Chemblog!

To help us reach that perfect 15 out of 15 (in three minutes or less) on "Question 4" of the AP Chem exam, this excellent "teaching" site will give you countless practice problems.
http://dwb2.unl.edu/apchem/main.html
Just create a free account and then you can practice at will and you can get instant feedback.
The good thing about descriptive chemistry is that, once it "clicks" and you can "see" the products that will form from any of the eight common chem. reaction types, you and others will think that you have magical powers as you spout off sound bites such as, "...(chortle) of course, double replacement with precipitation...solid magnesium phosphate forms from those reactants" or "...child's play, an obvious metal-ligand complex reaction forming hexaammine copper II ion complex; note the number of ligands is twice the transition metal's charge...tee-hee!" or "Why are you walking away from me? I can't quit you!"
:)
Mr.C.

Our Kinetics exam is on Day 4, as usual. This exam will be the first grade of the THIRD quarter. The second quarter grades are over with the exception of a couple of students who did not return their ligand-complex quiz grade to me as requested. Please do so on Monday.

Only four students in our small class are on track for a 5 on the AP exam, three are tracking for a 4 and the rest will get a 3 or lower. This prediction is not based on "FEELING" but on concrete evidence from past students' scores/performance at this point in the course. I always hope that you would ALL put in the time and effort to get a 5 on this exam; you have to be very honest with yourself and change what you have been doing if you are not yet achieving that goal, which is COMPLETELY equivalent to actually learning AP Chemistry. If you are not succeeding and you cannot/will not change, then the rest of this course will surely lower your average further. Again, these are just the facts.
Don't ever forget, I am after school EVERY DAY to help YOU review tests/ hw/ lecture/ do practice tests, etc. (until the LATE buses leave on most days). Also, you can email me questions. That is all I can do, I think.
The next four units will account for half of your AP score; the three extensive equilibrium units are the MOST challenging units of the course and we begin the first of those units this week.
In this course, the third quarter is even more work-intensive than the previous two. The fourth quarter grades are determined by your work over the course of only three weeks! Then, you take the AP exam (May 10, 2006). Most of your grade for that quarter is based on doing an ENTIRE part II AP exam PER NIGHT! The rest of your fourth quarter grade is based on a final exam which you take soon after the AP exam. If you do not have a solid base of knowledge from the first three quarters (by going to extra help to correct and understand what you did not get the first time around), the fourth quarter will net you the most work with the worst results. If you have a lot of other commitments that quarter, you will not be able to keep up with the requirements of this course unless it is your top priority. Typically, students who did poorly the first two quarters do much worse the last two quarters (most of those students fail - in the 50's- the fourth quarter). I would hope that those students would avoid that outcome this year. Again, just the facts.

We will start the review book "5 Steps to a 5" review sessions this week (day to be announced tomorrow) with a floating day schedule in upcoming weeks.

Congratulations to all of the Honors classes, especially the now puissant (that's a compliment! look it up) B-Period, for doing an excellent job on the comprehensive Bonding unit exam. Though you did well, the exam was not easy and there were many ways to get the questions wrong if they were not read carefully and thought about. I noted the care that was given to the exam: work shown, molecules drawn out, keywords underlined. That is always going to pay off for you.
Class averages:
B = 97 (holler!)
D = 96 (sweet)
E = 95 (remember when you used to beat B period?)
As for Monday's Lab exam, though it is a multiple choice exam, you will not be able to figure out most of the questions without writing out/drawing/giving an example of what the question is asking for. If you try to do the test solely in your head (never a good idea on any test), you may actually do very poorly (as many did last year; then they kicked themselves for not writing out information that they KNEW which would have led them to the correct answer). The labs performed this quarter reflected the class topics: the Periodic Table, Bonding and Inter-particle attractions so, if you know those topics well and connect how they were applied in lab, you are studying correctly. Some are not taking notes when I explain or describe what is going on in lab. Those students will have trouble answering some of the lab exam questions so be wary of that for our future lab class discussions(always take good notes in EVERY class so that you can study effectively; the pre-printed notes are necessary BUT in no way SUFFICIENT for success in this class!).

So, let's finish the second quarter with a positive, legitimate (no free grade inflation), grade-boosting effort.

On the "Monster Equation Balancing/Reaction Type Worksheets" from 012106, on page 2 of the file, problem 6 d, there is a subscript error that makes balancing impossible.

The correct equation should have iron II chloride (FeCl2)and NOT iron III chloride (FeCl3) as the first reactant. This is a double replacement reaction so, as you will eventually learn, nothing happens to the charges of the cations or anions in such a reaction. Therefore, iron starts as a +2 ion and ends up as a +2 ion.

Thanks to Evelyn for pointing this out to me. It's good to know that some people are doing the hw carefully. Cheers.

