Blog Reflection; Week of 9/22/13

Blog Reflection by Raymond Zhao hour 1

    In the past week, we changed topics from stoichiometry to Lewis structures. The first half of the week was all review from the stoichiometry ideas we learned the week before, which included doing stoichiometry with limiting reactants, stoichiometry with calculating the yield, and Empirical Formulas. On Thursday and Friday, the Lewis structure was taught. The stoichiometry ideas was related to each other because they all involved the same calculations and conversions, as described in my last blog post. The Lewis structure, which was a very new concept, is so far by itself. I did not see any connections of Lewis structure to anything that was taught these past weeks (excluding the basic chemistry ideas like the periodic table ideas and atom structure). However, I did learn some very important details for the Lewis diagram. I learned that the diagram depended on the number of the valence electrons and the element/molecule being drawn.
     What really helped me a lot was the pogils done in class. I worked with my tablemates and we talked about the important ideas. When someone didn't get an idea, others would teach them. Since students usually understand other students very well (because  students have same type of tone and not super scientific language), the ideas were taught quickly too. Excluding the pogil, lectures, and powerpoints, I also learned from outside sources. I found chemistry.about.com really helpful too. I read that "A Lewis structure is a type of shorthand notation. Atoms are written using their element symbols. Lines are drawn between atoms to indicate chemical bonds. Single lines are single bonds. Double lines are double bonds. Triple lines are triple bonds. " which summed up everything really quickly.
     Overall, my understanding of the Lewis diagram is still about a 5/10. I get the core concepts a bit, but I do not get many things about it. It may because I forgot some stuff about valence electrons. I want to know where to put the dots (valence electrons) around the atom. I need to work on understanding Lewis diagrams more. I think some more online resource searching will help me. Although my understanding is a 5/10, I would say my participation is good, maybe a 9/10.
     After this week, I learned a little bit more about stoichiometry but I learned mostly about Lewis diagrams. The Lewis diagram, although the idea still a bit foggy in my head, is the diagram of the valence electrons of a molecule or atom. Now, after last week, I am thinking about the relationship of valence electron to other properties like conductivity and reactivity.

 <------lewis diagram for chlorine

chemistry.about.com for Lewis diagrams: http://chemistry.about.com/od/generalchemistry/a/lewisstructures.htm

Blog Reflection; Week of 9/15/13

Blog Reflection by Raymond Zhao hour 1
     In the past week, we dived deeper into stiochiometry. This included doing stoichiometry with limiting reactants and calculating the yield. Also, Empirical Formulas was taught. Stoichiometry with limiting reactants was calculated by doing the conversion from the limiting reactant to the final product. Since that reactant was the one limiting, the result for that one is taken. Also, for questions that the limiting reactant is not given, you need to calculate the final mass of the product for all reactants. Then, the  reactant that resulted in the lowest mass of the product would be the limiting reactant. Stoichiometry 3 through Stiochiometry 7 all greatly helped my understanding of limiting reactants. Stiochiometry 8 taught the yield of of reactions. This meant finding doing the actual yield divided by the theoretical yield. It is important the the yield in % is not above 100. Empirical Formulas, taught by Empirical Formulas 1 sheet, was the the simplest ratio among the elements of a compound. It is found by first making all the percentages into grams by making  the total mass 100g. Then with the mass, convert it into moles and divide the moles by the smallest amount. With the numbers that result, use them as the coefficients for the ratio. 
     All these ideas all use stoichiometry. They require conversions from mass to moles or moles to mass. They are all very similar but just a little bit different. However, I found that I understood the concepts very well because I had a good knowledge of stoichiometry. The earlier stoichiometry lectures and activities all greatly help me come to a understanding of the ideas this week because it established a good base for it. Thus, I rate the difficulty regarding last week about a 7/10. This is because it was challenging, but not such much that it can't be learned. I still wonder why that the yield is always supposed to be lower than 100%. I only know that its supposed to be, not why so much. I think it might be because that the reactants all don't fully react. Since that this my only question from last week, I'd say that my understanding is 9.5/10.
     Likewise, my participation was a good 9.5/10 too. I asked question and actively learned. Because of my good participation, my understanding was good. 
     I feel fairly confident in my math capabilities for doing stoichiometry calculations  But, I still need to work on memorizing to slow down while doing my calculations because I sometimes make silly mistakes. For example, I didn't use significant digits once by accident. The concepts taught in last week have made me feel more confident about stoichiometry. I now know the concepts a lot more clearly and I know how to calculate equations with limiting reactants.  Also, I need to remember to always write down units, no matter if its the answer or during calculations. This should help greatly for fixing silly errors.
    Overall, the past week has been great. I learned a lot, including: stoichiometry with limiting reactants, stoichiometry with yield, and empirical formulas. Activities such as worksheets and white boarding greatly helped my understanding and development. I loved the time with groups to work together because it allowed interaction with each other. I feel like this helped me the most. I hope next week is just as great!

