We can not break it and find other particles inside. We could call it a bubble or a hole for lack of a better word. A hole is a thing that is not made of something else. So called empty space is really the only thing there is. It is the opposite of what is commonly accepted.
Steam is molecules of water vibrating at an increased rate.
The steam's vibration produces a lower density than water and therefore it floats in water. A body is more dense than another when it contains more particles per same unit of volume. This page was written by Alfredo A. Barrera P. July 15, 1997. Last updated June 4, 2000.