Molar mass Molar mass In chemistry, the molar mass "M" is a physical property defined as the mass of a given substance (chemical element or chemical compound) divided by the amount of substance. The base SI unit for molar mass is kg/mol. However, for historical reasons, molar masses are almost always expressed in g/mol. In simple terms, molar mass of a substance is the total weight of that substance (in either kilogram or gram) for one mole of that substance. That is, the weight of a substance for 6.02214076×10^23 molecules or atoms of that substance. As an example, the molar mass of
Gray (unit) Gray (unit) The gray (symbol: Gy) is a derived unit of ionizing radiation dose in the International System of Units (SI). It is defined as the absorption of one joule of radiation energy per kilogram of matter. It is used as a unit of the radiation quantity absorbed dose which measures the energy deposited in a unit mass at a certain position, and of the radiation quantity kerma, which is the amount of energy that is transferred from photons to electrons per unit mass at a certain position. The corresponding cgs unit to the gray is the rad (equivalent to