Endothermic Reaction Examples

An endothermic reaction is any chemical reaction that absorbs heat from its environment. The absorbed energy provides the activation energy for the reaction to occur. A hallmark of this type of reaction is that it feels cold. Here's a list of examples of endothermic reactions. You can use these when asked to cite an example or to get ideas to set up a demonstration of an endothermic reaction or process.

A good examples of an endothermic reaction includes dissolving a salt. It doesn't have to be table salt, nor does the solvent need to be water.

• the reaction of barium hydroxide octahydrate crystals with dry ammonium chloride
• dissolving ammonium chloride in water
• the reaction of thionyl chloride (SOCl₂) with cobalt(II) sulfate heptahydrate
• mixing water and ammonium nitrate
• mixing water with potassium chloride
• reacting ethanoic acid with sodium carbonate
• photosynthesis (chlorophyll is used to react carbon dioxide plus water plus energy to make glucose and oxygen)

These examples could be written as chemical reactions, but are more generally considered to be endothermic or heat-absorbing processes:

• melting ice cubes
• melting solid salts
• evaporating liquid water
• converting frost to water vapor (melting, boiling, and evaporation, in general, are endothermic processes)
• making an anhydrous salt from a hydrate
• forming a cation from an atom in the gas phase
• splitting a gas molecule
• separating ion pairs
• cooking an egg
• baking bread

Some chemistry projects involve endothermic reactions:

• Ice Cream and Freezing Point Depression
• Icy Endothermic Reaction
• Make a Cold Pack from Hot Ice