Week 3 Blog Entry

This week we said goodbye to stoichiometry and started to learn about the Lewis Dot structure of elements and compounds. We started reviewing for the big unit test we had on Wednesday, and did some whiteboarding in class. On Tuesday, we brought our cell phones and did a sort of iClicker type activity where we were given a question that was picked from one of the HotPots on the board, and we had to solve that question without a calculator. Once we felt like we got the right answer, we pressed that button on our phones and then Dr. J would display the distribution of choices. A lot of times, all of the choices were picked. If there was a dispute between two or three answers, we would confer as a table group and discuss the question until we all came up with a common answer. Afterwards, we would go through the question as a class and try to find the right answer. Sometimes we would eliminate some of the given choices, and other times we would run through a full stoichiometry problem using whole numbers in our heads.

 I was feeling a little uneasy while answering the problems because I’m so used to having a calculator in my hand. When I did the hotpots later that night, I was truthfully a little embarrassed when I realized how much trouble I was having when I didn’t have a calculator. I even had to Google how to perform some simple mental math functions such as long division! But I kept practicing the HotPots over and over until I was averaging at least a 90% on them. I went through nearly three full sheets of scratch paper (front and back)!

The chat room discussion at 8:00 PM was also very helpful. Although at first I wasn’t able to see the questions of my peers, it later got fixed and I was able to get see everyone’s questions and answers. The chat room overall was very helpful; I received the answers to questions I didn’t realize I had myself! Even after Dr.J left a few other students and I continued discussing the test and even answered a few of each other’s questions, too. It was very helpful discussing these questions, and it was nice to have some company too as we all studied far past 11 or 12.

The test itself was challenging, for I still felt shaky on mental math. I felt much more confident when I was completing the short answer than the multiple choice. I realized that doing the HotPots repeatedly was very helpful, because many of the questions on the tests seemed familiar. Somehow, I received a great score on the test (I was ecstatic when I saw my grade on PowerSchool) and I was pretty glad that my studying paid off. I’m definitely going to keep working hard to keep my grade.

On Thursday, we began Lewis Dot structures and completed a POGIL. I feel pretty good about it so far, but I still need some practice when drawing the models of more complex substances (HCN was a bit tough when I tried it). I just need to remember that each element needs to have a full octet of electrons, excepting Hydrogen which has a duet because its shell is full with two electrons.

Overall, I’m quite relieved that the first actual test is over. I will continue reviewing the material for this Unit throughout the days leading up to the next test so all of the material stays fresh and secure in my mind.

Week 2 Blog Entry

This week in AP Chem, we focused on stoichiometry. On Monday, we turned in our first lab report of the year done on carbon copies. Being in the Health and Medicine magnet, I was very familiar with using lab journals; we use them everyday in health and med. During the first half of the week (Monday and Tuesday), we reviewed the stoichiometry we had been practicing ever since the first day of school. We completed problems dealing with a certain amount of an atom/compound reacting with another atom/compound in excess, and creating a product.

This week I was very happy with my progress regarding stoichiometry. I was having a lot of trouble last week with these kinds of problems because I kept insisting on using proportions; they may have worked, but they don’t do a very good job of organizing my units. However, one day I sat down and did stoich problems over and over again by following the lectures online, and after one specific problem, I suddenly understood the method by which I should solve these problems. I now use the “times and a line” method whenever I am solving these kinds of problems. I now realize how great of an organizing tool the actual process is. Although the mole to mass and mass to mole conversion can be tedious along with writing the actual name of the molecule next to it, the process has really helped me cancel out my units and get the correct answer. Because I finally understand it, I really like doing stoichiometry problems now!

Later on in the week we made stoichiometry a little more complicated. We actually started limiting the reactants instead of having an excess of the other reactant. In order to find the limiting reactant (the reactant that produces less of the final product), we found the amount of product that would come out of each given amount of reactant. The reactant that came up with less of the product would be the limiting reactant. Now that I finally understood the stoichiometry process, limiting reactants was not too challenging for me.

