Barrons SAT Subject Test Chemistry, 13th Edition

Figure 32. Size of Particles in Water Mixture

The basic difference between a colloid and a suspension is the diameter of
the particles dispersed. All the boundaries marked in Figure 32 indicate only the
general ranges in which the distinctions between solutions, colloids, and
suspensions are usually made.
The characteristics of water mixtures are as follows:

Solutions

Colloids

Suspensions

................. 1 nm.............. .1,000 nm...................

Clear; may have color

Particles do not settle.

Cloudy; opaque color

Settle on standing

Particles pass through

ordinary filter paper.

Do not pass through

ordinary filter paper

Particles pass through

membranes.

Do not pass through semipermeable membranes such as animal bladders,

cellophane, and parchment, which have very small pores*

Particles are not visible.

Visible in ultramicroscope

Visible with microscope or naked eye

(^) Show Brownian movement^ No Brownian movement
*Separation of a solution from a colloidal dispersion through a semipermeable membrane is called
dialysis.
When a bright light is directed at right angles to the stage of an
ultramicroscope, the individual reflections of colloidal particles can be observed
to be following a random zigzag path. This is explained as follows: The
molecules in the dispersing medium are in motion and continuously bumping into