Dispersed Phase and Dispersion Medium - Definition, Examples and FAQs

A colloid is a substance wherein minute, microscopically dispersed insoluble debris of a substance is suspended in some other substance. The length of colloidal debris varies from 1-1000. A solution exists in a single-phase only, and no visible interface exists. Whereas in a colloid, unique phases, particularly the dispersed section and dispersion medium, exist. An interface among them may be observed.

The dispersion medium, also known as the continuous phase, in which the dispersed phase is distributed. It can be a solid, liquid, or gas. In a colloidal mixture like milk, for example, the dispersion medium is water, and the dispersed phase consists of fat globules.  

Common examples are: 

• Fog in which the dispersed phase is water droplets, the dispersion medium is air
• Smoke in which the dispersed phase is solid soot particles, and the dispersion medium is air.
• Milk in which the dispersed phase is fat globules, the dispersion medium is water.

The normal range of particles in a colloidal solution is 1- 1000 nm.

Dust is an aerosol type of colloid where a solid is suspended in a gas.

A supersaturated solution is a solution that contains more solute than what can normally be dissolved in a given amount of solvent at a specific temperature. This state is achieved by dissolving more solute than usual, often at elevated temperatures, and then allowing the solution to cool without any crystallization occurring.

To create a supersaturated solution, you typically heat a solvent and dissolve solute into it until no more solute can dissolve. Once the solution is saturated and no solid remains, you slowly cool the solution. If cooled carefully without disturbing it, the solution can remain supersaturated.

Common examples include rock candy, where sugar is dissolved in hot water and then slowly crystallizes as the solution cools. Another example is carbonated beverages, which can contain dissolved carbon dioxide under pressure, creating a supersaturated solution that releases gas bubbles when opened.

Common liquid-in-liquid dispersions include:

Surface tension affects the stability of dispersed systems by influencing the interaction between the dispersed phase and dispersion medium. Lower surface tension typically leads to better dispersion and increased stability of the system.

Heterogeneity in dispersed systems refers to the non-uniform distribution of the dispersed phase within the dispersion medium. This results in different properties and compositions at different points within the system, unlike homogeneous mixtures.

Smaller particle sizes in the dispersed phase generally lead to more stable dispersions. This is because smaller particles have a larger surface area-to-volume ratio, which increases their interaction with the dispersion medium and reduces the tendency to settle or separate.

A dispersed system is a mixture where one substance (dispersed phase) is distributed throughout another substance (dispersion medium). The dispersed phase exists as small particles or droplets within the continuous dispersion medium.

Examples of solid-in-liquid dispersions include:

The concentration of the dispersed phase can influence:

The continuous phase, also known as the dispersion medium, is the substance in which the dispersed phase is distributed. It forms an unbroken, interconnected region throughout the entire system, surrounding the discrete particles or droplets of the dispersed phase.

Particle shape affects:

Electrostatic forces in dispersed systems:

Temperature can significantly impact dispersed systems by:

The dispersed phase consists of small particles or droplets distributed throughout the system, while the dispersion medium is the continuous phase in which these particles are suspended. The dispersed phase is discontinuous, while the dispersion medium is continuous.

The substance present in smaller quantity is typically the dispersed phase, while the substance present in larger quantity becomes the dispersion medium. However, this can also depend on the physical state and properties of the substances involved.

Surfactants (surface-active agents) can:

Flocculation is the process where dispersed particles come together to form loose aggregates called flocs. This can occur due to attractive forces between particles or the addition of certain chemicals. Flocculation can lead to settling or separation of the dispersed phase from the dispersion medium.

Ostwald ripening is a phenomenon where larger particles or droplets in a dispersed system grow at the expense of smaller ones. This occurs because:

Kinetic stability and thermodynamic stability in dispersed systems differ as follows:

The critical micelle concentration (CMC) is the concentration at which surfactant molecules in a solution begin to form micelles. In dispersed systems:

Brownian motion is the random movement of particles in a fluid, caused by collisions with molecules of the surrounding medium. In dispersed systems, Brownian motion helps keep the dispersed phase particles suspended and prevents settling, contributing to the system's stability.

The addition of electrolytes to charged dispersed systems can:

Gas-in-liquid dispersions, also known as foams, have gas bubbles as the dispersed phase within a liquid dispersion medium. They are unique because the dispersed phase is compressible and can easily change shape, affecting the system's stability and properties.

The Tyndall effect is the scattering of light by colloidal particles in a dispersed system. When a beam of light passes through a colloid, the dispersed particles scatter the light, making the beam visible. This effect helps distinguish colloids from true solutions.

Zeta potential is the electrical potential difference between the bulk of the dispersion medium and the stationary layer of fluid attached to the dispersed particle. A high absolute value of zeta potential (positive or negative) indicates greater electrostatic repulsion between particles, leading to increased stability of the dispersed system.

Suspensions and colloids are both types of dispersed systems, but they differ in particle size:

Emulsifiers are substances that stabilize emulsions by:

The HLB system is a numerical scale used to classify emulsifiers based on their relative affinity for oil and water. It helps in selecting appropriate emulsifiers for specific types of emulsions (oil-in-water or water-in-oil) and predicting their effectiveness in stabilizing these systems.

Creaming and sedimentation are both forms of phase separation in dispersed systems:

Phase inversion is a phenomenon where the dispersed phase and dispersion medium switch roles. For example, an oil-in-water emulsion may transform into a water-in-oil emulsion. This can occur due to changes in temperature, composition, or the addition of certain chemicals, and it significantly alters the properties of the emulsion.

Polymeric stabilizers differ from traditional surfactants in several ways:

Depletion flocculation occurs when non-adsorbing polymers or small particles in the dispersion medium create an osmotic force that pushes dispersed particles together. This happens because:

The DLVO theory (named after Derjaguin, Landau, Verwey, and Overbeek) is crucial for understanding the stability of dispersed systems because it:

Rheology in dispersed systems refers to:

Yield stress in dispersed systems:

Shear-thinning behavior in dispersed systems:

Bridging flocculation occurs when:

Non-spherical particles in dispersed systems can:

Depletion stabilization and flocculation are opposing phenomena:

Synergistic effects in mixed surfactant systems refer to:

Pickering stabilization refers to:

The interfacial layer in dispersed systems:

The cloud point in non-ionic surfactant-based systems:

The effective volume fraction in dispersed systems:

Jamming in concentrated dispersed systems: