Date: Wed, 10 Sep 2003 09:21:41 -0600

Author: Jerry DiMarco

Subject: Re: Capillary

Post:

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I've wondered about oxygen dissolved in water for a long time. It
helps to understand what "dissolved" means in this case. Here is a
definition from a Water on the Web webpage at the Univ. of Minn.:

"Dissolved Oxygen (DO or O2):
The concentration of free (not chemically combined) molecular oxygen (a
gas) dissolved in water, usually expressed in milligrams per liter, parts
per million, or percent of saturation. "

According to the above source, dissolved oxygen is actually in the form of
microscopic bubbles. Since the oxygen is not chemically combined and is in
the form of microscopic bubbles, it is probably not affected by capillary
action (which is a surface tension phenomenon). So the oxygen, in effect,
is left behind.
And while we're at it, why do bubbles form in a glass after a few
hours? Here is another quote from the same webpage:

"Another physical process that affects DO concentrations is the
relationship between water temperature and gas saturation. Cold water can
hold more of any gas, in this case oxygen, than warmer water."

So my guess is that as the tap water warms up to room temp, more oxygen
molecules are forced out and combine with other molecules to make larger
bubbles...

Jerry


At 08:52 AM 9/9/2003, you wrote:

> September 9, 2003
>
> tap-l@listproc.appstate.edu
>
> Subject: Capillary
>
> Tappers:
>
> Today's homeschool experiment was to set two drinking
> glasses (we used plastic) side by side, one full of
> water, the other empty. Roll up a paper towel and
> insert it into both glasses, with the connection above
> the rims of both, well above the water line. Within a
> few minutes, water appeared at the bottom of the empty
> glass, transported through the towel. In a bit over 12
> hours, the two water levels were indistinguishable.
>
> That satisfied the student. But I am mystified by one
> effect. Within a few hours, bubbles (presumably from
> dissolved air) appeared throughout the inside of the
> formerly full glass, but none appeared in the receiving
> glass. What process inhibits dissolved gases from
> passage through a towel?
>
> Robert T McQuaid
> Orangeville Ontario Canada
> email: rtmq@stn.net

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     I've
wondered about oxygen dissolved in water for a long time.  It helps
to understand what "dissolved" means in this case.  Here
is a definition from a
Water on the Web
webpage at the Univ. of
Minn.:


"Dissolved Oxygen (DO or
O2):


  The concentration of free
(not chemically combined) molecular oxygen (a gas) dissolved in water,
usually expressed in milligrams per liter, parts per million, or percent
of saturation. "


According to the above source, dissolved oxygen is actually in the form
of microscopic bubbles. 
Since the oxygen is not chemically
combined and is in the form of microscopic bubbles, it is probably not
affected by capillary action (which is a surface tension
phenomenon).  So the oxygen, in effect, is left behind.

     And while we're at it, why do bubbles form in a
glass after a few hours?  Here is another quote from the same
webpage:


"Another physical process
that affects DO concentrations is the relationship between water
temperature and gas saturation. Cold water can hold more of any gas, in
this case oxygen, than warmer water."


So my guess is that as the tap water warms up to room temp, more
oxygen molecules are forced out and combine with other molecules to make
larger bubbles...


                                                                        Jerry




 At 08:52 AM 9/9/2003, you wrote:


    September 9,
2003


    tap-l@listproc.appstate.edu


    Subject:  Capillary


    Tappers:


    Today's homeschool experiment was to set two
drinking

    glasses (we used plastic) side by side, one full
of

    water, the other empty.  Roll up a paper towel
and

    insert it into both glasses, with the connection
above

    the rims of both, well above the water line. 
Within a

    few minutes, water appeared at the bottom of the
empty

    glass, transported through the towel.  In a bit
over 12

    hours, the two water levels were
indistinguishable.


    That satisfied the student.  But I am mystified
by one

    effect.  Within a few hours, bubbles (presumably
from

    dissolved air) appeared throughout the inside of
the

    formerly full glass, but none appeared in the
receiving

    glass.  What process inhibits dissolved gases
from

    passage through a towel?


    Robert T McQuaid

    Orangeville Ontario Canada

    email:  rtmq@stn.net



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From dimarco@physics.montana.edu Wed Sep 10 11:29:11 2003

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