Droplet of ballpoint ink in water (why)

[Willsr]

I was wondering, a ballpoint pen ink droplet is droped on water, it floats and moves, why?
Is it density, viscosity, surface tension or something else. I am pretty stuck

 

[Doug Huffman]

If it is indeed floating then its density is less than water.

It may be light enough and hydrophobic to not exceed the surface tension that also causes the motion due to variations in the force potentials between the water and the ink - electrostatic is the obvious one.

 

[Danger]

Brownian motion might also contribute.

 

[Meir Achuz]

It could be held up the surface tension of the water. When that happens, the small object on the surface will move back and forth due to slight perturbations of the water surface.

 

[PJC01]

I can explain the behavior of a droplet of ballpoint ink in water using the principles of density, viscosity, and surface tension.

Firstly, the ink droplet floats on top of the water because it has a lower density than water. The ink is made up of pigments and solvents that are less dense than water molecules, allowing it to stay on the surface rather than sinking to the bottom. This is also why the droplet appears to spread out on the surface of the water, as it is being supported by the water molecules underneath.

Secondly, the viscosity of the water and ink also play a role in the droplet's movement. Viscosity is a measure of a fluid's resistance to flow, and water has a lower viscosity than ink. This means that the water molecules can move more easily and quickly, causing the ink droplet to move and spread out on the surface of the water.

Lastly, surface tension is the force that allows the surface of a liquid to resist external forces. In this case, the surface tension of the water molecules is strong enough to hold the ink droplet together and prevent it from breaking apart. This is why the droplet maintains its shape and moves as a cohesive unit on the surface of the water.

In summary, the behavior of a droplet of ballpoint ink in water can be explained by the differences in density, viscosity, and surface tension between the two substances. I hope this helps to clarify your question.