Transcript Science and chemistry

What is Chemistry?
the study of the composition of matter
and the changes it undergoes
 comes from the word alchemy

 refers to both an early form of the investigation of
nature and an early philosophical and spiritual
discipline, both combining elements of chemistry,
metallurgy, physics, medicine, astrology, semiotics,
mysticism, spiritualism, and art all as parts of one
greater force
○ example- making lead into gold (tomorrow’s lab- sort
of)

five main areas of chemistry one can
study--
1. Organic Chemistry
Organic is the study of matter
that contains carbon
 Organic chemists study the
structure, function, synthesis,
and identity of carbon
compounds
 Useful in petroleum industry,
pharmaceuticals, polymers

2. Inorganic Chemistry
Inorganic is the
study of matter that
does NOT contain
carbon
 Inorganic chemists
study the structure,
function, synthesis,
and identity of noncarbon compounds
 Polymers, Metallurgy

3. Biochemistry
 Biochemistry
is
the study of
chemistry in living
things
 Cross between
biology and
chemistry
 Pharmaceuticals
and genetics
4. Physical Chemistry
 Physical
chemistry is the
physics of
chemistry… the
forces of matter
 Much of p-chem
is computational
 Develop
theoretical ideas
for new
compounds
HONK if you passed p-chem
5. Analytical Chemistry
Analytical
chemistry is the
study of high
precision
measurement
 Find composition
and identity of
chemicals
 Forensics, quality
control, medical
tests

Scientific notation consists of
two parts:

A number between 1 and 10

A power of 10
nx
x
10
Examples
 Given:
289,800,000
 Use: 2.898 (moved 8 places)
 Answer: 2.898 x 108
 Given:
0.000567
 Use: 5.67 (moved 4 places)
 Answer: 5.67 x 10-4
Example
5.093 x 106
 Answer: 5,093,000 (moved 6 places
to the right)
 Given:
1.976 x 10-4
 Answer: 0.0001976 (moved 4 places
to the left)
 Given:
Dimensional Analysis
figure what you have and where you are going
 “cancel out” what you don’t want
 Use conversion factors (fraction that equals one)
 example: 23,532 seconds = ? hours
23,532 sec. X 1 min. X 1 hour = 6.5 hours
1
60 sec.
60 min.
 example: 7463 mm = ? meters
7463 mm X 1 m
=
7.463 m
1
1000 mm
 is your answer reasonable?

How many minutes are in 2.5 hours?
Conversion factor
2.5 hr x
60 min
1 hr
= 150 min
cancel
By using dimensional analysis / factor-label method, the
UNITS ensure that you have the conversion right side up,
and the UNITS are calculated as well as the numbers!
Sample Problem
 You
have $7.25 in your pocket in
quarters. How many quarters do you
have?
7.25 dollars
4 quarters
X
1 dollar
= 29 quarters
A rattlesnake is 2.44 m long. How
long is the snake in cm?
b) 244 cm
2.44 m x 100 cm
1m
= 244 cm
Wait a minute!
What is wrong with the following setup?
1.4 day
x 1 day
24 hr
x
60 min
1 hr
x 60 sec
1 min
1.4 day
x 24 hr
1 day
x
60 min
1 hr
x 60 sec
1 min
Chemistry In Action
On 9/23/99, $125,000,000 Mars Climate Orbiter entered Mars’
atmosphere 100 km lower than planned and was destroyed by
heat.
1 lb = 1 N
1 lb = 4.45 N
“This is going to be the
cautionary tale that will be
embedded into introduction
to the metric system in
elementary school, high
school, and college science
courses till the end of time.”
Precision vs. Accuracy
 Precision
 the exactness of a measurement
 you get almost the same number
every time, even if it is wrong
 Accuracy
 how close the measurement is to the
correct answer
precise
accurate
Percentage Error
% error =
[error]
X 100%
accepted value
What is the percent error if the boiling point of
water is measured at 99.2° Celsius?
% error = 99.2°C- 100.0°C
100.0°C
= 0.8°C X 100%
100°C
= 0.008 X 100%
= 0.8%
X 100%
Significant Figures

sig fig video
the numbers that are known, plus one more
number that is estimated
 Significant values:
Every nonzero digit- 24.7, 0.743, 714
2. Zeros between nonzero digits- 7003, 40.79, 1.503
3. Zeros at the end of a number and to the right of a
decimal point= 43.00, 1.010, 9.000
1.
 Not Significant values
Leftmost zeroes acting as place holders- 0.0071,
.00090
2. Rightmost zeros acting as place holders- 300, 7000,
27,210
1.
Number (m)
Significant
figures
47.7
3
0.43
2
1.304
4
0.00023
2
8.00
3
300
1
3.00X102
3
Significant Figures When Calculating:
•
Addition and Subtraction
– an answer should not be more accurate than your
measurements!
– the answer should be rounded to the same
number of decimal places as the measurement
with the least number of decimal places
• 22.75 cm + 98.457 cm + 10. 1 cm
• = 131.307 on your calculator
• however, 10.1 cm has the least number of
decimal places
– therefore, the answer is 131.3 cm
 Multiplication
and Division
 an answer should not be more accurate than your
measurements!
 the answer should be rounded to the same
number of significant figures as the measurement
with the least number of significant figures
○ 0.7 m + 98.457 m
○ = 68.9199 m2 on your calculator
○ however, 0.7 m has the least number of
significant figures
 therefore, the answer is 60 m2
International System of Units (SI)
adopted in 1960
 seven base units which all others can be derived
 m, kg, K, s, mol, cd, A

Common Metric Prefixes