Editing Making a Comet (section)

== Demonstration ==

# Set out your ingredients around the plastic lined box. Turn the hot plate on, and set to medium. For a younger audience (k-6th), set the small blast shield in front of the box. For an older audience (7-12th), you may ask the students if they would like to assemble the comet.
# Assemble the comet: Put about two cups of dirt in the box, and add a half cup of water to it. Add some soy sauce sparingly, and add a small amount (one capful) of ammonia to the mix. Start mixing the ingredients with one hand, and while doing so add several pieces of the dry ice to the mix with the other. Compress the mixture into a ball, and add more dry ice as needed until the ball freezes together.
# After explaining to the students what the ingredients represent, move your comet from the bag into the small bowl and place it on the hot plate. As it heats up, you will see the coma, or tail, of the comet form!
# After building the first comet, you can keep it displayed for students to look at, and add dry ice as needed to keep the ball frozen. You should consider making a new comet every two hours or so, depending on the length of the event. At the end of the event, break apart the comet and lay it out for a few days to let the dirt dry out.