Home Experiment Demonstrates How Freezing Water Produces Heat
This enlightening video from The Action Lab clearly explains how ice is exothermic.
As odd as it sounds when water freezes it is actually producing heat. The Action Lab YouTube Channel created an experiment that clearly shows and explains how it works.
First, a giant 2" steel ball is dropped into a beaker of liquid nitrogen so that the ball cools to a chilly -321°F. Once the ball is at liquid nitrogen temperature it is dropped into a beaker of water where it forms a shell of ice.
The experiment shows that ice formation is exothermic. So water freezing actually gives off heat.
The heat from the ball goes into the liquid nitrogen, causing the nitrogen to boil. You can see when the ball has reached its lowest temperature when the boiling is coming from the bottom of the beaker and not from the ball itself.
As soon as the ball is dropped into the water, large bubbles rise from its surface. This is actually the air that is in the water escaping as ice forms around the ball.
You can see a similar demonstration for this if you look at ice cubes in your freezer that have tiny air bubble on their surface or are cloudy. These are signs that the trapped air in the water needed to escape as the water froze.
So there you have it; water produces heat as it freezes. Take that little nugget with you to the next dinner party to be the smartest person in the room.