1. Measurement
Day 1 – Sig Figs

2. Significant Figures (SIG FIGS)
7.0 does not equal 7.00 in chemistry class
If your lab partner has 5.50 cm as an answer and you have 5.5 cm, one of you will not earn credit!!
In Science 5.50 cm does not equal 5.5 cm

3. Significant Figures (SIG FIGS)
1. Rule
All non-zero digits are significant
143 has 3 significant digits
1,276 has four significant digits

4. Significant Figures (SIG FIGS)
2. Rule
Leading Zeros – NEVER significant
Middle Zeros – ALWAYS significant
101
Trailing Zeros – SOMETIMES significant
Depends on a decimal point
If decimal is present then they ARE significant
If decimal is not present then they ARE NOT significant

5. Practice
23.50
402
5280
0.080

6. A Memory Trick – The USA Pacific Atlantic
Start at the left and stop at the first non-zero.
That # and everything after it is significant!!
____ sig figs
Atlantic
Start on the right and stop at the first non-zero.
3500
That # and everything after is are significant!
____ sig figs

7. Significant Digits (13.91)(23.3) = 324.103 324
Calculating with Significant Digits
Multiply/Divide – Your answer should be equal to the number of significant digits in the least accurate factor.
This is the one with the fewest sig figs
(13.91)(23.3) =
4 SF
3 SF
3 SF
324

8. Significant Digits 224 g + 130 g 354 g 224 g + 130 g 354 g 3.75 mL
Calculating with Significant Digits
Addition and Subtraction – Your answer should be simplified according to the number with the fewest decimal places
224 g
+ 130 g
354 g
224 g
+ 130 g
354 g
3.75 mL mL
7.85 mL
3.75 mL mL
7.85 mL
 350 g
 7.9 mL

9. When performing calculations, you should do the calculation using all the digits allowed by the calculator and round off only at the END of the problem!!

10. Significant Digits 2. 18.9 g - 0.84 g 18.06 g Practice Problems
1. (15.30 g) ÷ (6.4 mL) =
4 SF
2 SF
= g/mL
 2.4 g/mL
2 SF g g
 18.1 g
18.06 g

11. Significant Digits 4. 1.942 + 26.93 28.872 Practice Problems
3. (12000) x (1.53)
2 SF
3 SF
= 18360
 18000
 28.87
28.872