Friday, April 6, 2012

Co-op Science Week 26

Week 25 ended up not happening as a science class -- a couple of people wanted to test a 4th and 5th grade VBS curriculum they were writing, and asked if they could use one of our co-op's class periods for that.  Since science is the biggest group of 4th and 5th graders we had them use that class hour for their field testing.

On week 26, then, we took a look at states of matter.  I really diverged from the Inquiry in Action curriculum that we've been using this week.  Part of the reason was that I just couldn't face an hour of making condensation appear on glasses.  Another part was that Easter is approaching, so I decided to come up with a couple of Easter-centric demonstrations.

We began the class by discussing the states of matter, particularly solid, liquid, gas, and plasma.  I mentioned that there are lots of others such as Einstein-Bose condensate, but that by the time they would need to know those (say, college) there would probably be even more, so don't worry about them now.

We discussed how the molecules become more energized and further apart in solid, liquid, and gas.  I did the demonstration in the curriculum of using a glass of cold water and a glass of hot water to show the rate of mixing for a drop of food coloring -- the hot water molecules seemed to be moving around more quickly since the food coloring mixed in hot water much more quickly.

We also discussed how water moves from solid to liquid to gas (melting, evaporation) and from gas to liquid to solid (condensation, freezing).  I also explained sublimation and deposition, and gave example of each -- ice cube in the freezer becoming smaller, frost forming.  The kids then kept going off on tangents about dry ice, which is an excellent example of sublimation, but, yoohoo, IS NOT ICE MADE FROM WATER (so, for example, saying that the ice in your freezer was so cold that it was "dry ice" is incorrect ... unless your freezer is somehow putting carbon dioxide under enough pressure to liquify it and then freeze it.

Anyway, forward with the lesson, after yet more digressions to discuss ice on lakes in northern states (yes, you can drive on it).  To show how gas contracts when it cools, and also demonstrate a handy use for all of those hardboiled eggs leftover from dying Easter eggs, we did the ever popular egg in a bottle trick.  A couple of the kids had seen it before.  I used a glass bottle from Santa Cruz juice -- I'd taken in 2 bottles and 2 eggs in case we had a flop the first time.

And to show how gas expands when heated, what could be better than blowing up Peeps in the microwave?  This was accompanied by much discussion of the relative likability of Peeps, including some among us who've never tried them.  The leftover Peeps were handed out to those who wanted to eat one, which turned out to be a really small segment of the class.  By the way, although the church that hosts our co-op meetings has a couple of microwaves in their kitchen, I opted to take in a small, cheap microwave we have in the basement so I could use it in our classroom rather than trooping down to the kitchen.

Finally, thus far we'd been talking about changes in states of matter due to temperature change.  Matter also changes due to change in pressure.  As a reminder of the change in pressure, I also brought in everything needed to make Oobleck -- cornstarch and water.  Oobleck, of course, seems solid when pressure is applied, and liquid when it isn't under pressure. To make Oobleck for 14 kids without making a gigantic mess, I put a 1/2 cup of cornstarch in small ziploc-type bag2 (one for each child).  Each child then got a plastic cup and a plastic spoon.  I had water in plastic bottles.  The kids dumped their cornstarch into the plastic cup, and my assistant and I added about 3 tablespoons (plus a bit) of water to each cup.  The kids then stirred with spoons, and used their hands to mix it up.  We also had pitchers of water and paper towels on hand for clean ups.  And, most importantly, we had all gone outside before we started this particular adventure, so cleaning up spills consisted of dumping water on the sidewalk.

The entire lesson took less than our hour classtime, so the rest of the hour was spent enjoying the incredible weather -- sunny and in the 80s at the beginning of April.

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