what changes does electricity cause in water?

Answer 1

you can separate water into its constituents by passing electricity through it

Answer 2

You can set up two electrodes in water - usually platinum and pass electricity from the anode to the cathode through the water. If I remember rightly you have to add something to the water to make this work. But as water is basically H2O - that's 2 atoms of hydrogen and one of oxygen - the water is split and hydrogen is given off at the one electrode and oxygen at the other. This is handy and both can be compressed and compressed to a liquid. When combined again they will burn and you basically have rocket fuel!

Answer 3

It depends on how clean the water is.
Water will not conduct electricity if there are no foreign, disolved minerals in it, so no electrolysis occurs and there cannot be any separation of Hydrogen and Oxygen, as in one of the above answers. The desolved minerals are called "electrolytes", in which sea water would be a good example. You could add sodium sulphate and/or sodium chloride to distilled water and it would then conduct electricity;