# Ch 2 Review of Scientific notation, significant digits, density, precision, and accuracy.

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Ch 2 Review of Scientific notation, significant digits, density, precision, and accuracy

Scientific Notation Perform these calculations: (3.2 X 10 5 ) (6.02 X 10 23 ) = 1.9 X 10 29 (9.23 X 10 -8 ) / (6.1 X 10 23 ) = 1.5 X 10 -31 (7.9 X 10 -6 ) + (4.0 X 10 -8 ) = 7.94 X 10 -6

Starting from the Atlantic Side If you “run across” zeros before you cross a non-zero digit on the Atlantic side Those Zeros ARE Significant! 10.04000 0.00400

Starting from the Pacific Side… 12.00300 Zeros on the pacific side Are NOT Significant 0.00456 0.0045600

A tlantic: A re significant P acific: P lace holders 0.009 11.009 11.090 0.0090

Significant Digits 1. 45,000 2. 4.1005 3. 1,234,567,891 4. 1,234,056,789 5. 0.005 6. 0.0050 7. 1.0050 8. 0.00304 9. 10.00304 10. 1 dozen eggs 11. 1 mile 12. 8 cats 13. 1 000 m = 1 km 14. 23.14

Round to the correct number of significant digits 12.30 X 0.003 = 12.30 X 0.0030 = 12.30 X 0.00300 =

Answers 1. 12.30 X 3 = 36.9, 40 2. 12.30 X 3.0 = 36.9, 37 3. 12.30 X 3.00 = 36.9

Round to the correct number of significant digits 4. 120 / 3.14 = 5. 14 / 32.00=.4375 or.44 6. 200 X 0.500 = 100

Answers 4. 120 X 3.14 = 380 5. 0.0120 X 0.7 = 0.008 6. 0.23 X 0.50600 =0.12

Round to the correct number of significant digits 7. (6 X 10 4 ) (5.27 X 10 -6 ) = 8. (6.809 X 10 4 )/(9.200 X 10 -6 )

Answers 7. (6 X 10 4 ) (5.27 X 10 -6 ) = 0.3 or 3 x 10 -1 8. (6.809 X 10 4 )/(9.200 X 10 -6 ) = 7.401 X 10 9

Density Density = mass volume Mass in grams Volume in ml or cm 3 Units: g/ml or g/ cm 3

Precision and accuracy Accuracy-how close a measured value is to an accepted value Precision – how close a series of measurements are to 1 another. Show little variation over a series of trials.

accurate (the average is accurate) not precise precise not accurate accurate and precise

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