r/BeAmazed • u/himmokala • Dec 15 '24

Science Using red dye to demonstrate how Mercury cannot be absorbed by a towel

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u/BassicallySteve Dec 15 '24 edited Dec 16 '24

Why is that? Is it a density thing? I guess i’ve never looked at the physics of absorption lol

Edit: thanks everyone! I learned a thing

62

u/Rattus375 Dec 15 '24

This is just based on my understanding so it could be wrong, but I'm pretty sure absorption is just capillary action, where the attraction of each water molecule to the cloth is strong than the force of gravity holding them down. Water is a highly polar particle which is strongly attracted to things, while mercury is just a single element, so it would make sense that it wouldn't have any attractive force

34

u/Strategy_gameR_31415 Dec 15 '24

Water has sticky parts, mercury doesnt.

3

u/sweetpotato_latte Dec 15 '24

Does this mean water has a higher viscosity than mercury?

5

u/Strategy_gameR_31415 Dec 15 '24

By sticky I was referring to the charge of water not the viscosity, water is shaped a how it has a weak positive and negative end much like a magnet. When other things with positive and negative ends get in water the water molecules grab on to it and it dissolves. Also it depends on which type of viscosity you are talking about.

1

u/[deleted] Dec 15 '24 edited Dec 15 '24

[deleted]

1

u/PM_ME_happy-selfies Dec 16 '24

From what I found online it says it’s primarily the surface tension that stops it from being able to be absorbed but also has to do with the molecular structure. I don’t completely understand though lol

11

u/FerociousDiglett Dec 15 '24

Part of what makes capillary action work is that the water molecules are attracted to the fibers of a towel more than they're attracted to other nearby water molecules. Mercury is the opposite - each mercury atom is strongly attracted to its neighbors and absolutely does not want to stick to a cloth fiber if it means separating from the group. That strong cohesion is also why it forms nearly spherical beads when it's resting on a surface.

2

u/judgmentalbookcover Dec 15 '24

Without the dye, if you tried to wipe up mercury, would your towel remain dry?

3

u/Rattus375 Dec 15 '24

Yes it would

11

u/SpiderSlitScrotums Dec 15 '24 edited Dec 15 '24

Here is a nice diagram showing how capillary action works with water and mercury (note the shape of the miniscus):

https://www.researchgate.net/figure/Example-of-capillary-action-of-water-and-mercury_fig7_323958362

Mercury has strong cohesion relative to its weaker adhesion. So it does not adhere to dissimilar materials and will bead up. Water is the reverse.

If you pour a small amount mercury on a towel, you will just get beads on the surface, while in the case of water, it would be pulled into the towel.

1

u/[deleted] Dec 15 '24

Surface tension