# water

1. ### I Air pressure holds coaster on glass: What if only half full?

Hi. If I fill a glass with water up to the top and close it with a coaster, I can turn it upside down without the coaster falling off and spilling everything. Usually, this is explained with the atmospheric air pressure being bigger than the pressure of the water inside the glass (hence, it...
2. ### I Can you separate hydrogen and oxygen molecules?

Is separating hydrogen and oxygen molecules possible? If so, how?
3. ### Why is octanol prioritized for partition coefficients?

Hi, it is well established that octanol is the preferred solvent for partition coefficient studies in environmental chemistry, however, some studies ui.e Noble A. Parition coefficients (n-octanol-water) for pesticides) J Chromat. 642 3-14, mention that estimating toxicity based on solubility in...
4. ### Height of a Heron's fountain

Homework Statement I have this homework on how a Heron's fountain works. The exact assigment is as follows: "Construct a Heron's fountain and explain what (which variables) influences the height of the fountain." I've already constructed it and it works well, but I'm not so sure about the...
5. ### A Do Falaco solitons also occur in water on a microscopic scale

Falaco solitons are unique in their longevity, reportedly up to 15 minutes on the surface of a body of still water. For details and the math see {{ http://www22.pair.com/csdc/pdf/pdf/falsol.pdf }} In addition, this persistence occurs at relatively macroscopic sizes in the range of 10 to 40 cm...
6. ### Chemistry ORGO: What does it mean when a molecule is 'quenched?'

Homework Statement n/a Homework Equations n/a The Attempt at a Solution n/a Just a question. I keep seeing that in SN2 reactions, sometimes a molecule is quenched by H2O or H3O. I've seen it turn an O- into an OH and also a heteroatom into an H. What exactly is going on here?
7. ### I Divergence of downhill flowing water

I just learned that an incompressible fluid must have zero divergence within a given control volume. Given that the divergence of a fluid at a point(x,y,z) can be found by taking the scalar sum of the of the x, y, z acceleration vectors at the given point, wouldn't this mean that water flowing...
8. ### Is water really necessary for life?

You know how they always say that without water there would not be life, right? Astronomers also look for life on planets with hints of water in their spectrum. But is water really necessary for life? Some ET life could not be a tiny bit similar to ours and might not even need water or water...
9. D

### A Does capillary action use water heat energy?

Capillary action is a form of work, i.e. an object (water) moved by a force (capillary action) over a distance. Since all work requires energy, what supplies the energy for capillary action? Is the chemical energy of the water increased by adhering to a surface? Perhaps the heat energy of the...
10. ### B Why does bathwater in a plughole spin AT ALL

I don't care whether it goes clockwise or anticlockwise so this is not the usual Coriolis conversation. Why doesn't it just go down straight?
11. V

### Help to determine convection coeficent or temperatures

Homework Statement This is more like a design problem, I'm to evaporate water at 20°C and 2000 psi(Tsat=335.472°C), I have the heat flux the water is going to absorb during heating, and If that flux remains constant during all the length then, how can I find the surface temperature for the...
12. ### I Distortion in water stream

I observed something which I've never seen before. We left the tap open and the water stream was flowing in a particular pattern. When we placed a beaker under the water stream, the pattern disappeared. And the pattern itself was oscillating. Here's the video link. Below the the photos of the...
13. C

### Paint mixing - without mixing

I am looking for a way that I can mix many colours of paint into the same container without it blending together and making other colours. I make liquid art and have seen others make images where i can see many colours in the liquid. The base of what I use at the moment is methycelluslose ...
14. J

### Directional Grooves on the Interior of Pipes

Hey everyone! My name is Jing and I am participating in a one month summer program called SHAD where 800 high school students across Canada come together to try and solve some of the world's most multi-dimensional problems. One of the aspects of this program is the Entrepreneurial Project, where...
15. S

### Van der Waals vs. Hydrogen bonds

I know that the two are different thing, that vdW appears in inert gas crystals and alike while hydrogen bond bonds molecules of water. My question is, how does the potential look for hydrogen bond? For vdWaals we have the two terms proportional to 1/R^6 that describes attraction and 1/R^12...
16. ### I What happened to the boiling water

