Significant Figues - Units - Density

# Significant Figues - Units - Density - Rules for SF...

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1 Significant Figures, Units, Percentages, and Density J.P. Harris CH104/Fall 2003 Lecture 3 Rules for SF Exact numbers have an infinite number of SF (ex. 100 cm = 1 m EXACTLY) SF must be counted for measurements – Nonzero digits are always SF – Zeros • Leading zeros are never SF In the middle zeros are always SF Trailing zeros – with a decimal point are SF – without a decimal point are not SF How many significant figures are in each of the following numbers? 1. 0.02050 2. 0.205 3. 2.05 4. 20.5 5. 205 6. 2050 7. 2.05 × 10 4 8. 2.050 × 10 6 1. 4 SF; 0.02050 2. 3 SF; 0.205 3. 3 SF; 2.05 4. 3 SF; 20.5 5. 3 SF; 205 6. 3 SF; 2050 7. 3 SF; 2.05 × 10 4 8. 4 SF; 2.050 × 10 6 SF, ppd, and Calculations × and ÷ – The product or quotient of this operation will have the same number of SF as the number ×’d or ÷’d with the fewest SF. + and - – The sum or difference of this operation will have the same number of places past the decimal (ppd) as the number +’d or -’d with the fewest ppd. Calculate the answers for the following problems and express the answer using an appropriate number of significant figures. Assume all of the numbers are the results of measurements. 1. (1.02 × 10 -21 )(1.1 × 10 9 ) 2 = 1.2 × 10 -3 2. (251)(3.1×10 -1 ) = 1.1 (24)(3.0) 3. (2.93 × 10 -1 ) + (6.2 × 10 -2 ) = 3.55× 10 -1 4. 471.19 - 365.09 = 106.10 5. 17.76 - 0.0479 = 17.71 SF, ppd, and Calculations (part 2) Calculations with more than one step – Don’t round until the end of the problem! – Trace SF and ppd through the problem from the beginning of the calculation If the result of a multiplication step is used in an addition step, use SF for the multiplication step, then “translate” the SF into ppd. If the result of an addition step is used in a multiplication step, use ppd for the addition step, then “translate” the ppd into SF.

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2 Calculate the answers for the following problems and express the answer using an appropriate number of significant figures. Assume all of the numbers are the results of measurements.
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• Spring '07
• ARNEY
• Orders of magnitude, Joule, ml, Calorie

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