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Sunday, October 11, 2015

The One Where We Explode A Gummy Bear

Unit 1.B: Intramolecular Structure 

Part 1: Ionic Compounds


"If H2O is water and H2O2 is hydrogen peroxide, what's H2O4?  
Drinking."


Practice Problems:

     Problems that involved Electron Configuration were a little confusing at first, but once I got used to reading the chart I was able to solve them quickly. It was the same with Lewis Structure mechanisms, once I understood how atoms with different levels of electronegativity formed different compounds I could quickly draw the mechanisms. What challenged me the most were problems that asked for the formula of a certain compound. I tended to rush and just use the shortcut instead of actually thinking about the number of valence electrons each element had and how this affected the formula.
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Ex. of Understood Problems

Provide the Electron Configuration for iron, Fe.
Iron (Fe) 1s22s22p63s23p64s23d6
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Ex. of Challenging Problems

Provide Ionic Compound formula for Carbon Dioxide.
CO2  (NOT C2O4)
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Activities:
     We constructed our own conductivity probes and tested various things around the room to see if they were conductive. After, we were given two different compounds, AB and CD. We then tested each to see which one would be conductive as an aqueous solution (dissolved in water) and find out why this happened.

   
 Our conductivity probe
  
Testing compound AB as an aqueous solution
     My group agreed that in water, whatever held compound AB disappeared, which allowed the electrons from the conductivity probe to pass through and form a complete circuit. In compound CD, water had little to no effect on the bond formed by CD and this bond meant that electrons weren't able to pass through the solution and form a complete circuit. We later learned that AB was an ionic compound and CS was a covalent one. 

Our model showing our visual observations and explanation AB's conductivity as an aqueous solution
     Another activity we did was observe the reaction that occurred when alkali metals with very low electronegativity levels were placed in water. 

As you can see, the experiment was a "blast"! 
     An interesting experiment we held was a mystery compound identification in which we had 4 unknown compounds and list of 4 compounds that each could be. To identify which was which, we had to mix each compound with another and observe the reaction. I really enjoyed how this activity integrated logic with chemistry concepts.

The petri dish where we conducted our tests
     An activity that deserves an honorable mention was one that we did near the beginning of the cycle. After learning that gummy bears were mostly made of carbon, we found that it would behave similarly to our bodies when put in a certain heated chemical compound. 

Needless to say, we got a lot of curious stares as we conducted this experiment in the courtyard. Poor gummy bear.
Quiz: 
      Since the skills needed for this cycle involved a lot of drawing, I went through the practice problems provided in both the Google Doc and the video to prepare for the cycle test. On the test, I thought it was interesting that we were given an element X and element Y and had to guess what each could be. It made me think more than if I simply had to provide Lewis Structure mechanisms for any two elements. The chart at the end of the test had one problem that confused me. In this problem, we were given manganese and oxygen. As a transition metal, Manganese had a roman numeral to indicate its charge. I was surprised when I saw that it had a charge of 5+, since I thought that the charge would always refer to a low electronegativity. Next time, I'll check my answers at least once since I could have easily written the wrong subscript for any of the formula.  I'll also try to explain things more clearly for the short answer portion.
Questions:
  • Are there any other differences between ionic and covalent compounds that we can test?
  • I'd like to learn a bit more about the s, p, d, f subshells.

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