What is the reaction between a copper anode and a zinc cathode?

I prepared a battery with $\ce{Zn}$ screws and a $\ce{Cu}$ wire, with water as an electrolyte. The $\ce{Zn}$ screw acted as the cathode, and the $\ce{Cu}$ wire acted as the anode. I got nearly $0.6\:\mathrm{V}$ as the emf. I placed numerous amounts of such cells in an ice cube tray. Each ice cube acts as a cell and i got nearly $6\:\mathrm{V}$ of emf. What is the reaction happening here? What is the reaction involved with the electrodes and the electrolytes?




Well the standard galvanic cell with $\ce{Zn}$ and $\ce{Cu}$ would usually look something like this, assuming there's a salt bridge.


![enter image description here](https://i.stack.imgur.com/sMTam.gif)


and the reaction could be written as 


\begin{align}
\ce{Cu^{2+}\_(aq) +2e^{-} &<=> Cu^0} & E^\circ &=0.34\\
\ce{Zn^0 (s) &<=> Zn^{2+} (aq) +2e^-}& E^\circ &=+0.76\\
\ce{Cu^{2+}(aq) + Zn^0 (s) &<=> Cu^0 (s) + Zn^{2+}(aq)} & E^\circ &= +1.10 
\end{align}


As for your measured emf, that can be calculated using the Nernst Equation.


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