Chem Lab Final

# Chem Lab Final - Re visions EXPERI MENT 1. Me asure e and S...

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7/26/11 Revisions EXPERIMENT 1 . Measurement and Significant Figures o The system of measurement in science is metric system o Metric system of measurement is a decimal system (factor of 10) o it has standard units Measurement Metric Unit Symbol - length meter m - mass gram g - volume liter L - temperature deg. celc., kelvin oC, K

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7/26/11 § when reporting a measurement, a unit must me included § a measurement without a unit is meaningless § prefixes are attached to the standard units for very large or very small measured values. Some prefixes in the metric system Prefix Symbol Meaning Example kilo k 1000 2.5 kg = 2500 g deci d 0.1 0.5 dL = 0.05 L centi c 0.01 2.4 cm = 0.024 m milli m 0.001 12 mm = 0.012 m
7/26/11 Measured Numbers and Exact Numbers Ø if a quantity is determined by using measuring tool the quantity is a measured number - e.g. 14 inch, 20.5 kg, 25 oC, 10:00 AM Ø exact numbers are: a) counts of objects b) define relation ship b/n two quantities -e.g. 2 beakers, 6 years, 12 students there are 7 days in a week, 100 cm in 1 m.

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7/26/11 Significant Figures in Measurements Ø all reported numbers including the estimated digit in a measurement are called significant figures Ø Rules:- - all non zero digits are always significant (26.25 L, 4 ) - a zero b/n non zero digits is significant (1.02 cm, 3 ) - a zero at the beginning of a decimal number is not significant (0.063 g, 2 ) - a zero used as place holder without a decimal point is not significant ( 10,000 kg, 1)
7/26/11

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7/26/11
7/26/11 EXPERIMENT 2 . Conversion Factor in calculations A. Rounding off - Measured numbers have fewer sig. figs. than the calculater display - the calculated results are adjusted by rounding off if the number to be dropped is less than 5 it& following #s are dropped if the number to dropped is 5 or greater than 5 , the value of the last retained digit is increased by 1 . when numbers are dropped, the correct magnitude is retained by replacing the dropped digit with place holder zero a. 75.6243 75.6 76 b. 0.528392 0.528 0.53 c. 387,600 388,000 390,000 d. 4 4.00 4.0 three sig.fig two sig fig

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7/26/11 B) Significant Figures in Calculation Multiplication and division - The answer is reported with the same no of sig. figs
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## This note was uploaded on 07/26/2011 for the course CHEM 1151 taught by Professor Staff,u during the Spring '08 term at Georgia Perimeter.

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Chem Lab Final - Re visions EXPERI MENT 1. Me asure e and S...

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