Lecture_2--Measurements_in_Chemistry - Measurement in...

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1 Measurement in Chemistry Chapter 1 Measurement in Chemistry Qualitative measurements Observations that describe a substance, mixture, reaction, or other process in WORDS . Quantitative measurements Observations that describe a property with NUMBERS and UNITS . UNITS and Quantitative measurements Numbers often make no sense if we do not have some sort of reference or standard to compare them to. Nearly all numbers MUST be followed by a unit label. The unit indicates the standard against which the number is measured.
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2 UNITS and Quantitative measurements The metric system is a system of measurement based on multiples of ten. In the metric system, a prefix may be added to the base unit to change the value of the unit by a factor of ten. The base unit is a reference to the standard. The English system of measurement is not based on powers of ten, and is therefore more difficult to use in calculations. Scientists almost exclusively work in the metric or SI system. Base units: The Système Internationale (SI) base units are defined from some physically observable and reproducible quantity. The base units are: Quantity Unit Symbol Length meter m Mass kilogram (gram) kg (g) Time second S Temperature kelvin K Amount of a substance mole mol Electric Current ampere A Luminous Intensity candela cd Prefix Symbol Multiple Multiple Tera- T 10 12 1,000,000,000,000 Giga- G 10 9 1,000,000,000 Mega- M 10 6 1,000,000 kilo- k 10 3 1,000 hecto- h 10 2 100 deka- dk 10 1 10 base unit 10 0 1 deci- d 10 1 0.1 centi- c 10 2 0.01 milli- m 10
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This note was uploaded on 10/19/2011 for the course CHEM 230 taught by Professor Levi during the Spring '11 term at Skyline College.

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Lecture_2--Measurements_in_Chemistry - Measurement in...

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