Saturday, September 18, 2010

Chapter 4 Concept Review


        I feel that I understood a lot of the information and material that we covered throughout Chapter 4 "The Structure of the Atom". First we started off learning about the philosophers. Many of the early philosophers were Greek including: Democritus, Aristotle, and Dalton. Democritus's ideas were definitely a beginning point. He believed different kinds of atoms had different size and shape, different properties of matter were due to different atoms movements, and matter was composed of empty space through which atoms traveled. This ideas were rejected by Aristotle who didn't agree that empty space "nothingness" could exist. Later on Dalton created his atomic theory. He said all matter was composed of extremely small particles, all atoms were identical, atoms couldn't be created, divided, or destroyed, and in chemical reactions atoms combine, separate,or rearrange. These ideas I understood very well. I also see how the theories have changed over the years with advancements in knowledge & technology. One thing I'm having a hard time grasping is how small an atom really is. In our books it gives an example: In 2000, the world population was estimated at 6 billion. Atoms in a penny is 5 billion times as many atoms in a copper penny than humans in the world! That is a hard concept to grasp!
         I really liked the hands on work with the Cathode Ray Experiment. It was easy to see how the Cathode Ray travels to the Anode side of the tube. I understand how if there were magnetised plates on both sides of the tube electrons could have easily been discovered. From here, Millikan discovered the mass of an electron & that just goes to show me how strong these particles are. They are 1/1840 the mass of a hydrogen atom. If one electron is equal to one proton that just shows its strength when their masses are compared. Then, came Rutherford's discovery of the nucleus. It makes sense how the nucleus was discovered because the alpha particles all went through except where they were deflected by the nucleus. This led to the theory of the nucleus being positive which was later turned into the nucleus is a mix of protons & neutrons. I definitely understand how all the particles work. I understand their mass, placement, charge, & importance to every atom.

        Atomic number, mass number, and average atomic mass number make sense to me. Atomic number is the number of protons a atom has along with the number of electrons it has. Mass number is the total number of protons plus neutrons in an elements nucleus. Average atomic mass number makes sense to me, but it is not quite as clear as the other two yet. I understand how it works & I can do the problems fine, but my mind is still learning to process it. Average atomic mass number is a weighted average mass of the isotopes of that element. Isotopes are when the same element has the same atomic #, but a different mass # because it has more neutrons in its nucleus. I can figure out any of these numbers or any element if given the correct information. I understand all the parts of an atom & I feel very confident in the material I learned throughout Chapter 4.

Thursday, September 9, 2010

Separation Techniques

      Our chemistry class had a few days where we did a separation lab. We focused on separation, distillation. filtration, chromatography, and magnetism. My group did a project where we had a mixture of salt, sand, and iron fillings. First, we used a magnet to separate the iron fillings from the sand and salt (magnetism). We went through our mixture multiple times to make sure that we had all the iron we could collect & all the sand & salt was separate from the iron in the original container. From here we took our salt and sand mixture & added warm water to separate them. We knew salt was soluble so that was one way we could separate our mixture. Then we used filtration paper to separate the salt water from the sand (filtration). This caught the sand & let the salt water into another pan where it was its own mixture. We let our sand dry & our iron was separate too. If we wanted to separate and time had allowed we would have followed through with a distillation process to extract the salt from the water. Then we would have completely had 3 separated substances. Obviously, we lost some countable mass due to moving & touching our mixtures, but if this was done in a closed lab none of the mass would be lost because the law of conservation of mass.
     Another lab we did was on chromatography. Chromatography separates mixtures due to their absorbency. We used water to separate different types of ink into different colors due to their absorbency. These showed up as water absorbed up a paper towel & into filter paper onto the different inks. Some inks spread and others did not.
     A few other techniques that were used by different groups included distillation and separation. Distillation is a process of extracting  substances from a mixture (physical). Heat boils water or a mixture & some properties of this mixture are carried over to the other flask through a tube. In the tube it condenses the mixture with cooler air and the newly distilled product is in the receiving flask. Separation is simple. Separation is completely physical change & all that happens is two object such as rocks & sand are moved into two separate piles without much hard work.
     These are some different types of techniques to separate mixtures that we worked with in my chemistry class. Hopefully I explained myself well.. if you have any questions just ask. :)