Mass (from Ancient Greek: μᾶζα) is one of the most important quantities used in chemistry.
Definition
Mass is the quantity of matter present in an object. Mass is measured with a balance (not a scale).
Units
The SI Unit for mass is the kilogram - one thousand grams. The quantity is based on 40 platinum-iridium cylinders manufactured 130 years ago (1889) in France. In contrast, other SI units are defined by universal constants not by physical objects.
"Two major standardization strategies have surfaced. One proposes a numerical unit built on Avogadro’s number, derived from the number of atoms in 12 grams of carbon-12. The other approach makes use of Planck’s constant and the Watt balance, which measures the electromagnetic force needed to hold a kilogram. [1]
Extension
Another important use is the molar mass of a substance; that is, the mass of one mole of the substance.
PPT
Lesson 15 discusses mass and length.
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References
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