Towards the end of the reaction process, bubbles may be forming at both electrodes. Light a match, remove the lid from the dish, and hold the burning match to the bubbles. Vary spacing of the electrodes by setting the tips of the wires at different distances apart. Vary the orientation of the electrodes by placing them parallel instead of tip to tip. Where explanations are not possible, it may still be possible to make hypotheses.
Deposits start to form around the cathode as soon as electrolysis begins.
The rate at which these develop varies as the electrolysis proceeds. Bubbles formed at one electrode may stream through the electrolyte towards the other electrode. The colour of the solution tends to fade, more quickly at the cathode side of the drop of solution. When a growth of metal from the cathode reaches a grain of copper oxide, it grows very rapidly through or around the grain. Fine drops of liquid form under the lid of the petri dish, mainly just above the anode.