Question

What causes a small scrap of paper placed on top of the water droplet to float , although the object is denser (heavier) than the water?

Answer 1

surface tension

a small scrap of paper onto a droplet of water, the paper floats on top of the water droplet, although the object is denser  heavier  than the water. This occurs because of the surface tension that is created by the water molecules. Cohesion and surface tension keep the water molecules intact and the item floating on the top. It is even possible to float a steel needle on top of a glass of water if you place it gently, without breaking the surface tension  Figure 2.11 .