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

Science is a fascinating subject that studies nature and the surrounding environment. In this chapter, Class 9 students will  learn about the purity of matter in the environment. For better understanding of the chapter, students are suggested to practise NCERT chapter end-text questions. To get accurate and detailed solutions of those questions,  students can follow Extramarks NCERT Solutions for Class 9 Science Chapter 2.

Class 9 Science Chapter 2 ‘’Is Matter Around Us Pure?’’ elaborates on the critical properties of pure substances, mixtures, and types of concentration of solutions. Students will get to learn about suspension and its properties. Furthermore, they will get a chance to learn the critical definitions of colloids solution, suspension, Tyndall effect, and aerosol.

The NCERT Solutions for Class 9 Science Chapter 2 and other study resources are available on the website or app of Extramarks. The solution assists students in gaining a thorough overview of the sub-topics and concepts through comprehensive explanations of the NCERT answers . It comprises 11 questions that include fill-in-the-blanks, multiple-choice-question, match the following and true or false. By accessing study material by Extramarks, students will become more efficient in their learning. . Through regular practice, students will be able to increase their understanding of the chapter and build a strong foundation on the concepts.

Extramarks is the trusted learning platform among students in secondary and primary Classes which provides the most effective study guide and solutions. Their solutions for Class 9 are developed in the highest quality and accuracy by adhering to  the CBSE board instructions and the latest syllabus. The aim is to enhance the students' learning experience and give them an in-depth understanding of the subject.

Students can visit Extramarks website for the latest updates. Further, they can also refer to other primary and secondary C class S solutions, including NCERT Solutions Class 10, NCERT Solutions Class 11, and NCERT Solutions Class 12.

## Key Topics Covered In NCERT Solutions for Class 9 Science Chapter 2

The Solutions provide helpful strategies and tips to earn extra marks in the CBSE Class 9 Science examination. It is richly illustrated with diagrams and illustrations to ensure that students can quickly grasp the concepts.

### Introduction

According to Science, a substance is a matter that cannot be divided into any other types of matter by physical technique. Substances are formed by one or more components that make up matter. These are frequently mixed, and the results are inferred as a mixture.

### Pure and Impure Substances

A pure material/substance consists of  one type of particle that any physical process cannot separate. It has a constant composition and a constant melting and boiling point. Pure substances are elements which have a fixed composition. Water, sulphur, hydrogen, carbon, and diamond are examples of pure materials.

Pure substances are Classified into two categories:

• Elements
• Compounds

An element is a pure substance which cannot be broken down into its chemical constituents by physical or chemical techniques. According to Dalton's research, atoms are the simplest form of matter, and they can be defined as a pure substance made up of only one type of atom. Hydrogen, carbon, and oxygen are some examples of elements.

Impure substance/ material is defined as one element made up of two or more types of particles which can be separated using physical methods. All the substances in the mixtures are impure. A mixture can be homogeneous or heterogeneous. Salt solution, sugar solution, milk, sugarcane juice, soft beverage,  rocks, minerals, petroleum, LPG, biogas, tap water, tea, coffee, paint, wood, soil and bricks are some of the examples of mixtures.

Students can refer to our NCERT Solutions for Class 9 Science Chapter 2 for learning the characteristics and features of impure substances.

Metals, Nonmetals and Metalloids

Elements are broadly divided into three types explained in NCERT Solutions for Class 9 Science Chapter 2 are as follows:

• Metals:

It is a malleable and ductile element which conducts electricity. Iron, copper, aluminium, silver, gold, platinum, chromium, sodium, potassium, and magnesium are some examples of metals.

• Nonmetals

A chemical compound or element that mainly lacks metallic characteristics. They make up approximately 14% to 15% of the elements in the periodic table. Carbon, phosphorus, hydrogen, oxygen, and sulphur are some examples of nonmetals.

• Metalloids:

It is defined as the type of chemical element which has properties between metals and nonmetals. Boron, Silicon, Germanium, Bismuth, and Tellurium are some of the examples of metalloids.

The comparison of properties of metals and nonmetals elaborated in NCERT Solutions for Class 9 Science Chapter 2 are as follows:

 Metals Nonmetals Metals have an extremely high tensile strength, and are durable and robust. Nonmetals have moderate tensile strength and are not durable. Metals have a resonant quality. They generate a ringing sound when struck. Nonmetals do not have a resonant quality Metals are solids at room temperature. Nonmetals can be solids, liquids, or gas at room temperature. Metals are excellent heat and electricity conductors. Nonmetals are poor heat  and electricity conductors. Metals can be polished and are lustrous Nonmetals cannot be polished

Mixtures and their Types

Mixtures contain two or more different kinds of particles. They do not react chemically but are physically mixed in any proportion. There are two types of mixture; homogeneous and heterogeneous mixture.

 Homogeneous mixture Heterogeneous mixture All the components of the mixture are uniformly mixed All the components of the mixture are not thoroughly mixed Homogeneous mixtures consist of a single phase A heterogeneous mixture consists of two or more phase Example: Sugar dissolved in water Example: Air, sand and common salt.

