Water Cycle in a Jar

Ever since we've moved past biology, zoology, and even botany, I am bored out of my skull with 7th grade Science. Right now we're studying, "The Amazing Atmosphere." After weeks of electromagnetic waves, thermospheres, ionospheres, and who-cares-ospheres, we're finally onto a topic I can teach with some degree of confidence: the water cycle.

Today we did a demonstration of how the water cycle works, albeit on a drastically smaller scale. First fill a metal can with ice and set it aside to get cold. Then put 1/2 cup boiling water into the bottom of a tall flask or canning jar. Quickly place the can of ice cubes on top of the jar. Notice what happens to the air inside the jar as the hot water warms the air. Since warm air can hold more water vapor than cool air, some of the water begins to change into vapor (evaporation).

As the vapor rises up towards the cool air near the can of ice on top, the vapor will begin to condense and form a cloud. Many of these droplets will combine to form larger water drops which will precipitate down the sides of the jar. Remove the can and watch your cloud float away.

Experiment taken from A Beka Science: Order and Reality; page 192.