Welcome to Pre-AP Chemistry!
The following information covers topics that will be used regularly throughout this course. Please read over and
study the information. There are two sections of practice that should be completed on a separate sheet of paper
to be turned in on the first day of school. The first section of practice covers scientific notation (ten problems).
The second section of practice covers conversion factors and dimensional analysis (eight problems). All work
must be shown (including units) on the dimensional analysis practice. There will be a quiz the first week of
school covering this information and practice. Have a great summer!
Scientific Notation
Numbers that are very large or very small are written in scientific notation. Scientific notation includes a
coefficient and 10 raised to a power. The coefficient should be a value between 1 and 10 (there should only be
one digit to the left of the decimal place). The exponent raised next to the 10 is an integer. A positive exponent
represents a larger number (this is how many times the coefficient must be multiplied by 10). A negative
exponent represents a smaller number (this is how many times the coefficient must be divided by 10).
Examples:
Original Number
Scientific Notation
630 g
0.0024 cm
0.13 s
5234000 mL
6.30 x 102 g
2.4 x 10-3 cm
1.3 x 10-1 s
5.234000 x 106 mL
Complete the following practice on another sheet of paper to be turned in the first day of school.
Convert each of the following numbers into scientific notation.
1.
2.
3.
4.
5.
6.
500 cm
23000 g
0.0012 L
0.075 kg
0.0000000043 g
864000000 s
Convert each of the following numbers out of scientific notation.
7. 2.45 x 10-3 g
8. 1.3 x 105 L
9. 8.653 x 103 cm
10. 6.4 x 10-6 kg
Metric Prefixes (Must be memorized for class)
Metric Prefixes
Prefix
mega
kilo
hecto
deca
deci
centi
milli
micro
nano
Symbol
Meaning
M
1 million times larger
k
1000 times larger
h
100 times larger
da
10 times larger
Base unit (grams, meters, liters)
d
10 times smaller
c
100 times smaller
m
1000 times smaller
µ
1 million times smaller
n
1 billion times smaller
Factor
106
103
102
101
10-1
10-2
10-3
10-6
10-9
Conversion Factors and Dimensional Analysis
A conversion factor is a ratio of equivalent measurements. The measurement in the numerator is equivalent to
the measurement in the denominator.
For example, the relationship between grams and kilograms is 1000 g = 1 kg. (The bigger unit should get the ‘1’).
The conversion factor for this could be either: 1000 g
1 kg
or
1 kg
1000 g
We can use these conversion factors to solve problems using dimensional analysis. Let’s start
with an everyday example:
How many seconds are in two hours?
Step 1: List the knowns and unknowns
Given = 2 hours
1 hour = 60 min
1 min = 60 s
Step 2: Solve for the unknown
Start with the number that is given. Then use the conversion factors to cancel out units. Units must cancel out
top to bottom diagonally. Multiply what is on top (all the numerators) and divide by what is on the bottom.
2 hrs x
60 min x
1 hr
60 s = 7200 s
1 min
Now try using dimensional analysis with the metric conversions.
How many mg are in 125 grams?
Step 1: List the knowns and unknowns
Given = 125 grams
1 g = 1000 mg (Remember: The larger unit gets the ‘1’).
Step 2: Solve for the unknown
Start with the number that is given. Then use the conversion factor to cancel out the units. The unit in the
numerator must cancel out with the unit in the denominator of the following conversion factor. Multiply what is
on top and divide by what is on the bottom.
125 g x
1000 mg = 125,000 mg
1g
The following problems need to be completed on a separate sheet of paper to be turned in on the
first day of school. Please show all work and include units.
1. How many hours are 2 weeks?
2. Convert 74 cm to meters.
3. How many kJ are in 2.5 Joules?
4. How many mm are in 0.44 km?
5. Convert 8.65 nm to cm.
6. How many MHz are in 943 Hz?
7. Convert 4.62 dg to dag. (dg = decigrams; dag = decagrams)
8. Convert 10.5 mL to L.