New Jersey NJSLA Science Grade 11 Practice Questions - New Jersey Student Learning Assessments - Science Grade 11 Exam

In Reaction A the bonds formed release more energy than is required to break bonds in the reactants; in Reaction B the bonds broken require more energy than the bonds formed release. Both reactions release energy because bonds are always formed during a chemical change. In Reaction B the bonds formed release more energy than the bonds broken require, making the change exothermic. The energy change depends only on the number of atoms, not on the bond energies of reactants and products.