Gas

• Steam is produced when the temperature of H2O exceeds 212 degrees F (the boiling point). In the gas phase, the molecules are moving very rapidly and will escape into the atmosphere if not contained. A tea kettle whistles when steam escapes through the spout.
  
  

Liquid

• If steam is cooled it becomes a liquid. This is the condensation on the inside of a lid. The molecules are moving rapidly, but will stay in their container and remain a liquid as long as the temperature does not drop below 32 F (the freezing point).
  
  

Solid

• When H2O is cooled the molecules slow down. It will reach its solid phase -- what we call ice -- at 32 F and remain solid as long as the temperature does not increase. The molecules in the ice are still moving, but very slowly, and are tightly packed together and retain their shape.