Mole Day is celebrated annually on October 23 from 6:02 a.m. to 6:02 p.m. It celebrates Avogadro’s Number (6.02 x 1023), which is a basic measuring unit in chemistry. Mole Day was created as a way to foster interest in chemistry, and schools throughout the United States and around the world celebrate with various activities related to chemistry and/or moles.

For a given molecule, one mole is a mass (in grams) whose number is equal to the atomic mass of the molecule. For example, the water molecule has an atomic mass of 18, therefore one mole of water weighs 18 grams. An atom of neon has an atomic mass of 20, therefore one mole of neon weighs 20 grams. In general, one mole of any substance contains Avogadro’s Number of molecules or atoms of that substance. This relationship was first discovered by Amadeo Avogadro (1776-1858) and he received credit for this after his death.

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