Measuring evaporation rate of boiling water for a coursework graph

[MelanieBrett]

Hi
I was thinking of doing an experiment for my maths coursework to plot a graph to, and was thinking of doing something related to the rate of evaporation of water. My thinking is that i conduct an experiment where I heat water to boiling point so it is at about a constant temperature with a constant power source and measure the rate that the mass decreases. I thought that if Q=mcT, then as the mass decreases a smaller amount of energy is required to in effect change the temperature.
I'm not too sure, I'd hope that if i plotted mass against time I would get a -ve log graph which I could determine a formula for?
If anyone had any comments/thoughts as to whether it would be viable or if I needed to clarify something I wold be grateful to hear them :)
Thanks, B

 

[MelanieBrett]

Maybe I should be referring to boiling rather than evaporation?

 

[stockzahn]

I thought that if Q=mcT, then as the mass decreases a smaller amount of energy is required to in effect change the temperature.

If you increase the temperature of the water to its boiling point, the temperature stays constant and all the heat input changes the water to steam (look up "latent energy"). So a constant heat input would cause a constant decrease of mass.