Colloidal State

Introduction to Colloids:

Colloids are medium with dissolved or scattered particles ranging in size from 1mm to several microns. Colloidal particles are smaller than filterable coarse particles but larger than atoms and tiny molecules.

The colloidal state is a granular state with particles ranging in size from 1 nm to 103 nm dispersed in a continuous phase called the dispersed medium. The colloidal state is thermodynamically unstable due to the extensive contact between the two phases. Two other factors that contribute to the colloidal system’s apparent stability are the presence of an electric charge at the interface and some form of structural interaction between the dispersed medium and the dispersed phase.

The relative impact of the two combinations is dependent on the dispersed phase and dispersed medium combination being considered. In addition, several physical parameters, including viscosity, are closely linked to the stability of colloidal systems. These features are explored in particle charge, particle-particle, and particle-solvent interactions.

Characteristics of Colloids:

The diffusibility of crystalloids via a mammalian membrane and the non-diffusibility of colloids was later discovered to be attributable to particle size differences. 

In solutions, crystalloids break down into smaller particles, which pass through the membrane. On the other hand, Colloids generated bigger particles in solutions (greater than the diameters of the membrane holes) that could not pass through the membrane.

Suspensions are another heterogeneous system with bigger particles. Particles in a suspension have a diameter of more than 1000 nm (i.e., >10-6m). 

These particles can be observed with the naked eye or with a microscope. However, neither an animal membrane nor conventional filter paper can pass through the suspensions. Suspensions include things like stirred murky water.

Colloidal solutions are transitional between real solutions and suspensions. Colloidal solutions can be made from any substance by subdividing or aggregating its particles in the size range of 1 nm-1000 nm, as indicated above. In theory, any substance can be produced to exist as a colloidal particle. As a result, rather than speaking of colloidal solution, it is more suitable to speak of the colloidal state of matter.

A colloidal system has a dispersed phase and a dispersed medium.

Dispersed phase (also known as the discontinuous phase) is the phase that is dispersed or scattered throughout the dispersion medium.

The dispersion medium, also known as the continuous medium, is the phase in which scattering occurs.

A colloidal state in chemistry can have a gas, a liquid, or a solid as its two phases. Fat globules are spread in water in milk, for instance. As a result, fat globules spread in water act as a dispersion medium. Solid dispersion in a liquid, solid, or gaseous media is called sol.

A colloidal solution is a liquid (dispersion medium) in which a solid (dispersed phase) is dispersed.

Solid aerosol is a term used to describe the dispersion of a solid (dispersed phase) in a gas (dispersion medium). An emulsion is a system that results from the dispersion of a liquid in another liquid. A gel is defined as a colloidal solution that has grown fairly stiff.

Physical Properties of Colloidal Solutions:

Heterogenous: Although colloidal solutions are heterogeneous, the dispersed particles present in them are not visible to the naked eye, giving the impression that they are homogeneous. This is the case because colloidal particles are too minute to be seen with the human eye.

Filterability: Colloidal particles pass through regular filter paper due to their small size. Animal membranes, cellophane membranes, and ultrafilters, on the other hand, can retain them.

Stability: Lyophilic sols in general and lyophobic sols in the form of significant electrolyte concentrations are quite stable. The dispersed particles included do not settle down even after prolonged storage. However, a few bigger colloidal particles may progressively sediment after a lengthy period.

The size of the colloidal particles in a colloidal solution determines the color of the solution. Larger particles absorb longer-wavelength light and transmit shorter-wavelength light as a result. For example, silver particles of 150nm appear violet, while those of 60nm seem orange-yellow.

Colloids with Macromolecular Structure

These are macromolecular colloids, which are macromolecular substances with large molecular sizes that, when broken down, generate a size in the colloidal run. As a result, the macromolecules that make up the dispersed phase are usually polymers with extremely high molecular weights.

Starch, cellulose, proteins, enzyme, gelatine, and other macromolecules are natural. As a result, nylon, polyester, plastics, polishers, and other macromolecular and synthetic polymers frequently have lyophobic sols.

Colloidal state in Chemistry is a multidisciplinary field, with physics and physical chemistry playing a significant role. Unfortunately, because most colloidal states are so complicated, they can’t always be treated with the precision that many of these major topic areas are known for. It is likely that a combination of this lack of accuracy and its interdisciplinary nature, rather than a lack of relevance, has caused an unjustified inclination to overlook colloid science throughout undergraduate academic training in the past.

Until the previous few decades, colloid science existed almost entirely on its own as a descriptive discipline that did not appear to fit into the broader framework of physics and chemistry. The employment of materials of dubious compositions, which placed significant demand on reproducibility and interpretation, contributed to this state of things. 

Nowadays, it is common to deal with well-defined systems (e.g., Pure surface-active compounds, monodispersed dispersions, and well-defined polymeric materials) that serve as models in and of themselves, as well as for real-world systems. Despite the vast number of variables sometimes involved, this type of research, together with breakthroughs in our understanding of fundamental physics and chemistry principles, has allowed us to build logical, if not necessarily comprehensive, hypotheses relating to many aspects of colloidal behaviour.

Because it is critical to understand colloid science on both a descriptive and theoretical level, research on the subject can vary from relatively simple descriptive material to exceedingly complicated theory.

CONCLUSION

Colloids are medium with dissolved or scattered particles ranging in size from 1mm to several microns.A colloidal system has a dispersed phase and a dispersed medium.Dispersed phase (also known as the discontinuous phase) is the phase that is dispersed or scattered throughout the dispersion medium.The dispersion medium, also known as the continuous medium, is the phase in which scattering occurs.The size of the colloidal particles in a colloidal solution determines the color of the solution. Colloids have unique properties like it show tyndall effect which make it different from suspension.