Introduction: spontaneity

A spontaneous process is one which, once started, continues without need for further input of energy.  It happens on its own.  We can recognize in our own experiences many spontaneous processes.  Wood burning, after the initial match is set, the burning continues until the fuel is consumed or until we stop it by some other means (dousing with water).  Many processes that seem spontaneous give off heat, as in, they are exothermic.  So it is clear that energy is involved in this process somehow. Yet, other processes that are spontaneous are, in fact, endothermic.  Take for example a cold pack used in sports to help prevent swelling of injuries, etc.  the person merely shakes or twists the package and mixes the ingredients and the pack spontaneously becomes cold (endothermic). 

Remember Joule's experiment, gas expanded from the high pressure bulb into the evacuated bulb with no temperature change.  This is clearly a spontaneous reaction but also clearly, it involves something other than heat transfer or work.  We need something else to predict spontaneity.

4.1  Statistics

4.2  2&3 Law  

4.3 Thermochem