"Ludwig Boltzmann... saw further into the nature of matter than any... contemporaries until... he hanged himself in the face of their incomprehension and rejection of his ideas. Entropy, he showed, is a measure of disorder... A solid... has a lower entropy that the liquid into which it melts. A gas... has a higher entropy than the liquid from which it evaporates. ...When a gas expands to fill an enlarged volume, its disorder and therefore its entropy increases even though we keep its temperature the same... [W]e become less confident... [that] a molecule will be found in a given small region. ...Entropy [also] increases as the thermal disorder of a substance becomes more vigorous, with increasing thermal motion of... atoms... [and] as... positional disorder increases... [the] available positions of... atoms."