 12% alcohol solution? Solution: Volume of solute =12 mL Let the volume of water = x mL Volume of solution = (12 + x) mL Concentration of solution = \(\frac{\text { Volume of solute }}{\text { Volume of solution }} \times 100\) \(12=\frac{12}{12+x} \times 100\) 12 + x = 100 x = 100 – 12 = 88mL So, 88 mL of water should be mixed.

Is Matter Around Us Pure Class 9 Extra Questions Hots (Higher Order Thinking Skills)

Question 1. (a) Under which category of mixtures will you classify alloys and why? (b) A solution is always a liquid. Comment. (c) Can a solution be heterogeneous? [NCERT Exemplar] Answer: (a) Alloys are homogeneous mixture of two or more elements because the constituent elements mix together and give a mixture which is uniform throughout. (b) No, solid solutions and gaseous solutions are also possible. Examples are brass, air. (c) No, a solution cannot be heterogeneous in nature.

Question 2. The teacher instructed three students A’, ‘B’ and ‘C’ respectively to prepare a 50% (mass by volume) solution of sodium hydroxide (NaOH). ‘A’ dissolved 50 g of NaOH in 100 mL of water, ‘B’ dissolved 50 g of NaOH in 100 g of water while ‘C’ dissolved 50 g of NaOH in water to make 100 mL of solution. Which one of them has made the desired solution and why? [NCERT Exemplar] Answer: ‘C’ has made the desired solution because 50% (mass by volume) solution means 50g of solute dissolved in 100 mL of solution. Mass by volume per cent = \(\frac{\text { Mass of solute }}{\text { Volume of solution }} \times 100\) = \(\frac{50}{100} \times 100\) = 50% mass by volume.

Question 3. Explain why filter paper cannot be used to separate colloids. Answer: The size of colloidal particles is less than lnm, while the size of pores present in an ordinary filter paper is larger than lnm. Hence, a colloidal solution cannot be separated by filtration.

Question 4. Three students A, B and C prepared mixtures using chalk powder, common salt and milk respectively in water. Whose mixture: (i) would not leave residue on filter paper after filtration? (ii) would show Tyndall effect? (iii) would give transparent/clear solution? (iv) would settle down at the bottom when left undisturbed? (v) could be filtered by filter paper? Answer: (i)

• Mixture of common salt and water.
• Mixture of milk and water.

(ii) Mixtures of chalk powder with water and milk with water. (iii) Mixture of common salt and water. (iv) Mixture of chalk powder and water. (v) Mixture of chalk powder and water.

Question 5. Can we separate alcohol dissolved in water by using a separating funnel? If yes, then describe the procedure. If not, explain. [NCERT Exemplar] Answer: We cannot separate alcohol dissolved in water by using separating funnel because both the components are highly soluble in each other. They can be separated by fractional distillation.

Question 6. What is the reason for running cold water through condenser from lower side to upper side in distillation process? Answer: In distillation process condensation of vapours take place. To absorb more heat, cold water is passed from lower side so that it will stay for longer time and absorb more heat from the vapours to form liquid state of the substance.

Question 7. You are given two samples of water labelled as ‘A’ and ‘B’. Sample ‘A’ boils at 100°C and sample ‘B’ boils at 102°C. Which sample of water will not freeze at 0°C? Comment. [ NCERT Exemplar] Answer: Sample ‘B’ will not freeze at 0°C because it is not pure water. At 1 atm, the boiling point of pure water is 100°C and the freezing point of pure water is 0°C.

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NCERT Solutions for Class 9 Science Chapter 2 Is Matter Around Us Pure

• Last modified on: 3 years ago
• Reading Time: 26 Minutes

Here we have given NCERT Solutions for Class 9 Science Chapter 2 Is Matter Around Us Pure.

INTEXT Questions

Question 1. What is meant by a pure substance? Solution: A pure substance is one which is made up of only one kind of atoms or molecules. Ex:  water is made up of only one kind of particles. So water is a pure substance,

Question 2. List the points of differences between homogeneous and heterogeneous mixtures. Solution:

Question 3. Differentiate between homogeneous and heterogeneous mixtures with examples. Solution:

Question 4. How are sol, solution and suspension different from each other? Solution:

Question 6. How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C), which are miscible with each other? Solution: The mixture of two miscible liquids such as kerosene and petrol whose boiling points differ by more than 25°C can be easily separated by the technique of simple distillation.

