$($c$)$ A student electrolyses copper sulfate using copper electrodes. Look at the diagram.

It shows the apparatus she uses.

She investigates the change in mass at each electrode before and after the electrolysis.

Look at her method.

Using a balance, measure the mass of the copper cathode and copper anode.

Set up the apparatus and run the electrolysis for $30$ seconds.

Remove the copper cathode and the copper anode and immediately place them on the

balance and measure their masses again.

$($i$)$ What improvements could you make to the student's experiment?

$($ii$)$ The student finds that:

the cathode gains mass

the anode loses mass.

Explain these observations in terms of the reactions at each electrode.