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An example in everyday life is the blue colour sometimes seen in the smoke emitted by motorcycles, in particular two-stroke machines where the burnt engine oil provides these particles. [1] The same effect can also be observed with tobacco smoke whose fine particles also preferentially scatter blue light.
The term colloidal suspension refers unambiguously to the overall mixture (although a narrower sense of the word suspension is distinguished from colloids by larger particle size). A colloid has a dispersed phase (the suspended particles) and a continuous phase (the medium of suspension).
This distinguishes a suspension from a colloid, in which the colloid particles are smaller and do not settle. [2] Colloids and suspensions are different from solution, in which the dissolved substance (solute) does not exist as a solid, and solvent and solute are homogeneously mixed.
A sol is a colloidal suspension made out of tiny solid particles [1] in a continuous liquid medium. Sols are stable, so that they do not settle down when left undisturbed, and exhibit the Tyndall effect, which is the scattering of light by the particles in the colloid. The size of the particles can vary from 1 nm - 100 nm.
Unlike solutions and colloids, if left undisturbed for a prolonged period of time, the suspended particles will settle out of the mixture. Although suspensions are relatively simple to distinguish from solutions and colloids, it may be difficult to distinguish solutions from colloids since the particles dispersed in the medium may be too small ...
Ketchup, for example, becomes runnier when shaken and is thus a non-Newtonian fluid. Many salt solutions and molten polymers are non-Newtonian fluids, as are many commonly found substances such as custard, [1] toothpaste, starch suspensions, corn starch, paint, blood, melted butter and shampoo.
Examples are suspensions of rod-like viruses such as the tobacco mosaic virus as well as synthetic macromolecules, such as Li 2 Mo 6 Se 6 nanowire [9] or colloidal suspensions of non-spherical colloidal particles. [10] Cellulose and cellulose derivatives form lyotropic liquid crystal phases as do nanocrystalline (nanocellulose) suspensions. [11]
When both large colloidal particles and small depletants are in a suspension, there is a region which surrounds every large colloidal particle that is unavailable for the centers of the depletants to occupy. This steric restriction is due to the colloid-depletant hard-sphere potential. [7] [8] The volume of the excluded region is