Further, students can also refer to other study materials created by the Extramarks for learning the types of mixtures in more detail.

Solutions and their Types

A solution is defined as a homogeneous mixture of two or more substances. Lemon water, sugar solution, and soda water are some examples of solutions.

Components of Solutions

• Solvent: The component of the solution dissolves the other component in it. Solvents are usually present in a more significant amount. Water and alcohol are the two examples of solvents.
• Solute: It is the component of the solution that dissolves in the solvent, and it is present in lesser quantities. Salt, sugar and iodine are examples of solutes.

Properties of Solutions

• Solutions are homogeneous mixture.
• A proper solution does not scatter the light.
• The solution is stable.
• Particles of a solution cannot be seen with a microscope, and the size of a particle is less than 1 nm in diameter.
• The solute  particles cannot be separated from the mixture.

Types of Solutions

• Solid in a solid solution.
• Solid in a liquid solution.
• The liquid is in a liquid solution.
• Gas in a gas solution.
• Gas in a liquid solution.

#### Solubility and Concentration of the solution

Solubility:

• The maximum amount of the solute which can be dissolved in 100 grams of a solvent at a particular temperature is known as its solubility. The solubility of solids in liquids increases when the temperature increases.
• The solubility of gases in liquids decreases when temperature increases.
• The solubility of gases in liquids increases when pressure increases.
• The solubility of solids in liquids remains unaffected by the change in pressure.

The concentration of a solution:

• It is defined as the mass of the solute in grams present in 100 grams of the solutions.
• Saturated Solutions are defined as a solution in which no more quantity of solute can be dissolved at a particular temperature.
• An unsaturated solution is defined as a solution in which more quantity of solute can be dissolved without raising its temperature.

#### NCERT Solutions for Class 9 Science Chapter 2: Exercise & Solution

Extramarks NCERT Solutions help students with the best study material and solution guide. It is one of the leading online learning platforms for  examination preparation. Students can start with a trial account by registering on their website.

NCERT Solutions for Class 9 Science Chapter 2 offer theoretical explanations and have step-by-step solutions. Students will get to understand the new concepts covered in this  chapter. The solution  is a guide developed by subject matter experts to make textbook exercises easy to solve, learn, retain and finally to achieve good academic results.

In addition, it provides a variety of solved questions with which students can analyze their mistakes and gain more confidence.

Click on the below links to view exercise specific questions and their solutions as covered in our NCERT Solutions for Class 9 Science Chapter 2:

• Chapter 2: Exercise 2.1 Solutions: 2 Questions
• Chapter 2: Exercise 2.2 Solutions: 3 Questions
• Chapter 2: Exercise 2.3 Solutions: 3 Questions
• Chapter 2: Exercise 2.4 Solutions: 2 Questions
• Class 9 Science Chapter 2 Question Answer

Along with this, students can explore other Classes Solutions on our website:

• NCERT Solutions Class 1
• NCERT Solutions Class 2
• NCERT Solutions Class 3
• NCERT Solutions Class 4
• NCERT Solutions Class 5
• NCERT Solutions Class 6
• NCERT Solutions Class 7
• NCERT Solutions Class 8
• NCERT Solutions Class 9
• NCERT Solutions Class 10
• NCERT Solutions Class 11
• NCERT Solutions Class 12

#### NCERT Exemplar for Class 9 Science

Science is a subject that can be difficult to grasp. NCERT Exemplar aids in developing the learning ability of the students. It helps them develop their knowledge of the subject and makes it easier to complete exercises of various difficulty levels ranging from easy to moderate and very hard. Students can establish a solid foundation of every concept when solving Exemplar questions.

The NCERT Exemplar consists of various questions, including multiple-choice, long answer, and short answer types. Students will also witness fill in the blanks, match the following, and true or false types of questions. Through regular practice of the  Exemplar, students will be able to score well in the examinations.

NCERT Solutions for Class 9 Science Chapter 2 offers examples from the Exemplar that deal with mixtures, elements and compounds. Students will increase their understanding of subjects, such as the chemical and physical properties of nonmetals and metals.

#### Key Features of NCERT Solutions for Class 9 Science Chapter 2

Extramarks has a team of experts committed to providing appropriate solutions for each topic. ·  The answers in NCERT Solutions are explained in detail, which give students an idea of how to attempt a question in the board exam in the right manner

Some of the features and characteristics in NCERT Solutions for Class 9 Science Chapter 2 are as follows:

• Every kind of solution and mixture is properly illustrated using correct illustrations.

The NCERT Solutions for Class 9 Science Chapter 2 can help students with well explained answers of the end-text NCERT questions, which will further assist them in better comprehending of the chapter

• Each rule is elaborated with relevant  examples to ensure that students can easily retain and recall them during the examination.
• The solutions are prepared by subject experts who have years of experience in teaching.
• All the answers are stated stepwise for quick retention.
• The solution is prepared under the guidelines of the CBSE Board.

Q.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.

