At low temperatures, atomic motion is limited
to rotation and vibration, and the immobilized
atoms or molecules bond tightly to each other
in solid, closely packed, well-defined
structures. Such structures define the solid
phase. In a crystalline solid — salt, sugar,
tempered chocolate — the particles are
arranged in a regular, repeating array, while in
amorphous solids — boiled candies, glass —
they are randomly oriented. Large, irregular
molecules like proteins and starch often form
both highly ordered, crystalline regions and
disordered amorphous regions in the same
chunk of material. Ionic bonds, hydrogen
bonds, and van der Waals bonds may be
involved in holding the particles of a solid
together.
Liquids
At a temperature that is characteristic of each
solid substance, the rotation and vibration of