1. Significant Figures

2. Accuracy and Precision Review
What’s the difference in accuracy and precision?
Are they the same thing?
Are they related?
Accuracy: Proximity to the true value
Precision: Repeatability of the measurement

3. Precise and/or Accurate?
High Precision
Low Accuracy
Low Precision
High Accuracy
High Precision
High Accuracy

4. Rounding
When rounding, look only at the first number on the right of your objective
Example - Round to the nearest:
A.) 4 Decimal Places
B.) 3 Decimal Places
C.) 1 Decimal Place

5. Counting Sig Figs Why are Sig Figs Important?
You can’t be more or less precise than what you are measuring with
Nonzero Integer – Always significant!
Example: 15
28,853
5.364

6. “Sandwiched” or “Wedgie”Zeros
Any number(s) between two significant figures is significant, ALWAYS:
Ten Sig Figs
1.1074
Five Sig Figs

7. Leading Zeros
Leading Zeros – Zeros that precede all the nonzero digits are NOT significant Ex
Two Sig Figs
Three Sig Figs

8. Trailing Zeros Zeros that fall at the right end of a number
Significant if after a decimal:
Five Sig Figs
Not Significant if before a decimal: 150,000
Two Sig Figs
Examples
50.0
Three 50
One

9. An odd trailing zero… How many significant digits: 240 240.0 240. Two
Four
240.
Three
The decimal on the end makes the last digit significant
Practice:
5 Sig Figs only because of the decimal place

10. Exact Numbers Some numbers are exact
Numbers from counting (3 Apples)
Conversion Factors (1in = 2.54 cm)
Exact numbers have an infinite number of significant figures

11. A Special Note Why do scientist like scientific notation?
Significant digits can be vague without it
All digits before the multiplier are significant, always!
Example:
200 mL
2.0 X 102g

12. Pacific-Atlantic Rule

13. Practice – Think/Pair/Share
Determine the number of significant figures in the following examples: g
1.270 X 102 m
125g
10g L
4.0 X 10-1 cm3

14. Rounding With Sig Figs How many sig figs are needed?
You will be told!
From the leftmost sig fig, count digits until you get to how many you need. Then round there.
Example
Round 1355 to three sig figs
1360
Round to two sig figs

15. Calculations with Sig Figs
Multiplication and Division:
Answer can have only as many significant figures as the measurement with the least significant digits
Ex: 150.0/10
Addition and Subtraction
The limiting term is the one with the smallest number of decimal places
Ex:

16. Practice
Determine the answer of the following. Be sure to include the correct significant digits
A.) =
B.) 47.2 – 9
C.) 1.27 x
D.) 0.072/4.36