Question

How can we separate the hydrogen from the oxygen `H_2O`?

Answer 1

One method is through electrolysis - using an electrical current to separate the hydrogen and oxygen.

Explanation:

One method is through electrolysis.

Electrolysis = "the passage of an electric current through an electrolyte with subsequent migration of positively and negatively charged ions to the negative and positive electrodes" (http://www.dictionary.com/).

This decomposes the water into oxygen gas (`O_"2"`) and hydrogen gas (`H_"2"`) due to the electric current passing through the water.

The electricity enters the water at the cathode - a negatively charged terminal, and passes through the water and exists via the anode - the positively charged terminal.

The hydrogen is collected at the cathode and the oxygen is collected at the anode.

The resulting products are very pure and is a reliable, yet expensive method.

Hope this helps :)