Ans-

(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: Filtration
(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

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

Ans-

Tea can be prepared by following steps:

1. Take some water as solvent in a kettle and boil it for few minutes.
2. Now add one tea spoon sugar, one tea spoon tea leaves and some milk as solute to water. They all together form a solution.
3. Now boil the solution again for few minutes so that sugar dissolves in solution as sugar is soluble in water.
4. Now filter the solution through a strainer. The insoluble tea leaves remain on the strainer as residue and the filtrate is collected in cup.

Q.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?

Ans-

$\begin{array}{l}\text{(a) Solubility of potassium nitrate at 313 K =}\frac{\text{62}}{\text{100}}\text{}\\ \text{100 g of water contains potassium nitrate = 62 g}\\ \therefore \text{50 g of water contains potassium nitrate=}\frac{\text{62}}{\text{100}}\text{x 50 = 31 g}\\ \text{Thus, 31 g potassium nitrate would be needed to}\\ \text{produce a saturated solution of potassium nitrate in}\\ \text{50 g of water at 313 K}\text{.}\end{array}$

(b) On cooling the solubility of salt decreases with the falling temperature. Hence, the crystals of potassium chloride will separate out on cooling.

(c) The maximum amount of the salt which is dissolved in 100 g of water to form a saturated solution at the given temperature is known as solubility. The solubilities of different salts at 293 K in 100g of water are given in column 2 in the table.

1. Solubility of potassium nitrate at 293K is 32g.
2. Solubility of sodium chloride at 293K is 36g.
3. Solubility of potassium chloride at 293K is 35g.
4. Solubility of ammonium chloride at 293K is 37g.

From the above data it is clear that ammonium chloride has the highest solubility at 293 K.

(d) Generally, the solubility of a salt increases with the increasing temperature. However, from the data given in the table, the increase is different for different salts. For example the solubility of potassium nitrate increases appreciably, that of ammonium chloride increases slightly, that of potassium chloride increases marginally while that of sodium chloride almost remains constant.

Q.4 Explain the following giving examples.
(a) saturated solution
(b) pure substance
(c) colloid
(d) suspension

Ans-

(a) Saturated solution: A solution in which no more solute can be dissolved at a particular temperature is called as saturated solution. For example: Soft drinks are saturated with carbon dioxide, hence it gives off carbon dioxide through bubbles, the Earth’s soil is saturated with nitrogen.

(b) Pure Substance: A substance that shows same characteristics at a given temperature and pressure is called a pure substance. For example distilled water is a pure substance.

(c) Colloid: A colloid is a heterogeneous mixture that consists of particles bigger than that of a solution and smaller than that of suspension. For example: Smoke, butter, milk, etc. are colloids.

(d) Suspension: A suspension is a heterogeneous mixture in which solid is dispersed in liquid. The solute particles in suspension do not dissolve but remain suspended throughout the medium. The particles are large in size and visible to naked eye. For example: Chalk particles, muddy water etc.

Q.5 Classify each of the following as a homogeneous or heterogeneous mixture.

soda water, wood, air, soil, vinegar, filtered tea.

Ans-

Homogeneous mixtures: Soda water, vinegar, filtered tea

Heterogeneous mixtures: Soil, wood

Air is a homogeneous mixture of different gases. However, if some dust or other particles are also present, then air becomes heterogeneous mixture.

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

Ans-

Every liquid has a characteristic boiling point. Pure water has boiling point of 100 °C (373 K) at 1 atmospheric pressure. Hence, the purity of water can be confirmed by determining its boiling point.

Q.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) Brick

(h) Wood

(i) Air

Ans-

Ice, iron, hydrochloric acid, calcium oxide and mercury fall in the category of pure substance.

Q.8 Identify the solutions among the following mixtures.

(a) Soil

(b) Sea water

(c) Air

(d) Coal

(e) Soda water

Ans-

Sea water, air and soda water are solutions.

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

Ans-

Milk and starch solution will show Tyndall effect because they are colloidal solutions.

Q.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

Ans-

 Element Compound Mixture Sodium, Silver, Tin, Silicon Calcium carbonate, Methane, Soap, Carbon dioxide Soil, Sugar solution, Coal Air, Blood

Q.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

Ans-

Growth of plant, rusting of iron, cooking of food, digestion of food and burning of a candle are chemical changes.

1. What different nature of questions are covered in Science Class 9 Chapter 1?

A variety of questions are covered in the NCERT textbook and the NCERT Exemplar books. These include; multiple-choice questions, match the following, true or false and descriptive types of questions. Students should practise these various formats of problems in Class 9 Science, which will help them increase their knowledge of critical topics and finally leverage higher marks in their examination.

2. What are the essential points in NCERT Solutions for Class 9 Science Chapter 2?

The students need to remember the following essential points in Class 9, Chapter 2:

• A mixture is made up of many substances in any proportion.
• Mixtures can be separated into pure substances.
• The concentration of a solution is defined as the quantity of solute contained in the solution.
• Elements or compounds can be pure substances.

3. How to prepare for the Class 9 Science term one examination?

Students can refer to Extramarks NCERT Solutions for Class 9 Science Chapter 2. It offers complete detailed solutions for every end-text question given in the NCERT book  with illustrations and diagrams.