NCERT Class 9 Science Chapter 2 Notes Is Matter Around Us Pure- Download PDF Notes

It is very crucial to understand whether the matter around us is pure or not. Have you ever wondered why oil does not dissolve in water while salt dissolves in water or sugar completely dissolves in water while sand settles at the bottom? All these observations are linked to the concept of the purity of matter. Objects around us are categorised as either pure or a mixture. Examples of pure substances are Gold, oxygen, salt, etc while mixtures are milk, air, soft drinks, etc. Everything around us matters whether it is the air we breathe, the water we drink or the food we eat. Class 9 Science Chapter 2, Is matter around us pure? explains all the fundamental concepts of matters.

This Story also Contains

1. NCERT Class 9 Chapter 2 Class Notes
2. Is Matter Around Us Pure
3. What is a Mixture?
4. What is a Solution?
5. What is a Suspension?
6. What is a Colloidal Solution?
7. Separating the Components of a Mixture
8. Sublimation
9. Chromatography
10. Distillation
11. Crystallisation
12. What are the Types of Pure Substances?
13. Chapter-Wise NCERT Class 9 Notes Science
14. Subject Wise NCERT Exemplar Solutions
15. Subject Wise NCERT Solutions

These notes provide the basic and detailed knowledge needed to know if the matter around us is pure. The notes are designed by our subject experts and all the topics of NCERT books and the CBSE curriculum are covered in these notes. NCERT Notes for Class 9 Science helps students revise all the major concepts given in the Chapter. These notes will help students with quick revision.

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NCERT Class 9 Chapter 2 Class Notes

Topics covered in NCERT Book

Is Matter Around Us Pure

• When a scientist states something is pure, it signifies that all of the substance's constituent particles have the same chemical nature.
• A single sort of particle makes up a pure material.
• A substance, in other terms, is a single pure form of matter.
• When we look around us, we can see that most of the substance we observe is made up of two or more pure components, such as seawater, minerals, dirt, etc. These are all mixtures.

What is a Mixture?

• Mixtures are created by simply combining two or more pure substances (components) while maintaining each substance's chemical identity.
• Using the proper separation technique, a mixture can be separated into pure substances.

Types of Mixtures

• Different sorts of mixtures exist, depending on the nature of the components that make up the mixture.
• A homogeneous mixture or solution has a consistent or uniform composition throughout.
• A heterogeneous mixture has physically separate parts and a non-uniform composition.

What is a Solution?

Definition of Solution: A solution is a two- or more-component homogenous mixture.

• The major component of a solution is the solvent, whereas the lesser component is the solute.
• The amount of solute present per unit volume or unit mass of the solution/solvent can be used to determine the concentration of a solution.

Concentration of a Solution

Based on the concentration of the solution, there are three types of solutions: diluted, Concentrated and saturated.

• A dilute solution is one in which the amount of solute in a given mass is fairly minimal compared to the amount of solvent.
• A concentrated solution contains a large amount of solute.
• A saturated solution has dissolved all of the solutes it is capable of dissolving at a given temperature.
• In other terms, a saturated solution is one in which no more solute can be dissolved in a solution at a given temperature.
• The solubility of a solute is the amount of the solute present in a saturated solution at this temperature.
• An unsaturated solution is one in which the amount of solute in the solution is less than the saturation level.

A solution's concentration can be stated in a variety of ways-

Mass by the mass percentage of a solution =Mass of solute x 100/Mass of solution

Mass by the volume percentage of a solution =Mass of solute x 100/Volume of solution

Volume by the volume percentage of a solution =Volume of solute x 100/Volume of solution

What is a Suspension?

Definition: A suspension is a heterogeneous combination in which the solute particles do not dissolve but stay suspended in the medium's bulk.

Properties of a Suspension

• Suspension is a heterogeneous mixture. A suspension's particles can be seen with the naked eye.

• The particles in a suspension scatter a light beam travelling across it, revealing its path.

• When a suspension is left undisturbed, the solute particles settle down, making the suspension unstable. Filtration can be used to separate them from the rest of the mixture. The suspension breaks as the particles settle down, and light is no longer scattered.

What is a Colloidal Solution?

Definition: A colloid is a type of solution in which the size of solute particles lies between that of genuine solutions and that of suspensions.

• A colloid is a heterogeneous combination of particles that are too tiny to be seen individually with the naked eye.

• Colloids are large enough to scatter a light beam passing through them, revealing their path.

• When left undisturbed, they do not settle down, implying that a colloid is quite stable.

The scattering of light by particles in a colloid or particles in a very fine suspension is known as the Tyndall effect.

Dispersed phase: The dispersed phase of a colloid is the solute-like component of dispersed particles.

