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COLLOIDS of class 9 explained with the Presentation

 

COLLOIDS

 

SOME IMPORTANT TERMS: -

I) HOMOGENEOUS AND HETEROGENEOUS MIXTURES: -

A mixture that has a uniform composition throughout its mass, with no unique features that are visible in between the particles are called homogeneous mixtures. The exact opposite case is for heterogeneous mixtures.

HOMOGENEOUS--> Solutions

HETEROGENEOUS--> Colloids & Suspensions


 SOLUTE, SOLVENT, AND SOLUTION: -

        I) SOLUTION: -

A Homogeneous Mixture containing two or more solids, liquids, and gases.

Eg:- Sugar solution

       ii)   SOLUTE: -

The component that is present in a lesser amount in a solution is called a   solute.

Eg: In the Sugar solution, Sugar is the solute as its present in a lesser amount.

     iii)  SOLVENT: -

The component that is present in a larger amount in a solution is called a solvent.

Eg: - In Sugar solution, Water is the solvent because of its presence in a larger

quantity

 

SUSPENSION: -

•          A Suspension is a heterogeneous mixture

•          in which the small particles of solid-state are spread throughout a substance of liquid state without dissolving in it, these solid particles can easily be observed with our naked eye whereas it’s not possible in case of a solution.

•          Size of particles is greater than 10-5 cm.

•          Eg:- Sand water, Slaked lime used

for whitewashing, Chalk in water, etc.

WHAT IS A COLLOID?

•       A colloid can be defined as a heterogeneous mixture in which the dissolved particles are microscopic (they are not visible to our naked eye), they also do not settle down as in a suspension. They appear to be homogeneous but are actually not because the particles are not mixed uniformly (the particles can be seen). The particles of a colloid are larger than that of a solution but smaller than that of a suspension.

•       Size of particles varies from 10-7cm to 10-5 cm.

 

DIFFERENCE BETWEEN COLLOID & SUSPENSION: -

COLLOIDS

•          PARTICLES PASS THROUGH FILT ER PAPER. AS THEY ARE COMPARATIVELY SMALLER.

•          PARTICLES WON’T UNDERGO SEDIMENTATION.

•          PHASE SEPARATION MOSTLY WON'T TAKE PLACE.

•          PARTICLES CAN ONLY BE SEEN WITH A MICROSCOPE.

•          Eg: - Shampoo, blood, Milk.

SUSPENSIONS

•          PARTICLES DO NOT PASS THROUGH FILTER PAPER AS THEY ARE COMPARATIVELY LARGER.

•          PARTICLES UNDERGO SEDIMENTATION.

•          DISTINCT PHASE SEPARATION CAN BE SEEN.

•          PARTICLES CAN BE SEEN WITH THE NAKED EYE.

•          Eg: - Sand water, soot in air, oil, and water.

 

DISPERSED PHASE & DISPERSION MEDIUM:-

•       I) Dispersed phase: -

The phase of the collective colloidal particles dispersed in the dispersion medium is called the dispersed phase.

II) Dispersion medium: -

The medium in which colloidal particles are dispersed is called the dispersion medium.

Eg: - In smoke (a colloid) the dispersed phase is solids(particulates) and the dispersion medium is gas (any gas)

 

EMULSIONS AND AEROSOLS: -

  EMULSION: -

•       Emulsion is a      mixture of two or more liquids in which one is present as droplets or we can say that,

in microscopic size, distributed throughout the other liquid.

•       Eg: - Body Lotion, Mayonnaise, etc.

 AEROSOLS: -

•       An aerosol is a suspension of fine solid particles or liquid droplets, usually in the air or even in any other gas.

E.g.: - Room Spray, Mist, etc...

 

TYNDALL EFFECT: -

•       A Colloid scatter a beam of light passing through it, this phenomenon is called as Tyndall effect, this happens due to the scattering of light by the colloidal particles and can be clearly observed when light is passed through a colloidal solution placed in a dark room. It can also be observed in cinema theaters and when sunlight passes through a dense forest. This effect can't be observed in a solution, it may or may not be observed in a suspension

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