Enough already with a world
without chemistry!
Now we begin RS Chapter 3,
Evolution of Atomic Theory.
This is a historical perspective and preview.
1
There’s something very, very Wrooooong with
us: we don’t see the world as it is….quantized!
Bill Murray in Stripes.
http://www.youtube.com/watch?v=D8Q1fDf0GeY
The crucial line is at about 1 minute in this video
John Candy and Warren Oates in Stripes: on the difference between rank and leadership.
http://www.youtube.com/watch?v=w6Oy4Prsai0
Also fun>>> http://www.bing.com/videos/search?q=bill+murray+stripes+quotes&view=detail&
mid=7E6DBE7B4298FED91A267E6DBE7B4298FED91A26&first=0&FORM=LKVR1
2
Many ancient cultures contemplated the
composition of matter.
5 Ancient Chinese Elements:
Wood (木, pinyin: mù)
Fire (火, pinyin: huǒ)
Earth (土, pinyin: tǔ)
Metal (金, pinyin: jīn)
Water (水, pinyin: shuǐ)
http://en.wikipedia.org/wiki/Wu_Xing
http://chinese.phillipmartin.info/china_map.htm
3
Early Greeks listed five elements.
The four corruptible elements are shown.
The fifth (quintessential, uncorrupted, heavenly)
element was aether.
Alternative Fifth Element, Милица Јововић
More recognizable here: http://www.youtube.com/watch?v=2Ig-wrEGtKI
4
The modern view is still incomplete and
inadequate, but a lot more useful day-to-day.
If all the atoms in a given
sample of "material" are
"the same" then the chemical is said to be an
elemental form.
Actually, almost the same!
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Another definition of elements:
Difficult to purify further by the means
available to a 1930’s chemist.
Example:
•It is easy to break water down into oxygen and
hydrogen. We will do it (or see video) later.
•It gets a lot harder after that.
•Oxygen is an element.
•Hydrogen is another element.
There are about 118 elements….some of them man-made.
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This will become more and more clear as
the semester progresses.
7
Atoms: Trust me (for now)
The word means “indivisible”
Atoms are NOT indivisible!
Much effort went into cutting them up or otherwise
probing them to figure out how they work.
We will cover that fascinating history later.
8
We think atoms look like this.
All the mass is here!
The light red space
is mostly empty!
That is why almost everything is really empty!
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Some elements exist as single atoms.
Example: Xe, Ne
www.theroadwanderer.net/ 66NMex/gallneon.htm
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Some elements exist as arrays of atoms
with undefined size.
Example:
Carbon as diamond
Example:
Carbon as graphite (the little disk
floating above the cubical magnets,
same stuff as pencil “lead”!)
The 45.52 carat Hope Diamond
http://www.youtube.com/watch?v=CqcQ5GQ_SlA
http://www.phy.mtu.edu/nue/CubeHover_small.html
http://www.phy.mtu.edu/nue/CubeHover_small.html
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Of huge interest to chemists, and almost nobody else,
some elements exist as molecules.
Example: Hydrogen as H2
Molecules?
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Molecules might have just one single
element…..or….
Normal Oxygen, O2
Ozone, O3
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Molecules can have different types of atoms.
H2O
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A molecule is often a compound, but not
all compounds are molecules.
Molecule of water:
Barring total destruction, as in electrolysis,
these two hydrogens and the oxygen will stay with each
other “forever”.
A tiny chunk of the compound, sodium
chloride. Not a molecule.
Sodium ion, Na+
Chloride ion, ClLearn to draw it yourself:
http://www.chemguide.co.uk/atoms/structures/ionicstruct.html
http://www.chemguide.co.uk/atoms/structures/ionicstruct.html
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The difference between molecules and compounds is
like the difference between marriage and dating:
permanence.
Molecules = Atomic Marriage: you stay with a particular atom no matter what
(barring real torture, such as electrocution—i.e. electrolysis—or something
equally painful, like a chemical reaction).
Compounds = Atomic Dating: it’s a lot easier to break up and start seeing
other atoms. Later, you might get back together with the original atom….but
probably not. Thus, sodium chloride can be easily dissolved. If you dry out
that saltwater solution, the sodium and chloride atoms will attach to different
partners.
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Nomenclature matters…to some people.
•
•
•
•
•
•
•
H2O = water = two atoms of hydrogen per atom of oxygen.
Better name: hydrogen oxide (or dihydrogen oxide).
The name is for the compound. It DOES NOT say that the atoms
specified are really joined into a molecule (but they are in H2O).
MgCl2 = magnesium chloride, which is NOT a
molecule but a compound. Why not call it magnesium dichloride?
Confusing, eh? We’ll explain eventually. Or not…just using the
names in conversation makes it better.
