I was recently reading the March/April 2022 issue of "Science & Children" a publication of the National Science Teaching Association. In this issue, I read the Science 101 column, written by Matt Bobrowsky. He wrote an article entitled, "What's Cool About Water?"

Water is a good example to use when discussing how matter can be in different states — solid, liquid, or gas. Students are quite familiar with solid water and liquid water but gaseous water is a bit more abstract. Bubbles in boiling water are made of water vapor (gaseous water). They are not empty, they are not air bubbles, and they are not made of separate hydrogen and oxygen gases.