Why does an aluminum ball sink and a piece of foil float?

An aluminum ball sinks while a piece of foil floats due to differences in their densities and surface areas. The aluminum ball is more dense than water, causing it to displace a volume of water equal to its weight, resulting in sinking. In contrast, the piece of foil has a larger surface area relative to its volume, creating enough buoyant force to keep it afloat despite being made of the same material as the ball.