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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.
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.
Also, students can refer to
NCERT Solutions for Class 9 Science Chapter 2 Is Matter Around Us Pure |
NCERT Exemplar Class 9 Science Chapter 2 Is matter around us pure |
Topics covered in NCERT Book
2.1 What is the mixture? |
2.2 What is a solution? |
2.3 Physical and Chemical Changes |
2.4 What are the types of pure substances? |
Definition of Solution: A solution is a two- or more-component homogenous mixture.
Based on the concentration of the solution, there are three types of solutions: diluted, Concentrated and saturated.
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
Definition: A suspension is a heterogeneous combination in which the solute particles do not dissolve but stay suspended in the medium's bulk.
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.
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
On the basis of their chemical composition, substances can be classified either as elements or compounds.
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.
A compound is an entity that is made up of two or more components that have been chemically combined in a certain ratio.
NCERT Class 9th Science Chapter 2 Notes |
The main topics covered in Chapter 2 of NCERT Solutions for Class 9 Science are
Matter and its Types
Elements
Compounds
Metals
Nonmetals and Metalloids
Mixture and its Types
Solution and its Types
Solubility and Concentration of Solution.
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 mixture that is heterogeneous. A suspension's particles can be seen with the naked eye.
The particles in a suspension scatter a light beam traveling 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.
According to Class 9th Science chapter 2 notes
Heterogeneous mixtures | Homogeneous mixtures |
It shows visible boundaries of Separation. | No visible boundaries of Separation |
It doesn’t have a uniform composition. | It has a uniform composition. |
It consists of more than one phase. | It consists of only one phase. |
According to Class 9th Science chapter 2 notes,
Compounds | Mixtures |
The composition of a new substance is always fixed. | The composition of a mixture varies. |
Elements react to form new compounds. | Elements or compounds just mix to form a mixture and no new compound is formed. |
The new substance has entirely new properties. | The properties of the constituent substances are displayed in a mixture. |
Only chemical or electrochemical reactions can separate the constituents. | Physical methods can be used to separate the constituents fairly easily. |
According to Class 9th Science chapter 2 notes, we solve the numerical as follows,
Mass of solute (NaCl) = 56 g
Mass of solvent (H2O) = 100 g
Mass of solution (NaCl + H2O) = 156 g
Concentration = Mass of solute/Mass of solution x 100
Concentration = 56/156 x 100 = 35.89%
Hence, the concentration of the solution is 35.89%
These topics can also be downloaded from Is Matter around us pure? class 9 notes pdf download or Class 9 Science chapter 2 notes pdf download.
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