element song
http://www.youtube.com/watch?v=zGM‐wSKFBpo&feature=related
January 29th, 2014
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Chem 1A S2014
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What do we say in chem. 1A?
Chem 1A F2013
Chem 1A S2014
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If you have not taken and passed the chemistry 1A diagnostic placement exam, it is too late to do so.
The due date
is not
the start date!
10-23-13
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We will only add students that have passing diagnostic scores from F13 or S13.
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Lab begins this week!
Next week in disc:
Monday / Tuesday
Got goggles?
Next week in Lab:
No toes!
Wednesday / Thursday
•Nomenclature Handout
•There will be an online There will be an online Mastering Chemistry assignment this week assignment this week for for discussion covering dimensional
dimensional Analysis & Analysis &
nomenclature
Got lab coat?
•Experiment 1
•Practice Proficiency quiz
Got Gloves?
Got pre lab?
Got pre‐lab?
No pre‐lab, no lab!
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It’s time to play…
Chapter 1: Key Topics
Reading: Ch. 1.1‐1.7
II will only cover a few examples of calculations using unit ill l
f
l
f l l ti
i
it
conversions.
lead (II) sulfide
PbS
potassium permanganate
KMnO4
ammonium nitrite
NH4NO2
HC2H3O2(aq)
acetic acid Chapter 2: Key Topics
Reading: Ch 2 1 2 7
Reading: Ch. 2.1‐2.7
I will cover a few examples of calculations with isotopes and mole/mass concepts.
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Chem 1A S2014
BCl3
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boron trichloride Chem 1A S2014
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Problem Solving in Chemistry:
Many of the problems you will solve in chemistry involves a technique called Dimensional Analysis. (Ch.1)
Ch t 1
Chapter 1
Dimensional analysis converts one unit to another by using conversion factors.
conversion factors
Matter, Measurement,
and Problem Solving
and Problem Solving
unit (1) × conversion factor
= unit (2)
The resulting quantity is equivalent to the original quantity, it differs only by the units.
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Example problem:
Problem Solving in Chemistry:
A certain automobile has a fuel economy of 32 miles/gallon.
When submitting written work in this class:
•Labs
What is the same fuel economy in km/L?
•Quizzes
i
How do you start this problem?
•Exams
Ask what you need!
new distance and volume units
All work must be accompanied by units. What is given?
The work given must show a logical progression towards the answer given.
How do these quantities relate? gallons can be converted to L
ll
b
d L
Now you are ready to set up the problem using dimensional analysis!
There will be severe grading penalties if this is not the case!
Chem 1A S2014
miles and gallons
miles can be converted to km
il
b
d k
The answer must have units itself that match the work.
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Example problem:
Problem solving in chemistry:
You need to be systematic in your approach.
You can’t memorize every type of problem.
A certain automobile has a fuel economy of 32 miles/gallon.
What is the same fuel economy in km/L?
The Plan: The Plan: convert miles to km then gal to L
miles → ft → in → cm → m → km then gal → L
look this up!
you should know these cf
you
should know these cf’ss
X
32miles
5280ft
1m
1km 1gal
X 12in
X 2.54cm
X
X
X
×
×
×
× 2 × 3 ×
= 13.588 km/L
1 gal
1mile
1ft
1in
10
cm
10
m
3.79L
X
X
X
X
X
X
round to 2 sig figs: 14 km/L
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Here is how you should approach solving problems: 1 Put your calculator down.
1.
P t
l l t d
2. Read the problem.
3. Read it again! 4. Identify the units needed.
5. Identify the units given.
6. Set up a conceptual plan for the solution.
7 Write down any conversion factors you might need.
7.
Write down any conversion factors you might need
8. Set up a conversion from the starting units to the needed units using dimensional analysis.
9. Now use your calculator!
10. Check for sig figs, order of magnitude and units
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Examples of the wrong way to solve a problem:
What the solution to a problem should look like!
a plan in outlined
3 sf’s
X
X
No plan!
X
X
No Units!
X
Wrong cf’s!
X
X
X
You also expect a l
large number!
b
The correct sig figs are expressed in the answer:
Notice that all units are written:
No Partial Credit!
Conversion factors cancel out the units!
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??????
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Examples of the wrong way to solve a problem:
Examples of the wrong way to solve a problem:
There is no credit for magically pulling an answer out of your
pulling an answer out of your butt! No credit!
No Credit!
Work does not match!
Not
Even
Wrong
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See me in my office ASAP...
Correct answer...
Dr. Mack
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Example problem:
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Example problem:
The aluminum in a package containing 75ft2 of foil weighs 12 oz.
