CHEMISTRY
July 31st, 2012
Brain Teaser: Dollar Bill
2

What do think will happen if I dip a
dollar bill in a 50% ethanol solution
and light it on fire? Why?
Demo
Record
Observations
Was your prediction correct?
Explain the science behind this
Agenda
3



Brain Teaser
Demo: Dollar Bill
Lecture:
Introduction to Chemistry
 SI Units and Base Units
 Significant Figures


Homework

Intro to Measurement Worksheet
Unit 1 Objectives
Introduction to Chemistry
4
Define chemistry and matter
 Units of measurement

 SI
Units
 Base Units
Accuracy versus Precision
 Uncertainty in Measurement
 Significant Figures

Introduction to Chemistry
5

Chemistry: The
Central Science
Chemistry is the science
that investigates and
explains the structure and
properties of matter.
 Seeks to explain the
submicroscopic events that
lead to macroscopic
observations

Branches of Chemistry
6
Branch
Area of Emphasis
Examples
Organic
chemistry
most carbon-containing chemicals
pharmaceuticals,
plastics
Inorganic
chemistry
in general, matter that does not
contain carbon
minerals, metals and
nonmetals, semiconductors
Physical
chemistry
the behavior and changes of matter
reaction rates,
and the related energy changes
reaction mechanisms
Analytical
chemistry
components and composition of
substances
food nutrients,
quality control
Biochemistry
matter and processes of living
organisms
metabolism,
fermentation
Units of measurement
7
SI Units (Le Systéme Internationale)

Scientists need to report data that can be
reproduced by other scientists. They need
standard units of measurement.
Base Units
• A base unit is a defined unit in a system of
measurement
•There are seven base units in SI.
8
Base Units
9
10
SIGNIFICANT FIGURES
Significant Figures
11

Significant
Figures
Digits in a measurement that
have meaning relative to the
equipment being used
Significant Figures
12

Place
What is the increment on the
equipment?
What you know for sure.
13
Significant Figures

Digits with
meaning
Digits that can be known
precisely plus a last digit that
must be estimated.
14
Ruler
15

http://www.funbrain.com/measure/

What are the units?
Graduated Cylinder
16

http://www.uwplatt.edu/chemep/chem/chemsc
ape/labdocs/catofp/measurea/volume/gradcyl/
gradcyl.htm

What are the units?
Significant Figures
17

What do you
notice?
Depends on type of equipment
being used.
Depends on size of equipment
used.
Significant Figures
18

Raw Data Rules 1. All digits 1-9 are significant.
 How do you
2. Zeros between significant
know how many
digits are always significant.
sig figs?
3. Trailing 0’s are significant
only if the number contains a
decimal point
4. Zeros in the beginning of a
number with a decimal point
are not significant.
5. Zeros following a significant
number with a decimal are
significant.
Significant Figures
19

Pacific to
Atlantic Rule

Examples
Pacific = Decimal Present
Start from the Pacific (left
hand side), every digit
beginning with the first 1-9
integer is significant
20.0 = 3 sig digits
0.00320400 = 6 sig digits
1000. = 4 sig digits
Significant Figures
20


Atlantic Rule to Atlantic = Decimal Absent
Pacific
Start from the Atlantic (right
hand side), every digit
beginning with the first 1-9
integer is significant
Examples
100020 = 5 sig digits
1000 = 1 sig digits
Practice
21

1.
2.
3.
4.
How many significant figures are in
400.0
4000
4004
0.004
Rally Rows
22
How many significant figures are in
1. 0.02
2. 0.020
3. 501
4. 501.0
5. 5000
6. 5000.
7. 5050
8. 01.0050
9. 50300
10. 5.0300
Review Questions
23

Determine the number of significant figures
in the following:







1005000
1.005
0.000125
1000.
0.02002
2002
200.200
Review Questions
24
Determine the number of significant figures in:

72.3 g

60.5 g

6.20 g

0.0253 g

4320 g

0.00040230 g

4.05 x 10^5 g

4500. g
Why do we use the metric system?
25

Advantages
Simple to use
 Easy to convert from one unit to another

 Dimensional Analysis

Universal – used worldwide
 By
all scientists to communicate
 By all industrialized nations


Except United States
U.S. loses billions of dollars in trade