Questions on emergent property "wetness"

Magus
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Questions on emergent property "wetness"

I have heard it a few times on these forums and in other places, as neither hydrogen or oxygen have the property of wetness.  I was wondering if that were actually the case.  If we cool down oxygen or hydrogen enough doesn't it go into a liquid state?

http://www.rationalresponders.com/forum/16042#comment-209655

http://www.rationalresponders.com/forum/sapient/atheist_vs_theist/6534#comment-60039

Sounds made up...
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HisWillness
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Magus wrote:If we cool down

Magus wrote:
If we cool down oxygen or hydrogen enough doesn't it go into a liquid state?

Sure, but wetness is a room-temperature property. By that, I mean it falls under "breakfast-table physics": the stuff we can observe within a bearable range of temperatures to human skin. Hydrogen and oxygen in liquid form is less like "wetness" and more like "freeze your hand off-ness". Not that I'm saying it's not a liquid, it's just not one you'd want to handle.

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There are also other

There are also other properties which distinguish different liquids, which are a function of the size and shape of the molecules and how the electrons distribute themselves over the molecule leading to the molecules having positively and negatively charged regions.

These factors affect properties such as density, viscosity (is it like water or thick syrup), how it mixes with other liquids, what groups of other substances dissolve in it, and also a property which affects how it 'wets' a solid surface. This last corresponds closest to what we might informally think of as 'wetness', in that it determines whether the liquid tends to soak into a piece of cloth or not, for example. It determines whether it tends o spread out into a film covering the surface at one extreme, or remain as individual droplets.

I guess the point is that all of these properties of a given chemical compound, including whether it is even a liquid in a given range of temperature, are normally very different from those of the individual elements of which it is composed.

One of the key factors affecting 'wetting' of a surface by a liquid is the degree of polarity of the molecules, which is a measure of the degree to which different parts of the molecule display an effective electrical charge, and water is quite strongly polarised, which means that the molecules tend to attract each other, and other polarised molecules, fairly strongly. Whereas liquids hydrogen and oxygen do not show this property.

It is not a perfect analogy for emergent properties, I will concede, so you do have some point there.

It occurs to me that a better argument might be based on pointing to the huge range of properties exhibited within particular classes of substances which all have the same constituent elements, such as 'hydrocarbons' which include gasses, like methane, liquids (at normal temperatures) like octane and related substances making up the major components of gasoline, to polythene plastics. All of these are composed of the same two elemenst, hydrogen and carbon.

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Another bit to think

Another bit to think about would be who is in charge of defining what is wet? What criteria do they use to make the determination that a given substance is wet?

 

If wetness is one thing that you can look up in a text book and which applies in very many situations, then you can run with that. The problem being that wetness as offered is not really one thing that you can look up so easily.

 

For a luthier, water is considerably less wet than most organic solvents.

 

For a nuclear weapon designer, liquid hydrogen (deuterium actually) is what is needed to make a “wet bomb”.

 

For a conventional explosives manufacturer, wetting agents must be liquid at temperatures around -40 degrees.

 

For a condensed matter physicist, the concept of wetness is impossible to define.

 

So really, the idea of wetness is not one thing but rather it is quite dependent on the context in which the term is used.

 

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Answers in Gene Simmons

Answers in Gene Simmons wrote:

 

So really, the idea of wetness is not one thing but rather it is quite dependent on the context in which the term is used.

 

Perhaps, but in my materials science courses I learned that wetness is the ability of a substance to wet a surface. It a liquid will spread across a surface then that is wetness. But perhaps others use different definitions then my professors. We look at wetness in terms of surface energy. If someone wants I can go into this in more depth, but it is a rather dull subject. And for all I know my understanding of wetness is from a peculiar materials science point of view.

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BobSpence1 nails it on the

BobSpence1 nails it on the head. 

 

Wetness isn't the ability to enter a liquid state or the act of existing in a lquid state.  Wetness is essentially the ability to form a cohesive film over a surface and is largely determined by the surface properties of the liquid and the surface in question.  As a very sweeping generalisation, water is a wetting liquid (forms pools) while mercury is not (tends to form beads).

And as a random factoid, liquid oxygen is blue

 

M

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MichaelMcF wrote: And as a

MichaelMcF wrote:

 

And as a random factoid, liquid oxygen is blue

 

  Intersting little tid-bit of knowledge.  See, participating in an atheist forum isn't always about arguing over theism. Thanks MMF.

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ProzacDeathWish

ProzacDeathWish wrote:

MichaelMcF wrote:

 

And as a random factoid, liquid oxygen is blue

 

  Intersting little tid-bit of knowledge.  See, participating in an atheist forum isn't always about arguing over theism. Thanks MMF.

 

I would also like to add that liquid nitrogen is blue.  Given that, the next timethat a three year old child asks you why the sky is blue, you can tell him that the answer is because air is blue.

 

Your answer will be fully truthful but misleading.  If you work this one right, you will have encourged one more kid to ask the right questions.

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MichaelMcF
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Answers in Gene Simmons

Answers in Gene Simmons wrote:
I would also like to add that liquid nitrogen is blue.  Given that, the next timethat a three year old child asks you why the sky is blue, you can tell him that the answer is because air is blue.

 

Your answer will be fully truthful but misleading.  If you work this one right, you will have encourged one more kid to ask the right questions.

 

Liquid nitrogen blue?  I'd question the source of the nitrogen being chilled as it's undoubtedly contaminated with oxygen.  Liquid nitrogen is colourless.

 

M

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