Intermolecular Forces

Today was all about intermolecular forces. The first type is called a dispersion force. Dispersion forces are weakest type of intermolecular force, and it is present in every molecule. Dispersion Force also depends on the molar mass of a substance.

The second type of intermolecular force is Dipole forces. Every polar molecule has dipole forces. Since polar molecules have a negative and positive ends, dipole forces cause polar molecules negative ends to attract the positive ends of other molecules and then another molecule will attach and so on.

The third type of intermolecular force is Hydrogen Bond forces. Hydrogen Bonds are basically the same concept of dipole forces, where the negatives attach to the positives, but these forces are a lot stronger. However there is a catch, hydrogen bonds can only happen when a hydrogen bonds to a N, O, or F. These three atoms have the highest electronegativities, so they will create very very polar molecules. A great example of hydrogen bonds is H2O. The intermolecular force in water is great because of the hydrogen bonds. Because the forces are so great, it can cause water to stick together, or bead. These hydrogen bonds are the reason for these to events....

Today we also did a lab exploring the effects of intermolecular forces. These effects include...

-Evaporation Rates

-Capillary Action (A Liquids tendency to climb up the walls of a narrow column)

-Vortex Formation and Relaxation (The time it takes for a liquid to relax after swirling it)

-Viscosity (Resistance to flow)

-Surface Tension (Property shown by water in above photo of the water drops on the penny)

-Beading (Shown in the above picture of the water)

The homework for today is to keep up with the webassigns. There is a reading sheet due tomorrow and all the other HW WAs are due friday. The Lab is also due on friday

The next scribe is....STUART P. Good luck bud

Non-Polar Vs Polar Molecules

The main idea today in class was non polar vs polar molecules.....

Non Polar Molecules

Non polar molecules have symmetry (the charge is evenly spread throughout the molecule) They dont have a positive and negative side. Non Polar molecule NEVER have NON BONDING PAIRS. Non bonding pairs would give the molecule a higher concentration of negative charge on one side, making it polar. It is possible for non polar molecules to have polar bonds, so be careful when determining wether or not it is non polar, its all about the symmetry.

These 2 molecules (CCl3 & BF3) are non polar because the charge is evenly distributed. SYMMETRY!

Polar Molecules

Polar molecules do not have symmetry, they have negative and positive ends. This could be causes by non bonding pairs, which will cause a molecule to have a high concentration of negative charge on one end. It could also be caused by a molecule with more than 2 different atoms around the central atom, one of them having a higher electronegativity will cause more negative charge concentration on one side making it POLAR. A great example of a polar molecule is H2O, or water. Since O has a higher electronegativity then H, all the negative charge concentrates around the O. This causes the O side of this molecule to be negative, and the H side, to be positive. Here are some pictures of Polar Molecules...

Liebs did a demo to show the polarity of water. He had a balloon and he rubbed it against his head. This caused the balloon to take a negative charge. There was also a stream of water dripping from a glass cylinder. When liebs put the balloon close to the water, the water bends towards the balloon. What actually happens is the positive side of the H2O molecule (the H side) is attracted to the balloon. Hopefully now you know more about polar and non polar molecules....

The HW is to make sure you are keeping up with the webassigns

The Wild Wild World of Limiting Reactants

Today was a pretty big day in terms of learning the concept of limiting reactions, so if you weren't here today, sucks to be you. Hopefully this post will help you a lot though.

Today we kicked off class finishing our Copper and Silver Nitrate Lab. If you somehow lost your lab, here is a link. We went to go get the masses of the silver left in our beakers. (hopefully you didn't spill all of your silver in the sink). After massing our silver, we went back to our desks and we wentthrough how to do the post lab.

In the post lab, you have to find the mass and moles of copper wire that reacted. Then you have to find the mass and molesof the silver metal that was produced in the reaction. Using this data you have to find a mole ratio between the two elements. With this mole ratio, you have tocreate a balanced chemical equation for the reaction. We used this example in class....

If the mole ratio between silver and copper was 3 Ag : 1 Cu, then the balanced chemical equation for this reaction would be....

The whole point of this lab is to find the balanced equation. Oh and of course also to make silver for Mr.Lieberman to sell. So that was pretty much the first half of class.

The second half we looked at a single replacement reaction between Aluminum and Copper Chloride.

The Reactants, Copper Chloride on the left (we dissolved it in water before reacting it) & Aluminum foil

The reaction over time

What happened was the Aluminum bonded with the Chloride and that left the copper (the redish chunks at the bottom) alone by itself. As you can see the liquid went from blue to clear because the copper was taken out of the liquid.

