How does the Drinking Bird work?
Everyone has seen the drinking bird in all its glory, but how does it work? Well, there is more to it that you would think!
- The water evaporates from the felt on the head.
- Evaporation lowers the temperature of the glass head (heat of vaporization).
- The temperature decrease causes some of the dichloromethane vapor in the head to condense.
- The lower temperature and condensation together cause the pressure to drop in the head (by the ideal gas law).
- The higher vapor pressure in the warmer base pushes the liquid up the neck.
- As the liquid rises, the bird becomes top heavy and tips over.
- When the bird tips over, the bottom end of the neck tube rises above the surface of the liquid.
- A bubble of warm vapor rises up the tube through this gap, displacing liquid as it goes.
- Liquid flows back to the bottom bulb (the toy is designed so that when it has tipped over the neck's tilt allows this), and pressure equalizes between the top and bottom bulbs
- The weight of the liquid in the bottom bulb restores the bird to its vertical position
- The liquid in the bottom bulb is heated by ambient air, which is at a temperature slightly higher than the temperature of the bird's head.
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