How exactly can an increase temperature be used to break the chemical bonds of a gas [SO2, for example]?
As we provide heat to any molecule, the energy of the molecule increases. Specifically, the energy of atoms increases. Using the fact that stability is inversely proportional to energy, we can conclude that as energy increases, the bonds between the atoms become more unstable and eventually break and constituent atoms disassociate. 

This heat provided is known as bond disassociation enthalpy, or bond disassociation energy [BDE].