Unit 1 Introduction to Chemistry

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Unit 1Introduction to Chemistry

• Internet web site
• www.unit5.org/chemistry/

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Safety
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Basic Safety Rules

• Use common sense.

1 Rule
Others
No horseplay.
No unauthorized experiments.
Handle chemicals/glassware with respect.
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Safety Features of the Lab
safety shower fire blanket fire extinguisher eye
wash fume hood circuit breaker switch
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Material Safety Data Sheet (MSDS)
--

• gives information
• about a chemical

-- lists Dos and Donts emergency
procedures
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Chemical Exposure
acute exposure chronic exposure

• a one-time exposure causes damage

damage occurs after repeated exposure
reaction to drugs or medication
smoking, asbestos
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LD50

• the lethal dosage for 50 of the animals on which
  the chemical is tested

There are various ways an LD50 can be expressed.
For example, acetone has the following LD50s
ORL-RAT LD50 5,800 mg/kg IHL-RAT LD50
50,100 mg/m3-h SKN-RBT LD50 20 g/kg
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Example
Chemical A LD50 3.2 mg/kg Chemical B LD50
48 mg/kg

• Which is more toxic?

Chemical A is more toxic because less of it
proves fatal to half of a given population.
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Science
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The Functions of Science

• pure science applied science

the search for knowledge facts
using knowledge in a practical way
e.g., aluminum
strong
lightweight
good conductor
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Science attempts to establish cause-effect
relationships.
?
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• risk-benefit analysis
• weigh pros and cons before deciding

Because there are many considerations for each
case, 50/50 thinking rarely applies.
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How does scientific knowledge advance?

• 1. curiosity
• 2. good observations
• 3. determination
• 4. persistence

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The Scientific Method
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• Key Be a good observer.

observation inference
involves a judgment or assumption
uses the five senses
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Types of Data

• Observations are also called data.

qualitative data quantitative data
--
--
descriptions
measurements
clear liquid
e.g.,
e.g.,
55 L or 83oC
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Parts of the Scientific Method

• Identify an unknown.

Make a hypothesis
a testable prediction
Repeatedly experiment to test hypothesis.
procedure order of events in experiment
(i.e., a recipe)
variable
any factor that could influence the result
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A ScientificExperiment
Experiments must be controlled
they must have two set-ups that differ by only
one variable
conclusion must be based on the data
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Scientific Law vs. Scientific Theory
law
states what happens
--
does not change
never violated
--
-- e.g.,
law of gravity, laws of conservation
tries to explain why or how something happens
based on current evidence
Theory of Gravity, Atomic Theory
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Phlogiston Theory of Burning

• 1. Flammable materials contain phlogiston.
• 2. During burning, phlogiston is released
• into the air.
• 3. Burning stops when
• object is out of phlogiston, or
• the surrounding air contains
• too much phlogiston.

(superceded by combustion theory of burning)
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Chemistry
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The Beginning
early practical chemistry household goods,
weapons, soap, wine, basic medicine

• The Greeks believed there
• were four elements.

D
earth wind fire water
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Alchemy
(500 1300 C.E.)
the quest for the Philosophers Stone
(the elixir, the Sorcerers Stone)

• Allegedly, this substance would turn
• cheap metals into gold.

Alchemical symbols for substances
GOLD
SILVER
COPPER
IRON
SAND
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• transmutation

changing one substance into another
we cannot transmute elements into different
elements.
In ordinary chemical reactions
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• Alchemy was practiced in many regions of the
• world, including China and the Middle East.

Alchemy arrived in western Europe around the
year 500 C.E.
Modern chemistry evolved from alchemy.
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Contributions of alchemists

• experimental techniques
• new glassware
• information about elements
• developed several alloys

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What is Chemistry?

• the study of matter
• and its changes

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Areas of Chemistry

• organic

biochemistry
the study of carbon- containing compounds
the chemistry of living things
physical
inorganic
measuring physical properties of substances
studies everything except carbon e.g.,
compounds containing metals
e.g., the melting point of gold
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Careers in Chemistry

• research (new products)
• production (quality control)
• development (manufacturing)
• chemical sales
• software engineering
• teaching

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• The skills you will develop by an earnest
• study of chemistry will help you in any
• career field.

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The Scope of Chemistry
bulk chemical manufacturing
acids, bases, fertilizers
sulfuric acid (H2SO4) 1 chemical
petroleum products
fuels, oils, greases, asphalt

• pharmaceuticals

1 in 10,000 new products gets FDA approval
synthetic fibers
spandex
,
nylon, polyester, rayon
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• All fields of endeavor
• are affected by chemistry.

