Oh Dear, now you've got me hooked....I do love a themed party
Here's some ideas for experiments you could do, I always loved that egg experiment.
Acid & Base: Before the science birthday party, boil 1 cup of shredded red cabbage until water is dark. Dilute it with water until medium purple. The purple water will show if something is an acid or a base. If the water turns light green or yellow color (after adding the substance), then the substance is an acid. And if it turns dark green or blue - it is a base.
Divide this liquid solution in several glasses. Have the kids guess what color the water will turn. Add baking soda (turns green), bleach (turns yellow), sprite (turns light purple), etc. Get litmus paper to check the acidity levels.
*Static Electricity: Give each mad scientist party guest a balloon and an empty soda can. Have them blow up their balloons and rub them on their heads.
Put soda can on flat surface, and applying the balloon, see if the can moves. Next, get the kids to stick their balloons on the wall.
Suck the Egg into the Bottle: [/b]First, hard boil an egg. Next, get a glass bottle that has an opening smaller than the egg. (Starbucks' Frappuccino bottle will do the job.) Show the kids that the egg will not go inside the bottle on its own.
Pour boiling water into the bottle. Place the egg back on the opening of the bottle. The air pressure created by the hot water sucks the egg into the bottle.