Thursday, September 30

Meet the Elements, by They Might be Giants, was the first thing to greet us after entering Mr. Henderson's classroom. After the song ended, Mr. H said that today's lesson would be about forming the families of the Periodic Table. He then went over tonight's homework: a WebAssign on the PT due Friday and write ups on Labs 3 & 4 due near the end of next week.

After that, Mr. H quickly reviewed the periods and groups of the PT, organized by atomic number and chemical properties respectively. Then, we filled page 4 of our packet which covered the physical & chemical properties of certain elements.

Number 8 was reminiscent of the Mendeleev for a Day Lab as we had to organize the elements by atomic number and chemical property. Family # 1 included Aluminum and Gallium because 2 molecules of either and 3 molecules of Oxygen form a compound: Aluminum/Gallium Oxide. In addition, only one molecule of either and 3 molecules of Chlorine form the compound Aluminum/Gallium Chloride.

On the other hand, Family # 2 includes Beryllium, Magnesium, and Calcium. Only one molecule of any of the 3 and one molecule of Oxygen form Beryllium/Magnesium/Calcium Oxide. Plus, only one molecule of the 3 and 2 molecules of Chlorine are needed to form Beryllium/Magnesium/Calcium Chloride.

After organizing the elements into columns, they only needed to be rearranged into rows based on atomic number. The easier task, I'm sure.

The next thing Mr. H showed the class was last night's blog entry, it was quite impressive. Then he went over how to write up Lab AMI 4, the key point being that it be organized.

We skipped over to packet page 17, covering the specific groups in the Periodic Table. His word of advice? "Get to know your PT."

Probably the highlight of the day for most of the students was the "Potassium video." An educational video clip demonstrating how this particular element reacts violently with water. A lot of people found it funny and, well, just see for yourself.

Well, no one can say science is boring. Mr. H promised us the next day he would be dumping a chunk of Sodium, should be interesting to see it in person. Approaching the end of class, we concluded with page 3 of our packet.

(Pretend page 3 is here.)

For the groupings: AM=Alkali metals, AEM=Alkali Earth metals, and ML= Metaloids. Well, that's all for now. See ya tomorrow!

Wednesday, September 29

Today, Mr. H started off the class by telling us to wipe down the lab tables with a wet paper towel after a chemical lab. He said that we should do that every time we work with chemicals in order to have safety precautions. After that, we admired Natasha's blog that she did the night before. He reminded us that there is the site called DropShots and it is where all of the pictures go from a lab or a demo that day. If you are the scribe, then you can use it to get some pictures.

He then told us to get our lab notebooks out. We were to do Mendeleev for a Day Lab (AMI4) and the Oleic Acid Lab (AMI3). He summarized what we were supposed to do while we wrote down the purposes of the labs.

He told us to find a partner, or if we preferred, work alone to do this lab. Mendeleev for a Day is a lab that required the sheet that was given to us yesterday. It had 20 squares and we were supposed to cut them out for class. Each square had the Atomic Mass, the melting point (degrees C), the boiling point (degrees C), the number of O in oxide, and the number of Cl in chloride. Those were two chemical properties of the element and also two physical properties. We were to start putting the squares in order from least to greatest according to the atomic mass in a row. From there, you were to look for common points, and to move them into columns. More specifically, the number of O in oxide and the number of Cl in chloride. These columns are called families. Mr. H gave an example of his own family. Mr. H's father had a specific way of walking. If you look at him and then Mr. H, you wouldn't see a difference. He also gave us an example of the males in his family get gray hairs around their 30's. He told us this because it relates to the lab. Families have similarities and in the periodic table, the columns have similar properties, putting them in the same "family." Anyways, after we put them in columns, we taped them into the Data section in our lab notebooks. Remember to put the squares on the paper landscaped. This provides more room for the squares. Or, you could put it across two pages in your lab notebook like this (left):


The Oleic Acid Lab is much different. We were working with lycopodium powder. Lycopodium powder is made out of a type of moss, and can trigger some allergic reactions, if you are allergic. Oleic acid does not mix with water, but dissolves the lycopodium powder. The first thing we did was put our safety goggles on. At our lab stations, there was already a yellow tray with water. We were to gently put the lycopodium powder on the surface of the water until it looked a little filmy. Mr. H did a little demonstration on how to do it:
This is how it looked like (bottom):

Then, when we were ready, Mr. H came around each lab group to put a drop of oleic acid into the tray. What we observed was that the oleic acid dissolved in the lycopodium powder, but in the process, it spread out on top of the water. It had a large diameter. This is what the oleic
acid looked like after Mr. H put it in the tray. As you can see from the picture, it dissolved the lycopodium powder and made the water easier to see through. There is no more of that filmy look.