The balanced equation for this reaction is...

To begin with, we had .66 grams of Al and .64 grams of .

A limiting reactant is the reactant that runs out first, or the reactant that creates the least product. The balanced chemical equation and the mass of the reactants are crucial to finding limiting reactants. There are two ways to find the limiting reactant in this case....

Method # 1 : This is the way where we find out how much is needed to react with the .66 grams of Al.

This shows that you need 4.9 grams of Copper Chloride to react with .66 grams of Aluminum. Now you maybe thinking, "OH MY GOD!!!! WE ONLY HAVE .64 GRAMS OF COPPER CHLORIDE!!!!!" Well, congratulations my friend, you have just found the limiting reactant. Since there isn't enough copper chloride to react with .66 grams of aluminum, the copper chloride will run out first, making the copper chloride the limiting reactant. However, this way is not that great of an idea if you need to find out how much of a product is produced. For this, you probably shoud use method #2.

Method #2 : In this method, you take each of the two reactants and find out how much of the product that reactant produces.

(.66 grams of aluminum produces 2.32g of copper)

now you do the same thing with the other reactant

(.64 grams of Copper Chloride produces .30 grams of copper)

Since Copper Chloride produces less copper than Aluminum does, Copper Chloride is the limiting reactant. Also, with this method, you figured out that .30 grams of copper was produced by this reaction.

The last thing we learned how to do was find how much of the excess reactant will be left. Since we know that .30 grams of copper will be produced, we want to find out how much aluminum is needed to make .30 grams of copper. Than we subtract that amount from the amount of aluminum originally present, and, HA-ZAA! you have your excess reactant. Heres the work...

.085 grams of aluminum is needed to make .30 grams of Copper, so then you do .66 -.085=.575 There will be .575 grams of excess aluminum leftover.

That pretty much sums up todays class period. There is a quiz tomorrow so you better know your stuff, hopefully this post helped you learn your stuff. Also today Liebs gave us a homework sheet at the beginning of class which is like always due on the test day. If you forgot to pick it up or were absent today, you can find it here. It is called 02_stoichPrac.

Thats is for me guys. The next scribe will be Senor Trevor B. Have fun, you have five days to do this, so it better be good.

Just Another Exciting Day in 7th period Chem....

Today was just another exciting day of seventh period chem with D-Liebs. We kicked off class today with an ever so exciting discussion on the one and only...............HOMECOMING GENIE!!!!!!! Today being the first day of homecoming week at GBS, Mr.Lieberman told us the story of the homecoming genie. He showed us the bottle in which the homecoming genie is in. Liebs told us how the homecoming genie only comes out if the school is filled with homecoming spirit. Mr.Lieberman then opened the bottle and.................nothing happened. In a desperation move to get the genie out of the bottle, Chris and Artie proceeded to sing the fight song!.......FAIL. Artie didnt even know the words. The only one with spirit in the room today was Erika G. Nice job Erika! Tomorrow we are definitely getting the genie out of the bottle because like Mr.Lieberman said, homecoming is nothing without the homecoming genie. So, WEAR GREEN AND SILVER TOMORROW FOR SLYTHERIN (our class house for tomorrow)!

(look like this, we will for sure get the genie out)

After the talk on the homecoming genie, we got down to business. It was time for chemistry. First, we talked about alchemy. Alchemists were scientists hired by kings and queens to make immortality potions, turn random metals into gold, and other scientific things. Alchemists were the first people to record data like, data about elements, lab apparatus's, procedures, and experimental technique. After alchemists, we talked about Robert Boyle. Robert Boyle stated that a substance was an element unless it could be broken down into two or more simpler substances. Robert Boyle transitioned from some of the weird science of the alchemists, to some of the chemistry we use today. After Boyle, we talked about Dalton. Dalton was a religious school teacher/ principle at 13/ genius. Dalton said that atoms do indeed exist and they are indivisible and indestructible. Dalton provided the first atomic model backed by data/evidence. Later, this guy named Thompson disproved Daltons model by conducting this experiment...

This experiment showed that atoms do have negatively charged particles called electrons because electrons are the reason the beam was attracted to the positively charged magnet. He then proceeded to make an atomic model according to his findings. This model was called the "plum pudding" model. No, i dont know what he was thinking with the name.... So yeah that is where we left off today in 7th period chemistry with d-liebs.

Notes From Today

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Your homework for today is.....

1) DRESS GREEN and SILVER tomorrow!!!

2) Watch our 2-0 BEARS beat the cheese-heads of Greenbay on Monday Night Football today!!!! GO BEARS!!!!!

The next scribe will be......MATT BROWN