|Make a Comet|
The general outline is:
ASP's Project Astro Universe at Your Fingertips, section activity E-3 "Making a Comet in the Classroom "
This one is found in a number of places on the 'net, Dennis Schatz originated the one referenced above: http://www.musc.edu/cando/auast/makingac.html
See Activity E-3.
time: 90 minutes
Despite what the writeups say, 4th graders can handle this one fine. We work in teams of 4. Yeah, it's a bit messy but they will remember this activity for a long time.
here's pictures from one of the times this was done:
The presentation uses some movies, Powerpoint is flaky at best when it comes to playing them. I used the "package for CD option" and then zipped the results (about 14 MB). You'll want to modify the impact site for your location.
For the formation movie, the one found here might be better (note that .mov's won't play in powerpoint):
The recipe calls for 2 cups of dry ice. If they're pellets I get about 1.5 lbs for each 2 cups a few hours before the event, plus extra to make the teacher's comet.
Remember that each comet started with 2 cups of water, so when it melts it's gotta go somewhere - if they're going to leave them out to watch them melt have some buckets or be around to drain them off every 15 minutes or so.
If a group ends up with a "rubble pile" instead of a comet that's fine, as that is also a reasonable description of a comet.
We have the teacher demonstrate the whole procedure first, and then the students make theirs. Except for the dry ice all of the ingredients are premeasured into plastic cups.
The dry ice is placed in a 1 gal freezer bag, folded over but not sealed. Place the bag in 8 sheets or so of newspaper, folded over so that if the freezer bar breaks the dry ice can be poured out of the paper.
Remind the students not to pulverize the dry ice, small pebble sized pieces seem to be what to aim for.