Mr. H gave us a sheet of paper to record our data in, and the number of drops/mL of .500% oleic acid solution is 32. We decided that the average diameter of the drop was 14.8 cm. You are to find the surface area, height, length, width, volume, and mass. For homework, we are to finish the data sheet and the conclusion/discussion for both labs. See you tomorrow!

Tuesday September 28, 2010.

Today Mr. Henderson started out the class by reviewing last nights scribe's blog. He went over all the plus points of it and went into further detail on how the blog reviewed what we did in class the previous day. He also talked about the 5 postulates. He then told us a little about what we were going to do today in class. Today in class our main goal was to learn about the atomic structure, atomic number, and the mass number.He then started to review page one in the packet. We went over most of it yesterday but we finished up today. We talked about how the Dalton theory of an atom was just a circle with the element name inside. There was no proposed structure to it. The JJ Thomson theory of an atom was that it looked like plum pudding. The Rutherford theory was that positive charges were concentrated in the nucleus which was in the center of the atom and then the electrons surrounded the empty space outside the nucleus. Bohr's theory of the atomic structure was that electrons are in orbit around the nucleus. Bohr's structure also only worked for hydrogen.The picture on the left shows these structures.

Before we continued our lesson on the atomic structure, Mr. H gave us a demonstration on how the cathode rays work. He gave us a little background information on who and how it started. In 1896 British physicist J.J Thomson showed the rays were composed of a previously unknown charged particle, which was later named the electron. The first picture shows the cathode ray empty. After putting some electricity conductivity you see a neon greenish light go through the tube. The second picture shows what happened when the electricity is conducted through the cathode tube and a magnet is put on top. The ray is reflexed to the top when the positive side of the magnet is put up. The third picture shows the same thing as in picture two just a variation. Picture number four is what the cathode ray looks like when the negative side of the magnet is put above it. Picture five is just what the cathode ray looks like when electricity is conducted through it.

1. 2. 3. 4. 5. 6.

After the completion of page one, and the demonstration, Mr.H gave us a little lesson on the atomic structure and there were notes on the board so we could follow along. The notes basically summarized everything that we needed to know to do page number two. The atomic number is the number

of protons plus the number of electrons. It is the identifying property of what the element is. The mass number is the number of protons plus the number neutrons. The mass number is on top and the atomic number is on the bottom as showed in the picture. On the other side of the atomic symbol there would be either a +, -, or no sign there. This determines the charge of the electron and the over all change. It also determines whether it is a positive, negative, or neutral charge. The symbol and the subscript go together. We then continued to talk about isotopes. Isotopes are different types of atoms of the same chemical element, each having a different number of neutrons. They also differ in mass but never in atomic number. The number of protons is the same because that is what characterizes a chemical element. We took the element carbon as an example. On the periodic table when you see the element carbon, you see its atomic symbol, the number of electrons its has, and you see a number at the bottom called the super script. The super script is the average of the mass number of the atomic element. For carbon on the periodic table it shows 12.01. This means that the most abundant isotope of carbon has a mass of 12.01. Mr. H then explained the different between an Ion and an Atom. An Ion is a charged particle while an atom is a neutral particle.

We then turned to page to and completed the chart. The chart helped practicing important skills such as knowing how to find the atomic number and the atomic mass and the number of protons and neutrons and the number of electrons of any given element. Here are the answers to the chart.

The last ten minutes of class we reviewed our unit one tests. Mr. H went over the frequently missed problems. He went into much detail on why these problems were wrong. Toward the end of class he passed out a sheet of paper called the "Mendeleev For a Day." There are 20 squares on this paper that you need to cut out for tomorrows class to play the game! Cant wait!

Monday 27, September

To start off class, Mr. Henderson clarified any information that we may have missed concerning the TLC and the tutors there. He told us that if we were struggling in Chemistry, we could visit the TLC for help from actual science teachers or AP students as well as visit Mr. H early in the morning. We then moved on to the subject of the day; The history of the atomic model and the various scientists that helped create each one in their respective times.

On Pg. 15 in your chemistry Unit2 packet, there is a very general history concerning the atomic model starting with Dalton. However, Mr. Henderson told us that the first ever recorded theory concerning the atom dates all the way back to Ancient Greece and a philosopher by the name of Democritus. Democritus argued that he could chop a piece of papyrus into halves and halves and halves until he would reach some sort of building block that could not be broken down any further into a smaller or simpler form. He called these building blocks atomos and he believed they made up all matter. Democritus had no idea how accurate he actually was, but for nothing more than an educated guess, this was a remarkable theory. It is important to note that Democritus never actually tested this theory using science and therefore, he is regarded as a philosopher rather than a scientist. It was not until the late 1700's and early 1800's that the scientific revolution ushered in a new wave of interest in the field of atomic structure.

