Page 1 - Lesson note 6
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SUBJECT-CHEMISTRY
CHAPTER-SURFACE CHEMISTRY
SUBTOPIC- Properties of Colloidal solution.
KEY NOTES:
Properties of Colloidal Solutions :
(1)Colloidal solutions show colligative properties.
(2)Tyndall effect:
When a beam of convergent light is passed through a
colloidal solution. the path of the light is visible.This
phenomenon is called tyndall effect.
This isdue to scattering of light by the colloidal particles
present in the colloidal solution.
Tyndall effect is observed only when the following two
conditions are satisfied.
(i) The diameter of the dispersed particles is not much smaller than
the wavelength of the light used; and
(ii) The refractive indices of the dispersed phase and the
dispersion medium differ greatly in magnitude.
(3)Colour:
The colour of colloidal solution depends on thewavelength of
light scattered by the dispersed particles. The wavelength of
light further depends on thesize and nature of the particles.
(4)Brownian movement:
The colloidal particles appear to be in a state of continuous zig-
zag motion,This iscalled Brownian motion.
The Brownian movement has been explained to be due to the
unbalanced bombardment of the particles by the molecules of
the dispersion medium.
The Brownianmovement has a stirring effect which does not
permit the particles tosettle and thus, is responsible for the
stability of sols.
(5)Charge on colloidal particles:
Colloidal particles always carry an electric charge. The nature of
