The last process that we investigated was freezing. They set up an experiment to see how the amount of water affects the rate of freezing. The children used crushed ice, rock salt and styrofoam cups to make mini-freezers. There's a lot of ice and a little bit of water. Solids melt when they change to the liquid state.
Liquids freeze when they change to the solid state.
The change from a liquid to a gas is called evaporation. The change from a gas to a liquid is called condensation. The children learned that water in oceans, rivers, lakes, etc. evaporates from the heat of the sun. Tiny drops of water called water vapor are carried up by warm rising air. When the vapor hits the high cool air, it turns back to water drops that form clouds.