Avogadro constant Avogadro constant In chemistry and physics, the Avogadro constant, named after scientist Amedeo Avogadro, is the number of constituent particles, usually atoms or molecules, that are contained in the amount of substance given by one mole. Thus, it is the proportionality factor that relates the molar mass of a substance to the mass of a sample. The Avogadro constant, often designated with the symbol "N" or "L", has the value in the International System of Units (SI). (The parentheses there represent the degree of uncertainty.) Previous definitions of chemical quantity involved the Avogadro number, a historical term closely related to
Mass flow rate Mass flow rate In physics and engineering, mass flow rate is the mass of a substance which passes per unit of time. Its unit is kilogram per second in SI units, and slug per second or pound per second in US customary units. The common symbol is formula_1 (ṁ, pronounced "m-dot"), although sometimes "μ" (Greek lowercase mu) is used. Sometimes, mass flow rate is termed "mass flux" or "mass current", see for example "Fluid Mechanics, Schaum's et al". In this article, the (more intuitive) definition is used. Mass flow rate is defined by the limit: The reason for the dot