Week of 10/28/2013

This week covered intramolecular/intermolecular forces.

Covalent bonds are the bonds we have been studying until now, and they are an intramolecular force. They connect two nonmetals together. However, we were introduced to a new force between molecules called intermolecular forces. These forces are not as strong as intramolecular forces that bind atoms together, as these forces bind ions or full molecules together.

Other intramolecular forces are Ionic Bonding and Metallic Bonding, bonds between a metal/nonmetal and bonds between metals, respectively. Ionic bonding uses charge alone to combine two elements.

Week of 10/21/2013

Ions and metals and moles, oh my.

This week we covered a little about ionic and metallic bonding. That was the only new content covered this week, because we had a test over unit 2, and a pretest over the whole course next.

We started Monday with review for Tuesday's test over unit two. The test was simple enough. It was fairly well done as long you knew the basic concepts. I didn't understand formal charges and resonance until a few days before the test. I didn't do as well as I wanted to, so hopefully I'll study more for the next test.




Wednesday was mole day, 10/23. A celebration with cookies and mediocre mole puns.

Q: On which American mountain was Avogadro's face carved in stone?
A: Mount Rushmole 

Q: How would you describe Avogadro's room while he was a teenager?
A: A Molar mess 

Q: What are mammoles?
A: Four-legged animoles 

Q: What area did Avogadro explore?
A: The South Mole 

Q: What did Avogadro call his church service?
A: Molar Mass 

Q: How did Avogadro get through the desert?
A: He rode on a camole 

Q: What are school holidays for mole students?
A: Mole Day, October 23 and Mole-oween 

Q: What line from Shakespeare do high school moles have to memorize?
A: "To mole or not to mole, this is the question." 

Q: What sugar do moles prefer?
A: Mole-tose 

Q: How much does Avogadro exaggerate?
A: He makes mountains out of mole hills 

Q: What element do moles love to study in chemistry?
A: Molybdenum 

Q: What are moles made of?
A: Molecules 

Q: What kind of make-up does the mole wear on his eyelashes?
A: Molescara 

Q: What happens when a mole bites a dog?
A: He becomes Moleicious! 

Q: What is a mole's favorite soup?
A: Molestrone 

Q: What did the mole say to the cow?
A: Molek does a body good! 

Thursday we took a pretest on all of AP Chemistry. I was the only one in my table group who tried, and people asked me why. Apparently using a pretest to determine how much more you need to learn is a sin. However, I can't ever look at that pretest to see what I got wrong, so maybe it WAS pointless.

Friday we worked on an ionic bonding POGIL. Ionic bonding is simple, it's between a metal cation and nonmetal anion. However, metals often have different charges than nonmetals, so I have to make sure they balance properly.



Metallic bonding is special because when metal atoms bond, their electrons can move freely throughout the entire structure (The Electron Sea Model). This is why metal can ground you and hold a charge.


I did fairly well this week, but my retention of information is lacking, as shown by the test. Last minute studying does not work for me. I must become familiar with a subject before cramming it in.

(Here's your Halloween theme Dr. Evil)

Week of 10/14/2013

This week in class was spent doing two things: working on a Molecular Geometry VSEPR group project and solidifying our knowledge of Lewis Dot Structures for the test on Tuesday.

In class we started the week by finishing our work with balloons and molecular geometry. White balloons represented unbonded electron pairs, and red balloons represented bonded atoms. The colors are different, but you can see how we did it here:

 

Atoms always space themselves as far apart from each other as possible in a molecule. However, unbonded electrons push atoms closer together (as seen above) reducing dihedral angles.

The project was simple enough, and helped me grasp VSEPR theory a little more. My Lewis Dot Structure knowledge was already pretty firm, so this lab came easy.

We then moved on to the gumdrop models. Same concept, but they don't account for unbonded electron pairs (I think?) and they DO account for dihedral bonding angles.

This picture isn't from our class, but I don't have a camera, so I rely on other's pictures.

We also went over hybridization, which ties into VSEPR theory as another factor to help us determine the shape of a molecule, using the orbitals of atoms and how they bond. We also have to deal with resonance, the various forms a molecule can take.

Here you can see Benzene, in it's two resonance structures.

This unit as a whole started out very confusing for me, and it still is, at least a little bit. However, I feel like I've caught up a little bit. My knowledge of Formal Charges is still shaky, but my test is tomorrow, so clearly I've got to get ready in time.

Week of 10/7/13

This week was all about...more Lewis Structures and bonding. Lewis structures are diagrams that display valence electrons as dots to help people understand bonding and molecular geometry.

These diagrams are basically the basis of the whole unit, and they are how we express molecules on paper from now on (I assume?).


We started the week off by going over Formal Charges. These are a way to show the charge on parts of the molecule without having to put the charge around the whole molecule. It allows us to see the distribution of atomic charges in a molecule as well. Since opposite charges cancel each other out, we can simplify the diagrams as well.

(You can still bracket the entire molecule)


Then we did molecular geometry, with Valence Shell Electron Pair Repulsion Theory. As we learned earlier, unbonded electron pairs can affect molecular geometry, and the VSEPR model accounts for this. There are multiple shapes a molecule can take, and this is why. However, I'm still curious as to why this is actually useful in chemistry. Why does one need to know the shape of a molecule?

