Mole (unit) informal holiday in honor of the unit among chemists. The date is derived from the Avogadro number, which is approximately . It starts at 6:02 a.m. and ends at 6:02 p.m. Alternatively, some chemists celebrate June 2 or February 6, a reference to the 6.02 part of the constant. Mole (unit) The mole is the unit of measurement for amount of substance in the International System of Units (SI). Effective 20 May 2019, the mole is defined as the amount of a chemical substance that contains exactly (Avogadro's constant) constitutive particles, e.g., atoms, molecules, ions or electrons. This definition was
Defining equation (physics) of measurements to be made when they might appear ambiguous and unclear otherwise. A basic example is mass density. It is not clear how compare how much matter constitutes a variety of substances given only their masses or only their volumes. Given both for each substance, the mass "m" per unit volume "V", or mass density "ρ" provides a meaningful comparison between the substances, since for each, a fixed amount of volume will correspond to an amount of mass depending on the substance. To illustrate this; if two substances A and B have masses "m" and "m" respectively, occupying volumes