Chapter 17 // Spontaneous Processes and Entropy

This video introduces the concepts: Spontaneity and Entropy. A spontaneous change is one that occurs without a continuous input of energy from outside the system (Occurs by self-force action). A nonspontaneous change occurs only if the surroundings continuously supply energy to the system (needs external force to take place).
The driving force of any spontaneous process is probability. Because there are more ways of having the gas evenly spread throughout the container than there are ways for it to be in any other possible state, the gas spontaneously attains the uniform distribution. The probability of occurrence of a particular arrangement (state) depends on the number of ways (microstates) in which that arrangement can be achieved.
The type of probability we have been considering in this example is called positional probability because it depends on the number of configurations in space (positional microstates) that yield a particular state.
*** A gas expands into a vacuum to give a uniform distribution because the expanded state has the highest positional probability, that is, the largest entropy, of the states available to the system.

‘’Positional probability is also illustrated by changes of state. In general, positional entropy increases in going from solid to liquid to gas.’’