1. Introduction to Chemical Principles
CHEMISTRY 31A
Introduction to Chemical Principles
Your Instructors and Teaching Assistants
Mechanics of the Course

2. Powers of Ten and Scientific Notation
Very large and very small numbers are common in science.
MOVIE -- For more information on this topic, click on:
Need to use a number between 1 and 10 times ten (10) raised to a positive or negative power called its exponent.

3. Addition, Subtraction, Multiplication, Division of Numbers in Scientific Notation
Do some examples … …

4. Difference Between Accuracy and Precision
An example from archery … …

5. Experimental Error
A measurement without an error estimate is no measurement at all!
Estimates and bounds have considerable value in science.
A person with one thermometer thinks the temperature is known; a person with two or more thermometers knows that the temperature is not known but has a much better idea what the temperature is!

6. Random and Systematic Errors
Random errors arise from a lack of precision. They are best estimated by replicate measurements and the use of statistics.
Systematic errors arise from a lack of accuracy. They are best reduced by calibration against known reference standards.

7. Rules for Counting Significant Figures
1. Count all nonzero digits
2. Zeros that precede the first nonzero digit are never counted.
3. Zeros surrounded by nonzero digits are always counted.
4. Zeros that follow the last nonzero digit sometimes count and sometimes not, depending on whether they are present to position the decimal point or not. EXPAND.
Zare’s Rule: Put quantity in scientific notation and count the number of digits in the number in front of ten raised to a power.

8. International System of Units; SI Units
Quantity Unit Symbol
Length meter m
Mass kilogram kg
Time second s
Temperature kelvin K

9. Some Commonly Derived Units in the SI Unit System
Area length x length m2
Volume length x length x length m3
Velocity length / time m / s
Acceleration (length /time)/time m / s2
Force mass x acceleration kg m / s2 ≡ N
Pressure force / area N / m2 ≡ Pa
Energy force x distance N m ≡ J
Power energy / time J / s ≡ W

10. The Standard Prefix Game of Modifiers
Factor
Name 
Symbol
10-1
deci d
10-2
centi c
10-3
milli m
10-6
micro
10-9
nano n
10-12
pico p
10-15
femto f
10-18
atto a
10-21
zepto z
10-24
yocto y
Factor
Name 
Symbol
1024
yotta Y
1021
zetta Z
1018
exa E
1015
peta P
1012
tera T
109
giga G
106
mega M
103
kilo k
102
hecto h
101
deka da

11. The Standard Prefix Game of Modifiers
Factor
Name 
Symbol
10-1
deci d
10-2
centi c
10-3
milli m
10-6
micro
10-9
nano n
10-12
pico p
10-15
femto f
10-18
atto a
10-21
zepto z
10-24
yocto y
Factor
Name 
Symbol
1024
yotta Y
1021
zetta Z
1018
exa E
1015
peta P
1012
tera T
109
giga G
106
mega M
103
kilo k
102
hecto h
101
deka da
You need to learn the ones in red if you do not already know them.

12. Some Things are Dimensionless
Numbers are dimensionless
Numbers themselves come in groups:
dozens
grosses,
moles
Only exponentials and logarithms can be taken of numbers, so unit analysis becomes imperative.

13. Some Things have Dimensions
A dimensioned quantity without its dimensions is no quantity at all!
Don’t forget to express the units, where and when appropriate.

14. Converting from One Unit to Another and Keeping Track of What is Happening
Example: Conversion of year into seconds …