the colloidal particles, causing them to change direction in a random fashion. This
motion is called Brownian movement after the Scottish botanist Robert Brown,
who first observed it.
EXPRESSIONS OF CONCENTRATION
There are general terms and very specific terms used to express the concentration
of a solution. The general terms and their definitions are:
Dilute
=
small amount of solute is dispersed in the solvent.Concentrated
=
large amount of solute is dissolved in the solvent.Saturated
=the solution is holding all the solute possible at that temperature. This is not a static
condition; that is, some solute particles are exchanging places with some of the undissolved
particles, but the total solute in solution remains the same. This is an example of equilibrium.Unsaturated
=
more solute can go into solution at that temperature. The solvent has further capacity to
hold more solute.Supersaturated
=sometimes a saturated solution at a higher temperature can be carefully cooled so that the
solute does not get a chance to come out of solution. At a lower temperature, then, the
solution will be holding more solute in solution than it should for saturation and is said to be
supersaturated. As soon as the solute particles are jarred or a “seed” particle is added to
the solution to act as a nucleus, they rapidly come out of solution so that the solution reverts
to the saturated state.It is interesting to note that the words saturated and concentrated are NOT
synonymous. In fact, it is possible to have a saturated dilute solution when the
solute is only slightly soluble and a small amount of it makes the solution
saturated, but the concentration of the solution is still dilute.
Specific Terms of Concentration
The more specific terms used to describe concentration are mathematically
calculated.
- PERCENTAGE CONCENTRATION is based on the percent of solute in the
solution by mass. The general formula is: