Ch 2

Review of Scientific notation, significant

digits, density, precision, and accuracy

Scientific Notation

Perform these calculations:(3.2 X 105) (6.02 X 1023) = 1.9 X 1029

(9.23 X 10-8) / (6.1 X 1023) = 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 sideThose Zeros ARESignificant!10.040000.00400

Starting from the Pacific Side…

12.00300Zeros on the pacific sideAre NOTSignificant 0.00456 0.0045600

Atlantic: Are significant

Pacific: Place holders 0.009 11.009 11.090 0.0090

Significant Digits

1. 45,0002. 4.10053. 1,234,567,8914. 1,234,056,7895. 0.0056. 0.00507. 1.0050

8. 0.003049. 10.0030410. 1 dozen eggs11. 1 mile12. 8 cats13. 1 000 m = 1

km14. 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, 402. 12.30 X 3.0 = 36.9, 373. 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 .446. 200 X 0.500 = 100

Answers

4. 120 X 3.14 = 3805. 0.0120 X 0.7 = 0.0086. 0.23 X 0.50600 =0.12

Round to the correct number of significant digits

7. (6 X 104 ) (5.27 X 10-6 ) =8. (6.809 X 104)/(9.200 X 10-

6)

Answers

7. (6 X 104 ) (5.27 X 10-6 ) = 0.3 or 3 x 10-1

8. (6.809 X 104)/(9.200 X 10-

6) = 7.401 X 109

Density

Density = mass volume

Mass in gramsVolume in ml or cm3

Units: g/ml or g/ cm3

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