There are lots of rules for chemical names, but let
experience be your teacher.
Some chemists, like me, are not very fussy
about names. Others are! >>>>>>>>>>>>>>>>>
17
Trivia: Who was Bobby’s girlfriend?
“Water is H2O.”
Adam Sandler as The Water Boy
•Not the sharpest knife in the drawer, Bobby
Boucher still knew that water was H2O.
•That means two atoms of hydrogen and one
of oxygen.
•Any guesses how long humans have known
this?
•How do we know?
•Hey, what are atoms?
•How do we know?
•How long have we known about them?
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What’s in a name?
http://www.ndc.edu/sutheimer/dihydrogen%20oxide.htm
This page is only for people who wish to ban
dihydrogenoxide because of its toxic properties
•Causes excessive sweating and vomiting
•A major component of acid rain
•Can cause severe burns in the gaseous state
•Accidental inhalation can kill you
•Primary contributor to erosion
•Decreases effectiveness of automobile brakes
•Has been found in tumors of terminal cancer patients
•May dissolve metal ions especially in the presence of road salt
19
Demonstrate difference between physical
& chemical separation using 9-volt battery,
water & salt: for Recitation 3.
http://www.youtube.com/watch?v=cJmu
MBfVtLo (slightly lame, but….)
First: Who remembers what we said about pancake batter filtering?
20
Chemists use several shorthand representations of
molecules. And we like tinker toys. We will return to this!
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Isomers (Iso=same; mers=parts)
22
Physical States of Matter: Physical vs.
Chemical Transformations
•Big 3 are: Liquid, Solid, Gas
•Other, more nebulous states exist: glass, liquid crystal
•Ice to water to steam are physical transformations:
•no real change in chemical formula.
•Water electrolysis to Hydrogen and Oxygen gas
is a chemical transformation: not only does
the formula change, but a molecule is broken.
•In many practical operations, both physical and
chemical transformations take place.
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Polymer liquid crystal: J. Chem. Phys., 111(4), 1746-1752 (1999).
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Much chemistry (and physics) goes into making
small LC pixels. Each pixel contains LC mixture,
polarizers, plastics and some transistors.
iPhone 3G
C18H19N
iPhone 4 Retina Display
In a physical transformation, the chemical
composition does not change.
Example: laser welding.
http://www.youtube.com/watch?v=4Uek3qEb8TA&NR=1
Actually, it is a big deal in all kinds of welding to
keep any chemical reactions—particularly
oxidation (rust formation)—from occurring.
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Another Example
The decomposition of potassium chlorate
to potassium chloride and oxygen:
KClO3  KCl + O2
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KCl Problem
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Checkit, Dammit!
2 KClO3 ----» 2 KCl + 3 O2
Atom
On left side On right side
K
2x1=2
2x1=2
Cl
2x1=2
2x1=2
O
2x3=6
3x2=6
32
Some formulae are hard to read, but we
must do it. What about these monsters?
(NH4)2Cr2O7
PH4CH3(CH2)11SO3
These are molecular ionic compounds, by the way. Huh?
The Secret of Balancing
(and life)
Do it a lot! DRILL!
(You have lots of homework like this.)
Keep trying! PERSIST!
It is trial and error, so GUESS!
34
Try This Now!
___CH4 + ___O2  ___H2O + ___CO2
In today’s news about natural gas in Louisiana
http://www.kplctv.com/story/15452188/sasol-announces
selects-calcasieu-parish-as-location-for-potential-8-10billion-gas-to-liquids-complex
35
Stump the Professor*
Should be a problem from your book.
Worth 5 points to everyone who is here today if I get it wrong.
Worth 5 points to everyone who is here today if I get it wrong.
*With apologies to Johnny Carson and David Letterman
http://www.bing.com/videos/search?q=stump
+the+band&view=detail&mid=82CFBEF10C573
307767482CFBEF10C5733077674&first=0&FO
RM=LKVR12
Compute the force in Newtons exerted by your body mass when you stand on a scale.
Blank Screen
37
Here’s what people said they learned.
38
Here’s what people said they wanted to know better.
39
Rarely, people forget to tear off their “action item for
self study”; here is one such example.
40
Power Point Sucks
If you don’t believe me…..
Abraham Lincoln’s Gettysburg Address as a
Power Point Presentation.
41
Stop here & Go To “Live Mode”?
42
Stop here?
43
A good time to check out the ACS
Molecule of the Week
ACS is the world’s largest scientific society: 118,452 members.
http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pa
geLabel=PP_ARTICLEMAIN&node_id=841&content_id=CNBP_02
2917&use_sec=true&sec_url_var=region1&__uuid=10f892461897-473b-ae66-0e6d976fd936
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