Why Water isn’t H 2 O (short answer: cuz it’s a mixture!): A case study in how the history of...

Why Water isn’t H2O(short answer: cuz it’s a mixture!):

A case study in how the history of science and science itself loosens the

grip of Realist metaphors

Ken DickeyBoise State University Philosophy

Nyssa High School Chemistry

The Miracle of Semantic Realism

“Suppose I point to a glass of water and say ‘this is called “water”’…[T]he body of liquid I am pointing to bears a certain sameness relation (say, x is the same liquid as y…) to most of the stuff I and other speakers…have on other occasions called ‘water’.”

-- Hillary Putnam, “Meaning and Reference”

“Suppose I now discover the microstructure of water – that it is H2O.”

“…the extension of the term ‘water’ was just as much H2O on Earth in 1750 as in 1950…”

-- Hillary Putnam, “Meaning and Reference

In sum, I can point to one thing or one sample and utter a word. By the miracle of semantic realism, that word picks out all other parts of the world that have the same ?!? as my sample. Of course, this only works for natural kinds terms like ‘water’.

Characteristics of natural kinds terms

• “Carve nature at its joints”• Reveal fundamental patterns of the world• Pick out the final categories that scientists

ultimately strive for• Identify things by their “real essence”

(usually microstructural features), not their “nominal essence”

• Once dubbed, their extension does NOT depend on human decision-making

Putative Examplesof Natural vs. non-natural kinds terms

Natural vs. Non-natural

• Temperature (average kinetic energy of tiny particles)

• ‘x has a temperature of __ oC’

• Warmth (a judgement that varies from individual to individual)

• ‘x is warm’

• Plant (multi-cellular organism with cells containing chloroplasts and cell walls)

• ‘x is a plant’

• Mountain (vague rise in topography)

• ‘x is a mountain’• Mountain vs. hill

• Globular Cluster (group of stars formed from the same nebula and bound locally by gravity to form a spherical shape)

• Constellation (recognizable pattern of stars in the sky)

• Pattern varies with location in the galaxy

• Pattern identification reflects human interests

• Ant Colony (grouping of ants with inter-dependent roles and directed by a single queen ant)

• Penal Colony (a human institution created to fulfill human needs/goals)

It is the appeal to microstructure, I believe, which legitimates (in the minds of some) what I am terming the “miracle of semantic realism”.

Most people will agree that the extension (or “meaning”) of ordinary English predicates depends on human decision-making. For example, there is an active debate now over whether the term ‘marriage’ applies only to male-female unions, or could also apply to same-sex unions. Again, there was a recent debate within the scientific community over whether the term ‘planet’ should apply to bodies as small as Pluto.

But it is believed that some English predicates escape this reliance on on-going human decision-making (that’s the “miracle”). These are the so-called ‘natural kinds’ terms. What allows these terms to stand on their own, it is believed, is that, once dubbed, their extension is determined by a pure microstructure, one which could very well escape the notice of language users. Once this microstructure takes over the meaning of a word, connecting it to the fundamental patterns of nature, no amount of human decision-making can circumvent that (or so it is believed).

• Bird (warm-blooded, feathered creature with wxyz DNA characteristics)

• ‘x is a bird’

• Plane (a human invention)

• ‘x is a plane’

• Oxygen (element with atomic number 8)

• Phlogiston (substance with sometimes-negative weight, posited by scientists to explain experimental results but later rejected)

• Water (H20)

• ‘x is a bit of water’

• Mud (a mixture containing water and “dirt” in unspecified proportions)

• ‘x is a bit of mud’

A Lesson in the History of Science

Yawn…

How it was discovered that water is H2O

Joseph Louis Proust

French chemist

Born September 26, 1754)Angers, France

Died July 5, 1826 (aged 71)Paris,France

Law of Definite Proportions

Water sample A = 18 grams

16 g oxygen and 2 g hydrogen

16 g O / 2 g H = 8 O :1 H

Water sample B = 27 grams

24 g oxygen and 3 g hydrogen

24 g O / 3 g H = 8 O :1 H

Sample C = 32 g O / 4 g H = 8 O :1 H

LDP: In a chemical compound, the ratio of elements is always the same, regardless of sample.

* Note, this is NOT true of mixtures!

