13.3. Solids http://www.ck12.org
FIGURE 13.17
Diamond is a network solid and consists
of carbon atoms covalently bonded to one
another in a repeating three-dimensional
pattern. Each carbon atom makes four
single covalent bonds in a tetrahedral ge-
ometry.Amorphous Solids
Unlike a crystalline solid, anamorphous solidis a solid that lacks an ordered internal structure. Some examples of
amorphous solids include rubber, plastic, and gels. Glass is a very important amorphous solid that is made by cooling
a mixture of materials in such a way that it does not crystallize. Glass is sometimes referred to as a supercooled
liquid rather than a solid. If you have ever watched a glassblower in action, you have noticed that he takes advantage
of the fact that amorphous solids do not have a distinct melting point like crystalline solids do. Instead, as glass is
heated, it slowly softens and can be shaped into all sorts of interesting forms. When a glass object shatters, it does so
in a very irregular way. In contrast, a crystalline solid always breaks along specific planes as dictated by its crystal
system.
Lesson Summary
- Intermolecular forces keep the particles of liquids close together, though liquids are still able to flow. Surface
tension is a property of liquids that gives objects the ability to float on its surface. - Molecules of a liquid evaporate even when the temperature of the liquid is below its boiling point. Molecules
with high kinetic energies escape the surface of the liquid, leaving the remaining liquid cooler than it was
before. - The vapor pressure of a liquid is determined by the strength of the intermolecular forces. Vapor pressure
increases as temperature increases due to an increased rate of evaporation. The relationship of vapor pressure
to temperature is shown on a vapor pressure curve. - Boiling of a liquid occurs when the vapor pressure of the liquid is equal to the external pressure.