Questions tagged [water]

For questions relating to water (H₂O), specifically its structure, properties, and uses in chemistry. For questions not about water but rather about solutions in water, use tags [aqueous-solution] or [solubility] instead.

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129
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7answers
36k views

Why doesn't water burn?

Hydrogen is flammable, and for any fire to burn it needs oxygen. Why does a compound made of hydrogen and oxygen put out fires instead of catalyzing them? I understand that hydrogen and water are ...
80
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5answers
83k views

Does water really 'go bad' after a couple of days?

Among my friends it is a sort of 'common wisdom' that you should throw away water after a couple of days if it was taken from the tap and stored in a bottle outside the fridge, because it has 'gone ...
75
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4answers
17k views

Is it true that heavy water is not blue?

I believe I saw this claim somewhere on the internet a long time ago. Specifically, it was claimed that the difference could be observed by filling one long, straight tube with light water and one ...
50
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2answers
8k views

What is the pH of ice?

The pH of pure liquid water depends on temperature. It is about pH = 7.0 at room temperature, pH = 6.1 at 100 °C, and pH = 7.5 at 0 °C. What happens to the pH (or to the ion product) of pure water ...
49
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2answers
14k views

Why don't we explode after drinking water?

It is known that acid should be added to water and not the opposite because it results in an exothermic reaction. Our stomach contains HCl, so why don't we explode when we drink water?
41
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9answers
423k views

Why does ice water get colder when salt is added?

It is well known that when you add salt to ice, the ice not only melts but will actually get colder. From chemistry books, I've learned that salt will lower the freezing point of water. But I’m a ...
39
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3answers
9k views

Does heavy water taste sweet?

In this YouTube video from Cody's Lab, Cody claims that heavy water tastes sweet. He does some fairly convincing comparisons but still expresses a little doubt that the effect is real. Has this been ...
39
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2answers
3k views

Are the lone pairs in water equivalent?

I've read that the oxygen atom in water is $\mathrm{sp^2}$ hybridized, such that one of the oxygen lone pairs should be in an $\mathrm{sp^2}$ orbital and the other should be in a pure p atomic orbital....
38
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3answers
4k views

Why is fresh ice sticky?

Fresh ice cubes are almost instantly sticky and easily cling on to fabric and other similarly rough surfaces. A few minutes later, however, the effect almost completely disappears. What is the cause ...
33
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5answers
26k views

A glass of water with ice-cubes in it. Where's the water the coldest; at the top or bottom?

Suppose that I fill a glass with ice water. As the ice melts, it cools the water around it. Given that cold water is denser than hot water, I would presume that the cold water would sink to the ...
31
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4answers
8k views

Effect of drinking ultra-pure water

What would be the effect if someone were to drink ultra-pure water with an electrical resistivity of $18 \, \mathrm{M} \Omega \! \cdot \! \text{cm}$? Would they immediately die? Would they just ...
31
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2answers
2k views

What makes ice slippery?

I've heard and read (multiple times) two theories have have been around for a while, both of them obvious nonsense. One states that pressure and friction make the ice melt (turn to water) where the ...
28
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5answers
13k views

Why is water “the universal” solvent?

This is an old question that our textbook tried to answer but worsened the situation. Many things are soluble in water. So many, that studying solutions will always require studying aqueous ones. It ...
28
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2answers
5k views

What happens if you cool water in a container too small for it to freeze?

Freezing a full bottle of water tends to shatter the glass bottle. What if you used something tougher than glass, like diamond? What would happen if you kept dropping the temperature, but restrained ...
28
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2answers
2k views

Why is snow white?

I know that this is a rather ambiguous question; but my question is, whenever we take water and freeze it in the freezer, it still tends to stay clear. Since snow is just frozen water, why is it white?...
28
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2answers
14k views

Is methanol more acidic than water?

Methanol is slightly more acidic than water. Their $\mathrm{p}K_\mathrm{a}$ values, in water, are $15.5$ and $15.7$, respectively. All other aliphatic alcohols, however, are less acidic than water. ...
25
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4answers
19k views

Hypothetical: What happens to water as pressure increases to infinity? [duplicate]

I've asked a similar question here but the answer given shows the behaviour of water under general conditions. I'd like to know what the behaviour of water is like as pressures increase towards ...
24
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2answers
27k views

Why is water a dipole?