Discovering Water is H2O

John Dalton

Born September 6, 1766)

Died July 27, 1844 (aged 77)

Law of Multiple Proportions

40 g of Lye (Draino)

23 g Na, 16 g O, 1 g H

16 g O / 1 g H = 16 0 : 1 H

27 g of Water

24 g O / 3 g H = 8 O : 1 H

62 g of Ethylene glycol (antifreeze)

24 g C, 32 g O, 6 g H

32 g O / 6 g H = 5 1/3 O : 1 H

32 g of Methanol (wood alcohol)

12 g C, 16 g O, 4 g H

16 g O / 4 g H = 4 O : 1 H

John Dalton

Born September 6, 1766)

Died July 27, 1844 (aged 77)

In Lye 1 g H : 16 g O, the lowest ratio, so s’pose

Lye = 1 H : 1 0

In Water 1 g H : 8 g O or 2 g H : 16 g O

Water 2 H : 1 O

In Ethylene glycol 1 g H : 51/3 g O or 3 g H : 16 g O

E. G. = 3 H : 1 O

In Methanol 1 g H : 4 g O or 4 g H : 16 g O

Methanol = 4 H : 1 O

LMP: When the same elements combine into different compounds, they do so in the ratio of small whole numbers.

John Dalton

But the ratio of masses says nothing about the MICROSTRUCTURE of water.

For that we need…………

Dalton’s Atomic Theory(about 1803)

Various atoms and molecules as depicted in John Dalton's A New System of Chemical Philosophy (1808).

1. All elements are composed of tiny indivisible particles called atoms.

2. All atoms of the same element are identical. The atoms of any one element are different from those of any other element.

3. Atoms of different elements can combine with one another in simple whole number ratios to form compounds.

4. Chemical reactions occur when atoms are separated, joined into molecules, or rearranged. However, atoms of one element are never created nor destroyed by a chemical reaction.

Dalton’s Atomic Theory

2 Hydrogen atoms 1 Oxygen atom

1 molecule of water = H2O

Discovering water is H20

Ta da….

But this is not the end of the story…

What Came Next

• The Russian chemist Dmitri Mendeleev organized all of the known elements into a pattern that is today considered to be the first periodic table.

• Mendeleev’s table allowed him to predict the existence of previously unknown elements!

• Predictive power lent great credence to the emerging science of chemistry, founded on Dalton’s atomic theory. Mendeleev’s original periodic table

published in 1869 based the order of elements on their atomic mass.

What Came Next

However…

What Came Next

• Mendeleev’s table was arranged by atomic mass.

• This created puzzles where a few elements seemed to be “out of place”.

• Trusting the pattern-like character of his table, Mendeleev insisted the masses of elements simply had not been accurately determined.

• But the puzzles remained…

What Came Next

• The “fix” could not be had until the overthrow of Dalton’s atomic theory.

• It started with the discovery of the electron by J.J. Thomson in 1897.

What Came Next

J.J. Thomson’s famous cathode ray experiment. The degree of deflection indicated a very high charge-to-mass ratio. These deflected particles must have been much smaller than even a hydrogen atom.

What Came Next

1. All elements are composed of tiny indivisible particles called atoms.

Not anymore!

Comment on conceptual vs. empirical revision?

What Came NextRutherford’s famous experiments involving gold foil soon followed.

What Came Next

He discovered the atomic nucleus and the proton. His student Moseley introduced the concept of atomic number, which justified the correct placement of elements within the periodic table.

What Came Next

Still later (1922), the mass spectrometer was used to isolate different atoms of the same element with different masses. In 1932, neutrons were discovered and used to explain how these atoms differ.

Isotopes = atoms of the same element with different masses (same atomic number, but different numbers of neutrons)

What Came Next

2. All atoms of the same element are identical.

Not anymore!

What Came Next

The existence of neutrons and isotopes explained WHY Mendeleev’s arrangement of elements was flawed.

The chemical properties of atoms were determined by the number of protons (and electrons). But atoms with more protons did not necessarily have (on average) more neutrons.

So, in a few exceptional cases, elements with a greater atomic number could still have a lesser atomic mass.

Mendeleev, working with Dalton’s atomic theory, could never have known this.

