Simple Volcano

Science is very popular in a three and four year old classroom...and I'll do anything to keep those kids sitting still on circle carpet for more than thirty seconds :) I made a volcano with them today that they absolutely loved...and it was so cheap and simple that I'll probably do it a few more times before summer break.  All you need is baking soda, vinegar, two paper cups (one with a dime size hole cut in the bottom), and food coloring if you want to make colored 'lava'. Put about a quarter cup of baking soda in the bottom of one cup and add some optional drops of food coloring on top. Cut a dime size hole in the bottom of the second cup and tape it to the top of the cup with the baking soda. (Make sure you do this on some sort of tray or you'll have a huge mess) Slowly pour vinegar into the hole...the more vinegar you use, the more the 'volcano' will erupt. Simple, cheap and fun!