Transcript Kinds of Chemistry - Louisiana State University

About you!
Largest groups by college:
Largest groups by major:
Hobbies
1
Favorite music groups: Lemme Know!
2
Why you’re here (Fall 2011)
To get a degree, add a degree to all my experience
My parents will disown me if I don’t earn a degree
To better myself, to become a lawyer
To get smart, to prove my parents wrong
Math degree, so I can teach
To get an education in something I enjoy..
To prove my parents wrong/
Better than being homeless
To party!
Make my parents proud
To get a good job
Last resort, didn’t have a choice
Something beautiful about studying ideas.
Get wealthier
I value education
Secure future
To make a difference in peoples’ lives
To learn entrepreneurship
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Syllabus summary: Book
Russo (not me!) & Silver book: advised…or make a friend
Mastering Chemistry: required
Alternate book: advisable
Virtual book: how I see things = lecture
CEF study guides: Factoids that are useful; anything in
them is fair game for exams!
Problems from book: required
Fun books: Cartoon Guide to Chemistry &
P.W. Atkins’ Molecules
4
Syllabus Summary: Homework & Grades
3 varieties of homework
Assigned-but-not-graded (tied to unannounced quizzes in
lecture) Recitation Topics (tied to unannounced quizzes)
Mastering Chemistry on-line assignments
ING13: an “A” grade means you can go BEYOND what was
taught.
Approximate Grade Breakdown (see actual syllabus)
Quizzes: 45%
Graded Homework (mostly MC on-line): 20%
Midterms: 20% (3 midterms, drop lowest)
Final: 30% of possible points
Early Performance Bonus: 2.5%
Exit Tickets: 3.5% (depends on group performance!)
That’s 120%! Anything over 90% = A. Anything over 80% = B, etc.
5
There is much other stuff in the
syllabus, so please read it all.
Thank you.
6
Announcements
This Friday, we will meet here in Lockett again….I am
told we will have the TAs assigned soon so you can
do stuff on Fridays. Yay.
We will try to get 450 quiz points by end of the
course. We better start soon.
ING13: there is no study guide but ABNG problems.
The first MC assignment has been posted. Due
Friday, Feb. 1, 11:59 pm. Do it sooner!
We are about one day behind…don’t worry about it.
7
Whaddya know…it’s time to talk
about chemistry in some detail!
It is the subject of matter on a very fine scale.
What’s Matter?
8
Matter has mass and occupies space.
A solution is a very fine mixture
that eventually happens
without mechanical agitation.
9
A doughnut is the same as a
coffee cup (or a beer mug).
Can anyone think of a way
to make a material do this?
A doughnut is the same as a coffee cup (or a beer mug).
http://en.wikipedia.org/wiki/Topology
10
Hey….if we could change coffee cups into donuts,
we could do something dangerous and fun, like
make Wolverine claws!
Wolverine claws as we dangerously dream of them:
http://www.youtube.com/watch?v
=LPmbGzQaOCs&playnext=1&list=
PLD8C557850FB35C59
http://www.youtube.com/watch?v=LPmbGzQaOCs
&playnext=1&list=PLD8C557850FB35C59
Wolverine claws as we actually can make them:
http://www.youtube.com/watch?v=j0cs9j7HT-g
http://www.youtube.com/watch?v=j0cs9j7HT-g
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We need details about that matter
definition: has mass and occupies space.
•Mass: how easy is it to accelerate the object. F = ma
•Acceleration: change in speed with time
(dv/dt = d2x/dt 2 for you Calculus experts)
•Gravity provides a convenient, relatively constant,
acceleration: F = mg where g = 9.8 ms-2
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Mass is measured indirectly
• We could define one gram as the mass of one
cubic centimeter (or one cc) of water.
• Then see how much a spring is compressed
with this mass on it under Earth’s gravity.
• For a good spring, an object that compresses
it 2x more than one cubic cc of water must
have 2 grams of mass.
• When you weigh something, you indirectly
obtain its mass.
• The thing really being measured is a force,
which has other units (kgms-2).
• We’ll practice with compound units soon.
1 cm
1 cm
1 cm
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Here’s a picture of a spring scale.
If you look at old scales
of good quality, they
will often proudly
proclaim “No Springs”. Why?
http://www.medicalscale1.com/wp-content/uploads/2011/01/spring-scale.jpg
It actually took awhile to find a spring scale on the web---most scales
today are digital. Probably a piezoelectric transducer, not springs.
I have yet to see one that says “no transducers”.
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How would you measure mass without gravity?
View
from
inside
the
space
station.
15
http://spaceflight.nasa.gov/gallery/images/station/
Matter Occupies Space
What’s Space?