Water ($\ce{H2O}$) is a dipole. The reason why is simply because it is not symmetrical, there are more electrons on the oxygen side than on the hydrogen side, and the electronegativity of oxygen. But ...
23
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2answers
10k views

Why does water dissociate to H3O+ and OH- rather than H+ and OH-?

Why does water dissociate to $\ce{H_{3}O^{+} + OH^{-}}$ instead of $\ce{H^{+} + OH^{-}}$? This question came to surface when I was learning about acids and bases, and learned this definition: $\...
22
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5answers
5k views

How does water evaporate completely when at room temperature?

If water evaporates at room temperature because a small percentage of the molecules have enough energy to escape into the air, then why does a kitchen counter with a small amount of water eventually ...
22
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2answers
11k views

Why is distillation not a viable way to separate ammonia from water?

Since the steam pressure of ammonia is higher than that of water, I would expect distillation to be a reasonable way of separating a mixture of both. However, in industrial applications known to me ...
21
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1answer
1k views

Are there any known chemical properties of tritium water that make it unusually different from protium water?

I suppose the first question supporting the main question is, has tritium water ever been synthesized in sufficient quantity to test chemical properties? If so, and apart from the obvious radioactive ...
21
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3answers
7k views

Why does meltwater taste different?

I've noticed that water obtained from melting ice cubes (by keeping them in the open) tastes different from water cooled to the same temperature. Furthermore, the taste goes away if you keep it in ...
19
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2answers
44k views

Why does water evaporate at room temperature?

When water temperature reaches $100\ ^\circ \mathrm{C}$, the molecules get so excited that the hydrogen atoms lose the bonds to the oxygen atom and therefore the water starts to become gas. I get that,...
19
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5answers
51k views

Why does hydrogen fluoride have a boiling point so much lower than that of water?

$\ce{F}$ has more unshared electron pairs and is very electronegative, so $\ce{H}$ of another $\ce{HF}$ molecule can $\ce{H}$-bond with it. $\ce{HF}$ has normal boiling point of $\pu{19.5^oC}$ while $...
18
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3answers
58k views

What is hydrogen-rich water?

My question is: Is hydrogen-rich water true? I am aware of the alkaline water. I have read several articles in the Internet regarding this kind of water but I cannot seem to be convinced. Wikipedia ...
18
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3answers
12k views

What makes oceanic desalination so expensive?

What specifically makes oceanic desalination so expensive?
18
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2answers
517 views

What determines how much water of crystallisation a salt has?

Is there any reason behind the number of water of crystallisation? For example, $\ce{LiCl.2H2O}$ has two waters of crystallisation, and $\ce{MgCl2.8H2O}$ has 8 waters of crystallisation. Why does $\...
17
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2answers
11k views

Does water have a chemical name?

The title sums up the question: Does water have a chemical name? If so, what is it? P.S. I checked up the web and got all sorts of crazy answers like dihydrogenmonoxide, oxidane, ...
17
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7answers
43k views

Why can't pure water conduct electricity since it can be reduced at cathode and oxidised at anode?

We all know that pure water can't conduct electricity. But during electrolysis, if add a small amount of $\ce{HCl}$ acid inside, water could be decomposed to hydrogen gas and oxygen gas, as it is ...
17
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2answers
53k views

Why is water wet and fire hot?

This may be a silly question but why is water wet? All the previous questions on water do not explain the reason why is water wet. They assume that its a natural property. However we need to ...
17
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4answers
17k views

Why is H₂O V shaped? [duplicate]

We know that the molecule of H₂O is V-shaped. This is what makes it a dipole. But why is that? I mean, if the hydrogens have a partial positive charge, then they should try to get away from each ...
17
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3answers
2k views

Can an aqueous solution conduct electricity forever?

We know that pure water does not conduct electricity, but salt water is a decent conductor. This is commonly explained by saying that “the ions carry the current through the solution”, which is an ...
16
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2answers
63k views

EZ-Water - Fraud or breakthrough?

