C A Student A B Student B C Student C D Student D E None of them 4 Significant

# C a student a b student b c student c d student d e

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° C A. Student A B. Student B C. Student C D. Student D E. None of them 4
Significant Figures Represent precision of measurement Rules with zeros can be tricky Leading zeros (0.015) Captive zeros (Chem 101) Trailing zeros (150 vs. 150. vs. 150.0) Exact numbers (not measurements) 5
Math and Sig Figs Multiplication and division Take lowest number of sig figs Addition and Subtraction: Same # decimal places as least precise 1.33 1.225 + 1.4 3.955→4.0 6
The following calculation is an average of exam scores. What is the correct answer with appropriate sig. figs. 75.4 + 82.6 + 91.1 3 A. 83.03 B. 83.0 C. 83 D. 80 E. 80. F. None of these 7
Scientific Notation: A review 11000 = 1.4 0.00021 = 1.1 x 10 4 2.1 x 10 -4 1.021 x 10 -3 0.001021 = 1730= 6.022 x 10 -23 = 0.000,000,000,000,000,000,000,06022 602,200,000,000,000,000,000,000 = 6.022 x 10 23 Note: same number of significant figures on both sides of each example. 1.73 x 10 3 8
Units The unit is the scale of which a measurement is made All measurements should have a unit Units can help direct how a problem should go SI units: Standardized units: mass - kilogram (kg) length - meter (m) time - second (s) temperature - Kelvin (K) amount of substance - mole (mol) electrical charge- Coulomb (C) 9

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• Spring '08
• Kenney
• Chemistry, Review, Accuracy and precision, Chemical substance, Compound substance- substance

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