Properties of Colloidal Solution
Introduction to properties of colloidal solution:
A colloid is a heterogeneous system in which one substance is dispersed (dispersed phase) as very fine particles in another substance
colloidal called dispersion medium. The colloidal and the true solution differs in that of particle size. While in a solution, the constituent particles are very very small, in a colloid, the dispersed phase may consist of particles of a single macromolecule (such as protein or synthetic polymer) or an aggregate of many atoms, ions or molecules. Colloidal particles are larger than simple molecules but small enough to remain suspended. Their range of diameters is between 1 and 1000 nm (10–9 to 10–6 m).
Tyndal effect
The path of the light is not visibe when the light travels in a clear solution. The particle of the solution is not large enough to scatter the light beam. For the scattering to occur the lights wavelength should be same as the size of the partilce which scatters the light. If they are same then the scattering would be most effective. If a homogeneous solution placed in dark is observed in the direction of light, it appears clear and, if it is observed from a direction at right angles to the direction of light beam, it appears perfectly dark. Colloidal solutions viewed in the same way may also appear reasonably clear or translucent by the transmitted light but they show a mild to strong opalescence, when viewed at right angles to the passage of light, i.e., the path of the beam is illuminated by a bluish light. This effect was first observed by Faraday and later studied in detail by Tyndall and is termed as Tyndall effect.
Colligative property of colloidal solution:
Colligative poroperty deponds on the number of particle that is present in the solution. In colloidal solution the number of particle is smaller than the number of particle in the true solution because the colloidal particle is agglomerate of large number of particle to form a single particle. Hence, the values of colligative properties (osmotic pressure, lowering in vapour pressure,
depression in freezing point and elevation in boiling point) are of small order as compared to values shown by true solutions at
same concentrations.
Brownian movement of colloidal solution:
When colloidal solutions are viewed under a powerful ultramicroscope, the colloidal particles appear to be in a state of continuous zig-zag motion all over the field of view. This motion was first observed by the British botanist, Robert Brown, and is known as Brownian movement. This motion is independent of the nature of the colloid but depends on the size of the particles and viscosity of the solution. Smaller the size and lesser the viscosity, faster is the 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 Brownian
movement has a stirring effect which does not permit the particles to settle and thus, is responsible for the stability of sols.
A colloid is a heterogeneous system in which one substance is dispersed (dispersed phase) as very fine particles in another substance
colloidal called dispersion medium. The colloidal and the true solution differs in that of particle size. While in a solution, the constituent particles are very very small, in a colloid, the dispersed phase may consist of particles of a single macromolecule (such as protein or synthetic polymer) or an aggregate of many atoms, ions or molecules. Colloidal particles are larger than simple molecules but small enough to remain suspended. Their range of diameters is between 1 and 1000 nm (10–9 to 10–6 m).
Tyndal effect
The path of the light is not visibe when the light travels in a clear solution. The particle of the solution is not large enough to scatter the light beam. For the scattering to occur the lights wavelength should be same as the size of the partilce which scatters the light. If they are same then the scattering would be most effective. If a homogeneous solution placed in dark is observed in the direction of light, it appears clear and, if it is observed from a direction at right angles to the direction of light beam, it appears perfectly dark. Colloidal solutions viewed in the same way may also appear reasonably clear or translucent by the transmitted light but they show a mild to strong opalescence, when viewed at right angles to the passage of light, i.e., the path of the beam is illuminated by a bluish light. This effect was first observed by Faraday and later studied in detail by Tyndall and is termed as Tyndall effect.
Colligative property of colloidal solution:
Colligative poroperty deponds on the number of particle that is present in the solution. In colloidal solution the number of particle is smaller than the number of particle in the true solution because the colloidal particle is agglomerate of large number of particle to form a single particle. Hence, the values of colligative properties (osmotic pressure, lowering in vapour pressure,
depression in freezing point and elevation in boiling point) are of small order as compared to values shown by true solutions at
same concentrations.
Brownian movement of colloidal solution:
When colloidal solutions are viewed under a powerful ultramicroscope, the colloidal particles appear to be in a state of continuous zig-zag motion all over the field of view. This motion was first observed by the British botanist, Robert Brown, and is known as Brownian movement. This motion is independent of the nature of the colloid but depends on the size of the particles and viscosity of the solution. Smaller the size and lesser the viscosity, faster is the 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 Brownian
movement has a stirring effect which does not permit the particles to settle and thus, is responsible for the stability of sols.