Recently the quack medicine folks online have been promoting the research of a certain Dr. Gerald Pollack who claims to have discovered a "forth phase of water", and who has recently published a book ...
16
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3answers
34k views

Why there is no change in water level when salt is added?

Let us say we have one glass of water and after that when we add one or two spoon of salt then we notice that salt dissolves in it but when we measure the water level we found that there is no ...
16
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5answers
33k views

Is pure water very corrosive?

In other site, someone claimed that pure water is very corrosive. Water distilled for some laboratory uses (like the Z-pinch reactor) is distilled to 0.00000009% purity, and is caustic enough to ...
16
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4answers
13k views

How to RAISE the melting point of water?

It is common that adding common salt into water will lower its melting point. But, is there any way to RAISE the melting point of water? Does it lower the boiling point of water as well? Why?
16
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3answers
9k views

Is there a simple way to separate deuterium oxide from tap water?

I understand that tap water contains minute amounts of deuterium oxide (heavy water). Is there a simple way to separate, concentrate the $\ce{D2O}$?
16
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2answers
60k views

What is the difference between distilled water and rainwater?

I am studying different means of collecting water for consumption. From resources available on Internet, I understand that distilled water is not advised for regular consumption because of the lack of ...
16
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3answers
27k views

Why are water droplets shaped like that?

With nothing to do, I stared at the droplets that get condensed on the glass panel of my window. Upon examination, these droplets appear to be in some sorta pattern. There are big droplets as well as ...
15
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9answers
8k views

How can 30 ml of water be heated in less than 10 seconds?

How is it possible to heat a tiny amount (30 ml)[1] of water to a high enough temperature to make a coffee, in less than 10 seconds and possibly instantly? Most heaters that I know of heat water ...
15
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1answer
2k views

Why does adding salt to boiling water cause it to flare up suddenly?

I was expecting that the water would become less "boily" since the ions in $\ce{NaCl}$ would require energy to disassociate. Instead it turned whitish and the water level suddenly rose and then ...
15
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2answers
3k views

Does freezing a solution with water always cause the water to separate and form the ice lattice?

I'm curious, I was trying to look into the affect of freezing a solution with water even when the solution is completely miscible. I came across something that detailed this regarding salt water and ...
15
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4answers
700 views

Relative strength of desiccants

Is it meaningful to characterize the relative strength of desiccants? For example, is there a measure of hygroscopy, or an ordering of desiccants, such that higher ones will always dry lower ones? ...
15
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1answer
1k views

What is deuterium-depleted water actually used for?

I noted, flipping through the paperback Alfa Aesar catalogue today, that they sell deuterium-depleted water. Under the usage category, they list 'NMR'. I'm trying to work out what specific use this ...
15
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2answers
2k views

What is the cause of hygroscopy?

Hygroscopy is the ability of a substance to attract and hold water molecules from the surrounding environment. Why are some compounds hygroscopic and others are not? What is it about their ...
15
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1answer
9k views

Using table salt as a way to limit humidity in an unoccupied house

We own a static caravan in the UK (Snowdonia region, so rainy and wet all year round, moderately cold winters) and we leave it unoccupied during Winter (Oct-Feb). We were advised of an apparently ...
14
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3answers
9k views

Do chemists refer to water as “dihydrogen monoxide”?

Is the name "Dihydrogen monoxide" actually what chemists would use to refer to $\ce{H2O}$ (assuming there was no common name, "water")? Of course, this is all over the internet. I'm a little ...
14
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5answers
2k views

Is there a simple field test for heavy water?

Thought experiment Given two glasses of water, how would one detect which glass contains heavy water, and which contains potable water without using complicated laboratory equipment? Something like ...
14
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3answers
8k views

Why exactly does molten NaCl explode, when it is poured into water?

Why does molten $\ce{NaCl}$ explode, when it is poured into water? $\ce{NaCl}$ has a high melting point, $1074\ \mathrm{K}$ ($801~\mathrm{^\circ C}$). $\ce{NaCl}$ has a molar mass of $58.44\ \mathrm{...