A property having a fixed value for a given material or substance is called material constant or constant of matter.[1] (Material constants should not be confused with physical constants, that have a universal character.)
A material property may also be a function of one or more independent variables, such as temperature. Materials properties often vary to some degree according to the direction in the material in which they are measured, a condition referred to as anisotropy. Materials properties that relate to different physical phenomena often behave linearly (or approximately so) in a given operating range . Modeling them as linear functions can significantly simplify the differentialconstitutive equations that are used to describe the property.
Equations describing relevant materials properties are often used to predict the attributes of a system.
The properties are measured by standardized test methods. Many such methods have been documented by their respective user communities and published through the Internet; see ASTM International.
Atomic properties
Atomic mass: (applies to each element) the average mass of the atoms of an element, in daltons (Da), a.k.a. atomic mass units (amu).
Atomic number: (applies to individual atoms or pure elements) the number of protons in each nucleus
Relative atomic mass, a.k.a. atomic weight: (applies to individual isotopes or specific mixtures of isotopes of a given element) (no units)
Standard atomic weight: the average relative atomic mass of a typical sample of the element (no units)
