Colligative Properties | Brownian Movement for Class 12, IIT-JEE, NEET

Colligative Properties Definition

These properties depend on the number of solute particles in solution. In case of colloidal solutions, colloidal particles are the aggregates of many ions or smaller molecules and when compared to true solutions or normal solutions, the total no of particles of solute in solution are very less and hence these solutions exhibit Colligative properties to lesser extent. Learn more about Properties of Colloidal Solution. This includes: Tyndal effect, Brownian Movement etc.

Optical Properties of Colloids with the help of Tyndall Effect Example.

Kinetic properties of Colloids through Brownian Movement.

 

Properties of Colloidal Solutions 

1. Heterogenous- Colloidal particles in a solution differ in sizes and are not homogenously distributed throughout the solution.

2. Visibility- Colloidal particles can not be seen with naked eyes or with the help of microscope. It is a well-known fact no particle is visible if its diameter is less than half the wavelength of light used. The visible light has greater wavelength than the size of colloidal particle.

3. Filterability- Colloidal particles pass through an ordinary filter paper but do not pass through parchment and other fine membranes.

4. Surface tension and viscosity – For Lyophobic sols, surface tension and viscosity are not very different from. From those of the medium, as there is very slight interaction between the suspended particles and the medium. On the other hand, Lyophilic sols show a high degree of solvation of the particles and therefore, the properties of the One medium are modified. Thus, the viscosity is much higher for the solution for the medium. Furthermore, the surface tension of the sol is lower than that of pure medium.

Colour- The colour hydrophobic sol depends on the wavelength of the light scattered by the dispersed particles. The wavelength of the scattered light again depends on the size and the nature of particles. For example, the colour of silver sol changes with the particle (suspended) diameter in solution.

Optical properties

Solutions Exhibits Tyndal Effect.

When a beam of light is passed through a sol and viewed at right angles, the path of the light shows up as a hazy beam of cone ( lumited path by by bluish light). This was first observed by Faraday and later by Tyndal and in known as Tyndal effect. The bright cone of the light is called Tyndal cone. The tyndal effect-is due to the fact that the colloidal particles absorb light and scatter in all directions in space. The scatterise of light illuminates the path of the beam in the colloidal dispersion.

Some Examples of Tyndal Effect are

i. Blue colour of sky and sea water

ii. visibility of tails of comets

iii. Twinkling of stars

 

Kinetic properties

Brownian Movement 

When a sol is examined with an ultra-microscope, the suspended particles are seen as shining speaks of light. By following an individual particle, it is observed that the particle is in a state of continuous motion in zig-zag directions. The continuous rapid zig-zag motion of a colloidal particle in the dispersion medium is called “Brownian movement or motion (first observed by British botanist Robert Brown).

The Brownian movement has been explained to be due to the unbalanced bombardments of the particles by the molecules of dispersion medium

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