Lec2 - Lec2: RoyA.Lacey,;Che 131,Fall2010 1 ScientificMethod observations explanationofw

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1 Roy A. Lacey, Stony Brook University; Che 131, Fall 2010 Lec 2: Measurements and units
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2 Roy A. Lacey, Stony Brook University; Che 131, Fall 2010 Scientific Method A hypothesis is a tentative and testable explanation for an observation or a series of observations. A scientific theory is a general explanation of widely observed phenomena that have been extensively tested. Why are measurements important?
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3 Roy A. Lacey, Stony Brook University; Che 131, Fall 2010 ` Accurate measurements are essential for characterizing the physical and chemical properties of matter. ` Standardization of the units of measurements is essential. Measurements UNITS MATTER!! ` Quantitative easy to check ` Easy to agree upon, no personal bias ` The measuring instrument limits how good the measurement is.
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4 Roy A. Lacey, Stony Brook University; Che 131, Fall 2010 SI Units Quantity Base Unit Abbrev. Length Mass Time Temp meter kilogram second Kelvin m kg s K Amount mole mol Symbol l m t T n
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5 Roy A. Lacey, Stony Brook University; Che 131, Fall 2010 Prefixes for SI units Prefixes Value Name Symbol Exponential Mega M 10 6 Kilo k 10 3 Hecto h 10 2 Deka da 10 Deci d 10 -1 Centi c 10 -2 Milli m 10 -3 Micro μ 10 -6 Nano n 10 -9 Pico p 10 -12
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6 Roy A. Lacey, Stony Brook University; Che 131, Fall 2010 Derived units Area square meter m 2 Volume cubic meter m 3 Force newton N Pressure pascal Pa = 1N/m 2 Energy joule J = 1 Kg.m 2 /s 2 Power watt W = J/s Electric charge coulomb C Current ampere A = C/s Voltage volt V = W/A = J/C Frequency hertz Hz Quantity Name Symbol
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7 Roy A. Lacey, Stony Brook University; Che 131, Fall 2010 How good are the measurements? We use two words to describe how good measurements are ` Accuracy how close the measurement is to the actual value ` Precision how well can the measurement be repeated All scientific measures are subject to error.
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This note was uploaded on 09/23/2010 for the course CHEM 131 taught by Professor Wong during the Fall '08 term at SUNY Stony Brook.

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Lec2 - Lec2: RoyA.Lacey,;Che 131,Fall2010 1 ScientificMethod observations explanationofw

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