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Government Regulation of Chemicals

• The government
• regulates chemicals
• to protect the

worker
OSHA
environment
FDA USDA FAA CPSC
EPA
consumer
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Manipulating Numerical Data
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Graphs
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Bar Graph

• shows how many of something are in each category

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Pie Graph

• shows how a whole is broken into parts

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Line Graph

• shows continuous change

you will always use a line graph.
In chemistry
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Elements of a good line graph
1. title

• 2. axes labeled, with units

3. neat
4. use the available space
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Essential Math of Chemistry
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Scientific Notation

• -- used to express very large or very small
  numbers, and/or to indicate precision

(i.e., to maintain the correct number of
significant figures)
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• Put in standard form.
• 1.87 x 105 0.0000187
• 3.7 x 108 370,000,000
• 7.88 x 101 78.8
• 2.164 x 102 0.02164

Change to scientific notation.
12,340 1.234 x 104 0.369 3.69 x
101 0.008 8 x 103
1,000,000,000 1 x 109
6.02 x 1023
602,000,000,000,000,000,000,000
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Using the Exponent Key
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• The EE or EXP or E key means times 10 to the

How to type out 6.02 x 1023
How to type out 6.02 x 1023
not
WRONG!
WRONG!
or
and not
TOO MUCH WORK.
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• Also, know when to hit your () sign.
• (before the number,
• after the number,
• or either one)

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4.3 x 109
4.3 E 9
or
But instead is written
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6.5 x 1019
7.5 x 106 (8.7 x 1014)
5.35 x 103 or 5350
4.35 x 106 (1.23 x 103)
5.84 x 1013
2.9 x 1023
8.8 x 1011 x 3.3 x 1011
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Essential Mathof Chemistry
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• Units must be carried into the
• answer, unless they cancel.

0.64
0.57
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• Solve for x.

x y z
x and y are connected by addition. Separate them
using subtraction. In general, use opposing
functions to separate things.
x y z
y
y
The y and y cancel on the left,
x z y
leaving us with
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Numerical Example

• Solve for x.

x 24 13
x and 24 are connected by subtraction. Separate
them using the opposite function addition.
x 24 13
24
24
The 24 and 24 cancel on the left,
x 37
leaving us with
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• Solve for x.

F k x
x and k are connected by multiplication. Separate
them using the opposite function division.
The two ks cancel on the right,
leaving us with
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Numerical Example

• Solve for x.

8 7 x
x and 7 are connected by multiplication. Separate
them using the opposite function division.
The two 7s cancel on the right,
leaving us with
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• Solve for x.

One way to solve this is to cross-multiply.
BAH xTR
Then, divide both sides by TR.
BAH xTR
The answer is
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• Solve for T2, where
• P1 1.08 atm
• P2 0.86 atm
• V1 3.22 L
• V2 1.43 L
• T1 373 K

P1V1T2 P2V2T1
132
K
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SI Prefixes

• kilo- (k) 1000
• deci- (d) 1/10
• centi- (c) 1/100
• milli- (m) 1/1000

Also, 1 mL 1 cm3 and 1 L 1 dm3
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Conversion FactorsandUnit Cancellation
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• How many cm are in 1.32 meters?

equality
1 m 100 cm
(or 0.01 m 1 cm)
conversion factors
or
1.32 m
132 cm
We use the idea of unit cancellation to decide
upon which one of the two conversion factors we
choose.
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• How many m is 8.72 cm?

equality
1 m 100 cm
conversion factors
or
8.72 cm
0.0872 m
Again, the units must cancel.
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• How many kilometers is 15,000 decimeters?

15,000 dm
1.5 km
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How many seconds is 4.38 days?
4.38 d
378,432 s
If we are accounting for significant figures, we
would change this to
3.78 x 105 s
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Simple MathwithConversion Factors
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Find area of rectangle.
4.6 cm
A L . W
(4.6 cm)(9.1 cm)
9.1 cm
42
cm
2
. cm
cm.cm

• Convert to m2.

42 cm2
2
0.0042 m2
Convert to mm2.
42 cm2
2
4200 mm2
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• For the rectangular solid

Length 14.2 cm Width 8.6 cm Height
21.5 cm
Find volume.
V L . W . H
(14.2 cm)(8.6 cm)(21.5 cm)

2600
cm3
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Convert to mm3.
2600 cm3
3
2,600,000 mm3
2.6 x 106 mm3

• mm and cm differ by a factor of.
• mm2 cm2 .
• mm3 cm3 .

10
100
1000
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Basic Concepts in Chemistry
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• chemical

any substance that takes part in, or occurs as a
result of, a chemical reaction
All matter can be considered to be chemicals or
mixtures of chemicals.
chemical reaction a rearrangement of atoms
such that
what you end up with differs from what you
started with
products
reactants
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carbon dioxide
methane oxygen ?
water


H2O(g)
O2(g)
CO2(g)
CH4(g)

?
2
2
?
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sodium hydroxide
water
sodium
hydrogen

?

NaOH(aq)
Na(s)
H2O(l)
H2(g)
2
2
2

?

?
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Law of Conservation of Mass

• total mass total mass
• of products of reactants

Pmass Rmass
synthesis taking small molecules and
putting them together, usually in many steps, to
make something more complex
JENNY
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• How many feet is 39.37 inches?

equality
1 ft 12 in
applicable conversion factors
or
X ft 39.37 in

Again, the units must cancel.