Murder Lab Day 2

Day Two consisted of weighing the dry filter paper that contained the solid from the reaction. The solid was a pea green powder.

After weighing the filter paper, we subtracted this mass from the mass of just the filter paper to figure out the mass of the solid. Then, we calculated the molarity of this substance and found out that it was roughly 0.07 M. To figure out the identity of the unknown substance, we knew that it must have been silver nitrate because when silver nitrate combines with sodium carbonate, it should make a solid, which is exactly what happened in lab. The 0.07 molarity matched Mr. Green's description, as he was found with traces of silver nitrate with a molarity between 0.05 and 0.15 M.

Murder Lab Day 1

The murder investigation lab seemed to be a very interesting lab. I love the idea of solving a a mystery while incorporating chemistry into it. It gives a taste of what forensic investigators do in reality. Today's task was combining an unknown solution with sodium carbonate in a beaker. Both reactants were clear, but when combined, the product was a milky white substance.

Then, we poured this substance into a funnel with filter paper inside an empty Erlenmeyer flask to collect any solid. While letting the liquid drip down into the flask, I noticed there was a sand-like substance forming inside the liquid, showing that the reaction definitely produced a solid. Thus, it can be inferred that the unknown substance is silver nitrate, due to the fact that it should produce a solid when reacted with sodium carbonate based on solubility rules.

Murder Mystery Lab?

Today we started a lab where we are the chemists out to solve a murder staged in the common board game of Clue.  I was initially overwhelmingly confused, however, I was eventually able to figure out that we were mixing the poison that killed Miss Scarlet with sodium carbonate, and the result of this reaction would tell us whether the poison was potassium iodide or silver nitrate.  If a precipitate forms (which mine did), then the poison is silver nitrate.  However, if it doesn't form a precipitate, then the poison is potassium iodide.  Of course, this is only the first step.  To determine who had the murder weapon/poison, we next have to determine the molarity of the solution of the silver nitrate/potassium iodide.  I haven't gotten the details of this part 100% figured out, so I'll wait until next post to tell you about that.  One thing I learned this lab is to not mill around if you don't know what to do, just ask.  As I said earlier, I didn't really know what I was walking into, and if I had started by asking our teacher what on earth we were doing, I might have been able to finish filtering my solution.

In regards to the lectures we've seen so far, the lessons aren't too bad; it's just hard going through them so quickly, however, once I made the time to really learn the subjects, it hasn't been that difficult.  The only subject that confused me was the aliquot, but www.ausetute.com helped me out to understand it.

I'm still somewhat worried about the quiz, so I found some good websites for a little help:  www.youtube.com (a crash course chemistry video that explains dilutions, molarity, and polarity), www.youtube.com (a crash course chemistry video that explains more about polarity, molarity, and mass percent), and science.widener.edu (generates an infinite number of molarity problems and even varies whether you are given information on moles, molarity, or volume).

Getting back into the "funk" of things

While technically we started this unit a week ago, I'm betting most of us didn't look at the notes, do practice problems, or anything resembling normal unit work.  Today though, we learned about molarity.  It was a nice lesson to start the unit off on given that it wasn't too hard.  Regardless of the fact that I thought I had gotten the hang of it, I did the book work.  While I did it, i found an interesting little method that really worked for me.  Whenever I wasn't quite sure how to start off a problem, I wrote down the molarity expressed in mol/L.  For some reason (I think it's that it makes it look just like a regular dimensional analysis problem), this gets my brain in gear so that I can see in my head how the rest of the problem is supposed to run.  This got me the right answer every time because all that it does is flip the order of multiplication which we all know doesn't affect the product.

For more practice, I used www.chemteam.info which has 35 questions on molarity with full solutions.  To better understand the concepts, you can also use phet.colorado.edu which is a good way to learn if you're more of a tactile learner.  It also covers other subjects like saturation (and it's actually a little fun to mess around with).