Dispersion medium: The dispersion medium is the component in which the dispersed phase is suspended.

Aerosol: Aerosol is a colloidal solution containing a solid/liquid dispersed phase and a dispersing medium gas, such as clouds.

Foam: Foam, for example, is a colloidal solution with a dispersed phase gas and a dispersing medium solid/liquid.

Sol: Sol is a colloidal solution including a solid dispersed phase and a liquid dispersing medium. Magnesia milk and mud

Separating the Components of a Mixture

• To separate distinct components from a mixture, many separation procedures are used.
• Separation enables the study and use of distinct components of a mixture.
• Simple physical procedures like handpicking, sieving, and filtering that we employ in our daily lives can be used to separate heterogeneous mixtures into their constituents.
• Separating the components of a mixture often necessitates the employment of specialised procedures.

Separation of Two Immiscible Liquids

• A separating funnel is used to separate a mixture of two immiscible liquids.
• Application: When extracting iron from its ore, a mixture of oil and water must be separated.

Centrifugation:

• The separation of two liquids in a mixture is accomplished by centrifugation.
• The mixture's denser component migrates away from the axis, while the lighter component moves toward it.
• Application: Cream is separated from milk using this method.
• This approach can be used to separate clay particles suspended in water.

Sublimation

• Sublimation is the process by which a solid transforms into a gas without becoming liquid when heated.
• This method is used to extract components from a mixture that become sublime when heated.
• Application: Sublimation can be used to separate a mixture of common salt (sodium chloride) and ammonium chloride.

Chromatography

• Chromatography is a method for separating two or more dissolved materials in extremely tiny amounts.
• The separation is based on the notion that two or more compounds might be soluble in the same solvent yet have different solubilities.
• Application: Black ink is made up of several different coloured substances or dyes that can be separated using paper chromatography.

Distillation

• Distillation is a process that uses selective evaporation and condensation to separate constituent chemicals from a liquid mixture.
• Applications: Gasoline, distilled water, xylene, alcohol, paraffin, kerosene, and other products are all made from it.

Fractional Distillation:

• The separation of a mixture into its constituent components or fractions based on their melting points is known as fractional distillation.
• The boiling point is used to separate chemical substances.
• The mixture is heated to the point where one or more of the fractions evaporate.
• Applications: In the laboratory, fractional distillation is used to separate a mixture of miscible liquids such as acetone and water.
• It's used to separate air gases.
• It is used to separate crude oil, often known as "petroleum," into useful components including kerosene, gasoline, and diesel.

• We must separate all of the other gases present in the air if we desire oxygen gas.
• To obtain liquid air, the air is compressed by increasing the pressure and then chilled by lowering the temperature.
• In a fractional distillation column, where gases are separated at different heights depending on their boiling points, this liquid air is allowed to warm up slowly.

Crystallisation

• The cooling of a hot, concentrated chemical solution to produce crystals is known as crystallisation.
• The crystallisation process is used to transform an impure sample into a pure solid product.
• Applications: To obtain pure copper sulphate, impure copper sulphate can be refined using the crystallisation process.

Evaporation:

• Evaporation is a method of separating a solid object from water or any other liquid.
• This method is based on the fact that liquids are easily vaporised.
• When all of the water or liquid has evaporated, the dissolved substance is left as a residue.
• Applications: Evaporation can be used to separate common salt that has dissolved in water. Evaporation can be used to separate the coloured component of ink.

What are the Types of Pure Substances?

On the basis of their chemical composition, substances can be classified either as elements or compounds.

Elements

Elements are the most fundamental form of matter and cannot be broken down into smaller compounds by chemical reactions.

Metals, non-metals, and metalloids are the three types of elements.

Metals frequently exhibit one or more of the following characteristics:

• They have a lustrous shine to them.

• Their colour is silvery-grey or golden-yellow.

• They are heat and electricity conductors.

• They're ductile (they can be drawn into shapes).

• Metals are malleable (they can be hammered into thin sheets).

• They have a resonant tone to them (make a ringing sound when hit).

Gold, silver, copper, iron, sodium, potassium, and other metals are examples. Mercury is the only metal that is liquid at ambient temperature.

Non-metals typically exhibit one or more of the following characteristics:

• They come in a wide range of colours.

• They are poor heat and electrical conductors.

• They lack lustre, sonority, and malleability.

Hydrogen, oxygen, iodine, carbon (coal, coke), bromine, chlorine, and other non-metals are examples.

Metalloids are elements that have properties that are halfway between those of metals and non-metals; examples include boron, silicon, and germanium.

Compounds

A compound is an entity that is made up of two or more components that have been chemically combined in a certain ratio.

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