What happens if we put Styrofoam balls or steel balls into water on Earth?  What do you suppose will happen if we do the same thing in the free-fall condition on the ISS?

The STFS water cell is a sealed plastic vessel filled with water containing several Styrofoam and steel balls.  In the space experiment we will use a video camera to observe the balls.  Can we make them behave just as if they would in an Earth based experiment?