Elementary Chemistry

Today and last Tuesday I taught chemistry to the 3rd and 4th graders ar our elementary co-op.  It was fun, although tiring.  I was having a hard time keeping all the different classes I'm teaching right now separate, since they are all sort of related to chemistry!  I'm glad this teaching is now over, and I can just focus on the other three, lol.

 Last Tuesday we talked about the periodic table.  When I was hanging up my periodic table posters (yes, plural) before we got started, one of the boys in the 3rd grade who was just walking in said, "I don't really understand what the periodic table is, or what it's good for." How about that for an introduction?  I told him I hoped he wouldn't be able to say that anymore after we finished!

I told them about Mendelev, who is credited with discovering it (although if you read other books like The Disappearing Spoon, which I highly recommend and have all my regular chemistry kids read, you'll find out that it is a complicated and very interesting story involving several other people as well . . .).  But Mendelev is a character, and he looks like the kind of person who you would find doing crazy experiments in a chemistry lab, lol.  Even though others had the general idea of how most of the elements were arranged, and what the patterns were, he gets the credit for discovering the table mainly because he was brilliant enough to leave holes where he predicted other elements would be discovered (and they were).

We spent a long time on what an element is, and more importantly, what an atom is and how it is structured.  We made these atom mobiles of a carbon atom (with 6 protons, 6 neutrons, and 6 electrons).  Although we talked a lot about the atomic number, I didn't go into atomic mass too much, which is a change from when I taught this 7 years ago to the 5th and 6th graders.  We also talked about the elements that have seemingly crazy chemical symbols that don't relate to what we call the elements (eg. Pb is lead, etc.).  They thought those were pretty interesting--well, maybe that was just me, lol.  Thank you, Latin!  And lastly we talked about each column of the periodic table, and how those elements all have similar properties.  I love the periodic table!  I even wore my "I wear this shirt periodically" t-shirt with the periodic table on it.

Here's a closer picture of Faith's paper plate carbon atom, complete with 2 outer shells for electrons.  I used pompoms for the atomic particles, which I bought from amazon.

For this Tuesday, we went a more experimental direction.  We talked about how to tell the difference between a chemical and physical change.  I gave them 4 main "clues" that a chemical reaction occurred:  it produces gas, it emits heat, light, or a new odor,  a new solid is formed, and it changes color (but this is tricky, because color change does not definitely mean a chemical reaction!).  Then we did some experiments to demonstrate those clues.

First was the classic "vinegar in a bottle, baking soda in a balloon" one.  When you put the balloon over the bottle mouth and shake the baking soda down, it reacts, forming sodium acetate, water, and carbon dioxide, which foams up, filling the balloon.  Most people had done this before, but hadn't thought of what was actually happening in the reaction or what the gas was.

 Secondly, we did a reaction with hydrogen peroxide and yeast in a beaker with a thermometer in it.  I had made up observation sheets so they could write down something about each experiment, and for this one, they had to mark the starting and ending temperatures.  It rose almost 30 degrees (F, although I made sure to tell them the C temperature too all the time), and it also foamed and bubbled, so they knew gas (oxygen in this case) was also being produced.  We talked about other exothermic reactions, like the ones used in those handwarmers, as well as endothermic ones, like the ones in those instant ice first aid ice packs.

Thirdly, we made slime, which was a big hit.  This was glue dissolved in water, with borax dissolved in water added to it.  This was definitely the big favorite as far as experiments go, because who doesn't like slime??  The 4th graders added green food coloring, which is why the slime below is tinted.  It was a good demonstration of a solid coming from 2 liquids.

 And lastly, I had 3 test tubes with water in them and a drop of green food coloring.  In the first one, I put a dropperful of vinegar, in the second a dropperful of hydrogen peroxide, and in the third (which is the first in this picture, because it's turned around, lol), I put bleach.  The bleach immediately turned the green blue, which impressed them, but it kept getting lighter until it was a very pale yellowish green.  We talked about the bleach you might put on white baseball pants actually having a chemical reaction with the green from the grass stains.

 Here was my table with a lot of my stuff on it.

After all the experiments, I gave them a handout with a ton of different chemistry lab equipment pictured, and then I showed them most of the pieces, thanks to my incredibly well-equipped science armoire here at home.  They liked seeing an erlenmeyer flask, volumetric flask, graduated cylinders, beakers, a ring stand with ring as well as the holder for burettes and thermometers, wire gauze, ceramic triangle, evaporating dish, crucible, various tongs, wire loop, 24 well reaction plate, and other stuff.  They were all pretty interested, and one girl said wistfully that she really wished she could come visit my lab, lol.  Maybe I'll inspire some future chemists!  After that, they all played with slime while I cleaned up.  It was fun, but I'm glad it's over!