1. Shootout at the O.K. Corral (1881)
Mastering Chemistry #9 – Due Thursday by 11:59
Chapter 2 #’s 79-92,99,100, ,112,114,119,120
You’ll need table 2.4 on page 33 for #’s 107 and 108
Many of the values in these questions will not match the book
about 2.5 hours
Extra Practice
Print out and BRING TO CLASS
Conversion Sheet
In class problems
Exam next Wednesday

2. Things to Keep in Mind… When converting:
small unit  big unit gives SMALLER number
5 nm = 5x10-6 mm
big unit to small unit gives BIGGER number
8 kg = 8x109 mg
Getting Started in Word Problems
If possible, start with a number that has a SINGLE unit.
62.0 mL has a single unit
0.785 g/cm3 has 2 units (grams and cubic centimeters)
km has a single unit
has 4 units

3. Sig Figs and Conversion Factors
Conversion factors ALWAYS affect sig figs unless BOTH of the following are true:
all units are in the same system
all units measure the same quality

4. pound = standard
in2 = standard
sig. figs COUNT
pound = weight
in2 = area
3 sig. figs
mile = standard
in = standard
sig. figs DO NOT COUNT (∞ s.f.)
mile = distance
in = distance
mm = metric
m = metric
sig. figs DO NOT COUNT (∞ s.f.)
mm = distance
m = distance
m = metric
ft = standard
sig. figs COUNT (4 s.f.)
g = metric
mL = metric
sig. figs COUNT (6 s.f.)
g = mass
mL = volume