Learn the secret of the drinking bird, a glass bird that bobs into a container of water.
Utilizing certain physical principles, the drinking bird seems to be in perpetual motion once he is started. However, when demonstrated, it is possible to observe the process.
Step One: Its body is filled with liquid methyl chloride, and it is connected to his head by a glass tube. When the head is pushed into the water, capillary action wets the entire head-cover.
Step Two: Methyl chloride vapor that rose through the tube to the head has been condensed by the cooling effect of the evaporation of moisture in the cloth head-cover. Condensation lowers the vapor pressure in the head and the greater pressure of the vapor in the body forces liquid up through the tube into the head and beak, which then tips the bird forward to drink.
Step Three: When the bird has tipped all the way over, the liquid seal in the tube is broken and the vapor in the body flows into the head to equalize the pressure so that the liquid methyl chloride runs back into the body, pulling the bird's thoroughly soaked head out of the water. The flow of the liquid makes the bird return to the upright position.
Step Four: The water picked up in his head covering will evaporate again and he will take another drink, repeating the steps again.