Protium Deuterium Tritium

Three isotopes of hydrogen

More to the point…

In any actual sample of water, all of these isotopes will be integrated within water molecules. That means, we could have:

P2O (almost all naturally occurring water)

DPO (about 1 in 3200 natual water molecules)

D2O (about 1 in 41 million water molecules)

PTO (trace)

DTO (trace)

T2O (trace)

And all are “water” molecules!

A Strong Intuition of Mine

At the time of discovering isotopes of hydrogen, scientists COULD HAVE decided that only P2O is really water, and that DPO (and D2O) are impurities. Since they did not make that decision, it remains acceptable to say that water is H2O. Still, the fact that there was such a “decision point” casts doubt on whether the term ‘water’ uttered in 1750 referred to H2O once and for all, independently of all subsequent decision-making. That is, it casts doubt on whether the term ‘water’ IS a natural kind term.

• “Carve nature at its joints”• Reveal fundamental patterns of the world• Pick out the final categories that scientists

ultimately strive for• Identify things by their “real essence”

(usually microstructural features), not their “nominal essence”

Philosophical Upshot

• The discovery that water is H2O rests on a theory of the atom that has since been supplanted.

• A more modern theory of the atom still accepts the claim that water is H20, but would insist there is more going on than just that.

• This casts doubt on whether ‘water’ picks out a “final category that scientists ultimately strive for”.

So much for the history of science…

What about the science of water itself?

In sum, I can point to one thing or one sample and utter a word. By the miracle of semantic realism, that word picks out all other parts of the world that have the same ?!? as my sample. Of course, this only works for natural kinds terms like ‘water’.

Any sample of ordinary water dubbed as ‘water’ in 1750 was surely a MIXTURE of H2O with gobs of other stuff!

A new start to the debate…

So it will be difficult to isolate what the essential features of water are such that all subsequent samples of water have the same ?!? as the originally dubbed sample of water.

Another way to see this point is through pH or even perhaps taste testing.

Ordinary samples of water simply do not have the same pH (or taste!) as so-called “pure” water.

But surely we can PURIFY water to remove everything except the H2O, can’t we?

(Not really, as we shall see)

Even the ancients could collect RAIN water, which is free of original contaminants.

(But not of “new” contaminants, as we shall see)

The next step…

The Water Cycle

Meanwhile, high up in the clouds, chemical reactions are occurring…

Nitrous Oxide (from lightning or internal combustion)NO + ½ O2 NO2

3NO2 + H2O NO + 2 HNO3 (Nitric acid)

Sulfur Dioxide (from volcanoes or coal burning)

SO2 + ½ O2 SO3

SO3 + H2O H2SO4 (Sulfuric Acid)

Carbon Dioxide (from decomposition, burning, exhaling)

CO2 + H2O H2CO3 (Carbonic Acid)

The next step…

So regular rain water has a pH of about 5, and even lower (so-called “acid rain”), if it is subjected to very high levels of industrial pollution.

O.K. Appealing to rain water for “pure” water was a bad idea. Still, we can get pure water here on the ground through the process of distillation.

Another avenue for debate…

Distillation Apparatus

Impurities remain behind as only H2O boils and condenses

You don’t have to go up high into the atmosphere to run into the problem of atmospheric gases dissolving in water. The atmosphere will “come to you”!

(Note: this is why fish can breathe underwater)

Atmospheric and dissolved gases are continually exchanged through a dynamic equilibrium

Henry’s Law:

“At a given temperature the solubility of a gas in a liquid is directly proportional to the (partial) pressure of the gas above the liquid.”

Dickey’s Corollary to Henry’s Law:

“If there is any gas whatsoever near the surface of a liquid, some of that gas is going to get dissolved into the liquid.”

Upshot: Even distilled water is impure, insofar as it has dissolved gases in it.

*At 20oC and 1 atm, water is 0.0023% dissolved air (by mass).

All right, then. Let’s REMOVE the atmosphere entirely!

•Even if there isn’t a naturally-occurring place on Earth that is atmosphere-free, we can CREATE such a place in the lab.

•As philosophers can certainly IMAGINE water existing in the absence of any atmosphere to cause contamination.

Yet another try…

Interesting idea… Do you know what HAPPENS to water when you remove all of its atmosphere?

It boils! Check it out!

Then you don’t have water at all (which is a liquid), but instead a vapor.

