Answer:
I think the reason why ice is forming on the aluminium lumps and not the beaker, is because:
The beaker is already on the same temperature as the mixture inside it: as a result, there is no heat transfer.
on the other hand, the Aluminium Lumps is at a way lower temperature than the mixture and as a result, there is heat transfer from the water around the lumps to the aluminium Lumps itself.
turning the water into ice.
Heat is lost from the water, and gained on the aluminium.
Since the water was turned to ice.
we can say that the final temperature of the heat transfer process is 0°C.
Notice that we'll be making use of the latent heat of fusion for ice. since water is being converted to ice at 0°C.( workout is in above attachment)