ch_01_0830 - Summary of Concepts Matter is made up of atoms...

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23 Summary of Concepts Matter is made up of atoms and molecules and can be subdivided into two broad categories: substances and mixtures 8/30/2007 24 Chemical Symbols A one- or two-lettered designation derived from the name of the element Most symbols are based on English names: Hydrogen = H Helium = He Boron = C Carbon = C Nitrogen = N Oxygen = O • More than 110 elements are known. First 36 elements
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25 Scientific Methods • In one of the most common scientific methods, we begin by constructing a hypothesis –a tentative explanation of the facts and observations. • Then we design and perform experiments to test the hypothesis; collect data (measurements). • The hypothesis is revised and the process continues. 26 Scientific Measurements and Units All measurements contain two essential pieces of information: a number (the quantitative piece) a unit (the qualitative piece) A number is somewhat meaningless without units. Consider this for one’s wages: $ 100 per week $ 100 per hour which is preferable?!
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27 Scientific Measurements and Units Scientists worldwide use common measurement units called the International System of Units (SI) In SI, there is a single base unit for each type of measurement. 28 Size of an atom: 1×10 -10 m
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29 Common SI Prefixes Examples: Gigahertz (GHz) Megabytes (MB) Terawatts (TW) • Prefixes are used to indicate powers of ten of common units that are much smaller or larger than the base unit. • In measurements, kilo -, centi- , and milli- are the three most common prefixes. 30 • The base unit of length is the meter , a little longer than a yard. • Common derived units include: – kilometer (km; 1000 m), about 2/3 of a mile.
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This note was uploaded on 05/06/2008 for the course CHEM 103 taught by Professor Forgot during the Spring '07 term at CUNY City.

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ch_01_0830 - Summary of Concepts Matter is made up of atoms...

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