# Questions tagged [water]

Two Hydrogen atoms covalently bonded to one Oxygen atom. One of the more common compounds on the surface of the earth.

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### Under water light reflection of air in a cup vs water in a cup

The last time I was on vacation I was drinking on the swimming pool, and after I was finished with the drinks I started playing with the 2 plastic cups I had, and noticed that the air produces a ...
614 views

### Is evaporative cooling more efficient with dry or moist air?

I live in India, and in the summer season, the temperature can reach up to $45 \sideset{^\circ}{}{\mathrm{C}} .$ We use Split 1.5 Ton AC in our small office. The idea is to put an evaporative cooler ...
115 views

### Why does a salt water solution have a higher coefficient of thermal expansion (i.e. expands more) than distilled water?

I have found several different sources of data which show that a solution with a higher concentration of salt has a higher coefficient of volumetric thermal expansion than a lower concentration salt ...
38 views

### Energy density in pump storage power plant [on hold]

I have $1.5\ \mathrm{km}$ long and $10.0\ \mathrm m$ diameter pipe So it holds $V = \pi\cdot r^2\cdot h=\pi\times5^2\times1500=117\,810\ \mathrm{m^3}$ water. I have calculated that the pump storage ...
31k views

### How to calculate the volume of water in a certain amount of air, given the relative humidity?

If, according to the weather forecast, the current humidity is 90%, how can I calculate the volume of water that could be extracted from a certain volume of that air?
32 views

### How much steam must a planets atmosphere hold for no condensation to occur at bottom?

If a planets atmosphere contains steam how much would be required in order to have a temperature at the bottom, due to the adiabatic temperature gradient, to prevent condensation and thus rain in the ...
4k views

### What would jumping into a pool and feeling cold be called? Conduction, or convection?

This was another question from my son's workbook. It said: ...
29 views

### When does water decrease or increase friction?

Water often acts as a lubricant e.g. a wet floor or road, but sometimes the reverse happens e.g. putting on wet clothes. I understand that surface tension is involved e.g. microscope slides sticking ...
19k views

### When I boil a kettle, what stops all the water from turning (exploding!) in to steam in one go once it reaches 100°C?

While making a cup of tea in the office kitchen, a colleague asked me this question and neither of us could answer with any certainty. We're guessing it has something to do with the pressure of the ...
10k views

### Does ice made out of salt water melt slower than ice made of pure water?

I'm trying to make this whole bunch of ice bottles to cool down my little aquarium. What I want in the ice bottles is that, fter freezing the whole bottle full water into ice, I need the ice to melt ...
341 views

### Glasses underwater

So I figured the refraction of the cornea is based on the index of air and the vitrous humor to make a perfect image. Underwater this is messed with because water has the same index as the eye. Hence ...
65 views

### Shooting a glass made different with water!

I read about an experiment conducted long back ago. The experiment tells that shock waves are the reason for this. The experiment goes like this, shooting a drinking glass with bullet then bullet ...
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### Hot cup condensation

I was wondering if the condensed water dropplets that are left on the table from a PE film coated paper cup filled with water with a bottom headspace come from the air? And if the headspace would be ...
47 views

### How hot would it have to be for sweat to evaporate/dissipate before it hits the ground? [on hold]

Essentially this is "how hot a surface would have to be for a drop of water to evaporate before it hits a surface?" Lets say that the drop of water (2ml?) is being dropped from 2 meters. The surface ...
129 views

### What concepts/rules apply for multi-stage pumping of water

For single-stage (ie one pump) water transfers calculations for pressure loss are commonly done by adding the elevation difference of the start and end of the pipeline to the friction losses that ...
38 views

### Why is the kettle loud, but the induction hob is quiet

The question: "Why is a kettle loud?" has been asked and answered many times, including on here: Why is boiling water loud, then quiet? What is the reason for this pattern of noise in electric ...
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### Estimation of relative humidity

Assume that we have a box of $1\ \mathrm{m^3}$ with a constant wall temperature of $15\ \mathrm{^\circ C}$. The box was filled with air. The temperature of the air was $30\ \mathrm{^\circ C}$ and the ...
21k views

### Will a bathtub full of water weigh more if I add something that floats in the water?

Let's say I have a bucket or something bigger, like a bathtub full of water. I weigh that bath and get some value, $x$. Then I add a small boat made of wood to that bathtub that doesn't touch the ...
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### Is there an easy way to get water at roughly 70°C in our kitchen?

Some green tea requires to pour water at 70°C. I have no thermal sensor or kettle with adjustable temperature with me. Do you know a way to get water at roughly 70°C like “boil water and wait for x ...
231 views

### Why do random slabs stay dry in the rain? [closed]

The image below shows the slabbed area I can see from my work window Whenever it rains some of the slabs stay dry however, it is never consistent which ones. Can anyone explain why this happens to ...
20k views

### Why does water stop boiling immediately after turning off the heat?

When I am heating water on a gas stove, it begins to boil after some time and bubbles of air can be seen escaping out. However, as soon as I increase the amount of heat in the stove, the rate of ...
16 views

### would connecting a pipe that can carry twice the volume of water to a supply pipe reduce the water pressure in half? If not is there a formula? [duplicate]

I am trying to reduce water pressure by changing pipe size. I want to make a slow peaceful fountain spray.The end of the water line will be pointed straight up so will the weight of the water play ...
15k views

### Why should fluids be confined for Pascal's Law to be applicable

When is Pascal's law about fluid pressure propagation applicable? Is it applicable to a closed circular pipe with a pump rotating the fluid, but not to a tub of water. Most statements require only ...
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### Temperature dependency on $D_2O$ stratification

