Amount of substance Amount of substance Amount of substance is a standard-defined quantity that measures the size of an ensemble of particles, such as atoms, molecules, electrons, and other particles. It is sometimes referred to as chemical amount. The International System of Units (SI) defines the amount of substance to be proportional to the number of entities present. The SI unit for amount of substance is the mole. It has the unit symbol mol. The proportionality constant is the inverse of the Avogadro constant. The mole is defined as the amount of substance that contains an equal number of elementary entities as there
Work (physics) "weight "lifted" through a height", which is based on the use of early steam engines to lift buckets of water out of flooded ore mines. According to Dugas, it is to Solomon of Caux "that we owe the term "work" in the sense that it is used in mechanics now". The SI unit of work is the joule (J). The SI unit of work is the joule (J), which is defined as the work expended by a force of one newton through a displacement of one metre. The dimensionally equivalent newton-metre (N⋅m) is sometimes used as the measuring unit for