This is a quote from a book I am reading:
>Droplets of alcohol on a plate warmed on one side congregate toward that side, droplets of oil move in the opposite direction. Small beads of mercury in dilute nitric acid move in a purposeful manner over long distances toward a crystal of potassium dichromate. Indeed, there was once a theory that the motility of amoebae and other cells is driven by changes in surface tension similar to those displayed in some chemical systems.
Why does this happen? Evidently surface tension plays a role, but how does it work exactly?
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I know why it happens with alcohol but honestly I have no idea why would it be different for oil.
Increase in temperature naturally decreases surface tension because more temperature = more more movement on molecular level = higher chance that molecules hit one another and throw themselves out of intermolecular bonds, and because droplets get heated faster from the side where the heat source is the viscosity of each side is slightly different – the side facing the heat is more liquidy than the one facing away, so it starts to spill out while the other keeps shape. I would expect oil to behave in the exact same way, but maybe there is some other underlying mechanism connected to the way oil transfers heat that causes it to go in an opposite direction.
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