Colloids and Suspensions

A solution is a mixture of solvent and solute. A solvent is generally a liquid in which various materials or solutes dissolve to form a solution. A solute is a substance dissolved in a solvent and forms a solution.

The size of the substance or particles may vary such that the particles may be seen with the naked eye to be several micrometers small in a colloidal suspensions solution. The particles that are dissolved or dispersed in a solution, their size ranging from 1mn to several microns, are called colloids. The suspension particles are heterogeneous, and their sizes are more than 1000 nm.

Colloidal Suspensions and Colloidal Solution

A colloidal solution is a solution in which the substances are evenly and homogeneously suspended in a solvent. It is also known as a suspension and colloidal solution.

Colloidal suspensions are substances or particles suspended in the solution, for example, muddy water, gelatin, blood, whipped cream, milk, air and jelly. Colloidal suspensions can happen in any three states of matter, i.e., gas, liquid and solid. A true solution is a homogeneous solution of two or more substances in which the size of the particles that are dissolved in the solution should be less than 1 nm.

The colloids in a solution can be categorised into two types. The categorisation of the colloids in a solution is done based on the interaction between the phases. The two categories of colloids are lyophobic colloids and lyophilic colloids.

The lyophobic colloids are colloids in which the diversion phase has much less affinity for the diversion medium. They need unique methods, and external conditions as the colloid solution doesn’t form quickly. They are generally irreversible.

Examples of lyophobic colloids are paint, alloys, oxides, sulphides, etc.

The lyophilic colloids are colloids in which the diversion phase has much more affinity for the diversion medium. When they come into contact, they turn into a colloidal solution. They are reversible. Examples of lyophilic colloids are starch, protein, gelation, etc.

Colloidal Solution

A colloidal system of a solution has two phases. They have a dispersed phase and a dispersion medium. A dispersed phase is a phase that is dispersed or scattered by the dispersion medium. It is also known as the discontinuous medium. A dispersion medium is a phase where the scattering occurs in the colloidal solution. It is also known as the continuous medium. The two-phase that constitutes the colloidal solution can be in any state of matter, i.e., gas, liquid and solid. For example, milk, butter and whipped cream. The term ‘sol’ is used when a solid is dispersed in a liquid, solid or gas medium—for example, ink, butter, jellies, etc. The dispersion of a solid in a gaseous medium is called aerosol—for example, smoke, dust, soot in the air, etc. When the dispersion phase is a solid and the dispersion medium is a liquid, it is called a colloidal solution.

Colloidal Suspensions Properties

• A suspension is a heterogeneous combination of several substances

• There are many tiny particles of dissolved solute present in the suspension. It has a diameter of more than 100 mm

• The suspension’s particles are visible

• Suspension particles do not pass through a filter paper. Filtration can therefore be used to separate a suspension

Differences between Suspensions and Colloid Solution

The differences between suspension and colloid solutions are tabulated below:

Conclusion