The potential difference between the fixed charged layer and the diffused layer having opposite charge is called (a) Colloidal potential (b) Zeta potential (c) Electrostatic potential (d) Electrode potential

Colloidal systems are mixtures where one substance, usually a microscopic or nanoscopic particle, is evenly dispersed in another medium. These colloidal particles can be solid, liquid, or gas, and the medium can be any other state of matter.

For instance, milk is an emulsion where fat droplets are dispersed in water, a colloidal system. Because of the small size of these particles, they do not settle under gravity, allowing the colloid to appear uniform. However, despite this uniform appearance, colloids are heterogeneous at the microscopic level because they consist of two distinct phases: the dispersed phase (the colloidal particles) and the continuous phase (the medium in which these particles are suspended).

Furthermore, these colloidal particles can carry an electric charge, playing a crucial role in their interactions and stability. Understanding the nature and behavior of these charges in colloidal systems is imperative for a variety of applications, including food science, medicine, and material engineering.

Electrical potentials in chemistry refer to the energy difference that causes ions and electrons to move, creating electric currents. This concept is essential in various chemical processes, including those occurring in colloidal systems.

When discussing colloids, electrical potentials are most commonly brought up in relation to the surface charge of the particles involved. These surface charges create a potential difference which, in turn, affects how the particles will interact with each other and with the surrounding medium.

The potential difference typically results from the combination of the actual surface charge on the colloidal particles and the charges of the ions in the surrounding solution. The electrostatic forces that arise from these charge disparities prevent the colloidal particles from aggregating, thus stabilizing the colloid. Overall, these potentials are central to understanding the stability, reactivity, and behavior of particles in a colloidal suspension.

The surface charge of colloidal particles is cardinal in determining their interactions and stability within colloidal systems. These charges arise due to several mechanisms, including ionic dissociation of groups on the particle's surface, adsorption of ions from the solution, or ionization of the particles.

Once a particle acquires a surface charge, it attracts a thin layer of counter-ions (ions with the opposite charge) from the surrounding medium. This layer closely associates with the particle and forms what is known as the Stern layer. Beyond this layer is a more diffusive layer of ions, which gradually merges with the bulk solution, this is referred to as the diffuse layer.

Within the diffuse layer, there's a notional boundary known as the 'slipping plane', and the potential at this boundary is what we call the Zeta potential. This Zeta potential is crucial because it acts as an index of the stability of colloidal systems: high Zeta potentials indicate strong repulsions, thus more stable colloids, and vice versa. Understanding the surface charge and how it influences the Zeta potential is therefore quintessential for predicting and controlling the behavior of colloids in various applications.