The original problem is the research of low energy consuming process to take away D2O from drinking water. Reading the Q&As on this post, particularly the answer provided by @DjohnM, I would like ...
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### How can I reduce the surface tension to achieve realistic 1:43.5 scale waves etc

I want to achieve realistic flowing water instead of using polymers which produce static water. Ideally using a small wave making device to represent the sea.
11 views

### Air-Water mix flow and pressure

I'm using a system that creates water and air jets. The air line pressure is constant at 1.5 bar while the flow rate changes between 100-2500 cm³. The mixing is done with a water pump that operates ...
35 views

### How to avoid water tension in a hose?

I am doing a project in which I have to flow water between two containers, which are connected at the bottom by a 1/4" hose. Remarkably, the surface water tension is such that water does not flow ...
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### Can vaporization heat added to the whole volume of liquid before vaporizing it?

It seems, for example a volume of water is heated to boiling point, then part of the water is vaporized, while the remainder need much more heat to vapor, which means that part doesn't receive latent ...
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### Darcy applied to surface and groundwater interaction?

My question is, in which of these two scenarios would the ponded water drain more quickly? Darcy's law applied to falling head condition appears to indicate that it would be the a) scenario. I'm ...
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### Thickness and refractive index of silica gel layer between fused silica and water interface

I learned that when fused silica contact with water, a layer of silica gel will be formed. However, I cannot find any reference about the thickness and the refractive index of the silica gel. Can ...
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### What air pressure is needed on mars, to have fluid water?

The atmospheric pressure on the Martian surface averages 600 pascals (0.087 psi), about 0.6% of Earth's mean sea level pressure. There is a lot of frozen ice on mars, but it can't melt, because of ...
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### Why can't I see any bubble in my anode during my electrolysis experiment

I am doing an electrolysis experiment using this apparatus The left side is the anode and the right side is the cathode. I am using two 9v battery in series (total 18V DC) to power my apparatus. ...
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### Which one is better to boil water, using high heat or less heat?

Consider that I have a water boiling kettle as below. Assume that it is made of metal, not plastic (but plastic probably also will do). Assuming I can adjust the power it uses to boil the water with ...
34 views

### In swimming why does gliding help keep the head out of water

In relaxed non-competitive swimming, it is possible to keep the head out of the water while gliding. This can be breaststroke or backstroke (or doing the Tarzan stroke in waterpolo). What is the ...
17 views

### Influence of pressure on thermal conductivity of water vapour (steam)

I am looking for an analytical correlation of the thermal conductivity of water vapour (steam) in function of pressure. Apparently the effect is not large, but I would like to confirm this by some ...
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### How to calculate the energy and entropy content of an amount of substance?

The Energy $U$ and the entropy $S$ are extensive state variables, so it makes sense to talk about the energy content and entropy content of a given amount of substance at standard conditions. Texbooks ...
90 views

### QM explanation why hot oil explodes when water pours on it [closed]

I have read this question: Why does hot oil explode when pouring water on it? It explains in a classical way clearly, that the boiling point of oil is hotter then water, and water changes to steam ...
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### Why isn't the water moving when it is undergoing electrolysis

I understand that in electrolysis of water, the water around cathod is splited in the way of 4H2O + 4e => 2 Hydrogen + 4 OH- . And the hydroxide will move to the anode due to electric field in the ...
45 views

### Does water have a minimal thickness because of van der waals force?

I have read this question: The thickness of a puddled sheet of water https://en.wikipedia.org/wiki/Surface_tension#Puddles_on_a_surface The liquid mass flattens out because that brings as ...
1k views

### Could hydrogen liberated from water provide lifting energy which exceeds the energy it took to liberate it from water

I was thinking about Hydrogen balloons and that large ones which are used for weather balloons which sometimes go up to 100,000 ft (approx 30km). Then I was wondering, how much potential energy has ...
188 views

### Is water the only substance freezing at 0°C?

When reviewing with my son his science homework (12 years old = ~7th grade, 5ème in France), he told me that "when the phase transition graph shows a plateau between phases then the substance is pure. ...
379 views

### Why doesn't the water cycle stop, since it dissipates energy?

In artificial cycles like for example refrigeration cycle, because of irreversibilities extra energy is require to be provided so that the refrigerant is available at the same state as it was at the ...
44 views

### My soap produces less lather as it gets old

I don't know it you have encountered this too but I have observed this "phenomenon" from the last few hundred soaps I have used. As the soaps get older they produce less lather than they produced ...
102 views

### Why is more than one ripple created when a rock is thrown onto the still surface of a pond?

I have tried making an analogy with a simple pendulum: if you give it a push it will probably make several oscillations. But why isn't there just one ripple that would carry the energy of the several ...
51 views

### Density of water after absorption

I was wondering if I could assume a water density ~1.0 g/cm3 after it was absorbed by the skin, or other medium. I am particularly thinking on a molecular level, if the nanostructure and size of ...
22 views

### Does warmer air of the same humidity condense faster?

Warmer air can hold more moisture but can it also release it's moisture faster when touching a cold surface? If air is warmed (for example by the hot side of a thermoelectric cooler ) before it moves ...
11k views

### Does electrically heated water have an adverse effect on hair?

I know I should have asked this question on a different site. but this was the most suitable site available right now for my question. Perhaps after this proposed site goes on Beta, we can move it ...
11k views

### Why does water make a sound when it is disturbed?

When I disturb a body of water, what causes the familiar "water moving" sound?