“Water is H 2 O.”

1. “Water is H2O.” Today, we’ll see that water is the basis of how we measure mass. Later this week, we will use H2O and some of its component atoms to exemplify molecules, compounds and atoms.

2. A solution is a very fine mixture that eventually happens without mechanical agitation. Matter has mass and occupies space.

3. Definition of Matter: Details • Matter: 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/dt2 for you Calculus experts) • Gravity provides a convenient, relatively constant, • acceleration: F = mg whereg = 9.8 m-s-2

4. 1 cm Mass is measured indirectly 1 cm 1 cm • 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.

5. How would we measure mass without Earth’s gravity?

6. Or no gravity at all? View from inside the space station. http://spaceflight.nasa.gov/gallery/images/station/

7. Matter Occupies SpaceWhat’s Space?What does it mean to occupy the 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.

8. Space is volume. Our 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 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.) 1 cm 1 cm

9. S.I. Units* (Appendix C) Length Meter Mass Kilogram Time Second Temperature Kelvins Number of something Mole Electric current Ampere Luminous intensity Candela *The units have a bizarre history! On some other planet—did you know that there are billions of planets?—perhaps some other form of intelligent life is using altogether different units. Even here in the USA, we still dislike these units. Even most chemists prefer gram to kilogram, centimeter to meter, etc.

10. Prefixes—yes, you have to memorize them. Smaller than Larger than

11. Properties with Compound Units Billiard ball floating in mercury. 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: http://www.zyra.org.uk/mercury3.htm

12. Why do we care? • Density is an important, easily measured property that lets us gauge the purity of substances. • 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).

13. Acceleration, m/s2 Called a Newton, nt Mass in kilograms, kg Resulting physical unit Another property with a compound unit: force. Defining physical relation F=ma

14. Area, m2 Called a Pascal, Pa Resulting physical unit Still more complex: pressure Defining physical relation P = F/A Force, Newtons

15. p.s.i. = pounds per square inch These aren’t the usual units of pressure here in the USA! 101,325 Pa = atmospheric pressure = 14.7 p.s.i. Example: most cars use 32 p.s.i. in their tires. What’s that in Europe? See notes for harder problems—a little like the team homeworks.

16. Today’s Announcements Chancellor’s Distinguished Lecture Series “The Dark Side of the Universe: Beyond the Stars and the Starstuff We Are Made Of” Professor Michael Turner University of Chicago 5:00 p.m. 130 Nicholson Hall

17. Daily Evaluations We made the quota last Thursday; bonus points will be added. Biggest concern: Teams! PLEASE GIVE IT A CHANCE.

18. 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.

19. Write the given: 10 liters • Write the conversion: 1 deciliter = 0.1 liter • Divide both sides of the conversion by right side: • Divide both sides of the conversion by left side: • Multiply the “given” from step 1 with whichever • form of the number one from steps 3-4 • cancels the undesired unit. Or, you can do it very prim and proper (Appendix C of your text)

20. Try to learn to line things out Start by putting what you want at the left. Arrange conversion factors so as to cancel out the unit you do not want!

21. 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. You will need a smaller number. 1 inch = 2.54 centimeters (Appendix C of text)

22. 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. Cube both sides Now what?

23. Problem for your team: estimate the volume of this room in milliliters. This will also teach us a bit about scientific notation.

24. oF Slope = 1.8 32 oC 0 Mapping: conversions that involve more than multiplication & division. Example: Centigrade to Fahrenheit

25. K Slope = 1 273.15 oC 0 Kelvin temperature

26. Converting oC to oF in your head  Double the oC temperature. Subtract 10%.  Add 32. 

27. Facts of Life

28. Stop here?

29. Actually, almost the same! ElementsIf all the atoms in a given sample of "material" are "the same" then the chemical is said to be an elemental form.

30. 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. • 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.

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

32. Atoms: Trust me (for now) The word means “indivisible” Atoms are NOT indivisible! Much effort went into cutting them up to figure out how they work. We will cover that fascinating history later.

33. All the mass is here! The light red space is mostly empty! We think atoms look like this That is why almost everything is really empty!

34. Some elements exist as single atoms. Example: Xe, Ne www.theroadwanderer.net/ 66NMex/gallneon.htm

35. 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.phy.mtu.edu/nue/CubeHover_small.html http://www.phy.mtu.edu/nue/CubeHover_small.html

36. Of huge interest to chemists, and almost nobody else, some elements exist as molecules. Example: Hydrogen as H2 Molecules?

37. Molecules Normal Oxygen, O2 Ozone, O3

38. Molecules can involve different types of atoms. H2O

39. A molecule is 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, Cl- Learn to draw it yourself: http://www.chemguide.co.uk/atoms/structures/ionicstruct.html http://www.chemguide.co.uk/atoms/structures/ionicstruct.html

40. The difference between molecules and compounds is like the difference between marriage and dating. 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.

41. Different Representations of Molecules

42. A good time to check out the ACS Molecule of the Week ACS is the world’s largest scientific society: 118,452 members.

43. Daily Evaluation/Amusement Conversions! Cows! Notes. Meanwhile, download lectures! Do we need to know the m/s velocity stuff?

44. 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.

45. Polymer liquid crystal: J. Chem. Phys., 111(4), 1746-1752 (1999).

46. Isomers (Iso=same; mers=parts)

47. Chemical Equations • Chemists are good at converting one compound to another.  • We have discovered a few rules about doing this: • The total mass is never changed. • Atoms are not changed or lost.   • How the atoms are arranged, and which partners they choose, • can change a lot.  

48. Balancing Chemical Equations 1 H2(g) + 1 Cl2(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

49. Burning Hydrogen 2H2 + O2 2H2O Ooops…The blue H atoms should be smaller than the orange O atoms.

50. Another Example The decomposition of potassium chlorate to potassium chloride and oxygen:  KClO3 KCl + O2