endothermic

/ˌˈɛndəˌθʌrmɪk/

An endothermic reaction is one that absorbs or uses heat energy. Just ask a melting snowman about it.

What do green leaves, boiled eggs, and split gas molecules have in common? They have all undergone endothermic reactions, absorbing heat. But just because there’s heat involved doesn’t mean an endothermic reaction is the cause. Its polar — er thermal — opposite, exothermic describes a reaction that makes or gives off heat. It can be easy to confuse the two, but if you can remember that endo means “in” and exo means "out," the heat might not get to you so much.

Definitions of endothermic

1. adjective

   (of a chemical reaction or compound) occurring or formed with absorption of heat
   synonyms: endothermal, heat-absorbing

   endoergic, energy-absorbing

   (of a nuclear reaction) occurring with absorption of energy

   decalescent

   absorbing heat without increase in temperature when heated beyond a certain point

   antonyms:

   exothermic

   (of a chemical reaction or compound) occurring or formed with the liberation of heat

   energy-releasing, exoergic

   (of a nuclear reaction) occurring with evolution or releasing of energy
2. adjective

   having warm blood (in animals whose body temperature is internally regulated)
   synonyms: warm-blooded

   homeothermic, homoiothermic, homothermic

   of birds and mammals; having constant and relatively high body temperature