An aluminum can, with negligible heat capacity, is filled with 450 $\mathrm{g}$ of water at $0^{\circ} \mathrm{C}$ and then is brought into thermal contact with a similar can filled with 450 $\mathrm{g}$ of water at $50^{\circ} \mathrm{C}$ . Find the change in entropy of the system if no heat is allowed
to exchange with the surroundings. Use $\Delta S=\int d Q / T$ .