Yet another try…

Not if NOT ALL of the water boils! Then you could have an equilibrium with liquid water, H20 vapor, and H20 vapor dissolved in the liquid water.

The final rejoinder…

Then perhaps you could still say that water is a “mixture”, but it would be a mixture consisting ENTIRELY of H2O!

And this water “mixture” really DOES have a pH of 7

Is THAT supposed to be what people were talking about in 1750, when they used the term ‘water’ to describe what they were drinking, bathing in, watering plants with, etc.?

That’s the way natural kinds terms work!

You use a word, but neither you nor anyone has to know what the word refers to. That’s something to be discovered by scientists, no matter how long and complex the process is.

As it turns out, water – PURE WATER – really is nothing but H2O!

There is just one little problem…

H2O molecules are constantly in motion, crashing into one another, jostling, and even scraping parts off of one another.

Self-ionization of water shockwave animation

H2O + H2O OH- + H3O+

Hydroxide Hydronium ion ion

Self-ionization of H2O

At 25oC, Kw for this process is 1.0 x 10-14

(That’s why the pH scale ranges up to 14.)

This means that for “pure” water,

[H3O+] = 1.0 x 10-7 M (hence the “7” for pH);

[OH-] = 1.0 x 10-7 M

Combined, these impurities occur at a concentration of 2.0 x 10-7 M, and since water itself has a concentration of 56 M, this means…

One little problem…

[Ions] / [H2O] = 2.0 x 10-7 / 56 = 3.6 x 10-9

This means that for every sample of water,

0.00000036%

of the water is NOT H20, no matter what lengths one takes to purify it!

So water is not really just H2O, no matter how pure you try to make it.

Conclusions

1. That water is H2O is a prime exemplar of essentialism in semantics. ‘Water’ is held to be a natural kind term that “carves nature at its joints” because of the supposed truth of this claim.

Conclusions

2. But the discovery that water is H2O is part of an unfolding historical process, one which has since moved beyond the claim in question, onto what are arguably even more fundamental ways to “carve up reality”.

Conclusions

3. Furthermore, what ordinary people for centuries have taken to be water is NOT purely H20, but is instead a mixture that at the very least contains dissolved gases from the atmosphere.

Conclusions

4. And finally, there is simply no possible way to purify water so that it is not a mixture (i.e., so that it contains only H2O). At the very least, it must contain trace quantities of hydronium and hydroxide ions.

Conclusions

In sum, the term ‘water’ does not carve nature at its fundamental joints, and the identification of water with H20 is, strictly speaking, false.

It is, no doubt, and extremely useful idealization of what’s really going on with water.

But useful idealizations are not what Semantic Realism promises.

Limitations

Water being only one example, this argument certainly can not disprove realism in semantics, nor can it establish that there are no natural kinds terms.

Benefits

But: for those of us who are suspicious about claims that scientists have arrived at a final answer about anything, or claims that certain words carve reality at its joints, pointing out that ‘water’ is NOT the clear example that many take it to be does provide some satisfaction.

Benefits

And for those who are watching the debate from the sidelines, this argument might help them to remain in an appropriately skeptical state of suspended judgement.

Benefits

Finally, it is time to recognize that general plausibility of the view that there are natural kinds terms at all relies more on some compelling metaphors rather than a close examination of details. To learn that water is NOT H2O will, I hope, loosen the grip of those Realist metaphors.

A P.S. Rejoinder?

• O.K., so water is not just H2O; it is a mixture. Still, that doesn’t prove ‘water’ is not a natural kind term.

• Water, we have learned, is really a mixture consisting mostly of H20 with 1.0 x 10-7 M of hydronium ions and 1.0 x 10-7 M of hydroxide ions.

• People who have used the term ‘water’ throughout history, without realizing it, were referring to that mixture.

A P.S. Rejoinder?

• This response is really an example of getting the point but not getting the lesson.

• Any argument of the form ‘x is too simple because of y’ can be met with the response that ‘x is now modified to take into account correction y’.

• But to go on to assert that the modified x is now the final answer, or even that there is a final answer, is to make a leap of faith.

• The lesson of the case-study for ‘water’ is that this leap of faith is not justified.

Why Water isn’t H 2 O (short answer: cuz it’s a mixture!): A case study in how the history of...

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