empirical formulas- good information from website!

Blog Reflection; Week of 9/8/13

Blog Reflection by Raymond Zhao hour 1
     In the past week, we did and learned many things. Some significant ideas we learned were about Molarity, Stoichiometry, Absorbance, Transmittance, Concentration, Spectrophotometry, and the calculations involved with all the ideas.  I learned that:
-Molarity means moles/1 liter and it is unit for Concentration. Molarity was used in the lab we did about Concentration and transmitted light
-Stoiciometry is a branch in chemistry that involves balancing the chemical equation by alerting the coefficients of the reactants and products
-Absorbance is the amount of a certain wavelength of light absorbed by a solution. Is is related to transmittance by the beer's law; Absorbance = -log (percent transmittance/100)
-Transmittance is the amount of light transmitted through a solution it is related to absorbance by the beer's law; Absorbance = -log (percent transmittance/100)
-Concentration is the amount of something is in something and it is measured by the unit of Molarity (moles/1 liter)
-Spectrophotometry is the science of measuring the absorbance or transmittance and calculating the concentration from it\
-M1V1=M2V2
-Beer's law: absorbance=-log(%transmittance/100)

     These ideas all are very important to chemistry. After doing the concentration and transmitted light lab, I have learned that Absorbance, Concentration, Transmittance, Spectrophotometry and Molarity are all connected. Absorbance and Concentration has a direct relationship with each other because as concentration increases, absorbance increases and vice versa. Absorbance and Concentration has a negative correlation with  transittance. Also, Molarity is used to measure Concentration, like how the concentration of the blue dye was measured in micromoles per liter. All of these ideas are all used in Spectrophotometry to find the concentration.
     Learning these ideas was so-so regarding difficulty. I felt that learning them was challenging, but not so hard that I don't get it. The lectures, lecture quizes, class disscussions, and the lab all greatly helped my understanding of these key ideas. The most challenging part was finding the mass of the blue dye in the sports drink like G2 and power aid. However, working in groups allowed me to learn how to find the mass. Now, I almost fully understand the material taught for the past week; I would rate it about a 9.5/10. The thing I have a question about from last week is about Stoichiometry and how to do it correctly because Dr. Finnan does it a special way that results in less mistakes. My participation in the past week also greatly helped my understanding because I learned many new things by participating and asking questions. I would rate my participation a 9.5/10 too. My only question is what is the actual (accurate) relationship between the concentration and absorbance in the lab? I know different classes got different results. In addition, I still need some more practice with using M1V1=M2V2 because I get confused sometimes.
     After this week, my thoughts on the characteristics of solutions and light changed. In the past, I would never think about the transmittance or absorbance of a solution, but now i do. This is because I learned new ideas through the lectures, lecture quizzes, class discussions that we did. Each of the activities added to my knowledge and the result was me understanding about all of the required material.

This is the chart of concentrations and absorbances from the lab

 

This is a link to the lab introduction and procedure

This is a link to beer's law