1. Significant Figures (sig figs)
How do you know when numbers are significant figures?

2. Covered in this Lesson
This lesson will explain what significant figures are and why they are important.
Significant figures are the digits that represents the accuracy an experimental measurement is known to be (ACS, 2006).

3. Why Sig Figs?
In science the numbers we use are most often from measurements
Each device may have a different degree of accuracy; some measure to the ones, other to the tenths and so on.
The numbers you record using your measuring device are the sig figs.

4. Significant Figures (sig figs)
Determining sig figs depends on a decimal point.
There are two main rules:
Numbers without a decimal point.
Numbers with a decimal point.

5. Rule: Without a Decimal
If there is NO decimal point in the number, count all non-zeros digits and zeros between the non-zero digits.
non-zero digits
80,903,000,000
zeros between zeros not significant
This number has 5 sig figs.

6. Examples: Without Decimal Points
Example 1: 7000 L
The only non-zero digit is 7 and zeros are after the 7, there is only 1 sig fig.
7000 (1 sig figs)
Example km
The non-zero digits are 2, 4, 5 there is one zero between, there are 4 sig figs
(4 sig figs)

7. Rule: With a Decimal
If there is a decimal point in the number, go to the first non-zero digit and count all non-zero digits and zeros after.
These zeros are not significant
1st non-zero digit the rest of the digits are significant
This number has 4 sig figs

8. Examples: With Decimal Points
Example 1: L
The first non-zero digit is the 1 and there are two more digits for a total of 3 sig figs
0.103 L (3 sig figs)
Example km
The non-zero digit is before the decimal point so all digits are significant.
km (6 sig figs)

9. Practice Problems 711 kg B. 8.4745 cm C. 5.600 L D. 1,000,000 g
E Mm F mL
G. 901,001 ng H s

10. Answers Practice Problems
3 sig figs B. 5 sig figs
4 sig figs D. 1 sig fig
E. 2 sig figs F sig figs
G. 6 sig figs H. 4 sig figs