Why is water a good conductor of electricity?

[Archosaur]

Experience tells me it is, but my instinct tells me it shouldn't be.
If you place 2 leads of a dc source into water,
how does the charge get from one end to the other?

I can see how it would work with salt water, with the disassociated ions carrying the charge, but that doesn't really have anything to do with the water, other than its ability to dissolve ionic compounds.

My chem prof said that the electrons simply move through the water, never interfering with the molecules, but that doesn't seem right to me. Again, how does that have anything to do with the water? Also, if this were correct, then wouldn't a vacuum be an equally good conductor, if not better?

Just to be clear, I'm not claiming that it isn't a good conductor. I know it is.
I just need to figure out why my instincts are telling me it's not...

Thanks for any help

 

[pzona]

When you run a current through water, dissociation occurs (H2O -> H+ + OH-), but only to a very small extent. You're right to wonder why water itself conducts electricity; the short answer is that it doesn't. Distilled water is actually a very poor conductor of electricity because of the insignificant dissociation. When you deal with water on an everyday basis (tap water, rain water, etc), there are a ton of impurities in it, such as salts and metal ions. This is why water seems to be a good conductor of electricity, because you normally don't deal with distilled water in everyday situations.

 

[quicknote]

!

I can explain why water is a good conductor of electricity. Water is made up of molecules that contain both positively and negatively charged particles, called ions. These ions are constantly moving and interacting with each other, creating an electrically conductive environment. When an electric current is applied to water, these ions are able to move and carry the charge from one end to the other, allowing the electricity to flow through the water.

In pure water, there are very few ions present, which is why it is not a very good conductor. However, when impurities such as salt or other dissolved substances are added to the water, they break down into ions, increasing its conductivity. This is why salt water is a better conductor than pure water.

Your chem professor is correct in saying that the electrons do not interfere with the water molecules themselves. The movement of electrons through water is actually quite slow compared to the movement of ions. It is the ions that are primarily responsible for carrying the charge and allowing electricity to flow through water.

As for your question about a vacuum being a better conductor, this is not the case. In a vacuum, there are no particles present to carry the charge, so electricity cannot flow through it. This is why vacuum tubes are used in electronics to prevent the flow of electricity.

In summary, water is a good conductor of electricity because of the presence of ions that are able to move and carry the charge through the water. The addition of impurities, such as salt, can increase its conductivity. I hope this helps to clarify your instincts about water as a conductor of electricity.