"Igor" is a "musical chairs" game variant that can be played with more than 6 kids and can be adapted to any of the sciences. Give the kids names related to the science activity that you're doing (hydrogen, carbon, oxygen as an example or maybe plankton, shrimp, fish, dolphins, whales ... anything at all, including the names of forces.)
If the group is large, make two people the same item (have 2 foxes, for instance, or 2 levers....) This kind of 'team' works particularly well for groups of 12 or larger.
Have the kids form a circle around you and pick someone to stand next to you. This person is "igor". Call out two 'team names' ("foxes and geese", for example). Everyone has to swap places and Igor has a chance to grab a seat. Last one to sit down becomes the new Igor.
If you get a situation where several people are standing around because they ALL want to be Igor, then make it 'first person to reach their seat is the new Igor.'
As a variant of this, you can allow Igors to call the items to be swapped.
An "all swap" can also be called, which causes a lot of very silly fun.
