Lecture_02_010612

# Lecture_02_010612 - Lecture 2: Scientific Communication...

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Lecture 2: Scientific Communication • Outline (Zumdahl Ch. 1 & Appendix 1 & 2) : - Mathematical Procedures (A1.1, A1.5, A1.6) - Units of Measurement and Conversions Among Units (App. 2) • Problems for Extra Practice: - worksheet posted on web • Office Hours: Mon. 11:30 am±12:30 pm, Wed. 11:00 am±noon

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Scientific Communication • Measurements or observations must be communicated unambiguously – Reporting measurements • Units (SI) • Scientific notation • Prefixes • Significant digits – Describe as precise and/or accurate
Stating a Measurement In every measurement, a number is followed by a unit . Observe the following examples of measurements: Number and Unit 35 m 0.25 L 225 lb

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The SI System Scientists recognized that a standard system of units was needed if measurements were to be useful In 1960, an international agreement set up a system of units called the International System (SI) Based on the metric system and units derived from the metric system Related decimal systems based on 10
SI Base Units All other units are derived from this system.

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Quantity Definition of Quantity SI unit Area Length squared m 2 Volume Length cubed m 3 Density Mass per unit volume kg/m 3 Speed Distance traveled per unit time m/s Acceleration Speed changed per unit time m/s 2 Force Mass times acceleration of object kg·m/s 2 ( =newton, N) Pressure Force per unit area kg/(m 2 ) ( = pascal, Pa) Energy Force times distance traveled kg·m 2 /s 2 ( = joule, J)
Common SI b English Conversions

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Importance of Units!
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## This note was uploaded on 01/18/2012 for the course CHEM 142B taught by Professor John during the Winter '11 term at University of Washington.

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Lecture_02_010612 - Lecture 2: Scientific Communication...

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