Water and H2O

There is certainly some confusion around the term 'water'. Hopefully this helps clear things up:

Common usage: Water refers to the liquid state.

Scientific usage: Water refers to the substance regardless of whether it is in the solid (ice), liquid, or gaseous (vapor, steam) state.

/Kayyam

Correction:

In My Post: 3341147 - Of Fri Aug 01, 2008 4:20 pm where I stated that all molecules of water (H2O), no matter what their physical state would appear exactly the same, excepting their energy state, I left out the real possibility of selecting a molecule of water containing the Hydrogen isotope deuterium out of a given state. This molecule of "heavy water" would physically appear somewhat different from that of the more naturally occurring dihydrogen oxide. Sans this event, my observation that only the energy state of those molecules so selected would differ stands.

The nucleus of deuterium, called a deuteron, contains one proton and one neutron, whereas the far more common hydrogen nucleus contains no neutrons. The isotope name is formed from the Greek deuteros meaning "second", to denote the two particles composing the nucleus.

Apologies:

JM

I'm not sure what you mean by "appear exactly the same". Certainly a water molecule in the vapor phase would be undergoing different vibrational modes than one in any of the ice phases. This would be visually apparent (if you could actually see it).

And don't forget the even rarer isotope of hydrogen called tritium, as well as the three stable isotopes of oxygen. So although "heavy water" is typically of the D2O variety, it can actually come in several flavors.

/Kayyam

I thought the difference between ice, water and steam was a function of PV/T.

If you accept that water has a freezing point of 0C and and a boiling point of 100C under one atmosphere of pressure, then volume of the container holding the single molecule will determine its state. Just my 1.815606 cents worth (on today's exchange rate)

D'oh, didn't realise there were two more pages of postings after the first page.

Kayyam, Thanks for the reply.

Re:

Both my initial and 2nd post take into account "different vibrational modes" via my reference to their energy states. The phrase "appear exactly the same" references the ideal situation where we take "snapshots", in any given instant of time, of three separate molecules of water, each in different physical states of liquid, gas, and solid respectively. Given that all molecules are of the common type that make up the majority of the population of water (all isotopes of all atoms are equal ) and the "snapshot" effect eliminated the energy state so that we could clearly see only the atomic structure of each molecule they would be identical in appearance. Thus the point of my original post: the only difference between the said molecules would be their energy states.

This, of course is a story told with the molecular stance in mind. If we were to descend to that level of quantum physics and compare, all bets would be off, even if all three molecules were from the same physical state, say liquid water, a gander at atomic structure may reveal an electron or two "out of place". But what are the odds, eh?


JM