How Does It Work?
Only through this tiny glass tube can anything move between the two bulbs. The material that forms the beak is porous and resembles felt, covering the top bulb. There is a plastic top hat, purely decorative, atop the head. Tail feathers, which aid in balance, are attached to the bottom chamber. Everything is hanging from plastic legs, and it can bob up and down thanks to a horizontal metal piece that serves as a pivot. The drinking bird contains methylene chloride (CH2Cl2), a very flammable liquid.
Methylene chloride lacks color, so in order to improve the visual effect, coloring must be added. This liquid’s weak intermolecular bonds in the liquid state cause it to evaporate quickly, making it another highly volatile substance. Its boiling point is 39. 7 °C (103. 5 °F), and at room temperature, its vapor pressure is 46 kilopascals (while water’s vapor pressure is only 3 kPa). Because methylene chloride is somewhat toxic, cleaning up spills from drinking birds needs to be done carefully. Methylene chloride is frequently used as a paint remover, degreaser, and industrial cleaner. The majority of the residual air is then vacuumed out once the manufacturer adds the methylene chloride.
Now that the bird is almost completely empty, the extremely volatile liquid quickly evaporates, filling the area above the liquid with vapor. At this moment, the liquid and vapor above it reach a dynamic equilibrium inside the bird. As soon as equilibrium is reached, every time one molecule evaporates, another will condense, keeping the total amount of vapor inside the bird constant as long as the temperature doesn’t change. The drinking bird is activated by dipping its head into a glass of water and positioning it so that, when it tips its beak, it can reach into the glass of water. As soon as the head gets wet, an odd thing starts to happen. The liquid rises upward into his head like magic, filling it with liquid. The bird’s center of gravity then rises, making the head top heavy. The bird then topples over, takes another drink. The liquid returns to the bottom bulb as the bird topples over, reestablishing the low center of gravity. The bird returns to its upright posture and repeats the entire process.
Consider what happens to your own head when it gets wet to get an idea of what causes the fluid within the bird to rise. As long as the relative humidity remains below 10%, the water will start to evaporate right away. Furthermore, because evaporation is an endothermic process, it always results in cooling. This explains why you sweat when it’s hot; the sweat evaporates from your body to cool you instead of the sweat itself. Since breaking bonds requires energy, any phase change that necessitates this will be endothermic. As a result of this energy being extracted from the environment, the temperature there drops. As water evaporates from the bird’s head, the head starts to cool down right away. This is the most important thing to know about the functioning of the drinking bird.
The drinking bird would function the same if there was another way to cool the head. A portion of the vapor inside the head will condense into tiny liquid droplets when it starts to cool. A comparable process takes place at night when the air cools and water vapor condenses, resulting in the formation of dew on the ground. There is now less vapor pressure in the top bulb because some of the vapor condenses within the bird’s top chamber. Less vapor means less pressure. However, the bottom bulb’s vapor pressure has remained unchanged. The liquid is forced upward into the top chamber because the vapor pressure in the bottom bulb is now higher than the pressure in the top bulb. After the bird topples over, vapor rises to the top from the bottom until the pressure in both spheres equalizes, at which point the bird starts the process anew. Don’t say the liquid is sucked up into the top chamberscience never sucks!
Consider what happens when you use an ordinary drinking straw to get an idea of how a pressure differential causes the fluid within the bird to rise. There is a zone of lower pressure inside the straw when you suck liquid up into it. Due to the increased air pressure outside, the fluid’s surface is forced upward by downward pressure.
A student reading from ChemMatters magazine
This student reading is courtesy of ChemMatters, the ACS quarterly magazine division that explores chemistry behind everyday life. Learn more about ChemMatters, view free online content, or subscribe at acs.org/chemmatters.
For more than fifty years, both young and old have been enthralled with the captivating little science toy known as the drinking bird. The happy bird, the dippy bird, the happy dippy bird, and other variations on the same theme are some names for it. It resembles a bird and appears to be drinking from a glass of water as it bobs up and down. It will continue to bob up and down as long as it can get to the water. The drinking bird is made up of two long glass bulbs joined by a straight glass tube that extends deep into the bottom bulb.
Hold on, you say, run that by me once more. Wasn’t this article the reason behind your decision to route your cross-country road trip through southern Utah? Haven’t you been talking about this concert on social media for nearly a whole year in all caps? yes. I did, and I have. Guilty as charged. Simply put, I’m not sure if I like it or if it’s a good piece of music.
I was thrilled to learn that the St. Louis Symphony would be performing it at Walt Disney Hall tonight. Even though I have the least interest in Messiaen’s work, I was still excited. I was excited because I was hearing one of his orchestral works live for the first time, and sometimes things that sound terrible on recordings surprise you when you see them in person; also, even if nothing makes sense, it’s still Messiaen, and I have an unhealthy obsession with his music; and finally, it’s healthy to occasionally come across the enigmatic even in the absence of clear answers.
No other composer does this to me so consistently. With Messiaen, its virtually guaranteed. Des canyons is the exception. The one piece by Messiaen that I am aware of that I do not understand at all is Des Canyons. It is mysterious to me, and elusive. I keep returning to it, circling it, and trying to get a hold of it, but it eludes me. I dont know what to make of it.
____________________ *I think it does him a disservice, but I can see why music history classes choose this piece over any of his others because of its historical significance and because it creates a nice bridge to Pierre Boulez and his associates (after all, Boulez did study with Messiaen). This brief piano piece is not representative of Messiaen’s output, and I find it annoying when listeners assume it is If that’s all you know about him, I strongly recommend that you click on some of the other links in this article; his music is more complex than just a prelude to essential serialism.
Rather, all I can say in response to Messiaen’s music is “whaaaaaaaaaaaaaaaaaat.” That being said, something about his writing short circuits my brain. Perhaps it’s because of the flamboyant self-indulgence of his scoreshis orchestral works typically involve large forces with odd instruments and fiendish parts, and they show no regard whatsoever for brevity or other constraints of reasonableness; there is no element of earthly compromise sullying their obsessive, otherworldly vision, and I greatly appreciate such things. Whenever I listen to Messiaen, I am not thinking about modes, rhythms, or Catholic doctrine. I dont think at all. I feel as though every fiber of my being has been reduced to an excited hum of desperate resonance and recognition, akin to a lizard curled up on a warm, dry stone. This affirmation comes from the deepest recesses of my hindbrain and is inarticulate.
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