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Q & A: reducing rate of evaporation

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Most recent answer: 10/22/2007
Q:
What substances can reduce the rate of evaporation? From this site, i have already found that oil and salt may help. What about things like detergent and washing powder? Thank You
- Anonymous (age 15)
Australia
A:
Detergent and washing powder (which sometimes is a detergent) would probably also reduce the rate of evaporation of water, for the same reason that the salt would.

I'd imagine that substances that form some kind of layer on the surface of the water like the oil will slow the evaporation much more than substances that dissolve in water. A substance that doesn't dissolve but sinks (like mercury) won't do anything to affect the evaporation rate.

Tom

p.s. Detergent mighht help in two ways. A thin layer (probably one molecule thick) should form on the surface, slightly slowing down the water evaporation the way other surface barriers do. The rest of the detergent should go into solution, slowing the evaporation in the same way that any solvent does. mike w

(published on 10/22/2007)

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