At the boiling point of more volatile (low boiling) liquid of the mixture, the vapours almost exclusively consist of the more volatile liquid. Likewise at the boiling point of the less volatile (high boiling) liquid, vapours almost entirely consist of the less volatile liquid since the more volatile liquid has already distilled over.

Question 7. Name the technique to separate (i)  butter from curd (ii)  salt from sea water (iii)  camphor from salt. Solution: (i)  Butter from curd can be separated by the technique of centrifugation. (ii)  Salt from sea water can be separated by the technique of crystallisation or evaporation. (iii)  Camphor is sublimable but salt is not. So, camphor can be separated from salt by sublimation.

Question 8. What type of mixtures are separated by the technique of crystallisation? Solution: Homogeneous mixtures such as common salt solution and copper sulphate solution are separated by the technique of crystallisation.

Question 9. Classify the following as chemical or physical changes:

• cutting of trees
• melting of butter in a pan
• rusting of almirah
• boiling of water to form steam
• passing of electric current through water and the water breaking down into hydrogen and oxygen
• dissolving common salt in water
• making a fruit salad with raw fruits
• burning of paper and wood
• Cutting of trees is a chemical change since all chemical reactions stop and we cannot get back the original tree from the wooden pieces.
• Melting of butter in a pan is a physical change since there is no change in the chemical composition of butter, only the physical state changes from solid to liquid.
• Rusting of almirah is a chemical change since during rusting, a new chemical compound called hydrated iron oxide (rust) is formed.
• Boiling of water to form steam is a physical change because during this change only change of state occurs from liquid water to steam (gaseous) without any change in its chemical composition.
• Passing of electric energy through water to form hydrogen and oxygen gases is a chemical change since the properties of hydrogen (combustible gas) and oxygen (supporter of combustion) are altogether different from those of water which is neither combustible nor a supporter of combustion but it actually extinguishes fire.
• Dissolution of common salt in water is a physical change since salt can be easily recovered by evaporating water.
• Making a fruit salad with raw fruits is a physical change since there is no change in the chemical properties of the fruits but only the physical appearance has changed.
• Burning of paper is a chemical change since carbon dioxide, water vapours, smoke and ash which are the products of combustion cannot be converted back into paper or wood by any physical method.

Question 10. Try segregating the things around you as pure substances or mixtures. Solution: Pure substances : Distilled water, diamond, graphite, gold, sulphur Mixtures : Curd, ice cream, kerosene oil, cooking oil, steel, vulcanised rubber, solder wire (alloy of lead and tin).

NCERT Exercises

Question 1. Which separation techniques will you apply for the separation of the following? (a)  Sodium chloride from its solution in water. (b)  Ammonium chloride from a mixture containing sodium chloride and ammonium chloride. (c)  Small pieces of metal in the engine oil of a car. (d)  Different pigments from an extract of flower petals. (e)  Butter from curd. (f)  Oil from water. (g)  Tea leaves from tea. (h)  Iron pins,from sand. (i)  Wheat grains from husk. (j)  Fine mud particles suspended in water. Solution: (a)   Evaporation :  Water will evaporate leaving behind sodium chloride. (b)   Sublimation :  Ammonium chloride will be collected as sublimate. (c)   Filtration :  Pieces of metal can be separated by filtration. (d)   Chromatography :  Pigments (coloured components) from the extract of flower plants can be separated by chromatography. (e)   Centrifugation:  Butter will get separated upon centrifugation. (f)   Separating funnel :  Oil and water can be separated by the use of separating funnel. (g)   Filtration:  Upon filtration through a sieve, tea leaves will be collected on the sieve. (h)   Magnetic separation :  A magnet will attract iron pins and not sand particles. (i)   Sieving :  Wheat grains from husk can be separated with the help of sieves. (j)   Sedimentation :  As a result of sedimentation, mud particles will settle down and can be separated later on by filtration.

Question 2. Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue. Solution: Take 100 mL of water which acts as solvent. Boil water on a gas stove. Add one teaspoon of sugar which acts as solute. Sugar is soluble in water, so gets dissolved in water and forms a solution. Now add about half a teaspoon of tea leaves which are insoluble in water. Boil the contents for 4 to 5 minutes and add a half cup of milk and allow to boil again for 2-3 minutes. Filter the tea with the help of a sieve. Tea leaves will be left as residue while tea will be obtained as filtrate.

