1. Aim: Why are Significant Figures Important?
Do Now:
Read the ruler below. At what number is the pointer at. Be as accurate as possible.

2. Significant Figures All measurements are inaccurate
Precision of measuring device
Human error
Faulty technique

3. Let’s try graduated cylinders
Look at the graduated cylinder below
What can you read with confidence?
56 ml
Now estimate the last digit
56.0 ml

4. One more graduated cylinder
Look at the cylinder below…
What is the measurement?
53.5 ml

5. Significant Figures Significant figures in a measurement include
all of the digits that are known precisely
plus one last digit that is estimated.

6. Rules for Significant figures Rule #1
All non zero digits are ALWAYS significant
How many significant digits are in the following numbers?
3 Significant Figures
5 Significant Digits
4 Significant Figures
274
25.632
8.987

7. Rule #2 All zeros between significant digits are ALWAYS significant
How many significant digits are in the following numbers?
3 Significant Figures
5 Significant Digits
4 Significant Figures
504
60002
9.077

8. Rule #3
Zeros after non-zero digits are significant when a decimal is present.
How many significant digits are in the following numbers?
32.0
19.000
3 Significant Figures
5 Significant Digits
7 Significant Figures

9. Rule #4 All zeros that act as place holders are NOT significant
Zeros before non-zero digits are not significant
significant figures
Zero after non-zero digit with no decimal are not significant
significant figure

10. For example 1 Significant Digit 0.0002 3 Significant Digits
How many significant digits are in the following numbers?
1 Significant Digit
3 Significant Digits
6 Significant Digits
2 Significant Digits
0.0002
6.02 x 1023
150000
800

11. How many significant digits are in the following numbers?
0.0073
2500
7.90 x 10-3
670.0
18.84
2 Significant Digits
6 Significant Digits
3 Significant Digits
4 Significant Digits
1 Significant Digit

12. Sig Fig Rounding Example:
Round the following measured number to
4 sig figs:

13. Sig Fig Rounding Example
Round the following measured number to
4 sig figs:

14. Sig Fig Rounding Example
Round the following measured number to
4 sig figs:
ANSWER:

15. Adding Significant Zeros
Sometimes a calculated answer requires more significant digits. Then one or more zeros are added.
Calculated Answer Zeros Added to
Give 3 Significant Figures

16. Practice Rounding Numbers

17. Significant Figures Round each to 3 sig figsb) c) d)
e). 8

18. Significant Figures Round each to 3 sig figs
a) ANSWER: 28.4
b) ANSWER:
c) ANSWER: 2570
d) ANSWER: 2560
e) ANSWER: 8.00

19. Addition and Subtraction
When adding or subtracting, use
The same number of decimal places in your final answer as the measurement with the fewest decimal places (least precise measurement).
Use rounding rules to adjust the number of digits in the answer.
one decimal place
two decimal places
26.54 calculated answer
answer with one decimal place

20. Multiplication and Division
When multiplying or dividing, use
The same number of significant figures in your final answer as the measurement with the fewest significant figures.
Rounding rules to obtain the correct number of significant figures.
Example:
x = = (rounded)
4 SF SF calculator SF

21. Calculations

22. Calculations