Fabulous Drinking Bird?

Question

1.What is causing the motion of the bird?
2.How could you increase the bird’s speed? (2 ways)
3.How could you stop it? (no touching) (2 ways)
4.Discuss the physical characteristics of the “red liquid”?

Answer 1

If you are describing the bird where you wet the head and put it so it dips into a glass of water, and it keeps going:

The body of the bird has 2 chambers connected with a tube, there is a volatile liquid in the lower chamber. The connecting tube from the head dips part way to the bottom of the lower chamber. At room temperature, the liquid starts evaporating; the vapor can't go to the head because the connecting tube dips into the liquid, so the pressure of the forming vapor gradually forces the liquid from the lower chamber up the tube to the upper chamber. Because the head is wet, it is cooler (from evapoation) than the body, so the vapor pressure of the liquid is lower in the head. Once enough liquid enters the head it upsets the balance of the bird; (it tips over to "drink"), when this happens and the two chambers ar nearly horizontal the trapped vapor in the bottom can now get up the connecting tube into the head and the liquid in the head can run back into the body. Then the whole process starts over again. The "drinking" serves to keep the head moist and cooled by evaporation.

I] increase bird sipping speed 1] articicialy warm the body chamber. 2] Use a small fan to cool the head more effectively by evaporation of the water. 3] use a liquid that evaporates faster than water like methylene chloride, ether, hexane etc.

To stop it 1] Increase room humidity to 100% (no water evaporation; no cooling of head; no differential pressure between the 2 chambers; no force for liquid flow. 2] Cool the room to below the effective evaporation temperature of the liquid. 3] remove the glass of water (Note: this might be "cheating"). 4] Substitute another liquid for the water that only evaporates very slowly or not at all (ethylene glycol, oil, etc); there will be no cooling of the head.

The red liquid must easily evaporate at normal room temperature and have a relatively low density (so the slight pressure difference will be enough to force it into the upper chamber. Its vapor pressure at room temperatue should not be too high or the bird might explode on a hot day. Also it should not be too hazardous, as somebody will inevitibly break the thing!

Answer 2

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