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MEASUREMEMT ,GENERAL CHEMISTRY

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MEASUREMENTS Glenn V. Lo Department of Physical Sciences Nicholls State University MEASUREMENT assigning a value to an observation For science and trade: value assigned should be in referenc ... e to or traceable to a “standard” Reported measurement generally has 2 parts: ■ Number (indicates the value) ■ Unit (indicates the standard) ■ Ex: 5.0 kg ◆ (means 5.0 times the mass of a cylinder stored in a vault at the International Bureau of Weights and Measures in France; by agreement the cylinder is defined to have a mass of 1 kg) THE STANDARDS US Trade ■ National Institute of Standards and Technology (Gaithersburg, Maryland) http://www.nist.gov ■ English System of Units International/Scientific ■ International Bureau of Weights and Measures (BIPM) http://www.bipm.fr/enus/welcome.html ■ Systeme Internationale (SI) Units ◆ Evolved from metric system The SI Units Base units for seven fundamental quantities were officially adopted in 1960 What are they? ■ mass, length, time, temperature, etc. ■ http://www.bipm.fr/enus/3_SI/base_units.html All other quantities can be derived from measurements of fundamental quantities. ■ Example: speed = length divided by time ■ Units for derived quantities are combinations of base units (speed: m/s). Some are given names (ex. Joule, J = kg m / s2) special http://www.bipm.fr/enus/3_SI/siderived.html .............................................CONTINUED [Show More]

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