Endothermic Reaction

An endothermic process is a chemical or physical process that absorbs heat from its surroundings.[1] In terms of thermodynamics and thermochemistry, it is a thermodynamic process with an increase in the enthalpy H (or internal energy U) of the system.[2] In an endothermic process, the heat that a system absorbs is thermal energy transfer into the system. Thus, an endothermic reaction generally leads to an increase in the temperature of the system and a decrease in that of the surroundings.[1] The term was coined by 19th-century French chemist Marcellin Berthelot.[3] The term endothermic comes from the Greek ἔνδον (endon) meaning 'within' and θερμ- (therm) meaning 'hot' or 'warm'.[4]

Examples

• Evaporation
• Sublimation
• Cracking of alkanes
• Thermal decomposition
• Hydrolysis
• Nucleosynthesis of elements heavier than nickel in stellar cores[9]
• High-energy neutrons can produce tritium from lithium-7 in an endothermic process, consuming 2.466 MeV. This was discovered when the 1954 Castle Bravo nuclear test produced an unexpectedly high yield.[10]
• Nuclear fusion of elements heavier than iron in supernovae[11]
• Dissolving together barium hydroxide and ammonium chloride
• Dissolving together citric acid and baking soda[12]