When you make ice cubes,the entropy of water

$A$ hot piece of copper at $100^{\circ} C$ is dropped into a pond at $30^{\circ} C$. The copper cools down to $30^{\circ} C$,while the pond remains at its initial temperature due to its large size. Then,

During phase change,entropy

On a hot day,a cup full of ice water placed on a table heats up,while a cup of hot tea on the same table cools down. Explain the reason.

Write an example in which the first law of thermodynamics is allowed but is never observed.

Why can't the efficiency of a heat engine ever be $100 \%$?