Is Matter Around Us Pure Revision Notes

Notes Class 9

Please refer to the Is Matter Around Us Pure Revision Notes given below. These revision notes have been designed as per the latest NCERT, CBSE and KVS books issued for the current academic year. Students will be able to understand the entire chapter in your class 9th Science book. We have provided chapter wise Notes for Class 9 Science as per the latest examination pattern.

Revision Notes Chapter 2 Is Matter Around Us Pure

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Conceptual levels of comprehension on the basis of feedback taken from the students

Is Matter Around Us Pure Revision Notes
  1. Pure Substance & mixture
Is Matter Around Us Pure Revision Notes
Pure substance consists of a single type of substance .Mixture consists of two or more pure substances.
Pure substance cannot be separated into other substances by physical methods.Mixture can be separated into its components by physical methods.
Pure substance has its own definite properties.Mixture shows the properties of its components.

Elements are made up of one kind of atoms only. Compounds are made up of one kind of molecules only.

Difference between Compound &Mixture

2. Types of Mixtures

Mixtures can also be grouped

i) on the basis of their physical states:

SOLIDSalt and sugarSalt and waterDust in air
LIQUIDMercury and copperAlcohol and waterClouds
GASHydrogen and palladiumOxygen and waterAir

ii) on the basis of miscibility :

Homogeneous Mixture Heterogeneous Mixture
* It consists of single phase.
* Uniform composition.
* Example: Sugar dissolved in water
* It consists of two or more phase.
* Does not have uniform composition.
* Example: Air, sand and common salt.

4. Separating the components of a mixture

The components of a heterogeneous mixture can be separated by

simple methods like –

hand picking , sieving , & Winnowing

special techniques like –

i) Evaporation : a mixture of salt and water or sugar and water.
ii) Centrifugation : Butter from curd, Fine mud particles suspended in water.
iii) Decantation : (Using separating funnel) : Oil from water.
iv) Sublimation : Camphor from salt,
v) Chromatography : Different pigments from an extract of flower petals.
vi) Distillation and fractional distillation : Separating components of Petroleum
viii) Magnetic separation: Iron pins from sand.

5. Concentration of Solution

The amount of solute present in a given amount (mass or volume) of solution.

Concentration of a solution = Amount of solute / Amount of solvent


Amount of solute / Amount of solution

The concentration of a solution can be expressed as mass by mass percentage or as mass by volume percentage.

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

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

Types of Solutions

a) on the basis of size of solute particles:

True solutionSol [ Colloid]Suspension
Size of solute
particles is less than
1 n m or 10-9 m .
Size of solute particles
is between 1 nm to
1000 nm.
Size of solute particles is more than 1000 nm.
Particles cannot pass through filter paper.Particles can pass through filter paper.Particles cannot pass thorough filter paper.
StableStable and settle only on centrifugation.Unstable and settle down on its own.
Solution of sodium chloride in water,
sugar & water.
Milk , Fogmuddy water, chalk & water, smoke in the air.

types of colloids :

Colloidal solution is a heterogeneous mixture. It consists of two phases:-

(i) Dispersed phase : component present in small proportion
(ii) Dispersion medium : component present in large proportion

The particles of colloid are large enough to scatter a beam of light passing through it and make its path visible. Thus, they show Tyndall effect.

The colloidal particles are moving at random in a zigzag motion in all directions.

This type of zig-zag motion of colloidal particles is called Brownian movement.

b) on the basis of amount of solute:

Unsaturated solutionSaturated SolutionSupersaturated solution
A solution which has lesser
amount of solute that it can
dissolve at a given temperature
is known as unsaturated
A solution which has
maximum amount of solute
that it can dissolve at a given
temperature is known as
saturated solution.
A solution which can dissolve
amount of solute by increasing
temperature saturated solution
is known as supersaturated

c) on the basis of nature of solvent

Aqueous solutionNon-Aqueous solution
The solution in which the solvent is water is known as aqueous solution. The solution in which the solvent is other
than water (ether, alcohol or aceton) known as non-aqueous solution.

6. Physical & Chemical Changes

Physical changes – Changes that do not result in the production of a new substance.

  • If you melt a block of ice, you still have H2O at the end of the change.
  • If you break a bottle, you still have glass.

Examples : melting, freezing, condensing, breaking, crushing, cutting, and bending.

Chemical changes – Changes that result in the production of another substance.

  • As in the case of autumn leaves, a change in color is a clue to indicate a chemical change.
  • a half eaten apple that turns brown.

7. Alloys

A material that has metallic properties and is composed of two or more chemical elements of which at least one is a metal.

  • These cannot be separated into their components by physical methods.
  • However, these are considered as mixture because these show the properties of its constituents and can have variable composition.
    The benefit of alloys is that you can combine metals that have varying characteristics to create an end product that is stronger, more flexible, or otherwise desirable to manufacturers.
  • Aluminium alloys are extensively used in the production of automotive engine parts.
    Copper alloys have excellent electrical and thermal performance, good corrosion resistance, high ductility and relatively low cost.
  • Stainless steel alloys are used for many commercial applications such as watch straps, cutlery etc.
  • Titanium alloys have high strength, toughness and stiffness & are used in aerospace structures .