My science teacher friend says the blackened test tube is getting the least gas, which would mean it’s the oxygen side. This invalidates my guess and theory, so I’m asking here. Why is the tube getting black at the top? Is pulling in electrons breaking graphite covalent bonds? I thought supplying electrons would do that job, but I was guessing.
There should be no graphite in there. The tubes should have been full of just distilled water when the electrolysis started.
Water electrolysis anodes are prone to corrosion. You’re seeing surface oxidation and freeing of polyaromatic “soot”.
Maybe it’s me, but I see no wires providing the power for the electrolysis? And pencils as electrodes?
Understandable. It’s a single photo of a weird display of transparent tubes and transparent liquid using seemingly intentionally obscured wires carrying unseeable electrical currents to capture invisible gases while throwing us all off using household items as electrodes for some reason.
The least surprising thing about this exercise is that pencils blacken things.
ETA wrong link. But yes, the graphite makes for a reasonable home electrode.
Here’s the right link: