Difference Between True Solutions, Colloidal solution and Suspension || Surface Chemistry

Based on the nature of particle size, appearance and filterability solutions are classified into three main categories, namely (1) true solution, (2) Colloidal Solution and (3) suspension.

1. A true solution is a homogenous solution in which the solute particles have diameters lesser than 1nm i.e., the solute particles are of molecular dimensions. The particles are invisible even under powerful microscopes and cannot be separated through filter paper or animal membranes,

2. Colloids or colloidal solutions, represent an intermediate kind of a mixture between true solutions and suspension. Colloids consist of two parts: colloidal particles and the dispersing medium. It is in this dispersing medium that the colloidal particles are distributed.

3. Suspensions:  Suspensions consists of particles of a solid suspended in a liquid medium. Suspensions are heterogenous systems.

Difference Between True solutions, Colloidal solution and Suspension

(True Solutions vs Colloidal solution vs Suspension)

Property	True Solutions	Colloidal Solutions	Suspension
Size of the particles	1nm	1-1000nm	>1000nm
Nature	Homogenous	Heterogenous	Heterogenous
Filterability (Diffusion through parchment paper)	Particles of true solution diffuse rapidly through filter paper as well as parchment paper	Colloidal particles pass through filter paper but not through parchment paper.	Suspension particles do not pass through filter paper and parchment paper.
Visibility	Particles of the solution are not visible to naked eye.	Colloidal particles are not seen to naked eye but can be studied through ultra-microscope.	Suspension particles are big enough to be seen by naked eye.
Tyndall effect	True solution does not show Tyndall effect.	Colloids show Tyndall effect.	Suspension may or may not show Tyndall effect.
Appearance	Transparent	Translucent	Opaque
Examples	Sugar in water, Sodium chloride (NaCl) in water.	Starch dissolved in water	Oil in water, Sand in water.

Read more: Properties of Colloids