ok...
i didnt find that egg one from yesterday, but i think one's pretty good:
-using eggs to observe the effect coke, vinegar, orange juice etc has on teeth. apparantly teeth and eggshells have the same calcium salts, and the effect acids have on them are similar.
controlled variables: amount of liquid in each, same container, the same amount of time, same type(size, weight) of egg.
independent: the kind of substance the egg will sit in.
dependent: the effect it has on the egg.