9/11/2009

Oxygen atom on periodic table

8

O

15.9994

[He] 2s^2 2p^2

Isotopes

Isotopes are atoms of the same element that have different masses.

The Isotope of a particular element all have the same number of protons and electrons but different numbers of neutrons.

Most of the elements consist of mixtures of Isotopes .

Mass Number

Mass number is the total number of protons and neutrons that make up the nucleus of an isotope.

-The Atomic mass is a decimal

Designating Isotopes

Hyphen Notation: The mass number is written with a hyphen after the name of the element.

- Uranium – 235

Nuclear symbol: The superscript indicates the mass number and the subscript indicates the atomic number

- Mass Number Þ235 U

- Atomic NumberÞ92

The number of neutrons is found by subtracting the atomic number from the mass number.

- Mass number – Atomic number= Number of Neutrons

- 235 – 92 = 143 for U

Nuclide is a general term for a specific Isotope of and element.

9-9-09 The Atom

Discovery of the Atomic Nucleus

• 1911- Ernest Rutherford, Hans Geiger, and Ernest Marnden conducted the golden foil experiment.
• Discovered a very densely packed bundle of matter with a positive charge in the atom. Rutherford named it the nucleus

Composition of the Atomic Nucleus

• Made of protons and nuetrons
• Protons have a positive charge equal in magnitude to the chare of an electron
• Atoms/elements are electrically nuetral because they contain an equal number of protons and electrons
• Nuetrons have no charge
• Nuclei of atoms of different elements diifer in number of protons and nuetrons and therefore the amount of positive charges they posses.
• The amount of protons determines that atom's identity

Forces in the Nucleus

• When 2 protons are extremely close, there is a strong attraction between them. This attraction also exists between close neutrons or a proton and a nuetron that are close to each other.
• The forces that cause these attractions are nuclear forces.

The Sizes of Atoms

• radius-- distance from center of the nucleus to the outer portion of its electron cloud
• Atomic radii are expressed in picometers (pm).
• atomic number(Z)- the number of protons in each atom of an element

Pre Lab Stuff

Hey y'all. Having a good day? I guess not, since you're doing homework right now. Well you should get excited! We're doing a lab soon! YES!!!

POPCORN LAB- PROBABLY THURSDAY!
Pen. ALL pen! No PENCIL!


Popcorn packs come in little plastic packages. Take off the plastic, and mass the pack. Remember-

• this side up!
• Wait until 1 second between pops to stop popping

Clear the extra seconds off the microwave.
Mass at room temperature.
Open the bag a little.
Wait for it to completely cool ROOM temperature!
2 reasons for the kernels that don't pop

• not enough moisture

• hole in kernal
• http://www.rediff.com/getahead/2005/apr/19corn.htm
  

The Microwave was first used for popcorn. Excited the water molecule to boil, turns it to vapor, causes starch to expand. The starch, when cooled, turns to its sold form. We will be calculationg percent water/mositure in the popcorn.

(How Popcorn Works) http://dsc.discovery.com/videos/how-stuff-works-popcorn.html

Table 1
1. Mass of popcorn before popping
2. Mass of popcorn after popping (and cooling)
3. Mass of H2O in popcorn ( 1-2 )
4. % of H2O in popcorn (by mass) ( 3/1 * 100 )


Go to the white board (table 2) and write Group #, and # for data.

Table 2
Group #---Brand of Popcorn---% H2O by Mass
1
-
-
15


After everyone's finished:
1. Calculate Average
2. Calculate standard deviation (http://hubpages.com/hub/stddev)
3. Use your data for % error
4. Google % H2O in popcorn (http://en.wikipedia.org/wiki/Popcorn)

We will pick our own groups

PRE-LAB
Title of Lab

• write under the blue bar.

Purpose of Lab

• finding the percent of water by mass in popcorn.

Materials

• Popcorn Bag, Microwave, Balance Good Attitude

Procedure

• Bullets fine.
  
• Everyone's is different.
  
• Concise.
  
• Easy to follow
• Only lab notebook, pen, calculator, and good attitudes allowed at lab station

Data Tables

• Draw lines around- Use Rulers
• Give yourself Room.
• Double Spaced
• Error Correction- No white out/ Scribble. Draw one line through the incorrect measurement, then write the correct measurement underneath it.

Pre-Lab Questions

• What is the formula for standard deviation?
• Only the answer is needed
  

LAB
See information at Top^ DUH!

POST LAB

Calculations

• Do 'em well
• You can do them outside of class (She actually expects it)

Post Lab Questions

• Just answers needed
• Pg. 64-65
• 2nd one under Conclusions
• Both under extensions

Conclusion

• discusses mistakes made
• did you achieve goals?
• could any improvements be made in this lab?
• Minimum of 3 complete sentences
  

ENTIRE LAB DUE NEXT TUESDAY

Here are some great websites!

http://funnyjunk.com/movies/2219/Popcorn+In+Ultra+Slow+Motion/
http://www.youtube.com/watch?v=9N4ckFN96-k
(^ possibly the greatest video ever posted on this blog ^)

I love you guys. School's tough this year, but persevere.

