Science Party - 7 year old boy We had 10 boys at our party and held it outdoors, as it was a beautiful sunny day. We had a table set up for the kids, and one table for demonstrations.  My husband and I got lab coats and safety glasses for all the kids, as well as ourselves, and also filled out "ID badges" (name tag labels) for the kids when they arrived.  They had to choose names starting with Doctor ... or Professor ...  The kids all had fun making up their "scientist names." I started out by adding dry ice chunks (I bought it from an ice cream vendor) to 3 containers that had been filled with colored water.  This was a big hit! Next, I had a pie plate that I had made 3 holes and tied 3 pieces of string. When you place a cup of water and swirl the plate in vertical circles, the water does not fall out -- centripetal force!  I also had a giant magnet and suspended a paper clip that had string on one end taped to the table.  Next, we moved on to "volcanoes." The kids each had a rectangular disposable aluminum pan, a film canister, clay, and a platic bottle filled with vinegar.  There was also food coloring on the table.  I added baking soda and a drop of dish detergent to the film canisters, after the kids had molded the clay around them into volcanoes. They then added the vinegar and watched them erupt! Next, we moved into my front yard for a quick demo of big ball/little ball momentum bounce, where you hold both balls together and drop them; the little ball shoots sky high.  Then, it was on to alka seltzer rockets. Again, more film canisters (the clear ones), an alka seltzer tablet and water. We had built launchers out of pvc pipe and wood disks. Make sure they have their safety glasses on!  Then, it was on to the "block and tackle." My husband had borrowed a single pulley, and a triple pulley, and rigged them to a large tree branch with heavy duty rope from a maritime museum.  We clipped one end of the rope to a cement block and had the kids try to lift it first with the single pulley, and then the triple one. Mechanical sdvantage!  They had so much fun. We then had cake (I made a volcano cake). I did a quick demo with marshmallows and my vacuum packer, and then it was on to "oobleck" (slime) made with cornstarch, water and food coloring. I put a copy of the 3 experiments in each kid's goody bag. Everyone seemed to have a great time.  It was an inexpensive, fun party, and maybe they even learned a little bit about science in the process!