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Why does rubbing alcohol evaporate quicker than water?
Question Date: 2015-04-26
Answer 1:

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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