Yes, a gas is given off when water splits into hydrogen and oxygen. This is called electrolysis, and here's why:

* Water's Chemical Formula: Water (H₂O) is made up of two hydrogen atoms (H) and one oxygen atom (O).

* Breaking the Bonds: When electricity is passed through water, it provides enough energy to break the chemical bonds holding the hydrogen and oxygen atoms together.

* Gas Formation: The freed hydrogen atoms bond together to form hydrogen gas (H₂) and the oxygen atoms bond to form oxygen gas (O₂).

So, both hydrogen gas and oxygen gas are given off during the electrolysis of water.