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Delta G = 0
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The Drinking Bird
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| When the bird wets his beak, water is wicked on to the fabric on his head. Fluid is released from the head to the lower bulb. The fabric covers a glass bulb filled with a gas. |
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| As water evaporates from the head, heat is removed from the gas. The cooler gas exerts less pressure and the red fluid is sucked up the body. when the head is heavy with fluid, the bird dips down. |