Create a complete ecosystem within a terrarium and explore the water cycle as it occurs at your desk!
Heat from outside the jar will warm up the water in the "mini-lake", causing it to evaporate. As the water vapour cools on the lid, it will condense and precipitate (rain) down on the soil and the lake, and the water cycle will start all over again.
Moisture in an established terrarium is taken up by roots, and evaporates from the soil and plant leaves. It condenses on the terrarium roof and walls. Then, the condensed water falls down (like rain) and re-moistens the soil in a continual closed loop process. As long as the top is sealed, this process can continue cycling for months. This cycle mimics the water cycle found on a global scale.