Re: Electrolysis results

Nathan and Matthew:

The electrolysis that you did was that of salt water, not
simply water.  The addition of the salt created a different
system.  The reaction for your electrolysis is:

  H2O + NaCl ---> H2 + Cl2 + NaOH

You had hydrogen gas as the cathode, but chlorine
gas (luckily not much) at the anode with sodium 
hydroxide solution in the apparatus. 

Most likely the chlorine reacted with the copper
wire to form CuCl2 or Cu2Cl2 which then reacted
with the NaOH to form Cu(OH)2 which was most likely
your precipitate.

Fortunately you didn't try to breath the gas at the
anode as it wasn't oxygen but chlorine which can
be deadly causing severe erosion of mucous membranes
and pulmonary edema leading to death.

Improvising with different equipment variations
can significantly effect the outcome of a reaction.
Be very careful with any future experiments.