How is evaporation different in different liquids? Does it have anything to do with density or the kind of ingredients that the liquid contains?

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t-nez | High School Teacher | (Level 3) Associate Educator

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The rate of evaporation varies for different substances because they have different vapor pressures. Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid phase. A substance with high vapor pressure is more volatile than one with low vapor pressure so it will evaporate at a faster rate in an open system where equilibirum isn't reached. 

Density and rate of evaportation are both related to intermolecular attractions. Pure substances with stronger intermolecular forces are likely to be more dense because the are held more closely together and because they are more likely to have a higher molecular weight. Similarly, a substance with stronger intermolecular forces is less volatile (evaporates more slowly) because the molecules are attracted to others in the liquid phase. 

There's also a relationship between evaporation and other ingredients as you suggested. A non-volatile solute dissolved in a pure substance, for example salt dissolved in water, lowers its vapor pressure. When the vapor pressure is lower it exhibits less evaporation.

 

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