Dimensional Analysis

In class, we took notes over dimensional analysis. Dimensional analysis is when you convert one quantity to another. As we performed the equations, we also had to recognize how many significant numbers were in it in order to apply that number of significant numbers to the overall answer. One rule to remember is that when an exact quantity is in the problem, it is considered infinite, and is not counted as a significant number. An example of an exact quantity is 1 inch= 2.54 centimeters. Below, I posted a couple examples of dimensional analysis that we did in class. In the picture, you can see where we crossed out units of measurement as we worked our way through the problem. Also, there is a link of practice problems below the picture that I will use to study for the exam.

Dimensional Analysis Quiz with Conversion Charts

Quiz Relfection

Today we took a quiz over our measurement unit in class. I think I did okay. However, there were a few questions I wasn't too sure about, and I began to second guess myself. I especially doubted myself on multiplying, dividing, adding, and subtracting significant numbers. In  addition, I had trouble with a question asking about a pure substance. So, I went to find more practice questions online that combine multiplying/dividing and adding/subtracting with significant numbers, and a page explaining more about pure substances, elements, and compounds. I plan on looking back at these links as I study for our upcoming exam.

Chem Team: Elements and Compounds

Practice on Significant Numbers in Operations 

Practice Problems on Working with Significant Numbers

Mole

Over fall break, I sewed a stuffed mole in honor of Mole Day. On the paper with the patterns for the stuffed mole, it briefly explained what a scientific mole was. However, I decided to research the mole more to fully understand its significance. The Vision Learning website was very helpful. It explained how  a mole is simply a word that represents a measurement. It compared it to a "dozen" standing for 12. The website furthered explained that a mole is equivalent to 6.02 x 1023 and stressed its greatness. In addition, the website described how "A sample of any element with a mass equal to that element's atomic weight (in grams) will contain precisely one mole of atoms (6.02 x 1023 atoms). So, if an element had an atomic weight of 6.00 g., that amount of the element is equivalent to one mole of that element's atoms. I found this website very interesting and detailed, helping me fully understand what a mole is through examples and history. 

Vision Learning- Mole

http://www.jabebo.com/Scienceset.htm

Pre-test Reflection

Today in Chemistry class we completed the pre-test for our measurement unit. I did not know the majority of the concepts on the test. However, I think I will be able to perform all problems correctly once I know what certain terms mean and how to convert measurements. Two concepts that kept appearing on the test were significant figures and converting measurements, such as miles to km. Below, I found two measurement conversion charts that I can look back on when I study. One converts only length and the other converts a variety of measurements that will come in handy when I'm converting measurements for my Last Meal Project. In addition, I included a couple websites explaining what significant figures are and how to determine which digits are significant in a measurement. The second website also has practice problems for adding and subtracting significant figures.

http://www.math-salamanders.com/measure-conversion-chart.html

http://www.almanac.com/content/table-measurements

Khan Academy Video Explaining Significant Figures 

Tutorial on the Use of Significant Numbers with practice problems

Aspirin Lab

Buchner Funnel

Set- up

Scale

The past two days, my lab partner and I synthesized aspirin. First, we successfully passed the pre-lab. Then we went back into the lab and collected our materials. We mixed Salicylic acid, Acetic anhydride, and Sulfuric acid in a Erlenmeyer flask. We were careful not to breath in the fumes. Next, we placed the flask in a hot bath for about 15 minutes and let it cool for 3 minutes. Sadly, while the solution was cooling, we accidentally let it tip over, and was left with about half of what we started with. Then, I carefully added ice cold water to decompose the excess Acetic anhydride and start recrystallization. Over night, the solution crystallized and we put them in a Buchner funnel with ice cold water the next day to remove any residual crystals. After this, we finished the lab by pulling out the left over crystals from the funnel on filter paper to dry on the lab counter. We will continue to use our product once we get back from fall break. Below are some pictures of the lab and equipment.

Crystals the next morning

Crystals the next morning

 

Ending Product

Unit 2 Test Reflection

Today, our chemistry class completed the atomic structure and radioactivity unit by taking the final unit test. Throughout the past few weeks, I have learned several things about average atomic mass, atomic and mass number, radioactivity, fission and fusion, and the scientists who discovered the structure of an atom. I believe that I was well prepared for the test we took today. There were only a couple questions that I wasn't sure about. One of the questions had to do with half-life. Half-life is the only concept that I am a bit shaky on. So, before we move on to the next unit, I will make sure to practice more half-life questions until I fully comprehend them. Other than that, I think I did well and hope to do just as well in the next unit!