1. Bellringer: Write down the 3 Quick Rules for Sig Fig zeros:
Leading zeros are never significant
“Sandwiched” zeros are always significant
Trailing zeros are only significant when there’s a decimal

2. Bellringer: Finish the rules by memory
Leading zeros ________________
“Sandwiched” zeros ___________
Trailing zeros are _____________ ____________________________

3. How many Sig Figs?
76,000
56.706
7.00
0.0398
9,008,030,000 4 2 5 3 6

4. Wilson Physics/Chemistry
Significant Figures
Wilson
Physics/Chemistry

6. What is a significant figure?
There are 2 kinds of numbers:
Exact: the amount of money in your account. Known with certainty.
Approximate: weight, height; anything MEASURED. No measurement is perfect!

7. Why use Significant figures
When a measurement is recorded only those digits that are dependable are written down.

10. When to use Significant figures
If you measured the width of a paper with your ruler you might record 21.7cm.
To a mathematician 21.7, 21.70, or is the same.
21.700cm to a scientist means the measurement is accurate to within one thousandth of a cm!

11. But, to a scientist 21.7cm and 21.70cm is NOT the same
If you used an ordinary ruler, the smallest marking is the mm, so your measurement has to be recorded as 21.7_cm.

12. How do I know how many Sig Figs are in a number?
All digits are significant starting with the first non-zero digit on the left.

13. Sig Fig rules for zeros

14. 1st Rule
If there is no decimal, zeros at the end of the number are NOT significant

15. 2nd Rule
If zeros are sandwiched between non-zero digits, the zeros are significant.

16. 3rd Rule
If zeros are at the end of a number that has a decimal, the zeros ARE significant.
WHY????

17. 3rd Rule
They are showing how accurate the measurement or calculation is!

19. Quick rules for Sig Fig zeros:
Leading zeros are never significant
“Sandwiched” zeros are always significant
Trailing zeros are only significant when there’s a decimal.

20. Quick Example:
How many of the zeros in the following number are significant? Which ones?

21. Quick Example:
How many of the zeros in the following number are significant? Which ones?
10,720

22. How many sig figs?
1.2
2100
56.76
4.00
0.0792
7,083,000,000 2 4 3

23. How many sig figs here?
3401
2100
2100.0
5.00
8,000,050,000 4 2 5 3 6

24. Everybody’s favorite monster!
Scientific Notation
Everybody’s favorite monster!

26. Parts of a “scientific” number

27. Parts of a “scientific” number

28. In scientific notation, the coefficient must ALWAYS be a number between 1-10

29. 1. Adding & Subtracting with Sig Figs
Video Examples
1. Adding & Subtracting with Sig Figs
Multiplying & Dividing with Sig Figs
Scientific Notation & Sig Figs

30. What about calculations with Sig Figs?

31. Calculations with sig figs
Rule #1: Do the math FIRST, THEN calculate the number of significant figures!

33. Calculations with sig figs
Rule: When adding or subtracting measured numbers, the answer can have no more places after the decimal than the LEAST of the measured numbers.

34. Add/Subtract examples

35. Add/Subtract examples
2.45cm + 1.2cm = 3.65cm… = ?
Round off to = 3.7cm
7.432cm + 2cm = 9.432…= ?
Round off to 9 cm

36. Multiplication and Division
Rule #2: When multiplying or dividing, the result can have no more significant figures than the least reliable measurement.

37. A couple of examples 56.78 cm x 2.45cm = 139.111 cm2
Round to  139 cm2
75.8cm x 9.6cm = ?

38. Prepare For A Quiz!!!

39. Significant Figures Quiz
Tell the number of Significant Figures in the following numbers:
x 10-7
80, x 103

40. Significant Figures ANSWERS
Tell the number of Significant Figures in the following numbers:
4502 (4) (1)
(4) (4)
5.000 (4) x 10-7 (3)
80,000 (1) x 103 (2)
(2) (5)