4C31.30 Drinking Bird

Demonstrates evaporation is cooling process and pressure of gas decreases if temperature decreases. Evaporation causes air in head to cool. Reduced pressure allows liquid to move up tube. At some point head end becomes heavier than tail end. Head drops. This cause a tube between head and tail to equalize pressure and fluid runs back to tail. This causes tail end to drop and head to come out of water. If bill is kept wet process continues.

Setup Requirements: Dip birds head into cold water. Adjust position of bird so bill dips into water. May not work if room too cool or cool air is blowing on bird. Some adjustment of position of bird and metal supports may be needed. The difference between feather on head or feather on tail can make difference between working and not working.

Equations: None

Safety Issues: None