Hello! This question is not about a particular homework exercise, or any exercise, but rather an astonishing real life fact, which I just experienced, and, as I am still on my way to becoming educated in science, I would like to ask for your help on how to explain this phenomena. I had a...
17. ### I Water speed and bullet penetration

This may be an odd question but I am wondering if water speed affects a bullet's ability to penetrate water. Pardon my lack of knowledge, but I am aware that low caliber bullets can penetrate water past 3ft (Thank you Mythbusters). However, the tests they completed were all based around a pool...
18. ### Check valve for drops

I'm having trouble finding any valves to use for my certain application. What I'm doing is trying to capture water droplets into a sealed container. What I need is some sort of check valve that needs nearly no pressure to let water through, but keep it contained once it has gone through the...
19. ### Formation of petrified trees

My text book says that formation of petrified trees is a result of a degradation and a sedimentation action of theunderground water, and then it goes on explaining that the underground water replaces the plant material in the tree with silica and other inorganic materials, which I think is a...
20. ### Change in humidity with altitude

Homework Statement So I sent a humidity sensor up in a weather balloon, which gave a reading for relative humidity. I eventually want an absolute humidity, but I am unsure whether I need to correct the output based on the changing density and atmospheric pressure with altitude. Homework...
21. ### B Would this device(pic inside) work for boiling cold water?

Imagine some giant glass(or other material) dome placed on top of some ocean or lake. Then pump some air out of this dome, until the water level rises a few meters under the dome. Place another dome below the first dome, and repeat the process, resulting in a little less pressure in the second...
22. ### How does compression cool water in a household water cooler?

How does compression cool water in a household water cooler? I was reading and it says, " The water inside the water cooler is fed into a reservoir, where it is cooled using a refrigerant. A refrigerant is a cooling medium that is circulated in pipes that are located close to the reservoir in...
23. ### Simple Water Rocket

I'm going to make a water propelled pop bottle rocket for a competition. The bottle holds 1.5 liters and we are going to fill some amount of it with water and pressurize it to 75 psi. When triggered, water will come out of the hole in the cap and propel the rocket. The rocket is perfectly...
24. ### I The direction of electric dipole moment of water molecule

I was watching a video explaining how microwave ovens work when I found that there is a difference between my physics textbook and online images of the electric dipole moment of the water molecule, as well as the one shown in the video. Why do they differ?
25. ### Drag force with differential equations, finding max speed

Homework Statement A submarine engine provides maximum constant force $F$ to propel it through the water. Assume that the magnitude of the resistive drag force of the water experienced by the submarine is $kv$, where $k$ is the drag coefficient and $v$ is the instantaneous speed of...
26. ### 25 nm "cloth"

I am looking for 25 nm "cloth" (I'm using that term loosely) my goal is to create a cheaper water filter similar to "LifeSaver bottle" (https://en.wikipedia.org/wiki/LifeSaver_bottle) which is \$139
27. ### I Most efficient temperature to evaporate water?

Hello, I have a question for you guys and gals. I am working on a Desalination project and am ironing out questions about efficiency. What would be the most efficient temperature to evaporate water? 50, 100, 110 degrees? Does it make a difference, or is the energy required to evaporate a fixed...
28. ### B Water pressure in a sphere

I've been wondering how I can find the pressure water exerts on a sphere it's in. As for cyllinders and pyramids, and prisms - the thing is extremely easy - you just take the one formula and put in numbers. What about a situation when we have a sphere whose radius is R, and it's half full with...
29. ### I Dissolved gas concentration in undersaturated liquid column

Hi, In an enclosed system - of say Methane & water - in which the water column is sufficiently large to have significant pressure and some modest temperature difference due to gravity and geothermal effects, how would one calculate / predict the changing methane concentration (or partial...
30. ### A How does a hollow fiber membrane work to filter water?

What is the process? And can/cannot it filter out?