1. Which of the following is a difference between an endothermic and an exothermic chemical reaction?
a. Energy is only conserved in exothermic reactions.
b. The system absorbs heat during an endothermic reaction while the system releases heat during an exothermic reaction.
c. Endothermic reactions fuse nuclei whereas exothermic reactions cause nuclear fission.
d. Endothermic reactions are never spontaneous whereas exothermic reactions can be spontaneous.