How does Jell-O work? How come it congeals when it is cooled?
Jell-O is composed of long, stick-like molecules. When you dissolve it in hot water, those molecules separate, but as the liquid cools, they begin to stick together like a giant heap of straws. The water flows slowly through these straws because of frictional effects. The result is a stiff material that is given its structure by the straw heap. If you leave the Jell-O long enough, the water will seep out and make puddles on the plate.