of two or more substances are evenly dispersed throughout the medium (solution). For
example, if one dissolves sucrose in water, the sugar granules will break down into
individual molecules. This is to say, if one were to sample any two sections of the
solution, the same number of sugar molecules would be found per unit volume.
Solutions are not always liquids; that is, if liquid mercury is rubbed on solid gold, the
solid gold will dissolve the liquid mercury resulting in a solid solution.
A solution consists of two parts. The first part is the solvent, which is defined as
that portion of the solution that is either in greatest concentration or the portion of the
solution that is doing the dissolving. Water is usually considered to be the universal
solvent, no matter what proportion of the solution it is.
The solute is the second part of a solution. One can define the solute as the
substance that is being dissolved or the substance that is in lower concentration.
If one were to take 5 grams of sodium hydroxide and dissolve it in 100 milliliters
of deionized water, what would be the solvent and what would be the solute? If you
selected sodium hydroxide as the solute and water as the solvent, you were correct.
The reason the sodium hydroxide is the solute is because it is present in the lower
concentration and it is also the substance being dissolved. Water is the solvent
because it is (1) the universal solvent; (2) present in the greatest concentration; and (3)
the substance that is doing the dissolving.
Section IV. TYPES OF SOLUTIONS
As stated, a solution is a homogeneous mixture of gases, liquids, or solids in
which the molecules of two or more substances are evenly dispersed throughout the
medium. This can be more specifically defined as a true solution because the
substances are mixed on a molecular basis. There are two other types of solutions with
which one should be familiar--the colloidal solution and the emulsion.
2-22. COLLOIDAL SOLUTION
A colloidal solution is not a true solution since the individual molecules are not
mixed on a molecular basis; hence, the solution is not homogeneous throughout. This
type of solution contains aggregates of molecules with each individual aggregate being
denoted as a colloid or as a colloidal particle. The number of molecules in each
aggregate may be from several hundred to a few thousand. The size of each colloidal