Mole (unit) 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 adopted in November of 2018, revising its old definition based on the number of atoms in 12 grams of carbon-12 (C) (the isotope of carbon with standard atomic weight 12 by definition). The mole is an SI base unit, with the unit symbol mol. The mole is widely used
Elasticity (physics) types of material parameter. The first type of material parameter is called a "modulus", which measures the amount of force per unit area needed to achieve a given amount of deformation. The SI unit of modulus is the pascal (Pa). A higher modulus typically indicates that the material is harder to deform. The second type of parameter measures the "elastic limit", the maximum stress that can arise in a material before the onset of permanent deformation. Its SI unit is also pascal (Pa). When describing the relative elasticities of two materials, both the modulus and the elastic limit have to