What does it mean to “occupy” space?
In fact, for almost anything you can name, most of
the space is not occupied!
Before we can understand that, we have to have
ways to measure physical properties.
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Space means volume.
Our favorite unit of length in chemistry is often
the centimeter: one-hundredth of a meter.
Volume is length x width x height, or cm3
1 cm
1 cm
1 cm
1 cm3 of water is one milliliter of water
(one one-thousandth of a liter, and a liter
is almost the same volume as a quart.)
Maybe we should write this as 13 cm3
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Let’s practice some volume and area calculations.
18
The next part of the lecture is brought to you
by the number…
2
Chapter 2 is about
Quantitation, units and energy.
19
How many creatures can count?
“Recent studies…..have uncovered new
instances of a counting skill in different
species, suggesting that mathematical
abilities could be more fundamental in
biology than previously thought. Under
certain conditions, monkeys could
sometimes outperform college students.”
--Scientific American, September 15, 2009
One monkey was able to choose between two sets of identical objects, differing only by
the number of objects in the set. It was slightly less accurate than college students at
doing this, but it was faster. This suggests the monkey was less afraid of making mistakes.
Because there was a reward for performance (Kool Aid) the non-chagrinned monkey
moved on quickly to the next round. Freshmen apparently were more tentative about
making mistakes. Probably a lesson here for college students and entrepreneurs.
BTW, the blog after the article is intriguing, too—a little bit funny and a little bit sad.
http://www.scientificamerican.com/article.cfm?id=ho
w-animals-have-the-ability-to-count
http://www.scientificamerican.com/article.cfm?id=how-animals-have-the-ability-to-count
Clever Hans, a German horse
that could count, ca. 1910.
There is a Clever Hans effect in Psychology,
traced to this animal. Some animals (people, too?)
Detect subtle body language cues and respond
according to those. That is how Clever Hans could count.
It was not a fraud—the animal just sensed tension in the
People answering the question…only if
those people actually knew the answer to it.
Wikipedia article on Clever Hans
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Words matter! Precision is not Accuracy.
It is possible to be consistently wrong.
The difference between the right word and the almost right word is
really a large matter — it's the difference between a
lightning bug and the lightning.
Mark Twain (Samuel Clemens)
http://www.metacafe.com/watch/44666/like_no_other/
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What does this read?
60
40
20
80
The last number you
report is always a guess!
100
120
140
The  uncertainty is
something like 1/10th
of a decimal scale;
here that is  2 mph.
Noise: if the speedometer
wiggles, it adds even
more uncertainty.
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Some scales go by halves (thankfully)
How long is the pink line?
What’s the  uncertainty here?
Drag divisors to split the scale by twos 
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This joke is from Prof. Pojman: the guy with the tie.
A class is touring the Museum of Natural History on a field trip, and a
kid asks the guide, “How old is this dinosaur?”
The guide replies, “Sixty million years and six months.”
The teacher is astonished: “How can you tell the age so precisely?”
“I dunno,” says the guide. “When I started working here six months
ago, they told me 60 million years.”
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Significant Figures…just keep it reasonable (please!)
Wrong
Right
Why
1.867 + 2 = 3.867
1.867 + 2 = 4
Addition/Subtraction:
use least precise
places
1.867 + 2.000 = 4
1.867 + 2.000 = 3.867
1.867 x 2 = 3.734
1.867 x 2 = 4
1.867 / 2.000 = 1
1.867/2.000 = 0.9355
"
Multiply/Divide: use
smallest number of
significant figures
"
In this class, if it’s really a problem about significant figures,
you must get it exactly right. If the problem is about
something else, just try not to look ridiculous.
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Decimal points make things real.
2000 means 1900 to 2100
2000. means 1999 to 2001
2000.0 means 1999.9 to 2000.1
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A problem can come when you use
numbers ending in zero in a sentence.
The meter reading was 2000.
What does THAT mean? Is the period there
to end the sentence or describe the number’s precision?
The meter reading was 2.000 x 103.
Unambiguous! It means between 1999 and 2001
or….. 1.999 x 103 to 2.001 x 103
