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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25
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2answers
6k views

Why is boiling water loud, then quiet?

Water in my electric kettle makes the most noise sixty to ninety seconds before the water comes to a full boil. I have been fooled many times by the noisy kettle, only to discover that the water was ...
21
votes
4answers
50k views

How does water evaporate if it doesn't boil?

When the sun is out after a rain, I can see what appears to be steam rising off a wooden bridge nearby. I'm pretty sure this is water turning into a gas. However, I thought water had to reach 100 ...
15
votes
3answers
884 views

What is the status of Mpemba effect investigations?

There is this puzzling thing that is called Mpemba effect: paradoxically, warm (35°C) water freezes faster than cold (5°C) water. As a physisist, I've been asked about it several times already. And I ...
16
votes
3answers
734 views

How to show that the Coriolis effect is irrelevant for the whirl/vortex in the sink/bathtub?

There is a common myth that water flowing out from a sink should rotate in direction governed by on which hemisphere we are; this is shown false in many household experiments, but how to show it ...
16
votes
1answer
587 views

Could there be a body of water the size of a planet?

My friend and I were reading the news of the discovery of a black hole spewing huge amounts of water vapor into space, and it got us thinking: could there be a blob of liquid water in space the size ...
6
votes
1answer
929 views

Why does blowing on someone who is wet feel colder than on someone who is dry?

The title says it all. If I'm standing in the wind and I'm wet, I feel much colder than when I'm dry. This is true no matter how warm or cold the water. Why is this?
33
votes
6answers
10k views

Why does ice melting not change the water level in a container?

I have read the explanation for this in several textbooks, but I am struggling to understand it via Archimedes' principle. If someone can clarify with a diagram or something so I can understand or a ...
11
votes
3answers
12k views

Why does adding solutes to pure water lower the the specific heat?

We found that water with salt, sugar, or baking soda dissolved in it cools faster than pure water. Water has a very high specific heat; how do these solutes lower it? We heated a beaker (300ml) of ...
29
votes
6answers
8k views

Why is jumping into water from high altitude fatal?

If I jump from an airplane straight positioned upright into the ocean, why is it the same as jumping straight on the ground? Water is a liquid as opposed to the ground, so I would expect that by ...
14
votes
3answers
4k views

Why is there more steam after a pot of water *stops* boiling?

I have a pot of vigorously boiling water on a gas stove. There's some steam, but not alot. When I turn off the gas, the boiling immediately subsides, and a huge waft of steam comes out. This is ...
7
votes
2answers
573 views

Why water in the sink follow a curved path?

When you fill the sink with water and then allow the water to be drained, the water forms a vortex.. And then it starts to follow a curved path downwards by effects of gravity.. Why this phenomena ...
2
votes
1answer
318 views

Would Beetee's electrocution plan work and kill the tributes in the lake?

In Catching Fire, the second episode of the Hunger Games trilogy, one of the characters (Beetee) proposes a plan to kill some of the remaining tributes. He proposes wrapping a special wire that he has ...
32
votes
2answers
6k views

Before a once-warm lake starts to freeze, must its temperature be 4°C throughout at some point?

This is a problem I just started puzzling over, and I felt this would be a good forum to check my reasoning. So here are the relevant observations followed by my question: Water achieves its maximum ...
54
votes
3answers
2k views

What causes insects to cast large shadows from where their feet are?

I recently stumbled upon this interesting image of a wasp, floating on water: Assuming this isn't photoshopped, I have a couple of questions: Why do you see its image like that (what's the ...
17
votes
6answers
4k views

Why does ice form on bridges even if the temperature is above freezing?

So with this "arctic blast" continuing, I've noticed that for my area, the temperature drops below freezing just long enough to cause freezing rain, but then the sun comes out and the temperature ...
5
votes
1answer
688 views

Does a domestic microwave work by emitting an electromagnetic wave at the same frequency as a OH bond in water?