9/4/09

We watched a movie today: KABOOM!

• Ground zero is a test range for the FBI to test high-powered explosives.
• Detenation of an explosive is the rapid rearrangement of atoms.
• Sidney Hawford - internationally known explosive engineer
• Things needed for an explosive: 1)means of ignition 2)fuel source 3) oxygen
• Roger Bacon - investigated gunpowder, made of saltpeter, sulphur, and charcoal; also found a wat to get better quality of saltpeter
• 1 million frames/second is required to catch the detenation of an explosive on film
• Alfred Nobel - invented the detenator; Nitroglycerin - extremely dangerous explosive used in dynamite; Dynamite - mixed nitroglycerin with inert absorbants; Blasting gel - same amount of explosiveness as nitroglycerin, but as safe as dynamite

September 3, 2009

Law of Conservation of Mass (picture on the right)



a) an atom of carbon and an atom of oxygen can combine chemically to form a molecule of carbon monoxide; the mass of the carbon monoxide molecule is equal to the mass of the oxygen atom plus the mass of the carbon atom


b) the reverse holds true as well











Law of definite proportions and Law of multiple proportions (picture on left)
a) carbon monoxide molecules are always composed of one carbon atom and one oxygen atom
b) carbon dioxide molecules are always composed of one carbon atom and two oxygen atoms; note that a molecule of carbon dioxide contains twice as many oxygen atoms as does a molecule of carbon monoxide

Dalton's Atomic Theory

• all matter is composed of extremely small particles called atoms
• atoms of a given element are identical in size, mass, and other properties
• actually atoms of a given element have the same number of protons not mass
• atoms of different elements differ in size, mass, and other properties
• atoms cannot be subdivided (chemically, they can in a nuclear reaction however), created, or destroyed
• atoms of different elements combine in simple whole number ratios to form chemical compounds
• in chemical reactions atoms are combined separated, or rearranged

Modern Atomical Theory

• atoms are divisible into smaller particles such as protons, neutrons, electrons, etc.
• a given element can have atoms with different masses (isotopes)
• all matter is composed of atoms

Structure of the atom

• atom is the smalles particle fo an element that retains that element's chemical properties
• nucleus is the very small region located at the center of the atoms
• the nucleus is made up of at least one charged particle called a proton and usually of one or more neutral particles called neutrons
• surrounding the nucleus are negatively charged particles called electrons which are found in electron clouds
• all these are called subatomic particles

Discovery of electron

cathode rays and electrons-- experiments in late 1800s shoewd that cathode rays were composed of negatively charged particles called electrons

charge and mass of electron: JJ Thomson's cathode ray tube experiments measured the charge to mass ratio of an electron

Robert A. Milikan's oil drop experiment measured the charge of an electron

later scientists were able to combine the findings of these two experiments to figure out the mass of an electron

?

Why did Griff not post?

September 2, 2009

Chapters 1 & 2 Test
Answers to Monday's test:

Dr. Bautista: Griff had some trouble getting this to post yesterday so you guys can comment on this one or tonights posting!

1. periodic chart*
2. glue gun melts a glue stick
3. 3
4. 19.3 g/cm^3
5. g/m^2
6. 91.4 cm
7. 4.05 g
8. centimeter
9. 10,080 min.
10. equation graphs as a straight line
11. meter
12. vitamin C (absorbic acid)
13. the smallest unit of matter that maintains its chemical identity
14. 0.036 g.
15. 3
16. 4.3 x 10^-7
17. 9.30 x 10^-3
18. to gain knowledge
19. 4.5 g
20. millimeter
21. discarding data inconsistent with the hypothesis
22. any substance that has a definite composition
23. compound*
24. 1.246 x 10^8
25. precise, but not accurate
26. melting
27. salt crystals formed as the liquid evaporated
28. 0.202 g
29. brittle
30. long after the basis resaerch is complete
31. liquid
32. 4.1 cm^3
33. density
34. volume

1* If you answered "None of the above", and it would change your quarter grade, see Dr. Bautista at the end of the quarter and she may change it. 23* Compound is the answer given by the book but Dr. Bautista said it could be "element" so this question didn't count for anyone.

NOTES

Foundations of Atomic Theory:

- The transformation of a substance or substances into one or more new substances is called a chemical reaction

3 Laws:

The Law of Consecutive Mass

- Mass is neither created nor destroyed during ordinary chemical reactions or physical changes.

The Law of Definite Proportions

- A chemical compound contains the same elemens in exactly the same proportions by mass regardless of the size of the sample or source of the compound.

The Law of Multiple Proportions

- If 2 or more different compunds are composed of the same 2 elements, then the ratio of the masses of the 2nd element combined with a certain mass of the 1st element is always a ratio of small whole numbers.

P.S. -Our first lab will most likely be at the end of next week