NSCI 1322 Lecture Notes - Lecture 72: Molecular Solid, Phase Transition, Partial Pressure
12 Jan 2017
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Document Summary
According to kinetic-molecular theory, gases are composed of molecules or single atoms that are in constant random motion throughout mostly empty space (unless the gas is highly compressed). A gas is easily compressed because the molecules can be pushed into a smaller space. A gas is fluid because individual molecules can move easily relative to one another. According to kinetic-molecular theory, the molecules of a liquid are in constant random motion (as in a gas) but are more tightly packed, so there is much less free space. Because the molecules can move relative to one another as in a gas, a liquid can flow (it is fluid). But the lack of empty space explains why a liquid, unlike a gas, is nearly incompressible. Solids are nearly incompressible and are rigid, not fluid. This explains the rigidity of a solid. And, of course, the compact structure explains its incompressibility.