Due to the few who vented their puerile, vapid comments on this blog, the comments section, which I often find helpful and insightful, is closed indefinitely. I have never had to take such action even when the "debate" got lively in the past. As the saying goes, sometimes it just takes a few bad apples...
For those who still want to make constructive or helpful comments, just send me an email directly. Thanks and much respect to the vast majority of you who have not and would not abuse this free class forum.
Mr. Cicale

HW for tonight:
Honors: Read Ch.9.3 and do section review questions 3 and 4. Read Ch. 10.1 and do "Practice Problems" within (the answers are there; check them).
AP:Ch.14.3 and do questions 14.40 to 48 evens.
Answers are here for now:
https://www.edline.net/pages/St_Anthonys_High_School/Classes/6068/AP_HW_answers_14_30-48

I now recall that, due to the pep rally, we will have shortened periods on Friday. Even though some of you could finish a 33 question multiple-choice test in 30 minutes, you need a full period to work carefully and to check your answers.
So, the Honors multiple-choice Bonding test will be on Thursday.
The test will cover the entire unit: all of Bonding AND INTER-particle attractions. Review all of your worksheets from the beginning of the unit and the orange review book.
The second quarter ends with the lab quarterly multiple-choice test on Monday before grades are due. Make sure that all of your labs are up to date by then or you will fail the second quarter as per our course agreement.

Use these links for Kinetics tutorials. We move at an even faster pace from here on in so you may need the support:
http://www.wwnorton.com/chemistry/overview/ch14.htm
http://highered.mcgraw-hill.com/sites/0073656011/student_view0/chapter13/elearning_session.html

No doubt, that bakery's got all the bomb frosting.
i love those cupcakes like mcadams loves gosling
2 no 6 no 12, bakers dozen!
i told you that i'm crazy for these cupcakes, cousin!

AP: Two more descriptive chem quizzes this week (5 minutes each). One tomorrow and another after the Bonding II exam on Friday. You must study and learn to QUICKLY recognize every reaction type. I even posted yet ANOTHER review sheet over the weekend. Previous classes did not have such help.
Here is the ultimate help if you want to memorize (or, better, try to understand) descriptive chemistry: every AP Chem Question 4 set from 1981 through 2003
the link is on this page (tonight, I will add it to our class webpage also):
https://www.edline.net/pages/St_Anthonys_High_School/Classes/6068/
Like naming compounds in Regents Chemistry, this will not go away. In fact, MOST of you cannot even correctly translate a name to a formula, which means that you have to thoroughly review basic first-year formula writing! This course is about to get VERY demanding so you need to make more time for it or your average will mirror today's result. Tomorrow is day 3: I am in @ 7:30 AM in Room 229.

AP: Forgot to give you a quiz among the variety of things that we did today. Expect one at the end of class tomorrow: descriptive chem and metal complex naming.
I'll post the Raoult's Law Deviation chart on Edline because I can't connect to the server from school right now.
It should be at this address:
https://www.edline.net/pages/St_Anthonys_High_School/Classes/6068/

The file is also on our class website now. I corrected a few words in the file as of 8:30 PM. In some places, I elaborated and, in other places, I had to replace the incorrect term "bond" with the correct term "attraction". Semantics is important in Chemistry.

p.s. There is a nicely animated molecular orbital tutorial on this page:
http://www.wwnorton.com/chemistry/overview/ch6.htm

Honors: ALL (including the ones that were originally listed for the multiple choice test) of the objectives posted are for Wed. and Thurs. written-response test. There will be a multiple choice test next week on the entire Bonding and Intermolecular Forces Unit.
This upcoming test requires THOROUGH answers. All assertions must be supported with a scientific reason, law, or LABELED drawing. You should review all notes and homework and then start studying by writing out thoroughly all of the answers to the objectives. This is the last written test of the quarter and it will strongly influence your second quarter average.

I saw some recent articles that you can now comprehend using your chem knowledge:

Solid Gold!:This article demonstrates the phemomena of photon absorption and emission by (gold) atoms in order to detect cancer! Recall that electrons in atoms absorb photons (energy packets) and go to higher energy sublevels and then emit photons as these electrons go to lower energy sublevels.
http://www.livescience.com/humanbiology/060113_gold_nanobars.html

Snowflakes: this article relates to our recent discussions on "hydrogen bonding (NOT A BOND!) attraaaaactions". The article talks about crystals (of water!), which are solids composed of particles arranged in a regular geometric pattern.
http://www.livescience.com/forcesofnature/060113_snowflake_stamps.html

This is the site that I used to show the heteronuclear diatomic M.O. diagram. Check it out and notice that the respective atomic orbitals of the atom with more protons are lower in energy due to the greater attraction for the electrons in each orbital.
http://www.chem.latech.edu/~upali/chem281/281GRCc3.htm

Honors: some good animated links for our current "Intermolecular Forces" topic:
http://highered.mcgraw-hill.com/sites/0073656011/student_view0/chapter11/essential_study_partner.html

Here is a very good link to illustrated/animated tutorials on Bonding/VSEPR, Molecular Orbital Theory, etc. :
http://highered.mcgraw-hill.com/sites/0073656011/student_view0/chapter10/essential_study_partner.html

AP: be prepared for DAILY, three to five minute, descriptive chemistry quizzes for the foreseeable future.
Honors: be prepared for DAILY compound naming quizzes for the foreseeable future.

