Using Scientific Measurements

1
Using Scientific Measurements

• 2.3

2
Accuracy vs. Precision

• Accuracy the closeness of a measurement to the
  correct or accepted value of quantity measured.
• Precision the closeness of a set of
  measurements of the same quantity made in the
  same way
• 4 darts clustered together acc or pre?

3
Percent Error

• Always some error in a measurement
• Instrument, limits of measurer, calibrations
• error calculated by the following formula
• error Valueexp Valueacc x 100
• Valueacc

4
Significant Figures

• Sig figs all the digits known with certainty
  plus one final digit, which is somewhat estimated
  or uncertain
• Graduated cylinder example
• 42.5 mL - the 5 is the estimated number

5
Rules for Determining Sig. Figs.

• All non zero digits are significant
• No decimal book end
• Decimal go to 1st non zero and count everything
  to the right
• Exact numbers have infinite significant figures
  (1m 1000mm)
• Calculators exaggerate precision

6
Sig. Fig Examples

• How many sig figs are in
• 203000
• 1000.00
• 0.00052
• 0.06400
• 79.810

7
Significant Figures

• Multiplication and division sig. digs answer
  has no more figs. than the msmt. with the least
  of sig. figs.
• 12.257 5 s
• x 1.162 4 s
• 14.2426340 4 s 14.24

8
Significant Figures

• Addition and subtraction answer has no more
  numbers to the right of the decimal pt. than the
  number with the least numbers to the right of the
  decimal. 3.9 5
• 2.8 79
• 213.6
• 220.4 29 220.4

9
Scientific Notation

• 29640000000000000000000 copper atoms in 1 penny
• 2.964 x 1022 atoms
• 2 Parts to scientific notation
• between 1 and 10
• Power of 10

10
Scientific Notation

• 0.000000000000003332 kg
• 3.322 x 10-15 kg
• 1970000000 L
• 1.97 x 109
• What is .. In scientific notation?
• 4.58 x 105
• 9.05 x 10-3