Mass, Density, and Volume - Key terms


An SI unit (abbreviated amu), equal to 1.66 · 10 −24 g, for measuring the mass of atoms.


A figure used by chemists to specify the mass—in atomic mass units—of the average atom in a large sample. The average atomic mass of carbon, for instance, is 12.01 amu. If a substance is a compound, the average atomic mass of all atoms in a molecule of that substance must be added together to yield the average molecular mass of that substance.


A figure, named after Italian physicist Amedeo Avogadro (1776-1856), equal to 6.022137 × +023 . Avogadro's number indicates the number of atoms, molecules, or other elementary particles in a mole.


The ratio of mass to volume—in other words, the amount of matter within a given area. In the SI system, density is typically expressed as grams per cubic centimeter (g/cm 3 ), equal to 62.42197 pounds per cubic foot in the English system.


The amount of matter an object contains.


Physical substance that occupies space, has mass, is composed of atoms (or in the case of subatomic particles, is part of an atom), and is convertible to energy.


One of the most commonly used units of volume in the SI system of measures. The milliliter (abbreviated mL), also known as a cubic centimeter (cc), is equal to 6.10237 · 10 −2 cubic inches in the English system. As the name implies, there are 1,000 milliliters in a liter.


The mass, in grams, of1 mole of a given substance. The value in grams of molar mass is always equal to the value, in atomic mass units, of the average atomic mass of that substance: thus, carbon has a molar mass of 12.01 g, and anaverage atomic mass of 12.01 amu.


The SI fundamental unit for "amount of substance." A mole is, generally speaking, Avogadro's number of atoms, molecules, or other elementary particles; however, in the more precise SI definition, a mole is equal to the number of carbon atoms in 12.01 g of carbon.


The density of an object or substance relative to the density of water; or more generally, the ratio between the densities of two objects or substances. Since the specific gravity of water is 1.00—also the density of water ing/cm 3 —the specific gravity of any substance is the same as the value of its own density in g/cm 3 . Specific gravity is simply a number, without any unit of measure.


The amount of three-dimensional space an object occupies. Volume is usually expressed in cubic units of length—for instance, the milliliter.


The product of mass multiplied by the acceleration due to gravity (32 ft or 9.8 m/sec 2 ). A pound is a unit of weight, whereas a kilogram is a unit ofmass.

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