How does thermochemistry treat the making and breaking of chemical bonds?
Bond breaking requires energy; bond making releases energy. See if you can remember that mantra.
Whether a reaction is exothermic or endothermic depends of course on the balance between bond-breaking, and bond-making. When we look at combustion reactions, a typical reaction is the combustion of hydrocarbon (the which drives our industrial society). For combustion of hexane, we could write,
The reaction requires the breaking of bonds: viz. the breaking of strong