In what ways does the transfer of heat affect bond stability?
How does a certain added number of joules affect the orbital of a
  bonded electron


If you pump enough energy into an element\molecule you can promote an electron from one orbital to the next highest.  For example, the hydrogen atom has a single 1s electron, put enough energy in and you can promote that electron to the 2s orbital.  That means that, on average, the electron would spend more time further away from the nucleus.  In molecules, there are numerous "sub-levels" between each (molecular) orbital.  These "sub-levels" relate to rotational and vibrational energy.  So as you pump energy into the system the molecule will rotate and vibrate more violently.  If you put enough energy in, the bond will break and the atoms connected by that bond will fly apart.