Why does our mouth feel cold after eating peppermint

Why does our mouth feel cold after eating peppermint  

Natural peppermint contains several components that, if ingested, lead to a cold sensation in the mouth. The best known and best understood is (-)-menthol (IV), which is the dominant component of the peppermint oil extracted from Mentha piperita and M. arvensia. 

The cause of the cooling sensation is the unusually positive enthalpy of solution. Most values of A//.t o iiUoii i are positive, particularly for simple inorganic solutes. 

The other substance sometimes added to foodstuffs to cause cooling of the mouth is xylitol (V). It is added as a solid to some sweets, chewing gum, toothpastes and mouth-wash solutions. 

It is quite difficult to measure an accurate enthalpy of solution A//( olutioni with a calorimeter, but we can measure it indirectly. Consider the example of sodium chloride, NaCl. The ions in solid NaCl are held together in a tight array by strong ionic bonds. While dissolving in water, the ionic bonds holding the constituent ions of Na+ and Cl- in place break, and new bonds form between the ions and molecules of water to yield hydrated species. Most simple ions are surrounded with six water molecules, like the [Na(H20)6]+ ion (VI). Exceptions include the proton with four water molecules (see p. 235) and lanthanide ions with eight. 

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