How Do We Know if We Have Hydrogen and Oxygen?

electrolysis is a way of passing electricity through water. When the hydroden irons reach the negative electrode, which theyar attracted to, they will form hydrogen gas. And when the o h minus irons reached the positive electrode, they'll form oxygen gas. So you can see there's more bubbles being created on the hydrogen side than the oxygen side because water's h two o. You get twice as much hydrogen as oxygen. How do we actually know that we have hydrogen and oxygen? We're going to add some soap to this water - which will hopefully mean the bubbles will be more stable. And we can mix that in, and we will wait for a bit, and hope to