Physical Pharmaceutics-II - Unit 1: Colloidal Dispersion

Comprehensive vocabulary flashcards covering definitions, classifications, and properties of colloidal dispersions based on lecture notes.

Colloidal Dispersion

A mixture in which small particles of one substance are evenly distributed throughout other substance, with particle sizes ranging from $1\text{ nm}$ to $1\text{ μm}$. Or as micro-heterogenous systems with size ranging from $1\text{ nm}$ to $1000\text{ nm}$.

Dispersed Phase

The substance that is dispersed in the mixture.

Dispersion Medium

The substance in which the dispersed phase is distributed.

Molecular Dispersion

True solutions with a particle size less than $1\text{ nm}$ that are homogeneous in nature and invisible even under an electron microscope.

Coarse Dispersion

Heterogeneous dispersed systems with a particle size greater than $1000\text{ nm}$ that are large enough to be seen with the naked eye and tend to settle over time.

Solid Solution

A type of solution where a solid is dispersed in a solid dispersion medium, such as gemstones.

Sol

A colloidal dispersion where a solid is dispersed in a liquid medium, such as paints.

Aerosol of Solids

A dispersion type where a solid is dispersed in a gas medium, such as smoke or dust in air.

Gel

A colloidal system where a liquid is dispersed in a solid medium, such as jelly or butter.

Emulsion

A colloidal dispersion where a liquid is dispersed in another liquid, such as milk.

Aerosol

A dispersion type where a liquid is dispersed in a gas medium, such as mist or fog.

Solid Foam

A dispersion type where a gas is dispersed in a solid medium, such as foam rubber.

Foam

A dispersion type where a gas is dispersed in a liquid medium, such as shaving cream.

Lyophilic Colloids

Colloidal systems where the dispersed phase has a strong affinity for the dispersion medium, meaning 'solvent loving'.

Lyophobic Colloids

Colloidal systems in which the dispersed phase has very little or no affinity for the dispersion medium, meaning 'solvent fearing'.

Association Colloids

A type of colloidal system where the dispersed phase consists of aggregates of molecules or ions, called micelles, formed by surface-active agents.

Critical Micelle Concentration (CMC)

The specific concentration value above which surfactant molecules aggregate to form micelles.

Tyndall Effect

The phenomenon where a beam of light becomes visible when passing through a colloidal solution due to light scattering by dispersed particles.

Fluorescence

The property of some colloids to absorb light at one wavelength and emit it at a longer wavelength.

Opalescence

The milky or pearly appearance of a colloidal solution caused by the scattering and interference of light.

Brownian Motion

The random, zigzag movement of tiny particles suspended in a liquid or gas caused by constant collisions with molecules of the dispersion medium.

Diffusion

The movement of colloidal particles from a region of higher concentration to a region of lower concentration due to Brownian motion.

Sedimentation

The settling of colloidal particles under the influence of gravity or centrifugal force, occurring when particles are large enough to settle.

Viscosity

A measure of how thick or sticky a colloidal solution is when it flows, depending on size, shape, and concentration of dispersed particles.

Electrical Double Layer

A structure formed when a charged colloidal particle attracts opposite charges from the surrounding medium, consisting of an inner fixed layer and an outer diffuse layer.

Zeta Potential

A measure of the strength of charges in the electrical double layer that keep particles from sticking together; high zeta potential indicates a stable colloid.

Electrophoresis

The movement of charged colloidal particles toward the opposite electrode when an electric field is applied.

Coacervation

The phenomenon occurring when two oppositely charged hydrophilic colloids are mixed, resulting in the separation of a colloidal-rich layer called a coacervate.

Peptization

The process of converting precipitated particles back into a stable colloidal dispersion by adding a suitable electrolyte or peptizing agent.

Protective Colloid

A lyophilic colloid added to a lyophobic sol to form a thin protective layer around the particles, preventing coagulation by electrolytes.