           

Calculating yield of a reaction was also quite easy, it was a simple matter of finding how much of the product was actually made versus the amount we calculated. The equation was: (actual yield)/(theoretical yield) x 100 = percent yield.

           

We also worked on particle diagrams before and after a reaction. We were given a jar in which we had to draw the correct distribution of molecules derived from the chemical formula (after balancing it). What I had to wrap my mind around was that the jar wasn’t opened during the reaction, so the same molecules are still there, they’re just arranged in different molecules. I had to remember to draw the excess left from the reaction also. 

We whiteboarded the particle diagrams, just as we had been doing with the various stoichiometry problems earlier in the week. I realized how much whiteboarding helps me understand a concept. By viewing the thought process another student/table group took to solve a problem, I was able to compare it to my own and even adapt it, sometimes. If a mistake was made, we all went over it as a class so we would avoid making that mistake in the future. While whiteboarding, it’s okay to make mistakes.

By the end of the week, we started with empirical formulas. So far, I’m still somewhat new to the concept, but as I complete more problems, I’m starting to get the hang of it. Calculating the empirical formula using the percent composition of elements is somewhat daunting, but given enough practice, I know I can conquer those kinds of problems, also.

Overall, I’m very happy with my progress in stoichiometry this week. It has been a very rewarding learning process and I’m already surprised with the relative ease I feel with stoichiometry now. I am nervous for next week’s test, but I will practice and study everything we have done these past few weeks to ensure that I succeed!

Week 1 Blog Entry

            This week, we performed our fist-ever lab. Before the lab, however, we needed some background knowledge in order to ensure the lab went as smoothly as possible. At the beginning of the week, first we practiced some stoichiometry problems from our Brown and LeMay book. Due Monday was also a lecture quiz having to do with dimensional analysis and unit factoring. We had to memorize some conversions, such as how the prefix “nano” meant 10^-9 and “micro” meant 10^-6. We were also introduced to molarity, the equation of which is moles of solute/moles of TOTAL volume. The unit of the solution was to be given in Molars (M). Using the knowledge we got from these lecture quizzes and problems, we were nearly finished in our preparations for our lab. On Wednesday, we received a packet of the experiment we were going to perform and also a colorimeter manual. During class, we went over some of this packet and discussed what wavelength the blue #1 would absorb. At first, much of the class said that it would be wavelengths close to the blue end of the spectrum, due to blue#1 having a blue color. However, the blue#1 was reflecting this light. Since it was reflecting light of shorter wavelengths, this meant that light of longer wavelengths was being absorbed. After reading the experiment packet and writing down the procedure in our notebooks, we started the experiment the next day. We worked together as a class and recorded all of the absorbance values on the board. After the class deemed the values realistic, we calculated the averages and also the molar concentration. In order to find this value, we used Beer’s law with a given k. After we got the concentration of all of the solutions, we used the same formula to find the concentrations of blue #1 in Gatorade and Powerade. Our results showed a higher concentration of blue #1 in Powerade than in Gatorade, because it had a higher absorbance of red wavelength. After the lab, we dealt with some follow-up questions and practiced more stoichiometry. Stoichiometry is a subject that I struggle with a little bit. I used to solve all stoich problems using proportions until I realized that they made it hard for me to organize my units. Now, I’m trying to shift my style into the multiplication with canceling out units. I’m trying to practice stoich problems as much as I can, because I know that they're a very big part of finding measurements in experiments. I feel like it’s one of those subjects that once you get it, it’s something you completely understand. I haven’t really reached that point yet, but I know I’m getting close. I’m trying to tale notes on the dimensional analysis powerpoints to aid me in studying. I have some questions mostly about stoichiometry problems. In the problems I’m given, it’s usually clear what I’m supposed to find out and what I’m given. However, sometimes it’s hard for me to figure out the process that I should use to obtain the final result. I’m never sure if I added an extra step or if I’m missing one. The stoichiometry sheet we received on Friday was actually quite easy for me; I finally got the hang of how all the units should cancel out and I should be left with my desired units.

            Overall, this week has been a very exciting, albeit somewhat challenging one in chemistry. I’m sure there will be many challenges in the future, and I’m ready to face them head-on.