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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.

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Presentation on theme: "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."— Presentation transcript:

1 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

2 There’s something very, very Wrooooong with us: we don’t see the world as it is….quantized! Bill Murray in Stripes. 2 mid=7E6DBE7B4298FED91A267E6DBE7B4298FED91A26&first=0&FORM=LKVR1 The crucial line is at about 1 minute in this video Also fun>>> John Candy and Warren Oates in Stripes: on the difference between rank and leadership.

3 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) 3

4 4 Early Greeks listed five elements. The four corruptible elements are shown. The fifth (quintessential, uncorrupted, heavenly) element was aether. More recognizable here: Alternative Fifth Element, Милица Јововић

5 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! 5 The modern view is still incomplete and inadequate, but a lot more useful day-to-day.

6 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. 6

7 This will become more and more clear as the semester progresses. 7

8 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

9 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! 9

10 Some elements exist as single atoms. Example: Xe, Ne 66NMex/gallneon.htm 10

11 Some elements exist as arrays of atoms with undefined size. Example: Carbon as diamond The carat Hope Diamond Example: Carbon as graphite (the little disk floating above the cubical magnets, same stuff as pencil “lead”!) 11

12 Of huge interest to chemists, and almost nobody else, some elements exist as molecules. Example: Hydrogen as H 2 Molecules? 12

13 Molecules might have just one single element…..or…. Normal Oxygen, O 2 Ozone, O 3 13

14 Molecules can have different types of atoms. H2OH2O 14

15 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”. Sodium ion, Na + Chloride ion, Cl - A tiny chunk of the compound, sodium chloride. Not a molecule. Learn to draw it yourself: 15

16 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. 16

17 17 Nomenclature matters…to some people. H 2 O = 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 H 2 O). MgCl 2 = 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! >>>>>>>>>>>>>>>>>

18 18 “Water is H 2 O.” Adam Sandler as The Water Boy Not the sharpest knife in the drawer, Bobby Boucher still knew that water was H 2 O. 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? Trivia: Who was Bobby’s girlfriend?

19 19 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 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 What’s in a name?

20 Demonstrate difference between physical & chemical separation using 9-volt battery, water & salt: for Recitation 3. MBfVtLo (slightly lame, but….) First: Who remembers what we said about pancake batter filtering? MBfVtLo 20

21 Chemists use several shorthand representations of molecules. And we like tinker toys. We will return to this! 21

22 Isomers (Iso=same; mers=parts) 22

23 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. 23

24 Polymer liquid crystal: J. Chem. Phys., 111(4), (1999). 24

25 Much chemistry (and physics) goes into making small LC pixels. Each pixel contains LC mixture, polarizers, plastics and some transistors. iPhone 3GiPhone 4 Retina Display C 18 H 19 N

26 In a physical transformation, the chemical composition does not change. Example: laser welding. 26 Actually, it is a big deal in all kinds of welding to keep any chemical reactions—particularly oxidation (rust formation)—from occurring.

27 In chemical transformations, the atomic composition of the material changes. Chemists are good at converting one compound to another. We have discovered a few rules about doing this: 1. The total mass is never changed. 2. Atoms are not changed or lost. 3. How the atoms are arranged, and which partners they choose, can change a lot. 27

28 Balancing Chemical Equations 1 H 2 (g) + 1 Cl 2 (g)  2 HCl(g) H atoms on left: 1x 2 = 2 Cl atoms on left: 1 x 2 = 2 H atoms on right: 2 x 1 = 2 Cl atoms on right: 2 x 1 = 2 28

29 Burning Hydrogen 2H 2 + O 2  2H 2 O Ooops…The blue H atoms should be smaller than the orange O atoms. 29

30 Another Example The decomposition of potassium chlorate to potassium chloride and oxygen: KClO 3  KCl + O 2 30

31 KCl Problem 31

32 Checkit, Dammit! 2 KClO » 2 KCl + 3 O 2 AtomOn left sideOn right side K2 x 1 = 2 Cl2 x 1 = 2 O2 x 3 = 6 3 x 2 = 6 32

33 Some formulae are hard to read, but we must do it. What about these monsters? (NH 4 ) 2 Cr 2 O 7 PH 4 CH 3 (CH 2 ) 11 SO 3 These are molecular ionic compounds, by the way. Huh?

34 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

35 Try This Now! ___CH 4 + ___O 2  ___H 2 O + ___CO selects-calcasieu-parish-as-location-for-potential billion-gas-to-liquids-complex In today’s news about natural gas in Louisiana

36 Stump the Professor* Should be a problem from your book. Worth 5 points to everyone who is here today if I get it wrong. +the+band&view=detail&mid=82CFBEF10C CFBEF10C &first=0&FO RM=LKVR12 *With apologies to Johnny Carson and David Letterman

37 Compute the force in Newtons exerted by your body mass when you stand on a scale. Blank Screen 37

38 Here’s what people said they learned. 38

39 Here’s what people said they wanted to know better. 39

40 Rarely, people forget to tear off their “action item for self study”; here is one such example. 40

41 Power Point Sucks If you don’t believe me….. Abraham Lincoln’s Gettysburg Address as a Power Point Presentation. 41

42 Stop here & Go To “Live Mode”? 42

43 Stop here? 43

44 A good time to check out the ACS Molecule of the Week ACS is the world’s largest scientific society: 118,452 members. 44 eLabel=PP_ARTICLEMAIN&node_id=841&content_id=CNBP_ &use_sec=true&sec_url_var=region1&__uuid=10f b-ae66-0e6d976fd936


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