Chapter 3 Introduction Including Dimensional Analysis

Today in class we started off with talking about what would be on the test tomorrow. It will be similar to the first one: 35 multiple choice questions and then two show-your-work problems at the end of the test. Overall, the test will be worth around 80 points or a little more.

After wrapping up the discussion, we jumped into unit three, which was what today's lesson was about. We were introduced to the dimensional analysis method of conversion, which is quite simple, but will come in handy if you know it well now. So, make sure that you pay close attention in class for he next few days!! This method deals with multiplication and division for converting large numbers, or small numbers, into different units of measurement.

Dimensional Analysis uses what are called conversion factors. In the notes, the example was 12 donuts/1 dozen. We then took the next step and did a few sample problems. I will go over one of the ones gone over in class:

1) How many donuts are in 3.5 dozen?

--First, you should start with what you know/given. (3.5 dozen)

--Then, align the conversion factor so that the units cancel out and you are left with the ones you want. (12 donuts/1 dozen)

3.5 dozen x 12 donuts/1 dozen = 42 donuts

Since the units are dozen and it is both in the numerator and the denominator of the problem, they cancel out. You are then left with only the unit of donuts, all that is left to do is multiply 3.5 and 12. Now, the thing to keep in mind that really helps when setting up the problem is to underline the variables and pick out what values the word problem gives you. Also, even though this is a problem that is easily done in your head, when we start dealing with larger numbers and units that you may or may not be familiar with, knowing this method will make your life much easier. Another thing to remember is that when using the calculator to multiply and divide it IS IMPORTANT THAT YOU TYPE THE EQUATION IN AS SEEN, otherwise the answer will not be correct.

Mr. Lieberman went over a few more problems with the class so that we started to get the idea of this new concept and then he explained a worksheet that we picked up at the beginning of the class. It dealt with the same concepts that we worked with in class. So, for the last 15 minutes, people spent their time getting used to the method.

As everybody started to pack up, the bell rang and another day in chemistry was gone.

The next scribe is Kaitlin Y.

Naming Compounds Part II (featuring covalent and acid)

Today's class was no doubt fantastic. We started out the day with the wonderful news that the test has been moved back one day. The test is now on Friday, October 15. After the news had been bestowed upon us, we reviewed polyatomic ions, at the request of Ben. Polyatomic ions are groups of atoms that may carry a charge. Just a reminder, these are the six polyatomic ions we are supposed to know:

OH(^-) hydroxide
NH4(^+) ammonium
NO3(^-) nitrate
CO3(^2-) carbonate
PO4(^3-) phosphate
SO4(2-) sulfate
SORRY I DIDN'T GET THE FORMAT RIGHT. I TRIED MY BEST!

From there, we jumped right into the lesson. Today's lesson was a continuation of naming compounds. However, instead of naming ionic compounds, we named covalent compounds and acids. First, the covalent compounds. Here are a list of characteristics covalent compounds possess.

1) The suffix of the second word is -ide
2) Covalent compounds are comprised of nonmetals (and metalloids, on occasion)
3) The second word always contains a Greek prefix
4) The charges do not have to balance (which is awesome.)

According to Mr. Lieberman, covalent compounds are, "easier than ionic compounds because you don't have to balance all of that mumbo-jumbo..." That was pure insight. Incredibly whimsical.

To name a covalent compound, do the following:
1st word: Use prefix if there is more than one subscript number. If not, keep the same
2nd word: Always use prefix, and change suffix to -ide.
On a side note, there are no polyatomics (Prodigious!!!)

Here are a few examples of naming covalent compounds:
SiO2: silicon dioxide
NO2: nitrogen dioxide
S2Cl2: disulfur dichloride
PCl3: Phosphorous trichloride

Covalent compounds are also referred to as Binary Molecular Compounds. Unlike ionic compounds, there is no simple way to deduce the formula of a binary molecular compound. That being said, acids will be deciphered now...

Here are a couple characteristics of Acids:
1) Acids all start with H (Water is the only exception; it is not an acid)
2) Acids must be in water

To name an acid, just do the following:
IF THE ANION DOES NOT CONTAIN OXYGEN:
Change ending to "ic" and add prefix hydro
For example:
HF- Hydrofluoric acid
HCl- Hydrochloric acid
IF THE ANION CONTAINS OXYGEN:
- "ate" becomes "ic"
-H4SO4: sulfuric acid
- "ite" becomes "ous"
-HNO2: nitrous acid
To remember this, think of the joke: I'm coming down with a bad case of ateic iteous (I get it now Mr. Lieberman)

Then, we were done naming these compounds!!! After the lesson, we all took whiteboards; markers; and paper towels, and practiced naming compounds some more.

Then all of a sudden, amidst the rage and excitement, the bell rang. We proceeded to put our supplies away in a neat and orderly manner, and exited the classroom.

The next scribe is... Ben Ach!!! (no me grites)