heat, electricity, light
All chemical reactions involve energy. Some chemical reactions consume energy, whereas other chemical reactions release energy. Chemical reactions can be either spontaneous, which do not require an input of energy, or non-spontaneous, which does require an input of some type of energy. Energy may be in the form of heat, light or electricity. Each of the energy changes that occur during a reaction are graphed in Figure below . In the reaction on the left, energy is released. In the reaction on the right, energy is consumed.