We have not gone over 7 and 8 coordinate geometry, I assume because it's not necessary (citation needed)

Up until now, I had a weak grasp of things, but soon after this, I get lost completely. This is a complicated unit, and I'm not grasping things as fast as I do in other classes for whatever reason. I'm going to need to study these things, so I don't ruin my grade on that test.

We finished the week with a glimpse into Polarity and Hybridization (with Sigma bonding). These are all lecture quizzes assigned near the end of the week, but hybridization was a mess of words that did not go well for me. My classmates seem to agree.


I have a theory on why people hated that lecture quiz so much: it didn't have the answers in it like it usually does and you actually have to apply the things you know.

Week (Weak) of 9/30/2013

This week we covered many topics, and did a new lab in class.

The first thing we covered starting the week was bonding and bond order. When doing a Lewis Dot Diagram we represented a bonding pair with a line instead of two dots. Now we have to deal with double and triple bonds.

We went through bond order with a POGIL activity and learned that the bond order of a given molecule is the highest number of bonds it has between two atoms (which can be 1,2 or 3). We also learned that double and triple bonds have more energy stored in them, thus they are harder to form and harder to break. We then added bond length into the mix, where a higher bond length means less stored energy.

We then learned the exceptions to the rules for Lewis Structures. Boron and Beryllium are both electron deficient, with Boron only have 6 valence electrons and Beryllium only having 4. It is also worth noting that Hydrogen only has 2 valence electrons. A lot of elements are hypervalent, meaning they have more than 8 valence electrons.

We were then introduced to charges on atoms. Previously, we would put brackets around the whole molecule with the charge superscripted to denote charge. Now we can simply put the charge on the appropriate atom. We use formal charge to understand bonding better (unfortunately, it’s made my understanding worse).

Near the end of the week, we started a lab involving balloons and gumdrops about molecular geometry. Molecules can take a Linear, Bipyramidal, Trigonal, Octahedral, or Tetrahedral shape.

Friday night, we did lecture quizzes on molecular geometry and formal charges. Anything for extra credit.

This week was a good one, with a nice lab and a few new concepts thrown in. However, all these new concepts are still confusing to me, and I need to make sure I get them straightened out before the next test. I'm still bad at studying but I'll get better at it eventually.

Week of 9/23/13

Back to the blog.

This week was a test week in all but one of my classes, so I didn’t study for the Chem test as well as I should have (excuses, excuses). The test was on everything I covered in the last blog post, so I won’t go over it again.

However, there were some HotPot quizzes provided by the good doctor, and next time I should actually do them. Apparently there was a small correlation between people who studied with those quizzes and people who did well. 

(I’m not seeing it) 

Studying is something I've never been good at, and I've trained myself to learn and retain the knowledge the first time to make up for that. However, when I fail to do that I end up with a horrible score (it’s always hit-or-miss). Mr.Oleksinski will tell you all about it. I intend to study ahead for this next unit.

After the test, we started on the bonding unit. Lewis Dot Structures are the first thing we’re working on. Lewis dot structures (named for Gilbert N. Lewis) are simply a way to draw a molecule with it’s bonds, representing valence electrons with dots and two valence electrons as a line (if two atoms connect with it).

If you want to draw a Lewis Dot Structure, put the more electronegative ion in the center. You then make sure that the ions you’re putting on the outsides have eight valence electrons, unless they can be stable with less. 

We've only just started the bonding unit so I can't (officially) tell you more. Sorry.

Week of 9/16/13

This past week has been all about stoichiometry. Stoichiometry is the study of numbers in chemical equations.
So the past week was spent doing various combinations of finding limiting reactants, finding masses of reactants and products. Generally, in the problems we've worked on, one reactant is in excess and one is limited. In the real world, this is often the case, because having an excess of one (usually very common) reactant makes the reaction go faster.



We also messed with empirical formulas, the simplification of a chemical formula, Thus making C6H3 into C2H. Empirical Formulas are for finding the simplest isomer of a molecule. However, this does not mean C6H3 is the same as C2H, or that they share similar properties, but it does mean these elements have the same ratio of masses. In order to find an empirical formula, you must first find the molecular ratios of your chemical reaction. Then you simply reduce and simplify your equation as much as possible.

Yield was a simple matter. Given a chemical equation, an unlimited amount of one reactant, and a certain amount of a different reactant, you should be able to figure out how much of the products you are able to make. However, you should also know how to find the reactants when given the yield (products).

Finding mole ratios was harder for me. You use a mole ratio diagram to convert the reactants and their coefficients to masses, and then use those masses to find the mass of a product. You don’t need to deal with Avagadro’s number, but the method provided is a little complicated.

This past week hasn't been too hard for me, but I feel that I might have missed some details for not paying enough attention in class. We did a lot of POGIL activities, and I have very smart people in my group to help me when I don't get something. Mole ratios with "the bridge thing" especially went over my head. So I know what to study here. We also have a test this Thursday, so I have to hit the books pretty hard.

...At least it's not String Theory.