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Announcements
We will NOT meet here on Friday.
We don’t know exactly where we will meet yet, but….
watch for email.
Surely, it will be near Choppin and Williams Halls.
Download & attempt Recitation Topics 1 from website.
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Exponential (Scientific) Notation
Avogadro’s number
(the number of H2O molecules in 18.0 grams of water):
602,000,000,000,000,000,000,000 = 6.02 x 1023
Age of universe in seconds (somebody’s guess):
300,000,000,000,000,000 s = 3 x 1017
Learn to type exponents efficiently into your calculator!
(The E or EEX button)
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Exponent rules
2x2x2=
(23 )3
=
23
29 =
23 x 24 = 27
=8
83
= 512
m
m
x
x
m = m3
(m3 )4 = m12
m3
x
m4 = m 7
These rules make sense when you write them out term by term.
e.g. (23 )3 = 29 = 83 = 512
(2· 2· 2)3 = (2· 2· 2) · (2· 2· 2) · (2· 2· 2) = 29
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You can nudge the tens powers, but
usually we don’t leave it that way.
3.1 x 1017 is the same as 31 x 1016
Handy if you must add 2 x 1016 to 3.1 x 1017
3.1 x 1017 + 2 x 1016 <<<Nudge<<< 31 x 1016 + 2 x 1016
Result: 33 x 1016
>>>De-Nudge>>> 3.3 x 1017
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Suppose a speeding ticket is $50 plus
$10 x MPH in excess of speed limit (60 MPH).
What is the range of costs for that speeding
ticket if your car can go 125 MPH?
35
S.I. units were not chosen entirely by chemists.
Length
Mass
Time
Temperature
Number of something
Electric current
Luminous intensity
Meter
Kilogram
Second
Kelvins
Mole
Ampere
Candela
The original idea of the meter was
that there would be 1 x 107 of
them between the equator
and the North Pole.
The units have an unusual history! On some other planet—did
you know there are billions of planets?—perhaps some other
form of intelligent life is using altogether different units. Here in
the USA, we still dislike the SI units. Even most chemists prefer
gram to kilogram, centimeter to meter, etc.
36
Larger than
Smaller than
Prefixes—yes, you have to memorize them.
Prefix
Example Example means
Nano
Nanometer
0.0000000001 m or 10-9 m
Micro
Microliter
0.000001 L or 10-6 L
Milli
Milligram
0.001 gram
Centi
Centimeter
0.01 meter
Deci
Deciliter
0.1 liters (= 100 milliliters, by the way)
Deka
Dekameter
10 meters
Hecto
Hectogram
100 grams
Kilo
Kilometer
1000 meters (=0.6 miles, by the way)
Mega
MegaHz
1000 cycles per second, once a very fast
computer!
Giga
GigaHz
1,000,000 = 106 cycles per second, now an
OK computer (barely)
37
You can do anything you want
to both sides of an equation.
1 mile  5280 feet
Divide both sides
by 5280 feet
1 mile
1
5280 feet
Divide both sides
by 1 mile
5280 feet
1
1 mile
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And you can multiple anything by 1 without
changing it…except you might change the units.
A marathon is 26.4 miles. What’s that in feet?
26.4miles
X
5280 feet
 139392feet
1 mile
Is the number of significant figures correct?
39
Announcements
MT1 should be available tonight.
Unless you are pre-educated, you should WAIT!
Sign up for EITHER no-calculator OR with-calculator.
Yellow notes template forms available. You MUST
relinquish these when you leave the testing center.
Schedule on website has been pushed back a day or so.
40
Sample problems
How many clock cycles does a 3GHz
Pentium computer go through in one day?
How many molecules of water in a
nanogram of water?
41
The cost of disputing a grade.
In 1975, a promising young chemistry major
drove 42 miles from his new university to
his old one to dispute a grade with the
math department. If the 1967 Ford Galaxie
got 17 miles per gallon, and if gasoline cost
$0.54/gallon, what was the cost?
42
Let’s do a basketball question.
A basketball court
measures 94’ x 50’.
Compute its area
in square yards.
If you were the professor, how would you
modify this question for a quiz?
43
I married my lawnmower.
My yard consists of 3 major
segments measuring
(in feet) 70 x 30, 100 x 10
and 30 x 40. Can my
wife use one of the new
battery-powered lawnmowers without
recharging?
The lawnmower I am
considering claims it
can do 1/3 acre
without recharging.
Convert is free on TigerWare
or use your smartphone.
44
Let’s give it a try. Easy way that works here. Prim and
proper way that always works.
45
Practice!
http://www.youtube.com/watch?v=vjvJHsJD8ic
http://www.youtube.com/watch?v=vjvJHsJD8ic
This scene is about 1:20 into the video 46
Many important properties have
compound units.
Density is the mass per
unit volume. For
example, the liquid
mercury in a
thermometer has a
density of 13.6 grams
per cubic centimeter.
Units of density:
Billiard ball floating in mercury.
http://www.zyra.org.uk/mercury3.htm
g
g