I was told once that microwaves work by exciting water molecules in food. Also that this worked because the frequency in the microwave was the same as that in the bond between Oxygen and Hydrogen in ...
1
vote
3answers
39k views

Relation between water flow and pressure

Is there any equation that states the relation between pressure and water flow. I.e. Let's say that in 1 hour with 8mca (water collum meters) pressure I obtain 50m3. What if (giving the same ...
13
votes
4answers
4k views

Why are snowflakes symmetrical?

The title says it all. Why are snowflakes symmetrical in shape and not a mush of ice? Is it a property of water freezing or what? Does anyone care to explain it to me? I'm intrigued by this and ...
5
votes
3answers
13k views

Can pockets of air exist underwater?

If yes, why don't they fill up with water, and can you breathe the air there? Like, it's not exactly atmosphere there, but an underwater cave with higher ceiling. P.S. Possible that it has a ...
7
votes
4answers
5k views

Eyes open under water

Yesterday I looked underwater with my eyes open (and no goggles) and I realized I can't see anything clearly. Everything looks very, very blurry. My guess is that the eye needs direct contact with air ...
3
votes
3answers
352 views

Would a sea level rise (on the other side of the Earth) if you would dip your finger into the ocean?

(I'm not a physicist & I hope this question isn't too basic/lame) The question says it all & assuming: No atmosphere No Earth rotation Not a single object in the ocean(s) Ignore all other ...
2
votes
2answers
27k views

Freezing point of water with respect to pressure.

I know when the pressure is reduced, the boiling point of water is reduced as well. But how does the pressure affect the freezing point of water ? In a low pressure environment is the freezing point ...
12
votes
2answers
199 views

Do all phases of ice look the same visually?

I recently read about different phases of ice on Wikipedia. But I can't find any pictures of the different ice phases. Do they all look alike visually? If you weren't able to measure the pressure and ...
12
votes
5answers
4k views

Waves in water always circular

I have had a question since childhood. Why do we always get circular waves (ripples) in water even when we throw irregularly shaped object in it?
8
votes
5answers
3k views

Are water waves (i.e. on the surface of the ocean) longitudinal or transverse?

I'm convinced that water waves for example: are a combination of longitudinal and transverse. Any references or proofs of this or otherwise?
7
votes
5answers
1k views

What happens if you try to freeze water in an water tight container

If I have a container that is full of water and I attempt to freeze the water by freezing the container, what would happen if the container is strong enough to prevent the water expansion? Could the ...
4
votes
2answers
531 views

Why does evaporation take place? [duplicate]

I was looking at at puddle when I thought that this puddle will evaporate tomorrow but then it occurred to me that the boiling temperature of water (aka to turn into gas) is $100$ degrees under 1 ...
1
vote
1answer
8k views

Is sea water more conductive than pure water because “electrical current is transported by the ions in solution”?

Apparently, electrical charge is transported by the ions dissolved in water, is this true?
1
vote
3answers
2k views

Maxiumum weight a buoy can float [closed]

I have a buoy that can hold 2943.02 cubic millimeters of non-pressurized air, I need and equation to work out the maximum weight that the buoy can float.
0
votes
1answer
502 views

Calculation of pressure from flow rate of water

Anybody kindly help me to find how to calculate pressure in bar from flow rate. I have a pipe and from that I am transferring water at a constant flow rate of 5ml/min. At this flow rate, with a 0.5 cm ...
137
votes
3answers
40k views

Surviving under water in air bubble

An incredible news story today is about a man who survived for two days at the bottom of the sea (~30 m deep) in a capsized boat, in an air bubble that formed in a corner of the boat. He was ...
44
votes
4answers
4k views

Being in a solid state, why is ice slippery? [duplicate]

Saying that ice is slippery is like saying that water is wet -- it's something we've known for as long as we can be said to have known anything. Presumably, humans as a species knew ice was slippery ...
31
votes
1answer
4k views

Was Titanic's captain's decision correct?

