Question

Fully explain why a paper clip can float on water even though it is much more dense than water.

Answer 1

It is because of surface tension of water that the paper clip floats on it, though it is denser than water. Once it drowns it cannot come up, due to it's higher density.

To understand surface tension, we need to understand that there is cohesive force of attraction among water molecules. The water molecules attract each other because of intermolecular hydrogen bonding between them. Now the water molecules which are not on the surface and are below feels attraction in all directions and thus force is diffused.

Where as the surface layer is only pulled down and not upwards. So it is less diffused and together they form kind of layer which are attached to each other creating tension on the surface called as surface tension. This layer holds each with certain significant force and thus it needs certain amount of force to pierce it. So if paper clip is kept gently on the surface, horizontally, then it floats.