Polar and Non-Polar molecule

Today in chemistry class we started out by giving back pop quiz.
Mr. Liberman said most of us didn't understand about "stable."
When atoms are stable that means they don't want to bond or already bonded.
And he said we can't break octet rule except inside. In other words, outside of elctrons can't have electrons over 8.

After that he explaind about polar molecule and non-polar molecule by showing us a great demonstration.
He had two buret, a vertical cylindrical piece of laboratory glassware, that one has filled up with water and the other one has filled up with acetone.
By rubbing his hair with a balloon, that balloon has negatively charged.
As he moved the balloon close to the buret which has water, the flow of the water started to bend toward the balloon.  It happens because water is positively charged and it is polar molecule.
Theoretically, acetone has to be not bend but it did.  Mr. Liberman guessed the acetone mixed with water.
Anyway acetone can not be bend because it is negatively charged and non-polar molecule.

 + Non-Polar molecule
-charge is evenly spread out in the molecule
-NO NON-BONDING PAIRS

 + Polar molecule
-HAS NON-BONDING PAIRS
-the negatively charged center atom balances the molecule with positively charged outside of atoms

The main difference between non-polar and polar molecule is that non-polar molecule does not have non-bonding pairs and polar molecule has non-bonding pairs.

To determine polarity you should look for non bonding pair.

Mr. Liberman also explained different kind of forces-intermolecular, dispersion, and dipole forces.

Every molecules have intermolecular and dispersion forces.
Dispersion force is not that strong force but attractive.
Bigger molecule has lots of dispersion forces.
When he sprinkled acetone on his hand it disappeared very quickly but water did not.
This is a demonstration of dispersion forces.
Also we learned about hydrogen bonding which is strongest force.

I am really sorry that I couldn't explain very well..
So if you need more information about this stuff, I recommend you to visit here:
http://www.tutorvista.com/chemistry/difference-between-polar-and-nonpolar-molecules

And just a reminder, we have a lot of webassign to do.
Also we have a test on Friday.
The next scribe will be Alex K.

Gas gas gas

Half of our classmates were gone today...
because of ....... don't know...
Denna wasn't here today so I am the scriber for today

We started the class with a demontration.  Mr. Liberman put some melted dry ice into a styrofoam box and put a manometer,this manometer has a empty metal ball, into that box.  And the pressure went down because the moles which is in that ball starts to move slow.  Through this experiment we could make sure that when temperature goes down then pressure goes down and temperature goes up then pressure goes up.

After Mr. Liberman finish off with this experiment, we wanted him to dump the melted dry ice on the floor.
And he did....Twice :)
The melted dry ice started to move around the floor like when we spill some water on the hot pan.
We were all excited about the movement of  these little particles.
Also Mr. Liberman dumped the ice over my head accidently!
Korri screamed and called 911 immediately
So that's why I am in hospital right now...
hehe I'm just kidding~
Actually he poured vapor over my head. It just feel coooool~

Today, we learned about the Ideal Gas Equation.
The three important gas laws, Boyle's, Charles', and Avogadro's, derived relationships between two physical properties of a gas, while keeping other properties constant.
When we rearrange to a more familiar form we get                    PV = nRT

*In this equation R is the gas constant.

The conditions 0 *C and 1 atm are called Standard Temperature and Pressure (STD).

At STR R = (1 atm x 22.414L) / (1 mol x 273 K)

R = .0821

And experiments show that at STP, 1 mole of an ideal gas occupies 22.414 L.

If you know the formula with STD, we could convert to different forms.

The important thing is the value of R won't change!

Here is an example

 What is the volume(in liters) occupied by 49.8g of HCl at STP?

T = 0*C = 273K

P = 1 atm

n = 49.8g x (1 mol / 36.45g HCl) = 1.37 moles

V = (1.37 mol x 0.0821 x 273 K) / (1atm)

V = 30.6L

I hope you guys understand what I explained...

If you want more information about the ideal gas equation, I recommended to visit :

http://www.mikeblaber.org/oldwine/chm1045/notes/Gases/IdealGas/Gases04.htm

Today's homework is a Worksheet and Pre-Lab

http://gbs-moodle.glenbrook225.org/moodle/file.php/1814/Worksheets_Unit_6/08_ideal_probs.doc

http://gbs-moodle.glenbrook225.org/moodle/file.php/1814/Labs_Unit_6/lab-molar_volume.doc

The next scribe will be Denna M.

Empirical vs Molecular Formula

Today, we started class by getting back our quizes from last week.  I didn't take the quiz so I have no idea what happened in the beginning of the class.  I am sorry~  Anyway we went over the quiz about 15 minutes.
Then we started to learn what empirical formula is, and how this Empirical formula relates with Molecular formula.

Molecular formula = (Empirical formula)n

* n is an integer

Once you get Empirical formula, then easy to get Molecular formula.

The Empirical formula is the simplest form of the Molecular formula.
For example :
Molecular formula - C6H12
Empirical formula - Divide by 6 - CH2
Here is a sample we did in the class:

Determine the Empirical and Molecular formulas for a compound that gives the following %.
 - 71.65% (Cl)
 - 24.27% (C)
 - 4.07% (H)
The molar mass is known to be 98.96g/moles

First, assume a 100g of the sample
 - 71.65g (Cl)
 - 24.27g (C)
 - 4.07g (H)

Second, Convert gram to moles
 - 71.65g  x  1moles / 35.5g  =  2.018 moles of Cl
 - 24.27g  x  1moles / 12g  =  2.02 moles of C
 - 4.07g  x  1moles / 1g  = 4.07 moles of H

Third, divide each moles by smallest number of moles
 - Cl  :  2.018 moles / 2.018 moles  =  1 mole
 - C  :  2.02 moles / 2.018 moles  =  1 mole
 - H  :  4.07 moles / 2.018 moles  =  2 moles

Finally we can get the Empirical formula like this :  CClH2

Now, we can find the molecular formula by finding the mass of the Empirical formula and setting up a ratio:

CClH2 → C2Cl2H4


*If you want more information about Empirical formula
I recommend you to visit http://www.chem.tamu.edu/class/majors/tutorialnotefiles/empirical.htm


After we had finished the note, Mr. Liberman introduced an activity.  This activity is called Crash of Avogadro Airlines Flight 1023.
The goal of this activity is finding a murderer.
On the first and second side of the sheet, there are 3 tables which help to find the horrible murderer.
In this activity each chemical can be used once or no time.

Tonight's homework is to finish the hydrate lab, do a Magnesium Oxide pre-lab and Avogadro Airline activity which is due on Wednesday.
Just a reminder, the unit 3 test is on Thursday.


The next scribe is Ellen Hirsch