Properties of Colloids

Introduction to Properties of Colloids

A type of mixture consisting of particles whose size varies between 1 and 1000 nanometers is a colloidal solution. The particles are uniformly distributed in the colloidal solution. The particles do not settle down during this process. The properties and variability of colloids have been a well-known field since the primitive period. The best example to illustrate their familiarity with us is that we know that coagulation of milk results in the formation of curd from very early times.

In this article, we will study in detail-

  • The characteristics of colloids

  • The stability of colloids

  • The optical properties of colloids

  • The electrical properties of colloids

  • The kinetic properties of colloids


Properties of Colloidal Solution

  1. Heterogeneity - colloidal solution is heterogeneous in nature as it consists of the dispersed phase and the dispersion medium.

  2. The particles present in the colloidal solution are not visible and hence the solution appears homogeneous in nature.

  3. The particles of colloidal solution can pass easily through filter paper but can be retained through animal membranes, ultrafilters, and cellophane.

  4. Lyophilic sols in general and lyophobic sols in the absence of substantial concentrations are quite stable.

  5. The colour of the colour solution depends on the size of the particle. The larger particle will absorb the light of a longer wavelength and shorter particles will absorb the light of a shorter wavelength.


Optical Properties of Colloids

Tyndall Effect

  • When a beam of light is passed through a colloidal solution kept in dark, the path of the beam gets illuminated with blue colour.

  • This phenomenon is known as the Tyndall effect and the path is known as the Tyndall cone.

  • The Tyndall effect is due to the scattering of light by colloidal particles.

  • Tyndall effect is not exhibited by a true solution. This is due to the particles in the solution are too small to scatter light.


Kinetic Properties of Colloids

Brownian Movement

  • The continuous zigzag movement of particles in the dispersion medium in a colloidal solution is called Brownian movement.

  • Brownian movement is due to the unequal bombardment of the moving molecules of dispersion medium on colloidal particles.

  • Brownian movement decreases with an increase in the size of the colloidal particles. So suspension does not exhibit Brownian movement.


Electrical Properties of Colloids

  • The movement of colloidal particles towards a particular electrode under the influence of an electric field. 

  • The colloidal particle with a positive charge moves towards the cathode under the influence of the electric field and the colloidal particle with a negative charge moves towards the anode.


Electrosmosis

  • The movement of dispersion medium under the influence of an electric field in a situation when the movement of the dispersed phase is prevented by a suitable membrane.


Advantages of Colloids

  1. Colloidal particles allow the dispersion of insoluble materials such as metallic gold and fats. They can be used more easily and absorbed more easily.

  2. Colloidal gold can be used in medicine to carry drugs and antibiotics

  3. The paint industry uses colloids in the preparation of paints.

  4. In milk, the colloidal suspension of fats prevents the milk from being thick and allows for easy absorption of nutrients.

  5. Asphalt emulsified in water used in the preparation of roads.

  6. Soap solution is colloidal in nature which helps in removing dirt.

  7. Food particles like butter, milk, and ice cream are colloidal in nature.


Did You Know?

  • Coagulation is a phenomenon involving the precipitation of a colloidal solution on the addition of an electrolyte.

  • Flocculation value- The coagulating power of an electrolyte is expressed in terms of its flocculation value which is defined as the minimum concentration of an electrolyte required for the coagulation of a sol.

  • A smaller flocculation value shows the greater coagulating power of an electrolyte.

  • So coagulating power is inversely proportional to the flocculating value.

  • The coagulation of colloids can be achieved by various methods-

  1. By electrophoresis

  2. By mixing two opposite sols

  3. By persistent dialysis.

FAQs (Frequently Asked Questions)

1. Does blood show the Tyndall effect?

Blood is a colloidal solution as the blood cell size ranges from 1nm to 100nm and thus blood shows the Tyndall effect.

2. Why is milk a colloidal solution?

Milk is a colloid, suspended in the fluid with small globs of butterfat. Whipped cream is also a colloid. Typically, colloids don't separate over time into their individual components.

3. What are the electrical characteristics of colloids?

On both layers, the charge present is identical. This two-layer structure contributes to the growth of a potential called zeta or Electrokinetic potential. As a result of this potential that has formed through the particles, these particles shift under the influence of the electric field.

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