Question 3. Pragya tested the solubility of three different substances at different temperatures and collected the data as given below (results are given in the following table, as grams of substance dissolved in 100 grams of water to to from a saturated solution)

Question 4. Explain the following giving examples.

• Saturated solution
• Pure substance
• Saturated solution :  A solution in whichno more solute canbe dissolved ina given amount of solvent at a particular temperature is called saturated solution. For example, if we dissolve 40 g sodium chloride in 100 g of water at 293 K, it will form a saturated solution because the solubility of sodium chloride at 293 K is 36 g per 100 g of water.
• Pure substance :  A substance made up of only one kind of atoms or molecules is called a pure substance. A pure substance has the same colour, taste and texture at a given temperature and pressure. A pure substance also has a fixed melting and boiling point at a constant pressure. For example, hydrogen gas, sodium chloride, water, etc.
• Colloid :  A substance is said to be a colloid if the particle size lies between 1 to 100 nm. A colloidal solution is heterogeneous and consists of two phases. i.e., dispersed phase (colloidal particles) and dispersion medium in which colloidal particles are suspended. For example, colloidal solution of sulphur or starch, milk, etc.
• Suspension :  It is a heterogeneous mixture in which the particles of the solute do not dissolve but remain suspended throughout the bulk of the solvent. The size of the suspension particles is more than lCk7 m. For example, chalk powder in water is a suspension.

Question 5. Classify each of the following as a homogeneous or heterogeneous mixtures: Soda water, wood, air, soil, vinegar, filtered tea  Solution: Homogeneous mixtures :  Soda water, vinegar and filtered tea. Heterogeneous mixtures :  Wood and soil. Air is a homogeneous mixture of different gases. However, if some dust or other particles are also present, then air becomes heterogeneous mixture.

Question 6. How would you confirm that a colourless liquid given to you is pure water? Solution: If the boiling point and freezing point of the given liquid comes out to be 100°C or 373 K and d°C or 273 K respectively under one atmospheric pressure, it confirms that the given liquid is pure water.

Question 7. Which of the following materials fall in the category of a “pure substance”? (a)  Ice, (b)  Milk, (c)  Iron, (d)  Hydroelectric acid, (e)  Calcium oxide, (f)  Mercury, (g)  Brick, (h)  Wood, (i)  Air Solution: Ice, iron, calcium oxide and mercury are pure substances since they contain particles of only one kind of matter. In contrast, milk, hydroelectric acid (hydrogen chloride gas dissolved in water), brick and air cannot be called pure substances because they consist of particles of more than one kind of matter.

Question 8. Identify the solutions among the following mixtures. (a)  Soil (b)  Seawater (c)  Air (d)  Coal (e)  Soda water Solution: A solution is a homogeneous mixture of two or more substances. In the light of this, the solutions among the given mixtures are (b)  sea water, (c)  air and (e)  soda water.

Question 9. Which of the following will show Tyndall effect? (a)  Salt solution (b)  Milk (c)  Copper Sulphate solution (d)  Starch solution Solution: (b)  milk and  (d)  starch solution show Tyndall effect because they are colloidal solutions, whereas  (a)  salt solution and  (c)  copper sulphate solution are true solutions. Their particle size is too small to scatter light, so they do not show Tyndall effect.

Question 10. Classify the following into elements, compounds and mixtures. (a)  Sodium, (b)  soil, (c)  sugar solution, (d)  silver, (e)  calcium carbonate, (f)  tin, (g)  silicon, (h)  coal, (i)  air, (j)  soap, (k)  methane, (I)  carbon dioxide, (m)  blood Solution: Elements :  The elements are regarded as the building blocks of the universe. So (a)  sodium, (d)  silver, (f)  tin and (g)  silicon are elements.

Compounds :  It is a pure substance made up of two or more elements chemically combined in a fixed proportion by mass. So, (e)  calcium carbonate, (k)  methane and  (1)  carbon dioxide are compounds.

Mixtures :  It is a substance containing two or more substances (elements or compounds) in any proportion. So (b)  soil, (c)  sugar solution, (h)  coal, (i)  air, (j)  soap and (m)  blood are mixtures.

Question 11. Which of the following are chemical changes? (a)  Growth of a plant (b)  Rusting of iron (c)  Mixing of iron filings and sand (d)  Cooking of food (e)  Digestion of food (f)  Freezing of water (g)  Burning of a candle Solution: (a)  Growth of a plant, (b)  rusting of iron, (d)  cooking of food (e)  digestion of food and (g)  burning of a candle, are chemical changes.

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