The example above explains the use of salt on icy roads in the winter and the
increased effectiveness of calcium chloride per mole of solute. The use of glycols
in antifreeze solutions in automobile radiators is also based on this same concept.
CRYSTALLIZATION
Many substances form a repeated pattern structure as they come out of solution.
The structure is bounded by plane surfaces that make definite angles with each
other to produce a geometric form called a crystal. The smallest portion of the
crystal lattice that is repeated throughout the crystal is called the unit cell.
Samples of unit cells are shown in Figure 33.
The crystal structure can also be classified by its internal axis, as shown in
Figure 34.
Figure 33. Kinds of Unit CellsFigure 34. Crystal Structure Classified by Internal AxisA substance that holds a definite proportion of water in its crystal structure
is called a hydrate. The formulas of hydrates show this water in the following