The Water Cycle: Evaporation, Condensation and Precipitation

This demonstration shows the water cycle. We have looked at how rain is made before, but this time we are going to look at how water can go from a salty source such as the ocean and by the process of evaporation, condensation and precipitation, ends up in a freshwater source, such as a river.

Put some water in a saucepan, along with about 3 tablespoons of salt and begin to heat on the stove, stirring to dissolve. You can let your students taste the water as long as they know that they can't taste anything unless you tell them it is okay. This represents the salty ocean water. We are adding heat to it just to speed up the evaporation process.

 While you are waiting for the water to come to a boil, take a zippered sandwich bog and fill it full of ice and then zipper shut. Place a bowl next to the saucepan and get a pot lid that is larger than the saucepan. Put the bag full of ice on top of the lid and hold the lid so that part of it is over the pot of boiling water and part is over the bowl, tilting toward the bowl, as shown above. (You might want to use a potholder, so you don't burn your hand.) When the steam, or water vapor, hit the pan lid, the coolness caused by the ice should turn the vapor back into liquid form, or condensation. This represents what happens when clouds form.

Eventually you will see water dripping off the pot lid and into the bowl.  This represents precipitation. Wait until there is enough water in the bowl to be able to taste it.

Your students should be surprised that the water now is not salty!

The salt is left behind, and if you let all the water boil away, you will see the salt left on the bottom of the pan, just as salt is left in the ocean when the water goes through the water cycle.

source: Exploring Creation with Physical Science, Jay Wile