AP: expect a 15 minute quiz on some of the topics from the vacation; expect a Colligative Properties/van't Hoff Factor question, a Raoult's Law calculation, predictions of intermolecular forces, a "question 4" type question or two, and a transition metal complex naming question. You will have to work quickly so know your stuff...
Honors: a brief 5 to 10 minute quiz on compound naming (name to formula and vice versa) and a Lewis structure or two.

Both AP and Honors Classes are in the midst of their Bonding Unit. Though most of you can express the connection between attraction and potential energy or repulsion and potential energy, others have not expressed that connection and, instead, have developed a completely disproportionate sense of the relevance and/or importance of the octet "rule". This "rule" has about as much contribution/relevance to potential energy lowering or stabilization as an eyelash contributes to the mass of an ELEPHANT!
Before I reiterate what I said in class about "Attraction, Repulsion and Potential Energy", let me reiterate why the octet "rule" exists. Take a fluorine atom, for example. A fluorine atom tends to bond to ONE and ONLY ONE other fluorine atom to form a diatomic fluorine molecule. Why is there no stable triatomic fluorine molecule? Once a fluorine atom shares its one unpaired electron with another fluorine atom, each F atom has eight valence electrons. Big deal. There is actually MORE repulsion (which is ALWAYS energy raising) when the eighth electron enters the valence shell. This extra repulsion is compensated for A LITTLE BIT due to the symmetric distribution of the electrons about the nucleus when the s and p sublevels are completely filled (due to the symmetric orientation of s and p orbitals). This symmetric distribution of electrons causes LESS repulsion compared to the amount of repulsion when there is an asymmetric electron distribution (i.e. when at atom has 6 or 7 valence electrons). If a third F atom bonded to the molecule, the central F atom would have 9 valence electrons! There is no "room" (too much repulsion...i.e. Pauli Exclusion Principle, Aufbau Principle) for a 9th electron in the 2nd principal energy level (2s2 2p6) so the next bonded electron would have to go to the much higher potential energy 3rd principal energy level. This would have a destabilizing effect (higher potential energy = destabilizing by definition!). So, that is why most (BUT NOT even ALL!) non-metal atoms stop bonding once they acquire an octet.
To really blow your mind, let me tell you what you actually already know: a sodium atom, BY ITSELF, is MORE STABLE than a sodium ION even though the sodium ION has an octet. Didn't think that you knew that? I bet you do. Here's why: Recall the definition of ionization energy. Look at the table of ionization energies. Locate sodium. Aha, so energy is actually REQUIRED to remove the valence electron from sodium? YES! Why? Simple: the positive sodium nucleus attracts the negative valence electron! Energy is required to overcome that attraction. Why doesn't sodium lose two electrons then? The octet rule? NOPE! The second ionization energy of Na is so high because the second electron lost "feels" a Zeff of +9 AND it is in a closer (to the nucleus) principal energy level; therefore, too much energy is required for Na to lose a second electron.
You object: Why is the sodium ion so stable and unreactive? ahaaa! Sodium ions are NEVER by themselves! They are bonded (VERY STABILIZING!!!) to any and all surrounding anions!...or they are surrounded by the partially negatively charged oxygen end of a water molecule (very stabilizing) in any aqueous solution or mixture (saliva, blood, the ocean).

Now, the main reason for potential energy lowering WHENEVER a bond is formed: (write this out and MEMORIZE it if you have to)

Covalent Bonds: the (negative) electrons that are SHARED between the (positive) nuclei will ALWAYS have a potential energy LOWERING effect (whether OR NOT there is an octet of electrons i.e. in Hydrogen) because:
1. positive particles attract negative particles and vice versa
2. attraction is BY DEFINITION potential energy LOWERING!
3. relative to having a valence electron around one nucleUS, there is MORE ATTRACTION when a valence electron is shared/located BETWEEN TWO NUCLEI because there is more positive surrounding negative and vice versa!

Ionic Bonds: again, the octet rule is practically IRRELEVANT to ionic bonding:
the actual potential energy lowering effect is due almost SOLELY to:
1. the cations are the positive particles and the anions are the negative particles in all ionic bonds.
2. positive particles attract negative particles and vice versa
3. attraction is BY DEFINITION potential energy LOWERING!
4. since electrons are NOT shared in ionic bonds, each cation can have 4, 6, maybe 8 BONDS to surrounding anions and vice versa! Each individual bond is between TWO fully charged IONS of opposite charge.

That is the relationship among Attraction, Repulsion and Potential Energy. Pass it on.
p.s. as the AP class already knows, the next part of the bonding unit for Honors involves explaining physical properties of substances and mixtures. The cause(s) of attractions (potential energy lowering) and/or overcoming these attractions will be the key to EXPLAINING the rest of the unit. So, never forget, positive attracts negative and this attraction is potential energy lowering.