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Speaker 1: Welcome to Brainstoff front House, stuff works dot Com where

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Speaker 1: smart happens. Hi. I'm Marshall Brain with today's question, how

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Speaker 1: does a dippy bird work? A dippy bird is a

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Speaker 1: toy that you'll frequently find it toy shops or novelty shops.

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Speaker 1: They cost about five dollars and they look a little bizarre.

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Speaker 1: A dippy bird has the following parts. First, two equal

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Speaker 1: size hollow glass bulbs, a long glass tube that connects

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Speaker 1: the bulbs, a fuzzy water absorbent material covering the head,

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Speaker 1: and often some kind of little top hat on the

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Speaker 1: head as well. Two plastic legs with a pivot connection,

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Speaker 1: and then some methylene chloride in the abdomen. This is

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Speaker 1: usually a reddish liquid In real life. Methylene chloride is

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Speaker 1: an industrial paint stripper and a solvent one thing that

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Speaker 1: dissolves easily. A methylene chloride is caffeine, so you'll often

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Speaker 1: see it used to decaffeinate things. Methylene Chloride helps make

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Speaker 1: a dippy bird work because it evaporates very easily. It

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Speaker 1: boils it just a hundred degrees fahrenheit or forty degrees celsius.

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Speaker 1: To operate a dippy bird, you get its head wet.

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Speaker 1: As the water evaporates off the head, fluid moves up

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Speaker 1: into the head, causing the bird to become top heavy

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Speaker 1: and dip forward. Once the bird dips forward, fluid moves

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Speaker 1: back into the abdomen, causing the bird to become bottom

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Speaker 1: heavy and tip back up. It'll tip up, and back

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Speaker 1: up and back essentially forever, as long as there's water

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Speaker 1: that can cool its head and the room is at

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Speaker 1: room temperature. Here's how a dippy bird works. When water

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Speaker 1: evaporates from the fuzz on the dippy bird's head, the

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Speaker 1: head is cooled. The temperature decrease in the head condenses

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Speaker 1: the methylene chloride vapor that's floating around in the tube anyway,

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Speaker 1: decreasing the vapor pressure in the head relative to the

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Speaker 1: vapor pressure in the abdomen. The greater vapor pressure in

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Speaker 1: the abdomen forces fluid up through the neck and into

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Speaker 1: the head. As the fluid enters the head, it makes

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Speaker 1: the dippy bird top heavy. The bird then tips, liquid

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Speaker 1: travels to the head and the bottom of the tube

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Speaker 1: is no longer submerged in the liquid. In the lower bulb.

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Speaker 1: Vapor bubbles travel through the tube and into the head.

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Speaker 1: Liquid drains from the head displaced by the bubbles, and

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Speaker 1: the fluid drains back into the abdomen, making the bird

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Speaker 1: bottom heavy. Then the bird tips back up and starts

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Speaker 1: the cycle over again. If the bird dips into a

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Speaker 1: cup of water so it's heads stays wet, the fuzzy

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Speaker 1: material absorbs water over and over again, and the cycle

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Speaker 1: just keeps repeating. Your warm hand can cause fluid in

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Speaker 1: the dippy bird to rise as well. If you hold

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Speaker 1: a dippy bird upright in your hand touching the abdomen,

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Speaker 1: the following happens. Your body heat warms the fluid in

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Speaker 1: the abdomen. The heat increases the vapor pressure in the

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Speaker 1: abdomen relative to the head, the reverse of what happens

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Speaker 1: when you get the head wet. The fluid rises into

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Speaker 1: the head in response to the pressure difference, moving from

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Speaker 1: high pressure to low pressure. The bird becomes top heavy

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Speaker 1: and it tips forward. Either way, you've created a little

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Speaker 1: heat engine when you look at a dippy bird that's

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Speaker 1: using the evaporation and condensation of a liquid to cause motion.

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Speaker 1: For more on this and thousands of other topics. Because

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