Chemical reactions involve the transfer of energy, and this energy can either be given out or taken in. The energy transfer often occurs as heat energy, but it can also take other forms, such as light or sound.
Exothermic reactions release energy into the surroundings, leading to an increase in the surrounding temperature. Most reactions are exothermic.
Some examples of exothermic reactions include:
Hand warmers and self-heating cans of food use exothermic reactions to generate heat.
Endothermic reactions absorb energy from the surroundings, resulting in a decrease in the surrounding temperature.
Some examples of endothermic reactions include:
Instant cold packs become very cold almost instantly by using endothermic reactions. They can be used to treat injuries.