Single possible arrangement of the positions and kinetic energies of the gas molecules when the gas is in a specific thermodynamic state
Akin to taking a snapshot of the molecule's rotational, translational, and vibrational movements

-as number of microstates increases, so does entropy

-Increase in volume
-Increase in temperature
-Increase in number of molecules

Increases in which
-gases form from either solids or liquids
-liquids of solids form from solids
-number of gas molecules increases during chemical reaction

Entropy of a pure crystalline substance at absolute zero (0 degrees K) is 0.