Chemistry 2A Week 6 Review

     This week in Chemistry was a pretty busy one. With multiple experiments and the celebration of mole day, week 6 in Chemistry 2A was a fun one.
     On Monday we started things off with Dr. Finnan showing us the power of the tesla coil. I thought it was really neat how we could actually see the electric current traveling through the air.

 

     Dr. Finnan showing us the tesla coil

 

 

      On Monday we also learned about Thomson's model of the atom, plum pudding. Plum pudding is described as thousands of negatively charged corpuscles that swarm inside a sort of cloud of mass less positive charge. Thomson came to this conclusion through a series of experiments. In his first, he discovered that when he bent a cathode ray (charges of negative electricity carried by particles of matter) with a magnet, not as much negative charge came through. In his second experiment, he realized that charged particles will normally curve as the move through an electric field, but if it's surrounded by a conductor, this won't happen. In his final experiment, Thomson found out that the mass-to-charge ratio for cathode rays turned out to be far smaller than that of a charged Hydrogen atom.
     Thomson's experiments challenged the ideas that scientists believed about electricity. His experiments were ground breaking and opened up many new opportunities for research on electricity and charge.
     On Tuesday, we conducted the sticky tap lab. We charged up pieces of tape, the top and bottom, and tested to see what they attracted.
     Sticky tap lab setup

    At the end of the lab, we discovered that opposite charges attract, neutral attract with positive and negative but not other neutrals, and that positive on positive and negative on negative repel. Through this experiment we furthered our understanding on charges and discovered how they attract each other. In addition, through the Sticky Tape Post-Lab Worksheet, we discovered that electrons can move through metal objects, and cannot move through non-metal objects, but rather shift over to avoid the charge being applied.
Picture of our diagram explain how electrons can move through metals

 Also, I understand our conclusions we got from this lab.
     On Wednesday, we conducted the conductivity lab. We tested the conductivity of many different materials and recorded data in our notebooks.
Example of conductivity testing station

     After we tested everything, the class tried to categorize what was conductive and what wasn't. This I had trouble with. Through class discussion, I began to understand it. Conductors conduct because of little resistance to the flow of charge that goes through them. Metals allow electrons to move through them while ionic conductors allow free ions (charged atoms) to flow freely.
This whiteboard answered many of the questions I had about categorizing conductors.

I believe I have a pretty solid understanding of categorizing conductors. The key is that a conductor must give little resistance to the flow of charge.   
     On Thursday, we began the Electrolysis of CuCl2 (aq) lab and recorded data in our notebooks. When we plugged in the cables, we discovered the positive side began to bubble and smell like chlorine. There was no smell and no bubbles on the negative side. Later in the hour, w checked up on the experiment and found that the graphite on the negative side began to turn pink at the bottom. We waited until Friday to see the final results of the experiment.
     On Friday, we revisited the experiment, and found the following images.

 

 We concluded that copper was on the negative side and chlorine on the positive side. The electrons were traveling through the graphite, not the water. The copper ions were being converted into neutral metal, hence the pinkish brown trail beneath the graphite.
Example of white-boarded conclusions

 I sort of understand these conclusions. I get that electrons can't travel through water but I still don't really understand why the copper ions are being converted into neutral metal. Is it because copper and chloride ions break up in water?
   On Friday we continued work with Unit 6 Worksheet 1. I understood how to draw the particle diagrams for all the compounds given. The 3+ and 3- stuff confused me. I get that each compound has to be neutral. Like Ga2O3 is Ga+3, Ga+3 and O-2, O-2, O-2. It's Ga+6, O-6. Those add up to be zero, I get that. What I don't understand is how we found Ga+3 and O-2 in the first place. I hope to find out more next week and I will ask questions so I better understand this concept.
   Other that the confusion on Friday, this was a good week. The class got a lot done and I was attentive through most of class. I hope to clear my view and better understand Friday's concepts.
     Also thank you to Mrs. Finnan for the cookies!! They were really good and looked adorable.