Gas Chemistry

 After several times forgetting to take pictures during class, this time I gave Klenda the camera - thanks Klenda!

 We started out talking about how we know something is a solid, liquid, or gas.

The kids came pretty close with solids and liquids!  A solid holds it's shape, a liquid takes the shape of it's container.  But a gas is harder to define!  A gas takes the shape of it's container and is compressible!  Liquids, by definition, are not compressible, hence the field of hydraulics.

To show that a gas is compressible, I decompressed some gas in a way the kids could feel: I popped a balloon and let them feel the puff of expanding air!

Next we talked about mixtures.  Mixtures of solids (Old Bay), liquids (milk in tea), and gases (air).  The mixtures of solid and liquid (sugar in tea), solid and gas (smoke), liquid and gas (fog) and, the one we worked with most, gas in liquid (soda!)

I had bought 10 little "chubby" sodas in "blueberry."  These were selected primarily because I needed the bottles for the next experiment, but also because it was transparent.

First the kids needed to drink a little to make room in the bottle!  Then they dropped in alphabet noodles (uncooked).  The gas bubbles formed on the outside of the noodles, raising them to the top, and then dropping them back to the bottom as the gas released at surface.  Fun, dancing noodles!

Then we put salt in the soda.  The salt provides lots of surface area (nucleation sites) for the gas to form from the liquid, and it makes the soda foam and over flow!!

Then we rinsed the bottles and filled them partially with vinegar.  I had pre loaded balloons with baking soda and the older kids helped fit the necks of the balloons around the necks of the bottles.

The kids tipped the balloons up, the baking soda fell into the vinegar, and the balloons inflated with carbon dioxide!

This is my favorite kid experiment!  We tied off the balloons and had the kids experiment with them.  CO2  is heavier than air, so the balloons fall unexpectedly quickly.  I also provided some air filled, and some helium filled balloons for contrast.  So fun!  Try listening through the different balloons!

  Next I had the kids blow into lime water.  The water itself is made by putting canning lime in water overnight.  The excess lime settles out, leaving you with water containing a lot of calcium oxide (lime).

When calcium oxide meets carbon dioxide, it combines into tiny particles of calcium carbonate (limestone), and the water turns milky. You make rocks with your breath!!

 Eventually, the limestone settles to the bottom.  Very cool!

We also tried an experiment where we put yeast with sugar water in a sealed bottle with a tube to vent the CO2 into a container of lime water.

The water should turn milky over the course of a day or so. Unfortunately, I over did the yeast, and got an overflow of yeasty mess.  Oops!  My fault for not trying the experiment before hand.

But this was a super fun class, anyway!