The Dippy Bird (also called the Drinking Bird or the Dunking Bird) is a popular novelty item or toy in the United States and other countries.
The Dippy Bird
A Dippy Bird has the following parts:
To operate the Dippy Bird, you get its head wet. As the water evaporates, fluid moves up into the head, causing the bird to become top-heavy and dip forward. Once the bird dips forward, fluid moves back into the abdomen, causing the bird to become bottom-heavy and tip up.
- Two equal-sized, hollow glass bulbs
- A long glass tube that connects the bulbs
- Fuzzy, water-absorbent material covering the head
- Two plastic legs with a pivot connection
- Methylene chloride in the abdomen
- Methylene chloride is an industrial paint stripper and solvent (one thing that dissolves easily in methylene chloride is caffeine, so you can use methylene chloride to decaffeinate things -- see Question 480). Methylene chloride helps makes a Dippy Bird work because it evaporates very easily -- it boils at just 100 degrees Fahrenheit (40 degrees Celsius).
Here is how a Dippy Bird works:
If the bird dips into a cup of water, the fuzzy material absorbs water again and the cycle starts over.
- When water evaporates from the fuzz on the Dippy Bird's head, the head is cooled.
- The temperature decrease in the head condenses the methylene chloride vapor, decreasing the vapor pressure in the head relative to the vapor pressure in the abdomen.
- The greater vapor pressure in the abdomen forces fluid up through the neck and into the head.
- As fluid enters the head, it makes the Dippy Bird top-heavy.
- The bird tips. Liquid travels to the head. The bottom of the tube is no longer submerged in liquid.
- Vapor bubbles travel through the tube and into the head. Liquid drains from the head, displaced by the bubbles.
- Fluid drains back into the abdomen, making the bird bottom-heavy.
- The bird tips back up.
Your warm hand can cause fluid in the Dippy Bird to rise.
If you hold a Dippy Bird upright in your hand, touching the abdomen, the following happens:
Here are some interesting links:
- Your body heat warms the fluid in the abdomen.
- The heat increases the vapor pressure in the abdomen relative to the head (the reverse of what happens when you wet the head).
- The fluid rises into the head in response to the pressure difference (moving from high pressure to low pressure).
- The bird becomes top-heavy, and tips.