The Currency of Chemical Reactions

Think of bonds like bank accounts. Every bond has energy stored in it — like money saved up. To break a bond, you need to "spend" energy (it's endothermic). But when you make a new bond, you "earn" energy back (it's exothermic). Whether a reaction releases or absorbs energy overall depends on the balance sheet: did you spend more breaking old bonds, or earn more making new ones? This is the fundamental principle behind bond energy calculations — and it explains everything from why burning methane releases heat to why some reactions need continuous heating.