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
79.810

7. Significant Figures
Multiplication and division sig. digs = answer has no more figs. than the msmt. with the least # of sig. figs.
#’s
x #’s
#’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
2.8 79
= 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 kgL
1.97 x 109
What is ….. In scientific notation?
4.58 x 105
9.05 x 10-3