1. Warm –up #2
What is chemistry? Write what you recall about the definition and name 2 areas of study of chemistry.

2. Significant figures

3. Significant figures
What about when you receive data from another scientist?
“The carbon nanotube was 27 cm long”
“The carbon nanotube was 27.3 cm long”
“The carbon nanotube was cm long”
“The carbon nanotube was cm long”

4. Significant figures
Significant Figures (Sig Figs): include all the numbers that are known precisely plus one last digit that is estimated

5. Rules for Determining the Significant Figures
.RuLE•1. All non-zero digit are significant.
•Example (Ex): has 3 sig figs

6. Rules continues.... 2. Zeros between non-zero digits are significant
Ex: has 4 sig figs (the zero is between non zero digits)
3. Zeros appearing in front of all non-zero digits are NOT significant
Ex: has only 2 sig figs

7. Rules continues …
4. Zeros at the end of a number and to the right of a decimal point are significant
•Example: has 3 sig figs
•*The zero after a decimal point is significant only if a non-zero digit precedes it

8. Rules continues.....
5. Zeros at the end of a measurement and to the left of the decimal point are not significant unless the zero was measured
Example: 300 has only 1 sig fig
300.0 has 4 sig figs

9. Determine the number of sig fig:
a g
b mL
c kg
d cm
e mg
f m
g g

10. Review Determine the number of sig figs in: a. 456 b. 4.00 c. 6.090

11. Practice •Place the following numbers into 3 sig figs • 1) 45.2367
• 1) 2) 3) 4) 5)

12. Practice How many sig figs are in following: 1)0.001256 g 2)200.3 kg
3)1.520 4)

13. Practice •Write the following into three sig figs: a)134243.05
b)1.245 x 10-3
c)9.9003 d)

14. Rules for Sig Figs in Calculations
•An answer cannot be more precise than the least precise measurement from which it was calculated
•Basically, if you have to do a calculation with sig figs, your answer cannot be more precise than your least precise measurement

15. Multiplication and Division
Multiplication and Division: The number of significant figures in the answer (result) is the same as the number of significant figures in your least precise measurement

16. Example Problem
Report 6.3 * 6.45 * with the correct amount of sig figs

17. Solution

18. Additional Practice a. 2.7 / 5.27 b. 4.5 * 9.56 c. 2 * 5.6
d x x 2.10
e. [(9.714 x 105) ( x 10-9 )]
[(4.1212) ( x 10-5)]

19. Rules for Addition and Subtraction
Addition and Subtraction: The answer (result) has the same number of decimal places as the least precise measurement

20. Example Problem •
•1. Determine which measurement is least precise
•2. Calculate
•3. Place in correct number of sig figs

21. Practice
Report the following answers with the correct amount of sig figs: –

22. Practice Place the following equations in proper significant figures1)
2) 1.23 m * 0.89 m =
3) m – 0.54 m
4) (2.95 x 107) / ( 6.28 x 1015)

23. Practice Place in the proper sig figs1)
2)3.15 x 2.5 x 4.00
3)36 / 0.62 4) 5)