Effect of atmospheric pressure on evaporation

[ggiks]

I am trying to come up with a good way to measure atmospheric pressure and its effects on water evaporation. Can you please give me ideas on how to go about it.
Thank you
Abby (5th grade)

[rmarz]

ggiks and Abby - The rate at which water will evaporate into the atmosphere is definitely affected by several variables, temperature, humidity (water content of your atmosphere) and atmospheric pressure. Any meaningful experiment to measure one variable would have to control the others. Atmospheric pressure can change in a close range of between pressures of 29 to 31 inches of mercury, a range of only 10%. This seems like a bit of a challenge for the kind of environmental control equipment and measuring instruments you might have access to. I haven't looked online for similar experiments others may have done, perhaps you can get some ideas there. You may also find data that would allow you to correct for these variables, such as curves that show vapor pressure changes over temperature, or evaporation rates at different pressures and temperatures.

Sometimes a good experiment can be demonstrated just by showing the interacting complexities and how you would evaluate these effects if you had the right equipment and ability to control the process as opposed to actual physical measurement of these variables. Good luck.

Rick Marz

[catherineM99]

Hi Abby and Ggiks!

This sounds like an exciting project! Adding onto rmarz’ response, you could measure air pressure with a fan. You could set up a beaker filled with water next to a fan, and measure how fast the water evaporates under various speeds of the fan. With the fan at a higher setting, air pressure is higher, and thus you would expect the rate of evaporation of water to be higher. Like rmarz' mentioned, it will be important to control variables. When changing the fan speed, you will want to use the same amount of water, at the same temperature, and the surroundings should be at constant humidity.

Hope this helps!

~Catherine M.

[mattrosenthal26]

Abby and Ggiks,

In regard to measuring atmospheric pressure, it is typically done through a barometer. However, there are ways to make a barometer out of everyday materials (jars, straws, balloons, etc.). This homemade barometer could then be used to measure atmospheric pressure.

Hope this was helpful!

Matthew