3
cm
mL
47
Why do we care?
1.
Density is an
important, easily
measured property
that lets us gauge the
purity of substances.
2. Heavy stuff sinks, so
that tells us what we
might have to do to,
say, clean up a
hazardous waste site.
http://www.whistleblower.org/article.php?did=18&scid=28
http://murray.senate.gov/hanfordcleanup/index.cfm
The Hanford Nuclear Site: 50 million
gallons (more?) of contaminated wastes on
the beautiful Columbia River. Pricetag to
clean: $40,000,000,000 = $4 x 1010.
(I have seen much higher estimates, too).
48
Or we could care just because
density lets us do fun stuff.
http://www.youtube.com/watch?v=u19QfJWI1oQ
http://www.youtube.com/watch?v=u19QfJWI1oQ
49
Another property with a compound unit: force.
Defining physical relation
F=ma
Mass in
kilograms, kg
Acceleration, m/s2
Resulting physical unit
m
kg  2
s
Called a Newton, nt
50
Still more complex: pressure
Defining physical relation
P = F/A
Force, Newtons
Area, m2
Resulting physical unit
m
2
nt
kg
s


m2
m2
m s2
kg 
Called a Pascal, Pa
51
These aren’t the usual units of
pressure here in the USA!
101,325 Pa = atmospheric pressure = 14.7 p.s.i.
p.s.i. = pounds per square inch
Example: most cars use 32 p.s.i. in their tires. What’s that in Europe?
Harder (but fun) problems coming in the Recitations.
52
Conversions
Figure out the smaller unit.
You will need a larger number of those.
Example:
Q. How many deciliters in 10 Liters?
A. Deciliters is smaller, so you will need more
of them. Ten deciliters for each liter times
10 liters = 100 deciliters.
53
Or, you can do it very prim and proper
1. Write the given: 10 liters
2. Write the conversion: 1 deciliter = 0.1 liter
1 deciliter
1
3. Divide both sides of the conversion by right side:
0. 1 Liter
4. Divide both sides of the conversion by left side:
1
0.1 Liter
1 deciliter
5. Multiply the “given” from step 1 with whichever
form of the number “1” from steps 3-4
cancels the undesired unit.
1 deciliter
10 Liter 
 100 deciliters
0.1 Liter
54
Learn to line conversions out.
1 deciliter
10 Liter 
 100 deciliters
0.1 Liter
Start by putting what you want at the left. Arrange conversion
factors so as to cancel out the unit you do not want!
55
Despite the metric system, you must still to be
able to convert between different unit systems.
Example: the smallest MOPAR V8 engine of 1965 was 273 cubic
inches. Today, we’d quote that in liters, but how many liters?
Reason it out: A liter is like one quart, a cubic inch is like your thumb.
Going from cubic inches to liters should result in a smaller number.
1 inch = 2.54 centimeters (memorize!)
3
1L
 2.54 cm   1 mL 

