Wednesday, October 5, 2011

Co-op Science Week 6

I decided to work further with the idea of Alka Seltzer in film canisters, this time shooting them out of tubes.  

After last week's mayhem I had refined my idea about how to accomplish this type of thing with a group of 11 excited 8-11 year olds.

I cut up my Alka Seltzer at home, using a serrated knife to saw them in half on top of a textured cutting board.  The texture held them in place nicely, and I was able to make uniform pieces.  I packed them carefully in a plastic container so they wouldn't break more, nor would they get wet.

I also found 5 plastic water bottles in our recycle which I filled with tap water.  I handed these out to the kids for use filling their film canisters.

I also took along a white board and chalk.

Thus armed, I went to class.

We discussed what had happened last week --how the varying amounts of water affected the speed of the reaction.  Small amounts of water sometimes didn't even blow the lid up -- I asked the class to speculate on why.  The largest amounts of water gave the quickest, most satisfying explosion.

I explained to them that when I was messing around with this on my driveway I had filled the canister 2/3 with water then set it upside down.  I got a quick reaction, but the canister didn't shoot up very far.  I wasn't sure why that was since I had changed TWO things about how I did the experiment (how much water I put in the canister, plus how I set the canister on the driveway).  I wanted to explore this further with their help.  Which would shoot out a tube furthest -- 1/3 water, 1/2 water, or 2/3 water?  One of the kids asked if we could vote by show of hands, which we did -- I made tick marks on the pictures of canisters I'd drawn on the classroom whiteboard.  Some kids gave their reasons for their vote.

I explained in tedious detail what we would do outside, drawing pictures on the board.  Kids asked question about the sequence, I answered.

We went out to the parking lot, and it occurred to me that if we did this in an empty part we could use the painted yellow parking lines to have a launching line.  I asked the kids if they thought that was a good idea, which they did. ( I'm trying to involve them in thinking about how best to set up this stuff, weighing pros and cons.)

I distributed the parts -- I had gotten the plastic tubes from Steve Spangler Science, which is also where I got the film canisters, by the way (really simplified my life -- you can probably find all of this stuff here and there for free, but it was really easy peasy to order a set, plus they even include Alka Seltzer to get you started).  Everyone donned their safety glasses.

The kids had voted to start with filling the canisters 2/3 full.  Most of the canisters didn't even make it out of the tubes!  So, even though that gave us the fastest *POP*, it was sort of a dud insofar as shooting.  We speculated that the canister of water was too heavy to make it out of the tube.

Next they tried half full.  This was very satisfying, and started several arguments over whether one's canister should be measure insofar as its initial point of contact with the ground or where it eventually stopped.  The 1/3 canisters ended up flying about as far as the half full canisters -- interesting since last week several of them didn't even pop open when the kids set them on the ground.  Did we improve technique?  More pressure since the canister was upside down in the tube?  Hmmm ... I don't think we're going to spend anymore class time on figuring that out, but I like ending up with new questions about how something worked.  Always something new to think about, you know?

One boy didn't participate.  He said it was more fun last week.  I don't think it was the fact that we'd done Alka Seltzer/film canisters 2 weeks in a row so much as that last week was more freeform experimentation, and this week was more disciplined.  I have the impression he prefers mayhem.  But, other kids prefer organization.  I imagine we'll continue having a mix of organized activities and free-for-alls, since that's sort of my personality.

The entire demo took amazingly little time -- I think the prep helped, plus the kids are at this point experts in loading film canisters and shooting them.  I had them take their backpacks, etc., outside with them, and we spent the rest of the class (about half of it) enjoying the glorious weather on the playground.  I told them they were supposed to get all of their wiggles out so they could pay attention in their next class -- science is mid-morning, so having a recess tagged onto it makes sense to me.

(Of course, then I noticed one of the boys standing on the highest point of the equipment swigging out of a plastic water bottle ... "Um, where did you get that?  Is that one I brought?"  "Yeah"  "Do you realize I just found those laying around my house?"  "Oh."  Continues drinking.  I decide to not mention that one of them was on the garage floor next to the trash and I had simply brushed off the gunk on it.  "Well, I guess it will pump your immune system to deal with it."  Gotta love kids this age.)

No comments: