General Chemistry: Principles and Modern Applications (10th Edition)

At the inert $Pt_{(s)}$ electrodes, mass does not change. At the $Cu_{(s)}$ electrode, there is a mass gain through the half reaction, $Cu^{2+}$$_{(aq.)} + 2e^- \longrightarrow Cu_{(s)}. At the Zn_{(s)} electrode, there is a mass loss through the half reaction, Zn_{(s)} \longrightarrow 2 e^- + Zn^{2+}$${(aq.)}$.
At the inert $Pt_{(s)}$ electrodes, mass does not change. At the $Cu_{(s)}$ electrode, there is a mass gain through the half reaction, $Cu^{2+}$$_{(aq.)} + 2e^- \longrightarrow Cu_{(s)}. At the Zn_{(s)} electrode, there is a mass loss through the half reaction, Zn_{(s)} \longrightarrow 2 e^- + Zn^{2+}$${(aq.)}$.