Columbia CHEM UN0001 - Standards for Measurement (32 pages)

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Standards for Measurement



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Standards for Measurement

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Lecture Notes


Pages:
32
School:
Columbia University
Course:
Chem Un0001 - Preparation for College Chemistry

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Standards for Measurement Preparation for College Chemistry Columbia University Department of Chemistry The Scientific Method Observations analysis Laws Hypothesis explanation Experiment measurement analysis Theory Model Measurement and Interpretations Direct Measurement Diameter 2 5 cm 1 2 3 4 5 6 7 8 Interpretation Step Radius Diameter 2 Area x r2 8 04 cm2 Art of Scientific Measurement Recognize what can be measured directly Devise a way to obtain the desired information from measurement data Experimentation Measured Data Basic UNIT Resting Potential 65 mV Derived Affected by Uncertainty Accuracy NUMERICAL VALUE Precision Resolution Noise Significant Figures Sig Figs The mass of an object weighed on a triple beam balance precision 0 1g is found to be 23 6 g This quantity contains 3 significant figures i e three experimentally meaningful digits If the same measurement is made with an analytical balance precision 0 0001g the mass might be 23 5820 g 6 sig fig Evaluating Zero Zero is SIGNIFICANT when Is between nonzero digits 61 09 has four sig Figs Appears at the end of a number that includes a decimal point 0 500 has three sig Figs 1000 has four sig Figs Zero is NON SIGNIFICANT when Appears before the first nonzero digit 0 0025 has two sig Figs Leading Zeros are non significant Appears at the end of a number without a decimal point 1 000 has one sig Fig 590 has two sig Figs Exact Numbers Defined numbers like 12 inches in a foot 60 minutes in an hour 1 000mL in one liter Numbers that occur in counting operations Exact numbers have an infinite number of sig figs Exact numbers do not limit the number of sig figs in a calculation Scientific Notation Number written as a factor between 1 and 10 multiplied by 10 raised to a power 0 0468 4 68 10 2 0 00003 3 0 10 5 two digits or 3 10 5 one digit Useful to unequivocally designate the significant figures 1200 1 200 10 3 four digits 6 6 600 000 6 6 10 two digits Multiplication or Division The answer must contain as many



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