Half Life

In this unit we learned about how to calculate half lives. Half lives are the time it takes for half of a sample of atoms to decay to a stable form. For example, in the Forensic archaeology lab, we calculated half lives of the radioactive atoms in a sample. The formula for calculating half lives is listed below. Half lives can be used to trace the amount of time a sample/remain has existed. That can be used in crime scene investigations to determine how long a person has been dead. At first, when we started this section I was actually really confused and was confused especially when we were given word problems. However, the lab that we did (the forensic archaeology lab) helped me solidify my skills.

http://www.m2c3.com/chemistry/VLI/M3_Topic2/la_06_13.jpg

Useful links:
http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/halfli.html
http://www.coolmath.com/algebra/17-exponentials-logarithms/13-radioactive-decay-decibel-levels-01

Forensic Archaeology lab

In this lab, we used paper instead of radioactive molecules to get a feel for how half life works. This lab also helped us practice calculating half life and understanding what the calculations mean and why the specific formulas are used. The formula to calculate half life is: # of radioactive atoms initially/ 2^half lives. To calculate backwards to determine the original radioactive mass from the half life mass, we use the formula # of radioactive atoms*2^half lives. After calculating the data from this sample experiment, we use the collected information to apply it to the real world problem given and use the information of half life decay to determine how old in years an artifact (body) is. I think this is a good experiment that not only helps us practice calculating half life, but we also understand how half life calculations are used in the real world. I think applying acquired knowledge from lectures to real world or hands on activities really helps me understand concepts better.

Quiz

I think I did pretty good on this quiz. This unit, I am doing slightly better because I am getting more used to this class and getting more accustomed to how to study. This unit seems to consist more of the math skills that Chemistry is known for. I hope to do well in this unit because math is one of my strengths. This quiz reflects my understanding so far in this unit and I feel like I have a pretty good understanding of the material so far. I was also able to raise some of my grades in the previous objectives in the nomenclature unit. I am glad that I still remember that unit because I know that is a very important part of chemistry/this class. To prepare for the upcoming unit test, I need to practice with practice problems from schoology and from the textbook. That is how I studied for this quiz and I think it really helped. Therefore, I plan on using this study method more often.

Mass of Subatomic Particles

In today's lesson, we learned about masses of subatomic particles. First, we learned the labels of an element in a periodic table because that is what we use to determine a lot of things in this unit. (see picture below). The letters in the middle are the Element symbol, the name below is the element name, the number at the top is the atomic number (the number of protons and electrons), and the number at the bottom (usually a decimal) is the average atomic mass. Then we leaned the notation for recording different isotopes of an element. Which is done by using the element symbol and two numbers on the right (see picture below). The number on the top is the mass number and the number on the bottom is the atomic number (number of protons/electrons). The number of neutrons can be determined by subtracting the atomic mass by the number of protons. Then, we learned about calculating average masses and percent abundances of isotopes. The formula for calculating average atomic mass is (mass of one isotope)*(% abundance)+(mass of other isotope)*(%isotope). This same formula can be used to figure percent abundances when average mass and isotope masses are known.

Element on periodic table labels

picture

Isotope notation

picture

Extra resources:
calculating practice: http://www.chemteam.info/Mole/AverageAtomicWeight.html
http://blog.wsd.net/hewaite/2014/10/ 
http://ehschemcorner.blogspot.com/2012/09/the-atom-isotopic-notation.html 

Atomic Theory and Nuclear Chemistry

The notes that we took today seemed more informational than the last unit. The last unit felt like it was more of application of rules. Today, we took notes on Dalton's Atomic Theory, Law of Constant Composition, JJ Thomson, Rutherford's Gold Foil Experiment and the current Atomic Model (the cloud model). To remember each of these scientist's discoveries and importance, my friends in other chemistry classes made acronyms. Knowing those acronyms, its already easier for me to remember these scientist's roles than it would have been if I had just tried to memorize them today. The activity that we did at the end of the notes (the obscur-tainer lab) today was also fun. There was a small black dish with a shape inside and a small metal ball; and we had to roll the ball around to guess what the shape was inside. This kind of relates to how Rutherford did his Gold Foil Experiment because he used other elements (ex: the metal ball) to bounce off the gold (the shapes) to figure out unknown properties of Gold.

Gold Foil Experiment (Rutherford)

http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_04/FG04_04.JPG

Thomson's Cathode Ray experiment

                                                                                                                               http://www.physicsoftheuniverse.com/topics_quantum_atomic.html

Extra resource:
https://www.boundless.com/chemistry/textbooks/boundless-chemistry-textbook/atoms-molecules-and-ions-2/history-of-atomic-structure-32/john-dalton-and-atomic-theory-197-6138/
http://www.physicsoftheuniverse.com/topics_quantum_atomic.html

Unit 2 Pre-test

The pre-test that we took on Tuesday was really difficult. I didn't know the majority of the answers. However, on some of the questions, I was able to use prior knowledge of chemistry to make an educated guess. Also, as I continued I recognized that there was probably a pattern in the questions with the atomic masses and etc. The test also included sections where I had to read and answer questions about graphs which wasn't as hard as the rest of the test because we were able to use prior skills of reading scientific graphs.

Frontier Chemistry Reflection

I really enjoyed this project regardless of how stressful it was because it was an interesting real world application that we often look for when learning in school. Now, every time we go out I notice these plants that we have been identifying for this project and it makes me feel like I have learned something in school that I can actually use in the real world. Now, if I AM put in an emergency situation like this out in nature, I can use these skills and information I learned to help someone who is hurt. We also started identifying the active chemical ingredients in these plants so maybe when we come upon these ingredients in the future in the class we can identify what these ingredients may act against. This project required a lot of research and I had to know what sources were credible and I had to know how to find the information I was looking for. This was even harder because you couldn't just google the information and find it as one of the first few results. It took me a while to figure out how to find the information I need quickly and effect-fully. So, if I had to do this project again I might be able to find my information faster and be able to find credible sources.

Unit 1 Reflection post

From Unit One I learned how to read the periodic table of elements which helps you name compounds, acids, and polyatomic ions which was the main focus of this unit. At first, when I took the pre-test I had no idea what I was doing. However, the next day we started learning about the material and it started making sense. I really like this unit because even though it seemed like a lot that we were taking in at a really fast pace, as we moved on, we made our knowledge of the previous information stronger. Memorizing the polyatomics was probably one of the hardest parts but I used quizlet to name the compounds by looking at the chemical structure at first. Then, when I had mastered that, I moved on to labeling the chemical structure by looking at the name. As I moved on, it started making logical sense (such as when -ite and -ate was used) and it became easier and I was able to identify them faster. Then, when we learned naming acids, it was simple and quick to learn because we had a strong base of all the other topics and it was just a matter of application.