I just saw a documentary on Titanic. Someone in that documentary told Captain Smith "Shall we close the water tight doors, sir?" and the Captain replied "No, let it be open. Let the water ...
23
votes
9answers
13k views

How can water evaporate at room temperature? [duplicate]

Boiling point of water is 100 degree Celsius. The temperature at which water in liquid form is converted into gaseous form. Then how it possible for water to evaporate at room temperature?
14
votes
2answers
1k views

Why doesn't water come out of tap/faucet at high pressure when I turn it on?

(tap=faucet) When I turn a tap on full and then put my thumb over the spout covering, say, 90% of it, then the water spurts out. If I turn it on to, say 10%, then the water dribbles out. What's the ...
6
votes
2answers
3k views

How does the process of freezing water remove salt?

How does freezing water to make ice remove whatever salts were in the water to begin with?
6
votes
1answer
664 views

Microwave oven + water: dielectric heating or ion drag?

When you place a water or food in a microwave oven, it heats. Which process commits more energy to that: dielectric heating, or ion drag i.e. resistive heating? AFAIK, in distilled water (which is a ...
5
votes
4answers
930 views

Water in vacuum (or space) and temperature in space

So, water in vacuum will boil first and then freeze. I don't know how the freeze happens. As pressure lowers to zero, what happened to freezing point? (I know heat taken by vapor, and the water cool ...
4
votes
1answer
1k views

Cooking pasta: why does adding a lid lead to overflow?

When cooking pasta, some organic foam usually forms on the surface of the boiling water and the situation can be kept under control by adjusting the heat (and/or adding some oil). Covering the pot ...
16
votes
1answer
787 views

Why is boiling water the second time more quiet than boiling it the first time?

First of all: This is a different question than Why is boiling water loud, then quiet?, although the answers might be similar. When I wake up, I boil some water for a cup of tea. It happens quite ...
10
votes
2answers
3k views

Is there a way to fill Tank 2 from Tank 1 through Gravity alone?

I am a newbie in water system design but I am currently faced with the exact situation below on my land, and I need to know whether gravity alone is sufficient in order to fill Tank 2 from Tank 1, as ...
8
votes
2answers
4k views

273 + degree Celsius = Kelvin. Why 273?

Temperature conversion: 273 + degree Celsius = Kelvin Actually why is that 273? How does one come up with this? My teacher mentioned Gann's law (not sure if this is the one) but I couldn't find ...
8
votes
3answers
5k views

Why does the water level equalize in a series of tubes?

Say I have a series of tubes (not the internet) looking like this, where w represents water: ...
6
votes
1answer
7k views

How fast would someone have to run to run over water?

I was thinking about Flash, the superhero, or the little boy in the Incredibles. There is one Yahoo answer that doesn't answer a lot. Especially, I don't think surface tension would help a lot for a ...
4
votes
2answers
480 views

Why do some things crystallize? (And others don't, for that matter.)

Ice, for example, will form a crystal when frozen under certain circumstances. Why is this the case for ice? While on the subject of water crystallization, why do snowflakes usually form in base 6 ...
3
votes
3answers
3k 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 ...
12
votes
3answers
571 views

what is this force that is able to surpass an entire planet's force on it?

I have a wet teabag in an empty cup. If I will hold the teabag and touch the wall of cup with it, it will stick to the cup, like there would be glue or some magnetic field, but there's just water. ...
9
votes
4answers
10k views

Why does ice have a lower density than water?

Can someone explain me why is ice lighter than water? As I know, all solids are usually heavier than the liquids (correct me if I am wrong).
8
votes
1answer
1k views

water flow in a sink

When one turns on the tap in the kitchen, a circle is observable in the water flowing in the sink. The circle is the boundary between laminar and turbulent flow of the water (maybe this is the wrong ...
7
votes
3answers
517 views

Hot water freezing faster than cold water

This question has puzzled me for a long time. There is already a question like this on Physics.SE. John's answer to the question seems quite satisfying. But when I googled the cause I found this and ...