The next man to take a stab at an accurate atomic model was John Dalton. This scientist used the scientific method of developing a hypothesis and testing it to form a theory. He called these theories postulates, or basic rules. The five postulates that Dalton formed are as follows.
#1) All matter consists of atoms

#2) Atoms are indivisible (cannot be broken down any further)

#3) In a chemical change or reaction, atoms simply rearrange themselves but never turn into any other atoms. This is demonstrated in the picture below in which Hydrogen and Oxygen combine to form H20.



#3 (continued) Also, atoms never gain or lose mass in any way during any chemical or physical change.

#4) Compounds have a determinable amount of atoms and always have the same amount of each atom.

#5) Law of Constant Composition. All Compounds contain the same amount of each atom no matter where the compound is found or under what circumstances.

These 5 postulates are still seen today as a basic level in understanding the structure of atoms and compounds. Dalton never did create a finite model that he believed was what an atom might look like. He did however represent an atom as a circle with a symbol on it, such as H for Hydrogen.

Proceeding John Dalton, J.J. Thomson was at the forefront of the atomic model issue. J. J. Thomson believed that atoms did not only consist of alpha particles, but also possessed some other feature. By separating the alpha particles from a beam of light and firing this beam, known as a cathode ray, through a glass tube with positive or negative plates on either side Thomson was able to test this. After seeing the cathode ray bend towards the positive plate, Thomson was able to determine that the are other particles that make up an atom and that they are negatively charged. Thomson called these negatively charged particles electrons. This lead Thomson to relate his atomic model to the favorite desert of England at the time, earning it the name The Plum Pudding Atom. Thomson believed that atoms consisted of moving negatively charged electrons that are immersed in a sea of positively charged stationary particles. The model looked something like this picture, with the dots being electrons and the red material being the positively charged "sea".





For many years, A scientist by the name of Ernest Rutherford studied this model and debated it's accuracy. To test the Thomson models validity, Rutherford set up an experiment in which he took a thin (only a few hundred atoms thick) piece of gold foil and placed it in a container which had sensors on either side while shooting a stream of atoms in its direction. If Thomson's model was correct, the atoms should have gone through the gold foil with no problem and triggered only the sensors on the other side. What Rutherford found was that although most of the atoms did behave this way, 1 out of every 10/20,000 deflected off of the foil and reflected back at an acute angle. Rutherford was quoted saying "Its as if you shot 20,000 bullets at a tissue with most of them going through the tissue with no problem, but 1 out of every 20,00 of those bullets would reflect back at you!" Rutherford was amazed at this and determined that atoms were not full of positive particles, but were rather made up mostly of empty space with 99% of its mass concentrated in its nucleus, earning his model the name The Empty Space model. Rutherford still did not know how the electrons were distributed across the atom, leaving his model still somewhat inaccurate

Finally, one of Rutherford's colleagues, Niels Bohr, measured light energy to more accurately determine where the electrons would be relative to the nucleus of the atom. By measuring each layer of electrons of an atom and observing the light they emitted, Bohr was able to establish the general amount of electrons and their area relative to the nucleus. The downfall to Bohr's method was that once he began getting into the atoms with more electrons, such as Gold, his estimates were off by more than 20-40% at times. However, Niels Bohr was able to develop an atomic model, known as The Planetary Model.

Neils Bohr called it this because he thought that the electrons orbited the nucleus much like moons orbit a planet. This is the most accurate of all the depictions discussed so far.

To wrap up the class, Mr. Henderson gave us the answers to page 15 which are as follows:

1: b
2: d
3: c
4: a
5: c, b, a

We also drew sketches of what each scientist, (Dalton, Thomson, Rutherford, Bohr) believed
that atom looked like and those can be seen by asking me or any other student before or after class. Tomorrow, we will incorporate verbal explanations with these visuals models to describe each scientist views on concerning the structure of an atom.

Friday, September 26

Today’s class was very . Mr. Henderson was not in class today, so we had a substitute. Our class began when Mr. Doody from the TLC came to talk to our class. He told us about how great the TLC is for helping with chemistry, as well as all other classes offered at GBS. Mr. Doody also advised us to frequently use the textbook as a study tool and not to spend more than ten minutes on a problem. We then went to the computer lab to do the Rutherford Simulation Lab, which is a computer activity. We were given a sheet that gave us all of the directions for the lab. We went to the website http://phet.colorado.edu/simulations for the lab, which was completed in our lab notebooks. After completing this lab, we went to http://www.blogger.com/chemthink.com to do the atomic structure tutorial. After completing the tutorial, we filled out a table on the lab sheet.

The answers should look like this:

Once we completed the lab, we were supposed to cut the table and put it into the left side of our lab notebooks. For homework, we had to finish the lab if we had not already in class.

Today’s class was very productive!