In the first law of thermodynamics, it states when heat is converted into energy, where as the total energy in the room could transform into another but can never be created or destroyed. If you release 258J of energy in the room, 258J would also be removed from the food according to the isolating system.
Ionic compounds don't conduct electricity very well because the charge carriers can't move through the crystal. They can conduct heat because the kinetic energy itself is the "heat carrier”.
