System is in a closed container. So there will be no heat transfer. Therefore the heat is q=0. Now liquid is stirred with a paddle to increase the temperature which increases the internal energy ΔE of the system. ΔE=nCΔTΔE=0 Work is also done on the system when started with a paddle. W=0ΔE=q+W=0+W,ΔE=WΔE=ΔW=0,q=0