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Water Conducting Electricity
Name: Jack
Status: student
Age: N/A
Location: N/A
Country: N/A
Date: N/A
Question:
I am amid a debate on whether water conducts electricity
or not. One side says that pure water will not conduct electricity;
the other side says that with enough voltage it will. Can you
enlighten us? If possible, please explain the differences in water
types and what is required to get "pure H2O".
Replies:
Aah, semantic arguments...
With enough voltage (actually, the issue is an intense enough electric field),
any conducting material will experience "dielectric breakdown" and allow current
to flow. What happens is that the electrons are actually ripped away from their
atoms, disrupting the chemical structure of the material.
In the case of pure water, you'd be making a hydrogen/oxygen plasma, which would
conduct electricity. But would you call that water?
Richard E. Barrans Jr.,
Department of Physics and Astronomy
University of Wyoming
Commomnly demonstrated in sceince classrooms, using regular US household (110 volt)
AC current, pure water seems to fails to complete a circuit in order to light a
incandescent light bulb for example. Salts added to the water will result in a complete
circuit since they dissociate readily. This demonstration has a purpose in some
aspects, however, it often creates a misconception.
Water does dissociate into ions so their is some electricity flowing at all times
with even pure water, but not enough to heat up the tungsten element to glow in a
common bulb using house current. That said, with enough electron flow, any substance or solution will
conduct electricity.
Steve Sample
Absolutely pure water ionizes. The concentration of (H+1) and (OH-1),
each having a concentration of
10^-7 mols per liter. This means that "absolutely pure" water will conduct
an electrical current, so the determination needs to be carried out in
platinum vessels. Atmospheric gases such as N2, O2, and others must be
scrupliously removed and not allowed to come into contact with the test
sample Should you increase the voltage, other reactions will occur. In
practice it is very, very difficult to obtain "absolutely pure" water. Even
glass is sufficiently soluble to give a "false positive" signal for
conductivity.
There is another problem. If you "purify" the water, by whatever method,
a factor is the fractionation of various nuclear isotopes of water, the
largest being HDO and D2O.
So what seems like a simple measurement, in practice, becomes very
complicated. OH!! remember that all of the parameters above depend upon
temperature!!
Vince Calder
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Update: June 2012
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