Science Buddies: "Ask an Expert"

Although my experiment is actually focused on what sorbents remove oil most effectively from water, I need to know the evaporation rate of water on average at room temperature. I am testing different kinds of sorbents, which are materials that absorb liquid such as oil or water. These materials can include, but are not limited to, clay, sand, steel wool, and synthetic, or man-made, sorbents. I am going to be allowing the materials to soak in a mixture of oil and water to simulate the usage of sorbents on oil spills. I will then be measuring and comparing their mass with and without oil in them but the sorbents will also most likely absorb some water as well. To make up for this I would like to set the sorbents out for a time to let the water evaporate before I measure their new mass. I don't know how long to leave them out before I take their new measurents. Thank you.

Dear 13MJones,

The evaporation rate of water varies based on the environment and variables involved. We all know that water boils at 100 degrees Celcius, this is a material property of Water. However, for evaporation rate, there are other variables involved such as the temperature and humidity of the air, the area of the air/water surface, air flow past the sample which leads to convection heat transfer. Therefore, I suggest that you physically measure the evaporation rate at the location you plan to perform the experiment. Simply fill a measuring cup with a known quantity or mass of water. Wait and let nature do its thing for 24 hours and come back and record the remaining volume or mass of the water. You can then, for the sake of experimentation, go another 24 hours and get another measurement. The rate of evaporation will be the (change in water volume or mass)/time. As a data point, I performed an experiment with growing salt crystals with my daughter. It took two days for the water to totally evaporate....it was 77 degrees Fahrenheit and roughly 50% relative humidity in my house. If you live in a drier climate it should go faster....

I encourage you to measure and calculate the rate at your location to solidify your results!

Best of luck,

Marc