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Q & A: Evaporation Jars

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Most recent answer: 10/22/2007
Q:
If a glass jar is covered, but the lid left exposed, with thick black paper, foil or no covering which is likely to have the fastest rate of evaporation when left on a shelf?
- Kate (age 16)
Burwood Girls High, Sydney, Australia
A:
Kate -

The hotter the liquid in the jar is kept, the more rapidly it will evaporate. When light strikes the paper or foil, it will either be reflected or absorbed. Dark colors (such as the dark paper) absorb a lot of light, which will heat up the inside of the jar - this also why you will feel hotter if you wear dark colored clothes outside when it's sunny. Lighter colors absorb very little light, so the liquid in the jar will not get as hot if you wrapped it in, say, white paper instead of black. Shiny materials such as foil reflect the light, so practically none of it will go to heating up the liquid.

-Tamara

(published on 10/22/2007)

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