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.