Thank you for the question. Rubbing alcohol
consists mainly of ethanol or isopropanol.
Ethanol and isopropanol boil at a lower
temperature than water, which generally means that
they will evaporate quicker than water. The
boiling temperature is largely determined by
attractive interactions between the liquid
molecules. The attraction between 2 ethanol
molecules is weaker than the attraction between 2
water molecules, which means that the water
molecules do not want to be separated like they
would in a vapor or gas upon evaporation. Water
molecules attract each other strongly because each
molecule participates in 4 attractive "hydrogen
bonds," which are bonds between the hydrogen of
one water molecule and the oxygen of another water
molecule. Ethanol and isopropanol each only
participate in 2 hydrogen bonds.
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