Question

Two identical solid pieces,one of gold and other of silver,when immercesd

Answer 1

When an object is underwater, it has the force of gravity pulling it down and buoyant force pulling it up. The force of gravity is determined by mass, and buoyant force is determined by volume.

Since aluminium is less dense that steel, the aluminium piece has to be bigger than the steel block. Since it's bigger, it has more buoyant force, so it needs to be even bigger to have the same weight in water as the steel.

Once both are removed from the water, the buoyant force goes away. The aluminium, having more volume, loses more buoyant force, and so becomes heavier in air.