Boil red cabbage in water until you obtain purple water. When an acid, such as vinegar, is added to the water, it will turn light green. When a base is added, such as ammonia, the solution will turn darker. Distribute cups of cabbage water, along with safe chemicals, to children, and let them determine whether the chemicals are acids or bases. For good measure, have the junior scientists wear lab coats and gloves, to avoid staining their clothes!
Before the party, take close-up pictures of everyday household objects, so that the pictures look as if the object is under a magnifier. Blow up the pictures and mount them. Distribute to kids and have them guess what the objects actually are and estimate the factor of magnification. Award prizes to kids who correctly guess what the objects are, and send all participating kids, as a consolation prize, home with a magnifying glass party favor!
Making slime is a great favorite of many kids (and some adults). Enlist the help of your child's friends to mix together the necessary components. Give them real scientific measuring tools, such as glass beakers, to measure out 2 cups of glue and 1.5 cups of water. With a pipette, have them add a few drops of food coloring (caution: restrict where kids can play with slime to newspaper-covered areas, to avoid food coloring-related damage to your home). Then, dissolve 2 tsp. of Borax in 2/3 cup warm water. Let guests play with the resulting slime.
Volcanic eruptions are tremendously amusing and entertaining. The day before the party, use modeling clay to make a mountain shape, with a hollow in the center. The day of the party, enlist the help of your artistically inclined guests to make the volcano look realistic. Use brown paint to represent rocks, red paint to represent lava, and perhaps surround the volcano with rocks and twigs from the garden to make it more realistic. Then gather all the kids around and use baking soda and vinegar to make the volcano erupt. Enjoy being the center of their awe and admiration!