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Name: Harris
Status: student
Grade: 9-12
Location: IL
Country: N/A
Date: 2/18/2005


Question:
Does frozen water conduct electricity?


Replies:
Ice conducts electricity only about enough to dissipate static electricity. If it's far colder than freezing, it might not even conduct that much.

As water slowly freezes, it tries to exclude most ions from the growing solid, and they end up concentrated in the remaining liquid. The ions are what help water conduct substantial amounts of current. Very pure de-ionized water might not conduct enough electricity to electrocute you (from 120vac), for example. ice is partly de-ionized, plus the molecules and ions cannot move most of the time.

As the new ice gets colder and colder, the fraction of the time the ions succeed in moving a little goes down, and the ice gets less and less conductive. I suppose a snowstorm on Titan or some other cold moon might have static electricity in patches all over the icy ground, as well as in the flying snow.

If the outside of the ice is shiny-wet, that film is not frozen, and that film of water will conduct.

Especially if it's partly salty sea-water.

Jim Swenson


Good question Harris. As you probably already know, in order for anything to conduct electricity, there must be some mobile charge carrier. In metals, it is the loosely held electrons. In impure water, it is the ions dissolved in the water. Pure water (one with no ions) is a poor conductor of electricity because there are no mobile charge carriers. So we can imagine that pure ice having no charge carriers would also be a poor conductor. How about frozen tap water? While the liquid water may initially have charge carriers, on being frozen the mobility of these carriers become significantly diminished so that the conductivity drops dramatically. There have been studies of doping ice (adding charge carriers to the ice, and those can conduct electricity - at times up to the level of mercury) but that is not ordinary water.

Greg (Roberto Gregorius)



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