The aluminum in a package containing 75ft2 of foil weighs 12 oz.
If the density of aluminum is 2.70 g/cm3, what is the thickness of the foil in mm?
If the density of aluminum is 2.70 g/cm3, what is the thickness of the foil in mm?
How do you start this problem?
First find the total volume of the foil:
Ask what you need!
The thickness of the foil.
What is given?
area, mass and density
volume and area give thickness!
thickness =
Now you are ready to set up the problem using dimensional analysis!
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28.4 g cm3
×
= 126 cm3
1 oz 2.70 g
Keep the extra sig figs and round at the end.
Next find thickness from volume and area:
How do these quantities relate?
How do these quantities relate? mass and density give volume
12 oz ×
you may need to look up some conversion factors!
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volume
=
area
126 cm3
10 mm
= 0.018 mm
2
2 ×
1 cm
12 in ⎞ ⎛ 2.54 cm ⎞
75 ft2 × ⎛⎜
×
⎟ ⎜
⎟
⎝ 1ft ⎠ ⎝ 1 in ⎠
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It’s time to play…
What is the area of a circle?
A = πr2
What is the volume of a cylinder?
V = L×πr2
What is the volume of a sphere?
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V = πr 3
3
How many feet are in a mile?
I will place another dimensional analysis problem in the notes that is not covered in class.
5280 ft = 1 mile
You should know these and many other general knowledge facts from your K‐
facts from your K‐12 education!
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Example problem:
Example problem:
A certain wire alloy has a density of 7.65 g/cm3. What length (m) of wire corresponds to 25.0 lbs of the wire if the radius is 0.55 mm?
A certain wire alloy has a density of 7.65 g/cm3. What length (m) of wire corresponds to 25.0 lbs of the wire if the radius is 0.55 mm?
First one must realize that the wire is cylindrical in shape. 29
Conceptual Plan:
use density as a conversion factor
mass → volume → length (knowing the radius)
length (knowing the radius)
radius
You should know this from high school...
length
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To find the length of the wire, begin with volume:
mass is related to volume by density:
by density:
d=
L × πr 2 =
setting the two equal:
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m
V
L=
L=
Chem 1A S2014
mass
d × πr 2
Plugging in the values...
m
V=
d
solving for volume:
solving for L:
A certain wire alloy has a density of 7.65 g/cm3. What length (m) of wire corresponds to 25.0 lbs of the wire if the radius is 0.55 mm?
V = L × π r2
25.0 lb ×
L =
m
d
7.65
mass
d × πr 2
1 kg
103 g
×
2.205 lb 1 kg
(1 cm)2
g
× π× (0.55mm)
(0 55mm) 2 ×
3
(10 mm)2
cm
= 1. 5 595 × 103 m
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Watch your units, conversion factors are needed!
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or
×
1m
102 cm
1.6 × 103 m (2 sig. fig.)
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Chemical Symbols:
To what we can’t see!
What we observe…
Ch t 2
Chapter 2
Atoms and Elements
Chemical symbols (H2O) allow us to connect…
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Where do we begin…
The Periodic Table
Why do we call it the “Periodic Table”?
Because, “periodically”, we use it in chemistry…
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The Periodic Table:
The Modern Periodic Table
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Metals and Nonmetals
The modern organization of the periodic table came about as a result of the work of Dimitri Mendeleyev Characteristics:
•Ordered elements by atomic mass
•Repeating pattern of properties
Metals
•Elements with similar properties in the same column
Periodic Law – when the elements are arranged in order of increasing atomic mass, certain sets of d
fi
i
t i
t i
t f
properties recur periodically.
Patterns used to predict properties of undiscovered elements
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The Periodic Table:
Metaloids
The modern periodic table is defined by:
Groups (families)
G
(f ili )
(columns down)
Periods (rows across)
aka: Semiconductors
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Chemical Symbols and Formula:
Elements:
H = hydrogen
O = oxygen
Tin is in group 4A (14) in the 5th period. C = carbon
Molecules:
H2 = hydrogen
O2 = oxygen
some of the names are not systematic!
H2O = water
Uh‐‐Oh! Uh
this is confusing…
Yes it is…
Get over it
Get over it and get used to it!
CH4 = methane
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How do I remember all of these things:
To pass this class:
You are required to develop d d l
a working knowledge of
1: Memorize the common elements and their symbols:
How many? As many as possible!
How many? As many as possible!
2: Complete the worksheets provided on the web site. Do extra homework problems.
3: Make up flash cards and practice with your classmates, friends or family.
Practice
Chemical Nomenclature
Chemistry is really:
Chem ‐ is
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Practice
Practice
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Chem 1A S2014
try
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