text: how do you split water? science project hydrolysis is a chemical reaction or process in which a molecule is split into two parts by reacting with a molecule of water, which has the chemical formula h2o. one of the parts gets an oh from the water molecule and the other part gets an h from the water.  when performed using electric current, the process is called electrolysis  one important use of electrolysis is to produce hydrogen. the reaction that occurs is      2h2o(aq) → 2h2(g) + o2(g)  in the future, this could play a central role in shifting our society over to a reliance on hydrogen as an energy carrier for powering electric motors and internal combustion engines. (see hydrogen economy.) electrolysis of water can be achieved in a simple hands-on project, where electricity from a battery or low voltage dc power supply (eg computer power supply 5v rail) is run into a cup of water (in practice a saltwater solution or other electrolyte will need to be used otherwise no result will be observed). using platinum electrodes, hydrogen gas will be seen to bubble up at the cathode, and oxygen will bubble at the anode. using any other electrode for the anode however, the oxygen will react with the anode instead of being released as a gas. for example using iron electrodes in a sodium chloride solution electrolyte, iron oxide will be produced at the anode, which will react to form iron hydroxide. when producing large quantites of hydrogen, this can significantly gunge up the electrolytic cell - which is why iron is not used for commercial electrolysis.  the energy efficiency of water electrolysis varies widely. some report 50–70%, while others report 80–94%. these values only refer to the efficiency of converting electrical energy into hydrogen's chemical energy. the energy lost in generating the electricity is not included. for instance, when considering a power plant that converts the heat of nuclear reactions into hydrogen via electrolysis, the total efficiency is more like 25–40%.