273 in 
 
  4.5 L
3 
 1 in   1 cm  1000 mL 
3
3
3

2.54
cm
273in 3 
1 in

 1 mL  1 L 

 1 cm3  1000mL   4.5 L

56
You may find it much easier at first to do
these problems one step at a time.
For example, just compute the conversion factor for in3 to cm3 first.
1 inch  2.54 cm
Cube both sides
1 inch  (2.54) cm  16.4 cm
3
3
3
3
3
Now what?
57
What pressure do I exert on my feet?
English System
Metric System
P = Force/Area
= weight in pounds
/area in square inches
P = Force/Area
= mass x gravity
/area in square meters
58
BTW, if pounds in the English
system really is a unit of force,
what is the English unit of mass?
http://hypertextbook.com/physics/foundations/system-english/
http://en.wikipedia.org/wiki/Slug_(mass)
59
Problem: estimate the volume of
this room in milliliters.
This will also teach us a bit about scientific notation.
60
Mapping: conversions that involve
more than multiplication & division.
Example: Centigrade to
Fahrenheit
o
o
F  32
C
1.8
o
212
Slope = 1.8
oF
32
o
F  1.8 C  32
0
100
oC
61
The centigrade scale is coarser…
centigrade divisions are bigger.
An 18-degree change in Fahrenheit
temperature is a 10-degree change
in Centigrade.
o
F  32
C
1.8
o
o
o
F  1.8 C  32
62
Kelvin temperature is just offset from centigrade.
The “step size” (degree size) is the same, though,
because the slope = 1.
BTW, why 273.15 ???
K = oC + 273.15
K
Slope = 1
273.15K = 0°C
0
Zero K = -273.15°C
0
oC
63
Converting oC to oF in your head
Double the oC temperature.
Subtract 10%.
Add 32.
64
Converting oF to oC in your head
Subtract 32
Divide by 2
Add 10%.
It’s worth remembering some temperatures.
16 oC = 61 oF
July in Duluth = February in Baton Rouge
10 oC = 50 oF
May in Minnesota =January in Baton Rouge
98.6 oF = 37 oC
Body Temperature = Summer in Dallas
- 40 oF = - 40 oC
Winter in Minnesota, but hardly the coldest
day there (record = -60oF)
100 oF
77 oF = 25 oC
77 K = -196.15 oC = -321 oF
Rectal temperature of the cow
Room Temperature
Liquid N2
66
Now, let’s turn to a study of
temperature, energy and power –
what ARE these?
But first, remember that Sony movie with the bouncing balls.
http://www.metacafe.com/watch/44666/like_no_other/
67
Whiteboard or ELMO presentation
of energy, to include:
W = DE = mad
Q = m  C  DT
calorie, Calorie and Joule
How crazy it is that this all goes back to
choosing meter as our length and gram as
the mass of 1 cm3
68
The heat capacity equation involves
CHANGES in temperature.
Q
C 
m  DT
Q = heat added
∆T = temperature CHANGE
WHY does Gold have such a
low heat capacity?
High heat
capacity: the
material remains
“cool” about
having heat
added to it.
Example: water.
Low heat
capacity: the
material gets hot
quickly if heat is
added to it.
Example: gold.
Heat Capacity…or why it is actually
not hot in Baton Rouge in the summer
We mentioned that water had high heat capacity.
Water also forms the basis for defining heat capacity.
Heat capacity is how much energy it takes to raise the
temperature of something by a certain amount.
Define: 1 calorie = the amount of energy required to raise 1.00
grams of water by 1.00 degree centigrade.
Note: a "food calorie" is actually 1000 calories!
SI unit of energy is the Joule: 1 calorie = 4.184 Joules
A CHANGE in temperature is the same
in Kelvins as in degrees centigrade!
T1 = 0oC = 273K
T2 = 10oC = 283K
∆T = 10oC = 10K
Define:
A calorie is the heat
required to raise
1 mL (1 g) of water
by 1 degree Centigrade
(e.g., by 1 Kelvin)
71
Stop here?
72
Assume you are mostly water, then estimate how many
calories it takes to raise your body temperature from its
normal 98.6oF to a fever condition of 101oF.
Convert this to Joules.