Surface chemistry deals with the phenomenon that occurs at the surfaces or interfaces. The interface or surface is represented by separating the bulk phases by a hyphen or a slash. For example, the inetrface between a solid and a gas may be represented by solid-gas or solid/gas. Due to complete miscibility, there is no interface between the gases. The bulk phases that we come across in surface chemistry may be pure compounds or solutions. The interface is normally a few molecules thick but its area depends on the size of the particles of bulk phases. Many important phenomena, noticeable amongst these being corrosion, electrode processes, heterogeneous catalysis, dissolution and crystallization occur at interfaces. The subject of surface chemistry finds many applications in industry, analytical work and daily life situations.

For colloids, the experiment of electrophoresis proves

charge on colloidal particle

The correct answer is option 3. charge on colloidal particle.

Let us delve into the concept of electrophoresis and how it relates to colloids, specifically focusing on why it proves the charge on colloidal particles.

Electrophoresis is a laboratory technique used to observe the movement of charged particles in a fluid under the influence of an electric field.

In the context of colloids, electrophoresis is used to determine whether colloidal particles carry an electric charge and, if so, the nature of that charge (positive or negative).

Colloidal particles are often charged due to various factors such as the adsorption of ions from the surrounding medium, ionization of surface groups, or other interactions.

The charge on colloidal particles plays a crucial role in the stability of the colloid, as the repulsion between similarly charged particles prevents them from aggregating and settling out.

When a colloidal solution is subjected to an electric field, the charged colloidal particles move towards the electrode of opposite charge:

Negatively charged particles will move towards the positive electrode (anode).

Positively charged particles will move towards the negative electrode (cathode).

The movement of these particles under the electric field is what confirms that they are charged.

Charge on Colloidal Particle:

The primary observation in electrophoresis is the movement of particles towards one of the electrodes. This movement is direct evidence that the colloidal particles carry an electric charge.

The direction in which the particles move indicates whether they are positively or negatively charged. 

This movement is the key proof that colloidal particles are charged, which is critical in understanding their behavior, stability, and interactions within the colloid.

Size of the colloidal particle: Electrophoresis does not measure or directly provide information about the size of the particles.

Homogeneous mixture: Colloids are not homogeneous mixtures but are heterogeneous. Electrophoresis does not test or prove homogeneity.

Tyndall effect: The Tyndall effect relates to the scattering of light by colloidal particles, which is a different phenomenon unrelated to the charge and movement of particles in an electric field.

Electrophoresis is a method that reveals the charge on colloidal particles by observing their movement in an electric field. This movement towards the respective electrode demonstrates that the particles are charged, which is the crucial outcome of this experiment.

The correct answer is option 3: charge on colloidal particle.