1. 19th Amendment Takes Effect - 1920
Lecture Homework:
Reading
Chapter 2, sections 6-10
Mastering Chemistry Assignment #1
DUE MONDAY
PREREQUISITES!!!

2. How many Sig. Figs.? Two rules:
#1) If there IS a decimal point in the number:
Start at right of number and count until the LAST non-zero digit

3. 2 3 . 2 8 1 . 6 8 1 . How many Sig. Figs.? 9 significant figures2 8 1
9 significant figures . 6 8
4 significant figures 1 .
6 significant figures

4. How many Sig. Figs.? Two rules:
#1) If there IS a decimal point in the number:
Start at right of number and count until the LAST non-zero digit
#2) If there is NOT a decimal point in the number
Start at left of number and count until the LAST non-zero digit

5. 7 4 2 9 3 2 3 8 1 How many Sig. Figs.? 5 significant figures8
4 significant figures 1
1 significant figure

6. Significant Practice
0.0005
320000
8900.
0.1528
6 s.f.
7 s.f.
1 s.f.
5 s.f.
2 s.f.
4 s.f.

7. Rounding Numbers Find the last significant digit.
If the next digit to the right is 4 or less, leave the last significant digit alone.
If the next digit to the right is 5 or more, round the last significant digit up.
Put large numbers into scientific notation BEFORE rounding

8. (3 s.f.)
(3 s.f.) =
(5 s.f.)
(5 s.f.) =
(2 s.f.)
(2 s.f.) =
(3 s.f.)
(3 s.f.)
= 0.66
= 0.660
(5 s.f.)
(5 s.f.) =
(5 s.f.)
(5 s.f.) =

9. Sig. Figs. in Calculations
Two rules:
#1) Multiplication and Division
The value in the calculation that has the FEWEST number of sig. figs. determines the number of sig. figs. in your answer.

10. Calculations with Sig. Figs.
Multiplication and division
The value in the calculation that has the FEWEST number of sig. figs. determines the number of sig. figs. in your answer.
1.5 x
= 1
.9881
= 11
2 s.f.
5 s.f.
6.127 x = 6 09 =
4 s.f.
6 s.f.

11. Calculations with Sig. Figs.
/ 456.0
= 2.03 3
730263
= 2.034
6 s.f.
4 s.f.
/ 2
= 0.000 7 95 =
3 s.f.
1 s.f.
6 s.f.
3 s.f.
= 18 8 =
4 s.f.

12. Some Practice
x 112.3
78132/2.50
x x
500 x
99950
31300
0.0050
0.1

13. Sig. Figs. in Calculations
Two rules:
#1) Multiplication and Division:
The value in the calculation that has the FEWEST number of sig. figs. determines the number of sig. figs. in your answer.
#2) Addition and Subtraction:
The value in the calculation that has the FEWEST decimal spots determines the number of decimal spots in your answer.

14. Adding and subtracting with sig. figs.
7 decimal places
6 decimal places _ _ =
answer can only
be precise to the
6th decimal place

15. Adding and subtracting with sig. figs.
4 decimal places
7 decimal places =
answer can only
have 4 decimal places

16. Some More Practice 23.67 – 75 5502.8 + 24 + 0.01 0.109 + 0.09 – 0.955
-51
5527
-0.76
100.

17. Did you get it?
x 112.3
23.67 – 75
x x –
500 x

18. Did you get it?
x 112.3
23.67 – 75
x x
99950 or 9.995x104
-51
0.0050

19. Did you get it? –
500 x
2.5x10-8
0.1

20. Scientific Notation – Numbers > 1
Place a decimal so that there is a single digit to the left
Start counting from the right until you get to the decimal 1. 8 9 7 6 5 4 3 2 1
This becomes the exponent for “times 10 to the”
x107
Remove digits from the right until proper # of sig. figs.
x107
x107
x107
1.8900x107
1.890x107
1.89x107

21. Scientific Notation – Numbers > 1
Place a decimal so that there is a single digit to the left
716110
Start counting from the right until you get to the decimal 7. 1 6 1 1 5 4 3 2 1
This becomes the exponent for “times 10 to the”
x105
Remove digits from the right until proper # of sig. figs.
x105
7.1611x105
7.1611x105

22. Scientific Notation – Numbers < 1
Start counting from the decimal point to the first non-zero digit. This will be the exponent in the “times ten to the negative” 0. 5 1 2 3 4 5 6 7
Move the decimal point to the right of the first non-zero digit, drop all of the leading zeros, and add the “times ten to the negative” with the exponent.
x10-7

23. Scientific Notation – Numbers < 1
Start counting from the decimal point to the first non-zero digit. This will be the exponent in the “times ten to the negative” 0. 9
510 1 2 3 4 5
Move the decimal point to the right of the first non-zero digit, drop all of the leading zeros, and add the “times ten to the negative” with the exponent.
9.510x10-5

24. Did you get it?
s.f.
s.f.
s.f.
s.f.
5.124x108
6.0x10-4
2.5163x10-3
3.5400x109

25. A Few Sig. Fig. Notes
USUALLY, numbers with decimal points are MEASURED numbers
What does this mean for sig. figs.?
1 is USUALLY a DEFINED number
Put large numbers into scientific notation BEFORE rounding.

26. Types of Units (Quality Measured)
Distance (length)
foot, inch, mile, yard, meter, centimeter, rod
Mass/Weight
gram, kilogram, ton, pound, ounce, stone

27. Types of Units (Quality Measured)
Volume
gallon, quart, pint, milliliter, liter, cubic centimeter (cm3, cc)
Time
second, minute, hour, year, microsecond, eon

28. What quality is measured by…?kg
mass oC
temperature cm
length/distance
cm3
volume mL
volume
ft2
area

29. Dimensional Analysis (unit conversion)
Unit equation
12 in =
12 in
1 ft _
1 ft
1 ft _ = 1 =
12 in
12 in
12 in
12 in
12 in =
1 ft
1 ft
12 in = = 1
1 ft
1 ft
1 ft
Conversion between feet and inches can be written either:
1 ft _
12 in OR
12 in
1 ft
These are called “Unit Factors”

30. Dimensional Analysis (unit conversion)
The Goal:
Convert one unit to another
How:
Use conversion factors
Use them so that
1 ft _
12 in OR
12 in
1 ft
Unit you want to keep
____________________
Unit you want to cancel

31. Dimensional Analysis (unit conversion)
How many feet are in 51.5 inches?
1 ft _
12 in OR
12 in
1 ft

33. D.A. Practice
I have a fluid ounce CamelBak. How many gallons is my CamelBak?

35. D.A. Practice
I have a fluid ounce CamelBak. How many gallons is my CamelBak?

36. D.A. Practice
If a person weighs 208 lbs, what is their mass in amu?