Question

why does a soap dish float in a bucket of water while a cake of soap sinks

Answer 1

as the soap dish is made up of plastic with density less than the water and less is light it floats while the soap cake being denser than the water sinks.

Answer 2

A soap dish floats in a ‘bucket of water’ while a cake of soap sinks due to upthrust.

EXPLANATION:

‘Archimedes’ principle’ states that ‘when a body is immersed in a liquid it experiences an upward buoyant force called upthrust’. The greater the displacement the greater is the upthrust.

A soap dish is expanded in shape. It has a larger surface area than a cake of soap. So it displaces more water and experiences a greater upthrust than a cake of soap. A soap cake does not displace much water so it experiences less upthrust. Due to its weight the ‘gravitational pull’ becomes much greater than its upthrust and so it sinks.